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Establishing Causes of Eradication Failure Based on Genetics: Case Study of Ship Rat Eradication in Ste. Anne Archipelago
Conservation Biology
Abstract
Determining the causes of a failed eradication of a pest species is important because it enables an argued adjustment of the methodologies used and the improvement of the protocols for future attempts. We examined how molecular monitoring can help distinguish between the two main reasons for an eradication failure (i.e., survival of some individuals vs. recolonization after eradication). We investigated genetic variation in seven microsatellite loci in ship rat (Rattus rattus) populations from four islets off the Martinique coast (French Caribbean). In 1999 an eradication attempt was conducted on the four islets. Three years later rats were observed again on two of them. We compared the genetic signatures of the populations before and after the eradication attempt. On one of the islands, the new rat population was likely a subset of the pre-eradication population. A weak genetic differentiation was found between them, with almost no new alleles observed in the new population and moderate FST values (0.15). Moreover, assignment procedures clustered the two populations together. In contrast, on the other islet, many new alleles were observed after the eradication attempt, resulting in an increase in genetic diversity (from 2.57 to 3.57 mean number of alleles per locus) and strong FST values (0.39). Moreover, genetic clustering clearly separated the two samples (i.e., before and after the eradication attempt) in two different populations. Thus, to achieve long-term eradication on these islets, it seems necessary to redevelop the eradication procedure to avoid individuals surviving and to prevent reinvasion, probably from the mainland, by installing permanent trapping and poisoning devices and conducting regular monitoring. We strongly encourage wildlife managers conducting eradication campaigns to integrate molecular biological tools in their protocols, which can be done easily for most common invasive species.
... The re-invader hypothesis argues that eradications fail due to dispersal from a source population. This scenario can be particularly difficult to investigate without sufficient pre-and post-eradication genetic samples to adequately capture the extent of genetic variation in either population (Abdelkrim, Pascal, & Samadi, 2007;Howald et al., 2007;Savidge et al., 2012). Often, it is the lack of pre-eradication samples that acts as a barrier to effectively elucidate the origin of a population, as these are necessary to properly characterize the historical genetic composition (Abdelkrim et al., 2005(Abdelkrim et al., , 2007. ...
... This scenario can be particularly difficult to investigate without sufficient pre-and post-eradication genetic samples to adequately capture the extent of genetic variation in either population (Abdelkrim, Pascal, & Samadi, 2007;Howald et al., 2007;Savidge et al., 2012). Often, it is the lack of pre-eradication samples that acts as a barrier to effectively elucidate the origin of a population, as these are necessary to properly characterize the historical genetic composition (Abdelkrim et al., 2005(Abdelkrim et al., , 2007. ...
... The need for increased research when informing eradications, especially in terms of defining eradication units, has been highlighted as a means to maximize success (Buckley, 2008). Genetic data can be particularly informative in this context, providing insights on population connectivity to assist managers in defining eradication units (Abdelkrim et al., 2007;Dawson et al., 2015;Robertson & Gemmell, 2004;Russell et al., 2010). ...
Invasive species have led to precipitous declines in biodiversity, especially in island systems. Brown (Rattus norvegicus) and black rats (R. rattus) are among the most invasive animals on the planet, with eradication being the primary tool for established island populations. The need for increased research for defining eradication units and monitoring outcomes has been highlighted as a means to maximize success. Haida Gwaii is an archipelago ~100 km off the northern coast of British Columbia, Canada that hosts globally significant breeding populations of seabirds that are at risk due to invasive rats. Here, we paired sampling of brown (n=287) and black (n=291) rats across the Haida Gwaii archipelago (British Columbia, Canada) with genotyping‐by‐sequencing (10,770‐27,686 SNPs) to investigate patterns of population connectivity and infer levels/direction of gene flow among invasive rat populations in Haida Gwaii. We reconstructed three regional clusters for both species (north, central, south), with proximate populations within regions being largely more related than those that were more distant, consistent with predictions from island biogeography theory. Population assignment of recently detected individuals post‐eradication on Faraday, Murchison, and the Bischof Islands revealed all were re‐invaders from Lyell Island, rather than being on‐island survivors. Based on these results, we identified six eradication units constituting single or clusters of islands that would limit the potential for re‐invasion, some of which will need to be combined with biosecurity measures. Overall, our results highlight the importance of targeted research prior to conducting eradications and demonstrates a framework for applying population genomics for guiding invasive species management in island systems.
... However, there are examples of eradication campaigns that failed because of survival of a few alien individuals and/or recolonization of eradicated areas from nearby islands or the mainland (Thorsen et al., 2000;Courchamp et al., 2003;Parkes et al., 2011;Savidge et al., 2012). When a few individuals survive eradication, high reproduction rates typical of black rats and absence of predators that limit dispersal of aliens may lead to a relatively fast increase in population size (Abdelkrim et al., 2007;Russell et al., 2009a,b). If recolonization occurs, then absence of intraspecific competition allows the newly arrived individuals to rapidly spread across the eradicated area (Russell et al., 2010). ...
... According to the eradication unit concept (sensu Abdelkrim et al., 2007), recolonization of eradicated areas can be prevented if the interconnected populations are eradicated simultaneously (e.g. Robertson and Gemmell, 2004;Abdelkrim et al., 2005aAbdelkrim et al., ,b, 2007Abdelkrim et al., , 2010Capizzi et al., 2010). ...
... A common approach to uncover patterns of either natural or human-driven migration of invasive rat populations is by looking at nuclear DNA microsatellite allele variation (Fewster et al., 2011). Once the genetic profile and structure of eradication units are characterized, then simultaneous eradication can be implemented to prevent re-colonisation from nearby populations (Abdelkrim et al., 2007). ...
Invasive species are one of the main causes of biodiversity loss, and rodents in particular are regarded as a real threat worldwide, especially to island ecosystems. The Tuscan Archipelago National Park is the largest in the Mediterranean basin, it harbours a large number of autochthonous endemic species, mostly reptiles and insects, and hosts many migratory birds during their seasonal movements. Although a number of sites in the Archipelago are under strict protection regimes, the invasive black rat Rattus rattus has significantly affected survival of local wildlife. As part of an eradication campaign conducted in 2012 and 2017, we assessed genetic diversity and population differentiation of black rats from a total of six locations on the largest Elba Island, a possible source of invasion, and the southern, small islands of Pianosa and Montecristo using six nuclear DNA microsatellite loci. We recorded a strong population structure and identified the islands of Elba, Pianosa and Montecristo as three distinct eradication units. Despite some degree of admixture was recorded on Elba, the largest island of the archipelago was unlikely the main source of invasive rats to Pianosa and Montecristo. We also recorded evidence of past reduction in population size, particularly in Montecristo, probably due to repeated past founding events. Biodiversity management plans should consider monitoring vessels arriving to the Tuscan Archipelago from the mainland and the major Tyrrhenian islands in order to limit alien invasion. Moreover, as reinvasion can occur a few years after eradication, regular monitoring should be conducted thus to rapidly intercept the arrival of new invaders.
... Genetic approaches to understand spatial structure, dispersal and population genetics of invasive species have been considered for the management of several alien species, including American mink (Abdelkrim et al. 2005(Abdelkrim et al. , 2007Grapputo et al. 2005). In Spain, scarce gene flow and low migration rates among mink populations were found, suggesting that each population should be managed as an individual unit (Lecis et al. 2008). ...
... Knowledge of the genetic diversity and population structure of mink populations may help increase the success of population control and/or eradication in invaded areas (Abdelkrim et al. 2005(Abdelkrim et al. , 2007Zalewski et al. 2010Zalewski et al. , 2016. However, to date there are no genetic studies that support such actions or allow comprehension of previous and posterior scenarios regarding the introduction of the species in Chile (Valenzuela et al. 2016). ...
... Therefore, first control efforts should focus on these locations. On the other hand, even when it is feasible to eradicate an invasive species at a given location, likely recolonisation from adjacent areas will occur, so it is important to concurrently neutralise any source of immigration (Abdelkrim et al. 2005(Abdelkrim et al. , 2007Lecis et al. 2008;Fraser et al. 2013). In our case, we recommend that control efforts on the Puerto Cisnes population should be conducted simultaneously, because this population would be acting as a source of individuals for locations from all genetic clusters. ...
Abstract
Context. Biological invasions have caused dramatic changes in native biodiversity and ecosystem function. Studies of genetic variation and evolutionary changes are useful for understanding population dynamics during biological invasions, and shed light on management, prevention and restoration strategies.
Aims. This study aimed to investigate the structure and genetic variability of American mink (Neovison vison), an invasive species in southern South America, introduced for fur farming in the 1930s.
Methods. Samples from 153 mink were obtained from 12 locations in southern Chile to sequence the mitochondrial DNA (mtDNA) control region and to genotype 11 polymorphic microsatellite loci.
Key results. The highest mtDNA diversity was detected in Puerto Cisnes, suggesting multiple introductions and/or the most probable area where mink was first introduced. The latter is also supported by microsatellite data, because a high percentage of individuals from different locations were assigned to this location. All other locations showed low or no mtDNA diversity, possibly due to founder effect. The results also indicate marked population structure, with three genetic clusters coincident with the main historical introduction points, with low dispersal among them.
Conclusions. The results suggest that control strategies for American mink in southern Chile should be concentrated on these three genetically differentiated management units, and particularly on source populations and locations with low effective population size and restricted connectivity.
Implications. Genetic approaches have been used for the management of numerous alien species worldwide. Recommendations delivered here for American mink control could also be implemented in other regions and for other invasive species with similar genetic diversity distribution and connectivity.
... One potential method that could elucidate how coyotes respond to lethal control is population genetics because previous studies reported changes in genetic structure due to compensatory immigration (Abdelkrim et al. 2007, Pope et al. 2007, Gervasi et al. 2015, Oliver et al. 2016. One potential outcome of compensatory immigration occurs when separate populations colonize a culled or hunted area, which results in mixing from multiple genetic sources following lethal control and an increase in genetic diversity (Abdelkrim et al. 2007). ...
... One potential method that could elucidate how coyotes respond to lethal control is population genetics because previous studies reported changes in genetic structure due to compensatory immigration (Abdelkrim et al. 2007, Pope et al. 2007, Gervasi et al. 2015, Oliver et al. 2016. One potential outcome of compensatory immigration occurs when separate populations colonize a culled or hunted area, which results in mixing from multiple genetic sources following lethal control and an increase in genetic diversity (Abdelkrim et al. 2007). These situations typically occur on island eradications (Abdelkrim et al. 2007) or within metapopulations (Andreasen et al. 2012) where separate genetic populations colonize the culled area. ...
... One potential outcome of compensatory immigration occurs when separate populations colonize a culled or hunted area, which results in mixing from multiple genetic sources following lethal control and an increase in genetic diversity (Abdelkrim et al. 2007). These situations typically occur on island eradications (Abdelkrim et al. 2007) or within metapopulations (Andreasen et al. 2012) where separate genetic populations colonize the culled area. Other authors have reported changes in population genetic structure based on altered dispersal regimes within a single population (Pope et al. 2007, Oliver et al. 2016. ...
Despite efforts to reduce their effects on livestock and native ungulates within the southeastern United States, coyotes (Canis latrans) can recover from control programs. It is unknown how coyotes compensate for high mortality following trapping, so there is great interest to identify methods that can provide insight into coyote response to intensive trapping. To investigate if population genetic tools can decipher how coyotes recover from intensive trapping, we combined an empirical test of how genetic differentiation, diversity, and familial structure changed following trapping on the Savannah River Site (SRS), South Carolina, USA, with spatially explicit genetic simulations. The pre- and post-trapping periods had similar genetic diversities and were not genetically differentiated as expected by either compensatory reproduction or immigration from a single genetic source. The post-trapping coyote populations exhibited weaker signatures of philopatry with little evidence for increased dispersal distances of young coyotes, which suggests immigration caused a decrease in familial structure. Our simulations indicated that spatial autocorrelation coefficients and observed heterozygosities change as immigration increases, whereas population differentiation, allelic richness, and displacement distances do not. Collectively, our results suggest that coyotes recover from intensive trapping via reproduction and immigration, which likely makes preventing compensation difficult. Monitoring post-trapping populations may offer more insight into maximizing the effectiveness of control efforts, and based on our simulations, population genetics can provide critical information about the amount of compensatory immigration following trapping.
... Effective management and control of a non-native invasive species relies on understanding its biology (i.e., dispersal ability, physiological limits, and competitive ability), as well as the history and biogeography of the invasion, including the location and number of introductions, the pathway(s) of introduction, and the rate of spread of the invader (Sakai et al. 2001;Dlugosch and Parker 2008;Estoup and Guillemaud 2010). Genetic data can provide information on the number, location, and source of introductions Cameron et al. 2008;Brown and Stepien 2009), the pathways and rate of invasion (Grapputo et al. 2005;Abdelkrim et al. 2007;Cameron et al. 2008), and aspects of the biology of the invader, such as its reproductive biology, dispersal ability, and the extent of interpopulation connectivity (Wilson et al. 1999;Lott et al. 2003;Tepolt et al. 2009). This information can then be used to monitor and predict the rate of spread of an invader (Stepien et al. 2005;Jerde et al. 2011), delineate management units, and develop eradication or control strategies (Robertson and Gemmell 2004;Abdelkrim et al. 2007;Fraser et al. 2013). ...
... Genetic data can provide information on the number, location, and source of introductions Cameron et al. 2008;Brown and Stepien 2009), the pathways and rate of invasion (Grapputo et al. 2005;Abdelkrim et al. 2007;Cameron et al. 2008), and aspects of the biology of the invader, such as its reproductive biology, dispersal ability, and the extent of interpopulation connectivity (Wilson et al. 1999;Lott et al. 2003;Tepolt et al. 2009). This information can then be used to monitor and predict the rate of spread of an invader (Stepien et al. 2005;Jerde et al. 2011), delineate management units, and develop eradication or control strategies (Robertson and Gemmell 2004;Abdelkrim et al. 2007;Fraser et al. 2013). ...
... Understanding the structuring of genetic variation in an invasive species may also provide an indication of both the relative difficulty of eradication and the most effective eradication strategies. If there is strong genetic structure and little gene flow and dispersal among populations, then eradication efforts can target an entire genetic group, knowing that recolonizing migrants are likely to be very rare (Abdelkrim et al. 2007;Fraser et al. 2013). Conversely, an invasive species that exhibits little to no genetic structure among populations may lack barriers to gene flow/ dispersal, indicating that eradication efforts may be more difficult because of the ability of the invader to easily recolonize an area (Abdelkrim et al. 2007). ...
The success of a biological invasion and the ability to control an invader may partially depend on the genetic diversity of the invasive species and the amount of dispersal and gene flow occurring throughout its introduced range. Here, we used nuclear microsatellites to analyze genetic diversity and structure and whole mitogenomic sequences to analyze the phylogeography of Silver Carp (SC; Hypophthalmichthys molitrix) and Bighead Carp (BHC; H. nobilis) across their North American ranges. Our objectives were to assess: (1) the number of mitochondrial haplotypes that were introduced and how they are distributed in North America, which may provide insight into the history of the invasion, (2) how genetic diversity compares between the native Asian and introduced North American populations, (3) how genetic variation is structured across the North American ranges of SC and BHC as well as between the two species, and (4) whether patterns of genetic diversity and structure are likely to affect success of environmental DNA programs for monitoring these species. In both species, we found relatively few mitochondrial haplotypes, and most were present throughout the range. For both SC and BHC, unique haplotypes were found only in a portion of the species’ range, possibly indicating the location of additional, more recent introductions. In both species, genetic diversity was moderately lower in North American populations (i.e., 75–90% of that found in Asian populations), but genetic diversity still remained high. We found very little population genetic structure, consistent with a rapidly spreading invasive species, and did not find evidence of cryptic interspecific hybrids. The markers developed for eDNA monitoring will be effective for detecting the majority of individuals of these species in North America. The relatively high level of genetic variation and lack of population structure of SC and BHC in North America indicate that genetic diversity likely will not limit their persistence and that high connectivity will likely complicate efforts to control these invasive species.
... There are many genetic studies of black rats and house mice focused on diversification, phylogeographic patterns and invasion routes (e.g. Hardouin et al. 2010Hardouin et al. , 2015Aplin et al. 2011;Lack et al. 2013;López et al. 2013;Jing et al. 2014;Gabriel et al. 2015;King 2016), both in continental regions (Bastos et al. 2011;Jones et al. 2011;Lippens et al. 2017;Combs et al. 2018) and in islands (Abdelkrim et al. 2005a(Abdelkrim et al. , 2005b(Abdelkrim et al. , 2010Brouat et al. 2014;Babiker and Tautz 2015). Nonetheless, few studies have investigated their genetic and ecological dynamics associated with urban ecosystems specifically on islands (Gatto-Almeida et al. 2022). ...
... He = 0.76, Na = 10). These values are within the range found in other islands, like the black rat in Guadeloupe (He = 0.69, Na = 5), Madagascar (He = 0.72) and New Zealand (He = 0.75, Na = 5.7) (Abdelkrim et al. 2005a(Abdelkrim et al. , 2005b(Abdelkrim et al. , 2010Brouat et al. 2014), as well as the house mouse on islands of New Zealand (He = 0.51-0.56), Kerguelend (He = 0.40, Na = 2.8), Madagascar (He = 0.67, Na = 9.7) and Cyprus (He = 0.77, Na = 9.7) (Hardouin et al. 2010(Hardouin et al. , 2015Pichlmueller et al. 2020), despite the comparatively small size of Cozumel island. ...
Humans and wildlife experience complex interactions in urban ecosystems, favoring the presence of commensal species, among which invasive species are particularly successful. Rodents are the main vertebrate group introduced to oceanic islands, where the invasion process and dispersal patterns strongly influence their evolutionary and genetic patterns. We evaluated the house mouse Mus musculus and the black rat Rattus rattus on Cozumel Island, Mexico. We assessed genetic diversity and structure, connectivity, gene flow, relatedness and bottleneck signals based on microsatellite loci. Our genetic findings suggest that introduction of individuals of different geographic sources to the island promotes high allelic diversity and the effective establishment of migrants. We identified a clear genetic structure and low connectivity for the two species, tightly linked with anthropogenic and urban features. Notably, we found that the genetic structure of the house mouse sampled within the city of San Miguel Cozumel is associated with the historical human population growth pulses accompanying the urbanization of the city. At the fine-scale genetic level, the main urban drivers of connectivity of the house mouse were both the impervious land surfaces, i.e. the urban landscape, and the informal commerce across the city (a proxy of resources availability). Chances of a secondary invasion to natural environments have been relatively low, which is crucial for the endemic taxa of the island. Nonetheless, improving urban planning to regulate future expansions of San Miguel Cozumel is of the outmost importance to prevent these invasive species to disperse further.
... Understanding why management fails is critical for effective invasive species control going forward (Abdelkrim et al., 2007). Although these management failures have been studied on a case-by-case basis (e.g., Abdelkrim et al., 2007;Amos et al., 2016;Hoffmann, 2011), there are fewer general theories for understanding the ecological factors which may lead to failed management (see Pearson et al., 2016 for a weed management example and Hoffmann, 2011;Myers et al., 2000;Simberloff, 2009 for eradication examples). ...
... Understanding why management fails is critical for effective invasive species control going forward (Abdelkrim et al., 2007). Although these management failures have been studied on a case-by-case basis (e.g., Abdelkrim et al., 2007;Amos et al., 2016;Hoffmann, 2011), there are fewer general theories for understanding the ecological factors which may lead to failed management (see Pearson et al., 2016 for a weed management example and Hoffmann, 2011;Myers et al., 2000;Simberloff, 2009 for eradication examples). Here, we explore one possibility: management actions with off-target effects that harm native species in addition to invaders could reduce native populations, alleviating competitive burdens on the invader and inadvertently assisting invasion. ...
A wide range of approaches has been used to manage the spread of invasive species, yet invaders continue to be a challenge to control. In some cases, management actions have no effect or may even inadvertently benefit the targeted invader. Here, we use the mid‐20th century management of the Red Imported Fire Ant, Solenopsis invicta, in the US as a motivating case study to explore the conditions under which such wasted management effort may occur. Introduced in approximately 1940, the fire ant spread widely through the southeast US and became a problematic pest. Historically, fire ants were managed with broad‐spectrum pesticides; unfortunately, these efforts were largely unsuccessful. One hypothesis suggests that, by also killing native ants, mass pesticide application reduced competitive burdens thereby enabling fire ants to invade more quickly than they would in the absence of management. We use a mechanistic competition model to demonstrate the landscape‐level effects of such management. We explicitly model the extent and location of pesticide applications, showing that the same pesticide application can have a positive, neutral, or negative effect on the progress of an invasion, depending on where it is applied on the landscape with respect to the invasion front. When designing management, the target species is often considered alone; however, this work suggests that leveraging existing biotic interactions, specifically competition with native species, can increase the efficacy of management. Our model not only highlights the potential unintended consequences of ignoring biotic interactions, but also provides a framework for developing spatially explicit management strategies that take advantage of these biotic interactions to work smarter, not harder.
... We also hypothesised that no C. aestuarii individuals or Carcinus hybrids would be present in South Africa (Robinson et al. 2005). Lastly, we hypothesised that a Carcinus trial management programme would reduce the genetic diversity and structure of the Hout Bay harbour population, compared with the unmanaged Table Bay population (Hampton et al. 2004;Abdelkrim et al. 2007). ...
... Tracking temporal changes in genetic diversity can be useful in assessing the demographic responses of invasive species to disturbances (Mairal et al. 2021) and management interventions (Abdelkrim et al. 2007;Vardien et al. 2013). For example, three years after a ten-year-long management programme against Spartina alterniflora in California, significant changes in the genetic diversity of the species were observed (Ort and Thornton 2016). ...
Knowledge of the introduction history and spread dynamics of invasive species can provide important insights for management (Ens et al. in Environ Rev (in press), 2022), however such information is often unavailable for accidental introductions. Here we infer how the European shore crab, Carcinus maenas , and its congener, the Mediterranean shore crab, C. aestuarii , were introduced to and spread within South Africa. We do this using nuclear microsatellite data and Bayesian assignment tests and Approximate Bayesian Computation (ABC) modelling that included samples from the native and other invasive ranges of these two species. We also compared the genetic diversity and structure of one of the South African populations during and after intensive management, with that of another, unmanaged, population. South African populations had higher genetic diversity than invasive Carcinus populations from elsewhere in the world. Moreover, the ABC analyses suggest that South African populations originated from an admixture event between individuals of C. maenas from a population in the native range and an invasive population from Canada. We also identified instances of hybridisation between Carcinus maenas and C. aestuarii in South Africa. South African populations showed no genetic structure, suggesting either extensive migration between them or that populations arose from the same initial introduction. Management of Carcinus did not affect genetic diversity or structure, and we suspect that the management duration was insufficient to target a full generation of crabs. Together these results suggest multiple introductions and/or high propagule pressure to South Africa, crab (larval or adult) movement between existing populations, and some hybridisation. For eradication from South Africa to be achieved, management would need to concurrently target all known invasive populations and clearly establish that new introductions could be prevented.
... However, these tests for bottlenecks have not been in the context of a rodent-control campaign. Further, data comparing the genetics of pre-control samples to rats present after the control campaign are only available for island systems (Abdelkrim et al., 2007;Russell et al., 2010;Pichlmueller and Russell, 2018). For most eradication campaigns, the decline in rats happens within weeks, and the recovery within months. ...
... Population genetic structure around an eradication event has not received much research attention. However, Abdelkrim et al. (2007) used F-statistics and assignment probabilities (as measures of population structure) of individual rats remaining after an eradication of rats from two islands off the coast of Martinique, and found varying degrees of genetic structure and an increase in genetic diversity, suggesting a role for both internal rebound and recolonization on the two islands. Russell et al. (2010) compared the genetics of 51 samples from two species of rats on two islands near New Zealand, and found that the genetic structure before and after the control was consistent with those rats reinvading from the larger neighboring island, rather than internal rebound. ...
Rats thrive in human-dominated landscapes and have expanded to a near global distribution. Norway rats (Rattus norvegicus) contaminate food, damage infrastructure, and are reservoirs for zoonotic pathogens that cause human diseases. To limit these negative impacts, entities around the world implement intervention and control strategies designed to quickly and drastically reduce the number of rats in a population. While the primary goal of these interventions is to reduce rat numbers and their detrimental activities, there are important, yet unexplored, population genetic implications for these rapid population declines. Here, we compare the population genetics of R. norvegicus before, immediately after, and several months following a rodenticide-based eradication campaign targeting rats in an urban slum of Salvador, Brazil. This slum has been the focus of long-term research designed to understand and reduce the risk of leptospirosis for people in this area. We also look for a clear source of rats contributing to population recovery, by either rebounding through breeding of local survivors, or by immigration/reinvasion of the site. We found evidence of severe genetic bottlenecks, with the effective population size dropping 85–91% after eradication, consistent with declines in population sizes. These rapid declines also led to a strong shift in the genetic structure of rats before and after the eradication campaign. Relatedness increased in two of the three study areas after eradication, suggesting reduced population sizes and an uneven impact of the campaign across colonies within the population. Lastly, dozens of low-frequency alleles (mean frequency of 0.037) observed before the campaign were undetected after the campaign, potentially lost from the population via drift or selection. We discuss the public health and ecological implications of these rapid genetic impacts of urban control efforts. Our data suggests that targeting the genetic viability of rat populations may be another important component for integrated pest management (IPM) strategies, designed to reduce urban rats.
... Instead, efforts should focus on effectively identifying and targeting areas at the scale of "eradication units." These areas represent the spatial scale at which rats are interconnected, allowing for recolonization following a control intervention (Abdelkrim et al., 2007). For example, in Salvador, Brazil where the majority of Norway rat movement was found to occur within a valley, targeting rat populations at the level of the valley might be appropriate (Richardson et al., 2017). ...
... For example, in Salvador, Brazil where the majority of Norway rat movement was found to occur within a valley, targeting rat populations at the level of the valley might be appropriate (Richardson et al., 2017). In contrast, a study evaluating the genetic signatures of black rat populations before and after an eradication campaign on four islets in the French Caribbean, found that control efforts would need to extend to surrounding islands to minimize the potential for re-invasion (Abdelkrim et al., 2007). Because the extent of movement varies by location (Combs et al., 2018a), deriving specific recommendations as to the scale of pest control efforts is difficult. ...
Norway and black rats (Rattus norvegicus and Rattus rattus) are ubiquitous urban pests, inhabiting cities worldwide. Despite their close association with people, urban rats remain difficult to control. This can be partly attributed to a general lack of information on basic rat ecology to inform management efforts. In this systematic review and narrative synthesis, we collate the published literature to provide a comprehensive description of what is known about urban rat movement, including information on home range, site fidelity, dispersal, movement patterns, barriers to, and factors impacting, movement. We also discuss the methodologies used to track and infer rat movement, as well as the advantages and limitations of employing these techniques. Our review suggests that the distances traveled by urban rats are location-specific, determined by both local resource availability and barriers to movement such as roadways. Although roads may impede rat movement, genetic techniques suggest that rats traverse roadways more often than revealed by capture-based tools, while long-distance dispersal events by either natural migration or facilitated by humans (i.e., as stowaways in transport vehicles) can maintain connectivity among distant populations. Because rat movement patterns are related to the transmission of rat-associated pathogens and the success of rodent control programs, these results have implications for city planners, pest control efforts, and public health. Therefore, we emphasize the importance of understanding local rat movement patterns in order to devise and deploy efficient and effective rat mitigation initiatives in urban centers.
... However, rat numbers rebound quickly with population sizes reaching pre-intervention densities within six months (de Masi et al. 2009). Therefore, data on rat dispersal patterns is critical for designing more efficient rodent control programs, including where to target resources for intervention campaigns across large sections of urban habitat to impede recolonization of treated areas (Abdelkrim et al. 2007). Groups of vector organisms that are in close proximity and interconnected are defined as 'eradication units'. ...
... All rights reserved. units must be controlled simultaneously to prevent reinvasion and augment long-term success of control campaigns (Robertson & Gemmell 2004;Abdelkrim et al. 2007;Russell et al. 2010). ...
The Norway rat (Rattus norvegicus) is a key pest species globally, and responsible for seasonal outbreaks of the zoonotic bacterial disease leptospirosis in the tropics. The city of Salvador, Brazil has seen recent and dramatic increases in human population residing in slums, where conditions foster high rat density and increasing leptospirosis infection rates. Intervention campaigns have been used to drastically reduce rat numbers. In planning these interventions it is important to define the eradication units, the spatial scale at which rats constitute continuous populations, and from where rats are likely recolonizing, post-intervention. To provide this information, we applied spatial genetic analyses to 706 rats collected across Salvador and genotyped at 16 microsatellite loci. We performed spatially explicit analyses and estimated migration levels to identify distinct genetic units and landscape features associated with genetic divergence at different spatial scales, ranging from valleys within a slum community to city-wide analyses. Clear genetic breaks exist between rats not only across Salvador but also between valleys of slums separated by less than 100 meters – well within the dispersal capacity of rats. The genetic data indicate that valleys may be considered separate units and identified high traffic roads as strong impediments to rat movement. Migration data suggest that most (71-90%) movement is contained within valleys, with no clear source population contributing migrant rats. We use these data to recommend eradication units and discuss the importance of carrying out individual-based analyses at different spatial scales in urban landscapes. This article is protected by copyright. All rights reserved.
... Studies of the genetic diversity in weed populations is crucial as it provides a fundamental understanding for subsequent targeted research, including the identification of dispersal routes, source populations of weeds, their adaptive abilities to varying environments, and the selective pressure exerted by herbicide usage [7][8][9][10][11]. Such background information is indispensable in order to manage existing populations effectively and to elaborate strategies for the prediction and mitigation of new populations in agricultural settings [12][13][14]. Molecular methods have provided the opportunity to explore not only genetic diversity but also the spread of weeds and have allowed us to theorize about the origin of weed introductions and the formation of hybrids [15,16]. ...
Japanese brome (Bromus japonicus Thunb. ex Murr.) is a pervasive annual weed with wide distribution in winter wheat fields across the North China Plain. In this study, we researched the genetic diversity and phylogeography of 24 B. japonicus populations in China based on total genomic DNA and chloroplast DNA. The results showed that 106 fragments were scored using 12 inter-simple sequence repeat (ISSR) primers, and 101 fragments (95.28%) were polymorphic. The findings revealed substantial genetic diversity and differentiation among populations from different locations (Ht = 0.2125, Hs = 0.0730, Gst = 0.6562 and Nm = 0.2619). Mean values of Nei’s genetic diversity (H) and Shannon index of diversity (I) were 0.0731 and 0.1068, respectively. In addition, 15 haplotypes were identified based on combined cpDNA regions among the 24 populations exhibiting abundant haplotype (gene) diversity and nucleotide diversity. The AMOVA based on ISSR and cpDNA both showed that genetic variation mainly exists among populations rather than within them. The STRUCTURE analysises of ISSR and cpDNA indicated that geographical location and genetic relationship had no significant correlation. The haplotype network also illustrated that the widespread haplotypes (H1, H2) might represent ancient polymorphism. The results obtained in this study demonstrate the presence of extensive genetic variability among and within the Chinese populations of B. japonicus, which is likely to contribute significantly to its adaptability and infestation as a weed species.
... As historical methods of predator management in South Africa are unlikely to be reinitiated, it is imperative that the behavioural and physiological responses of jackal to lethal management are understood and how these responses in turn influence genetic structure (Abdelkrim et al., 2007;Gervasi et al., 2015). In this study, we investigated genetic structure, variation and relatedness of lethally managed jackals on smalllivestock farms (high resource availability, i.e. food resources) in the central Karoo region of South Africa. ...
Globally, levels of human–wildlife conflict are increasing as a direct consequence of the expansion of people into natural areas resulting in competition with wildlife for food and other resources. By being forced into increasingly smaller pockets of suitable habitat, many animal species are at risk of becoming susceptible to loss of genetic diversity, inbreeding depression and the associated inability to adapt to environmental changes. Predators are often lethally controlled due to their threat to livestock. Predators such as jackals (black backed, golden and side striped; Canis mesomelas, C. aureus and C. adustus, respectively), red foxes (Vulpes vulpes) and coyotes (C. latrans) are highly adaptable and may respond to ongoing persecution through compensatory reproduction such as reproducing at a younger age, producing larger litters and/or compensatory immigration including dispersal into vacant territories. Despite decades of lethal management, jackals are problematic predators of livestock in South Africa and, although considered a temporary measure, culling of jackals is still common. Culling may affect social groups, kinship structure, reproductive strategies and sex‐biased dispersal in this species. Here, we investigated genetic structure, variation and relatedness of 178 culled jackals on private small‐livestock farms in the central Karoo of South Africa using 13 microsatellites. Genetic variation was moderate to high and was similar per year and per farm. An absence of genetic differentiation was observed based on STRUCTURE, principal component analysis and AMOVA. Relatedness was significantly higher within farms (r = 0.189) than between farms (r = 0.077), a result corroborated by spatial autocorrelation analysis. We documented 18 occurrences of dispersal events where full siblings were detected on different farms (range: 0.78–42.93 km). Distance between identified parent–offspring varied from 0 to 36.49 km. No evidence for sex‐biased dispersal was found. Our results suggest that in response to ongoing lethal management, this population is most likely able to maintain genetic diversity through physiological and behavioural compensation mechanisms.
... Therefore, the choice of islands for the implementation of rat eradication appears to be crucial. Molecular techniques should be adopted to establish whether the eradication failed, or the island was reinvaded, as, in the absence of these analyses, it is difficult to support one of the two hypotheses (Abdelkrim et al. 2007). Advances in genetics make it possible to improve the management of alien species by evidencing colonisation pathways, the presence of individuals resistant to anticoagulants, and the origins of reinvasions (Ragionieri et al. 2013, Browett et al. 2020). ...
Impacts of alien invasive species on island communities and ecosystems may be even more detrimental than on the mainland. Therefore, since the 1950s, hundreds of restoration projects have been implemented worldwide, with the aim of controlling or eradicating alien species from islands. To date, no review has been focused on eradication on Mediterranean islands. To fill the gap, I reviewed the available information concerning mammal eradications so far carried out on Mediterranean islands, examining the details of several aspects of project implementation and monitoring.
I obtained data for 139 attempted eradications on 107 Mediterranean islands in eight countries, with Greece, Italy, and Spain accounting for the highest number. Eradication projects targeted 13 mammal species. The black rat Rattus rattus was the target of over 75% of the known attempted eradications in the Mediterranean Basin; other species targeted were feral goat Capra hircus , house mouse Mus musculus , European rabbit Oryctolagus cuniculus , and domestic cat Felis catus . The most widely adopted technique was poisoning (77% of all eradications), followed by trapping (15%) and hunting (4%). However, techniques were largely target‐specific.
The average failure rate was about 11%. However, this percentage varied according to the specific mammalian order, and eradications of Carnivora failed more often than those of other mammals. Among rodents, house mouse eradication attained a very high failure rate (75%). Reinvasion occurred after 15% of successful eradications.
A better understanding of the motivations of animal rights activists may improve the chance of success when eradicating charismatic or domesticated species. Furthermore, it is crucial to collect data and case studies about reinvasions, in order to strengthen biosecurity programmes following eradication. As in other parts of the world, the next frontier in alien mammal management on Mediterranean islands concerns the eradication of invasive species from inhabited islands.
... One of this is the high capability of rats to re-invade the same environment by swimming across islands if the appropriate conditions are restored (Courchamp et al. 2003;Russell et al. 2008). Another possible cause of an ineffective eradication campaign is the failure to eradicate all individuals of a population because of, for example, the occurrence of resistance to rat poisons (Abdelkrim et al. 2007). Since the 1950s, rodent pest control has been conducted using first-generation anticoagulant rodenticides, such as warfarin, diphacinone and chlorophacinone. ...
Biological invasions are a growing threat to biodiversity. The black rat, one of the worst pest in the world, is responsible for extensive population decline of many autochthonous and endemic species, particularly in island ecosystems. A number of rat eradication campaigns have been conducted, however, such endeavors do not always result in a complete removal of the pest. This may be due to the occurrence of individuals resistant to common rodenticides and/or a re-invasion of the same environment from interconnected areas when appropriate eradication units are not defined before starting an eradication campaign. Our study is a multidisciplinary approach whereby genetic and epidemiological methods were used to provide background information for successful eradication of black rats. We investigated the occurrence of mutations in the VKORC1 gene known to confer resistance to rodenticides and evaluated the spread of zoonoses across three islands of the Pontine Archipelago, an Italian hotspot of endemic Mediterranean biodiversity and a possible mainland source of invasion. As part of an eradication campaign, we also assessed patterns of genetic diversity at 10 microsatellite loci in order to identify eradication units. We recorded a strong population structure and revealed at least two distinct eradication units. Some degree of admixture was recorded on Ponza, the largest island and likely the main source of rats invading the other two islands. We did not record the occurrence of rats resistant to anticoagulants, but we revealed transmission of vector-borne pathogens in commensal habitats of the Archipelago.
... To improve the nutria eradication program, genetic information on populations in highly concentrated habitats near the Nakdong River basin is needed to estimate migration patterns for preventing the re-colonization of nutria. Microsatellite markers are broadly available and have been applied to study the population structures and dynamics in many invasive rodents, such as nutrias, ship rats, and Norway rats [23][24][25][26][27]. Eradication programs have failed due to the lack of ecological and population genetic information on target invasive species [28][29][30][31]. ...
The nutria (Myocastor coypus) is an invasive alien species that have had major adverse effects on biodiversity and the agricultural economy in wetland habitats. Since 2014, the Ministry of Environment in South Korea has been carrying out the Nutria Eradication Project, and we investigated nutria distribution and genetic diversity of nutria populations in South Korea. We estimated that 99.2% of nutria habitats are in the mid-lower Nakdong River regions. To further analyze the genetic diversity in eight major nutria populations, we performed a genetic analysis using microsatellite markers. Genetic diversity levels of the eight nutria populations in South Korea were relatively lower than those in other countries. The probability of migration direction among nutria populations was predicted from genetic distance analysis. Genetic structure analysis showed little difference among the nutria populations in South Korea. These results suggest that nutrias in South Korea originated from a single population. Our results provide important data for establishing management strategies for the successful eradication of nutria populations in South Korea, as well as in other countries with alien invasive species.
... One important use of genetic tools is determining if island-wide eradications of vertebrates have been successful. For example, Abdelkrim et al. (2007) and Savidge et al. (2012) used genetic evidence to determine whether rats observed after an eradication campaign were survivors of the eradication attempt or recent immigrants. Population genetics are often the only means of establishing non-native species introduction routes, and these methods and technologies can be used to inform island communities of management/ eradication units and biosecurity strategies. ...
Two small Indian mongooses (Herpestes auropunctatus) were livecaptured in 2012 at separate locations on the Hawaiian Island of Kaua'i, which was previously considered to be free of this invasive species. Genotypes from these two individuals were compared to genotypes of H. auropunctatus from the islands of Hawai'i (n = 39), O'ahu (n = 91), Maui (n = 39), and Moloka'i (n = 19) to determine the island of origin of the Kaua'i individuals. Genotypes were generated from each individual using five microsatellite loci. Genetic clustering was estimated by Bayesian inference of spatial clustering of individuals and clustering of groups of individuals. Both analyses separated the samples into three distinct genetic clusters (K = 3). Kaua'i individuals consistently formed a single cluster with individuals from O'ahu, whereas Hawai'i and Maui formed a second cluster, and Moloka'i was the third cluster. Thus, we conclude that the origin of two H. auropunctatus captured on Kaua'i was O'ahu. All three genetic clusters showed evidence of transportation of mongooses between islands, indicating that sampled islands in the archipelago are capable of acting as both donors and receivers of mongooses.
... In 2011, black rats were trapped, euthanised and samples taken (n=89) for future genetic analyses in case rodents were detected after the eradication attempt. If this occurred, as island populations of black rats can be diff erentiated in the Galapagos (Willows-Munro, et al., 2016), genetic samples from the pre-and post-eradication attempt could be compared to help determine whether reintroduction or eradication failure occurred (Abdelkrim, et al., 2007). ...
Invasive black rats (Rattus rattus) were successfully eradicated during 2012 from Pinzon Island in the Galapagos
archipelago using the rodenticide brodifacoum. Potential exposure to brodifacoum in Pinzon tortoises (Chelonoidis
ephippium), Pinzon lava lizards (Microlophus duncanensis) and Galapagos hawks (Buteo galapagoensis) was mitigated
by captive holding of subpopulations. This was successful for all species during and shortly after baiting, however
mortality of Galapagos hawks occurred post-release, likely due to the persistence of residual brodifacoum in lava lizards.
Since 2013, Pinzon tortoise hatchlings are surviving in-situ for the fi rst time in at least 120 years and the eradication of
black rats is expected to have signifi cant benefi ts for at least 15 other island-endemic species.
... In addition, lack of isolation by distance and strong population structuring could be the result of multiple introductions from different sources(Le Roux & Wieczorek, 2008;Roman & Darling, 2007) or of small founder sizes followed by genetic drift and isolation. Eradication efforts over the last 10 years, such as the removal of c. 56,000 crayfish in the Bachowey(Abdelkrim, Pascal, & Samadi, 2007;WUF, 2012), could have also contributed to decreasing genetic diversity and increasing population structuring, but the documentation of these events is too scarce to draw any conclusions.Evidence of four main genetic clusters in the introduced signal crayfish populations, the strong differentiation (F ST ) values and the most likely colonization scenario support the assumption that current crayfish populations in Britain are not genetically homogenous, a phenomenon common in invasive species originating from different origins (Zalewski, Michalska-Parda, Bartoszewicz, Kozakiewicz, & Brzeziński, 2010). The most likely colonization scenario for signal crayfish in the sites sampled in Britain suggested that populations most likely originated from six source populations with varying levels of genetic diversity, although some caution is warranted in the interpretation of the results due to the deviations from Hardy-Weinberg equilibrium. ...
Successful establishment of non‐native species is strongly influenced, among other factors, by the genetic variation of founding populations, which can be enhanced by multiple introductions through admixture. Coexisting pathogens can also facilitate the establishment of non‐native species by detrimentally impacting on the native fauna acting as novel weapons. The signal crayfish (Pacifastacus leniusculus) is a highly invasive species, which has caused mass declines of native crayfish in Europe through displacement and transmission of the oomycete Aphanomyces astaci (crayfish plague), which is typically lethal to native European crayfish. However, whether Aphanomyces astaci may have facilitated the invasion of the signal crayfish is not known. We estimated the genetic diversity at microsatellite DNA loci, effective population size, and potential origins of seven infected and noninfected signal crayfish populations in Europe and one founder population in North America. Approximate Bayesian computation analysis and population structuring suggested multiple host introductions from diverse source populations, as well as higher heterozygosity among infected than uninfected populations, which could reflect a fitness advantage. Low effective population size, moderate heterozygosity, and lack of isolation by distance suggest that some invasive signal crayfish populations may not be fully established or that their genetic diversity may have been reduced by eradication attempts. Widespread invasive signal crayfish populations have low genetic diversity despite their diverse sources of origin, which could be due to founder effects or eradication attempts. However, plague carrier populations display the largest heterozygosity. Genetic screening during eradication attempts is needed to clarify their effects on the genetic diversity of the invaders and understand the role of disease transmission in their spread.
... As demonstrated during the last decades, a translocation action must be supported by a genetic analysis of the target populations (Laikre et al. 2010;Schwartz et al. 2007). DNA profiling has proven to be an invaluable tool for describing levels of distinctiveness among target populations of invasive species, with the aim of defining eradication units (sensu Abdelkrim et al. 2007) and to uncover the origin of an invasive population (Abdelkrim et al. 2005;Russell et al. 2010). Eradication actions supported by DNA profiling have successfully been applied in the Tyrrhenian islands for another invasive species, the black rat (Iannucci et al. 2018;Sposimo et al. 2012;Ragionieri et al. 2013). ...
The introduction of allochthonous species represents a serious threat for the native gene pools and ecosystem biodiversity. The effect is particularly disastrous for insular biocoenoses, such as in the Tuscan archipelago, one of the most important biodiversity hotspot in the Mediterranean area. The EU tool LIFE + has funded an eradication project involving a set of allochthonous species on Pianosa Island (http://www.restoconlife.eu), including the European hedgehog (Erinaceus europaeus). Since eradication projects should not leave out of consideration a genetic analysis of the target species, the aim of our study was to characterize the genetic profile of the Pianosa hedgehog population. In particular, the data obtained had to help assessing the most compatible area for the release of all captured individuals. In the present work, eleven microsatellite loci and two mitochondrial gene portions (COXI and 16S) were characterized in individuals of E. europaeus from Pianosa, Elba, Sardinia Islands and mainland Italy. Both mtDNA and microsatellite data confirmed that the present-day population of Pianosa has an extremely low genetic diversity and a profile very similar to that of Elba. Consequently, our results do suggest that the Pianosa hedgehogs originated from a pool of individuals moved by human from Elba in recent times and could be relocated there.
... These samples will provide a scientifically valuable record of the genetic and morphological characteristics of the pre-eradication rodent population of Lord Howe Island. They will also enable the origin of any rodents discovered on the Island post-eradication to be genetically identified as either new immigrants or members of the original population that had survived the eradication attempt (e.g., Abdelkrim et al., 2007). In addition, introduced populations of R. rattus and M. musculus are of increasing scientific and historic interest. ...
The Australian Museum Research Institute Terrestrial Vertebrates team was on Lord Howe Island from 12th to 24th March 2017. Our aims were to improve the Museum’s specimen and tissue collection of birds and mammals from the Island, to collect base-line samples of the two introduced rodent species before their planned eradication, and to exhume the skeletal remains of three beaked whales which were buried on the Island in 2011. Samples were collected from 96 individuals of 10 species of birds on Lord Howe Island. Blood samples were collected from 30 individuals that were subsequently released, including representatives of three of the four extant endemic taxa. Feather samples were collected from a further 17 living individuals, while 47 specimens that had been found dead on the island by residents were transported back to the Museum for curation as skins, skeletons and tissues. Twenty-seven Lord Howe Woodhen, Hypotaenidia sylvestris specimens were included in this collection. These samples will be used in future research projects on the conservation ecology of the Woodhen, and microevolution of island avifauna. Fifteen genetic samples (4 specimens and 11 wing biopsy samples) were obtained from the Island's only extant native mammal, the Large Forest Bat, Vespadelus darlingtoni. Preliminary analysis indicated that the Lord Howe Island population was most similar to the north-east New South Wales population, but variation across the species’ range in calls, morphology and genetics warrants further investigation. Specimens and tissue samples were also collected from the Island’s introduced House Mouse, Mus musculus (n = 38) and Black Rat, Rattus rattus (n = 12) populations. These samples will provide a valuable record of the pre-eradication rodent population of Lord Howe Island. Three Dense-beaked Whale, Mesoplodon densirostris skeletons, two females and a sub-adult male were successfully recovered. Overall, these new specimens and tissue samples will significantly enhance the Australian Museum’s collection, provide documentation of the contemporary bird and mammal fauna of Lord Howe Island, as well as support current and future research projects.
... The role of disturbance in shaping spatial biodiversity patterns remains poorly understood (Banks et al., 2013). Putative examples of disturbance facilitating lineage turnover have been reported in New Zealand sea lions (Phocarctos sp.: Collins et al., 2014), European cave bears (Ursus spelaeus: Hofreiter et al., 2007) and following pest eradication (Abdelkrim, Pascal, & Samadi, 2007;Russell et al., 2010;Veale, Clout, & Gleeson, 2012). While small-scale disturbances seem unlikely to result in substantial genetic turnover, as offspring from the remaining, undisturbed locals will be most likely to colonise the limited new space, large disturbances that destroy much of an existing population might create opportunities for establishment by rare lineages. ...
Recent studies have suggested that spatial patterns of intraspecific diversity can be influenced by density‐dependent processes, which can inhibit effective migration of new lineages to established populations. How mechanisms such as dispersal and disturbance influence these processes is, however, still poorly understood.
We hypothesised that (1) species with leptokurtic dispersal (frequent on small scales but rare on larger scales) would show no spatial structure on small scales and strong structure on large scales, and (2) disturbance would influence the chance of genetic turnover in a population.
We tested these hypotheses using empirical genetic (mt DNA ) data from field observations of a model taxon (the buoyant, forest‐forming kelp Durvillaea , which exhibits leptokurtic dispersal distribution), and by conducting simulation analyses.
Our data supported the first hypothesis, with no spatial structure detected on fine (metres) scales despite evidence of strong structure on larger (tens to hundreds of kilometres) scales. The second hypothesis was also supported, with simulations showing that disturbance increased the rate at which structure developed, and reduced the time to fixation (monopolisation by a single lineage). The chance of any lineage reaching fixation was directly related to its initial proportion in the population, and this relationship was unaffected by changes in disturbance size or dispersal capacity. We conclude that, in the absence of selection, extirpation is typically a prerequisite for population‐genetic “turnover”, with remnant (refugial) individuals otherwise outnumbering immigrants.
Synthesis . Disturbance plays a critical role in releasing density‐dependent blocks to colonisation, and thus enables lineage turnover within species. Our results indicate that although both disturbance size and dispersal capacity play important roles in the formation of spatial structure within species, unless a population is totally extirpated, establishment of genetic lineages from elsewhere (turnover) is unlikely even for species that can disperse well.
... Il semble cependant que si des connexions avec d'autres populations de rats existent, cette réinfestation est généralement très rapide, éventuellement de l'ordre de quelques mois (ex. Andrews and Belknap, 1983 ;Channon et al., 2006 ;Abdelkrim et al., 2007). De plus, l'élimination d'une fraction importante de la population de rats dans une région donnée peut engendrer une réinfestation parfois massive de certains sites menant à des densités supérieures à celles précédant l'intervention, pour un temps du moins (Andrew and Beklnap, 1983). ...
Entre 2011 et 2013, plusieurs cas de typhus murin ont été détectés pour la première fois sur l’île de La Réunion. La Direction Générale de la Santé a saisi le CNEV afin d’évaluer la pertinence et la faisabilité de la mise en place d’une surveillance intégrée et de mesures de gestion contre cette maladie.
Après une synthèse sur la biologie des puces vectrices et les pathogènes susceptibles d’être transmis par celles‐ci, ce rapport présente la situation épidémiologique du typhus murin dans les différents territoires français. Le groupe de travail émet ensuite des propositions pour la prise en charge de la problématique sur l’île de la Réunion et dans les autres territoires français.
Le typhus murin est‐il une maladie émergente à La Réunion ?
A l’heure actuelle, il est difficile de savoir si la découverte récente de cas de typhus murin à La Réunion traduit une réelle émergence ou la mise en évidence d’une maladie endémique en raison d’un accroissement de la surveillance. En effet, en zone tropicale, les « fièvres d’origine indéterminée » sont fréquentes et la plupart des études spécifiques montre que les rickettsioses en constituent entre 10 et 20%.
A ce stade, la question de l’émergence reste donc en suspens et les résultats des études épidémiologiques, entomologiques et mammalogiques conduites actuellement à la Réunion apporteront probablement des éléments de réponse.
Mesures de gestion pour la prévention et le contrôle du typhus murin en France
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Sur l’île de La Réunion
Les principales actions de prévention doivent viser l’élimination des lieux de refuge des rongeurs, le blocage des lieux de passages des rongeurs par l’adaptation de l’habitat ainsi que l’amélioration de la gestion des déchets et du stockage des aliments. Une sensibilisation de la population contribuera également à la mise en oeuvre des mesures générales d’hygiène de l’environnement.
Le Port, principal port de La Réunion est le site présentant le plus haut risque d’introduction des réservoirs et des vecteurs de R. typhi, ainsi que d’autres agents zoonotiques à risque (ex. Yersinia pestis). Il apparaît donc prioritaire de mettre en place une surveillance des réservoirs et des vecteurs, en cohérence avec le RSI.
Les mesures environnementales devront être poursuivies voire renforcées en zone de foyers potentiellement épidémiques, notamment autour des cas humains. Une lutte contre les rongeurs devra par conséquent être précédée ou organisée en même temps qu’une lutte contre les puces, en particulier lorsque la lutte rodenticide est conduite à proximité d’habitations. Des dispositions similaires pourront être mises en oeuvre au niveau des bâtiments accueillant des populations sensibles (crèches, écoles, hôpitaux, maisons de retraite…) localisés à proximité des foyers. 1
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Dans les autres territoires français
Les installations portuaires ouvertes au trafic international sont les sites qui présentent la plus grande vulnérabilité en termes d’introduction de rongeurs allochtones, et donc de faune ectoparasitaire (puces en particulier). En ce sens, les ports et les villes portuaires devraient faire l’objet d’une veille sanitaire rigoureuse et constante afin de minimiser les risques d’introduction d’agents zoonotiques qui pourraient se propager sur le territoire.
Cependant, un déficit étonnant de connaissances scientifiques (voire une absence de données) est constaté au niveau des installations portuaires.
Des études scientifiques à visée opérationnelle doivent par conséquent être entreprises dans les meilleurs délais au niveau des grandes installations portuaires françaises afin de combler ces lacunes. Elles doivent notamment avoir pour objectif de fournir des informations quant (i) au mode, au tempo, à la provenance et au volume des introductions de rongeurs via le transport maritime, (ii) à la capacité d’implantation et (iii) de dispersion des rongeurs, des ectoparasites et des agents zoonotiques introduits.
... Examination of the patterns of genetic variation in a phylogeographic context can help identify the provenance of extant populations on individual islands. This can corroborate, or sometimes refute, historical human transportation routes [5], and simultaneously assist in developing rodent biosecurity and eradication programmes by identifying eradication units [6] and determining sources of reinvaders [7]. We analysed the phylogeography of Norway rats from several locations in both the North and South Atlantic Oceans in order to elucidate potential historical origin and to inform contemporary pest management for this invasive species. ...
Norway rats are a globally distributed invasive species, which have colonized many islands around the world, including in the South Atlantic Ocean. We investigated the phylogeography of Norway rats across the South Atlantic Ocean and bordering continental countries. We identified haplotypes from 517 bp of the hypervariable region I of the mitochondrial D-loop and constructed a Bayesian consensus tree and median-joining network incorporating all other publicly available haplotypes via an alignment of 364 bp. Three Norway rat haplotypes are present across the islands of the South Atlantic Ocean, including multiple haplotypes separated by geographic barriers within island groups. All three haplotypes have been previously recorded from European countries. Our results support the hypothesis of rapid Norway rat colonization of South Atlantic Ocean islands by sea-faring European nations from multiple European ports of origin. This seems to have been the predominant pathway for repeated Norway rat invasions of islands, even within the same archipelago, rather than within-island dispersal across geographic barriers.
... Russell et al. [35], for example, noted an unexpectedly rapid recolonization event following an island rodent-eradication program, suggesting "rats were swimming to the island at a rate much greater than anticipated"and that the previously established, genetically divergent population had effectively excluded dispersers prior to its eradication. Numerous similar examples of competitive exclusion of sister lineages by established populations have been noted [36][37][38]. ...
The spread of exotic species represents a major driver of biological change across the planet. While dispersal and colonization are natural biological processes, we suggest that the failure to recognize increasing rates of human-facilitated self-introductions may represent a threat to native lineages. Notably, recent biogeographic analyses have revealed numerous cases of biological range shifts in response to anthropogenic impacts and climate change. In particular, ancient DNA analyses have revealed several cases in which lineages traditionally thought to be long-established "natives" are in fact recent colonizers. Such range expansion events have apparently occurred in response to human-mediated native biodiversity declines and ecosystem change, particularly in recently colonized, isolated ecosystems such as New Zealand. While such events can potentially boost local biodiversity, the spread of exotic lineages may also hasten the decline of indigenous species, so it is essential that conservation managers recognize these rapid biotic shifts. .
... Ongoing intermixing between feral and domestic fancy breed cats, for example, may lead to an increased local genetic diversity and population growth (Dickman 1996;Oliveira et al. 2008;Say et al. 2012). The incorporation of population genetic and phylogeography approaches into various eradication and management campaigns has been found to enhance their success and can assist in recognizing possible positive outcomes of containment efforts (Abdelkrim et al. 2007;Allendorf and Lundquist 2003;Rollins et al. 2006;Schwartz et al. 2007;Veale et al. 2013;Waples & Gaggiotti 2006). This information consequently allows a management design specifically adjusted to population structure and their connectivity to other populations (Estoup & Guillemaud 2010;Rollins et al. 2006;Veale et al. 2013). ...
Endemic species on islands are highly susceptible to local extinction, in particular if they are exposed to invasive species. Invasive predators, such as feral cats, have been introduced to islands around the world, causing major losses in local biodiversity. In order to control and manage invasive species successfully, information about source populations and level of gene flow is essential. Here, we investigate the origin of feral cats of Hawaiian and Australian islands to verify their European ancestry and a potential pattern of isolation by distance. We analyzed the genetic structure and diversity of feral cats from eleven islands as well as samples from Malaysia and Europe using mitochondrial DNA (ND5 and ND6 regions) and microsatellite DNA data. Our results suggest an overall European origin of Hawaiian cats with no pattern of isolation by distance between Australian, Malaysian, and Hawaiian populations. Instead, we found low levels of genetic differentiation between samples from Tasman Island, Lana'i, Kaho'olawe, Cocos (Keeling) Island, and Asia. As these populations are separated by up to 10,000 kilometers, we assume an extensive passive dispersal event along global maritime trade routes in the beginning of the 19th century, connecting Australian, Asian, and Hawaiian islands. Thus, islands populations, which are characterized by low levels of current gene flow, represent valuable sources of information on historical, human-mediated global dispersal patterns of feral cats.
... Effective management programmes geared toward reducing the population size of an invasive species must also focus on defining management units [21][22][23]. To understand recolonisation scenarios, information concerning dispersal and gene flow of the species targeted for control is required. ...
Eradication and population reductions are often used to mitigate the negative impacts of non-native invasive species on native biodiversity. However, monitoring the effectiveness of non-native species control programmes is necessary to evaluate the efficacy of these measures. Genetic monitoring could provide valuable insights into temporal changes in demographic, ecological, and evolutionary processes in invasive populations being subject to control programmes. Such programmes should cause a decrease in effective population size and/or in genetic diversity of the targeted non-native species and an increase in population genetic structuring over time. We used microsatellite DNA data from American mink (Neovison vison) to determine whether the removal of this predator on the Koster Islands archipelago and the nearby Swedish mainland affected genetic variation over six consecutive years of mink culling by trappers as part of a population control programme. We found that on Koster Islands allelic richness decreased (from on average 4.53 to 3.55), genetic structuring increased, and effective population size did not change. In contrast, the mink population from the Swedish coast showed no changes in genetic diversity or structure, suggesting the stability of this population over 6 years of culling. Effective population size did not change over time but was higher on the coast than on the islands across all years. Migration rates from the islands to the coast were almost two times higher than from the coast to the islands. Most migrants leaving the coast were localised on the southern edge of the archipelago, as expected from the direction of the sea current between the two sites. Genetic monitoring provided valuable information on temporal changes in the population of American mink suggesting that this approach can be used to evaluate and improve control programmes of invasive vertebrates.
... Quantifying the genetic variability of invading populations is an important component in estimating the capacity of invaders to respond to new environments and expand from initial point of invasion (Lee 2002;Lavergne and Molofsky 2007). Understanding the invasion pathways and interisland movement of alien rodent species is important for managing and eradicating these taxa from the archipelago, as groups of islands with high rates of migration need to be considered as eradication units (Robertson and Gemmell 2004;Abdelkrim et al. 2007). Rodents have been successfully eradicated from several islets in the Gal apagos (DIISE Partners, 2014), and it is essential to understand the potential for their reinvasion. ...
Human activity has facilitated the introduction of a number of alien mammal species to the Galápagos Archipelago. Understanding the phylogeographic history and population genetics of invasive species on the Archipelago is an important step in predicting future spread and designing effective management strategies. In this study, we describe the invasion pathway of Rattus rattus across the Galápagos using microsatellite data, coupled with historical knowledge. Microsatellite genotypes were generated for 581 R. rattus sampled from 15 islands in the archipelago. The genetic data suggest that there are at least three genetic lineages of R. rattus present on the Galápagos Islands. The spatial distributions of these lineages correspond to the main centers of human settlement in the archipelago. There was limited admixture among these three lineages, and these finding coupled with low rates of gene flow among island populations suggests that interisland movement of R. rattus is rare. The low migration among islands recorded for the species will have a positive impact on future eradication efforts.
... More specifically, in the aftermath of a failure, it would be valuable for conservation planners to know whether a mere handful of rats survived the poison bait, in which case minor tweaking of the baiting protocol might ensure the success of a second attempt, or whether survivors numbered hundreds or more, suggesting the need for major revision of the eradication protocol [4]. The study we report here is, to our knowledge, the first attempt to use genetic data to estimate the number of survivors of a failed rat eradication operation (but see [5]). The project in question was undertaken in August 2011 on the 43 km 2 World Heritage site of Henderson Island (24°20 S, 128°19 W) in the Pitcairn group, South Pacific. ...
To enhance their conservation value, several hundred islands worldwide have been cleared of invasive alien rats, Rattus spp. One of the largest projects yet undertaken was on 43 km2 Henderson Island in the Pitcairn group, South Pacific, in August 2011. Following massive immediate mortality, a single R. exulans was observed in March 2012 and, subsequently, rat numbers have recovered. The survivors show no sign of resistance to the toxicant used, brodifacoum. Using pre- and post-operation rat tissue samples from Henderson, plus samples from around the Pacific, we exclude re-introduction as the source of continued rat presence. Microsatellite analysis of 18 loci enabled comparison of genetic diversity of Henderson rats before and after the bait drop. The fall in diversity measured by allele frequency change indicated that the bottleneck (Ne) through which the breeding population passed was probably around 50 individuals, representing a census population of about 60–80 animals. This is the first failed project that has estimated how close it was to success.
... The diversity of mtDNA haplotypes represented in New Zealand house mice offers useful clues to the historical geographic origins of their ancestors. Moreover, because house mice are a major international pest, and genetic data can provide information critical to efficient management of pest rodents on islands (Abdelkrim et al. 2005(Abdelkrim et al. , 2007, establishing the geographic origins of New Zealand mice could have a conservation management application (e.g. MacKay et al. 2013). ...
We mapped the distribution and diversity of mitochondrial D-loop haplotypes among 502 New Zealand house mice (Mus musculus). By widespread sampling from 74 sites, we identified 14 new haplotypes. We used Bayesian phylogenetic reconstructions to estimate the genetic relationships between the New Zealand representatives of Mus musculus domesticus (all six known clades) and M. m. castaneus (clade HG2), and mice from other locales. We defined four distinct geographic regions of New Zealand with differing haplotype diversity indices. Our Results suggest (a) two independent pre-1840 invasions by mice of different origin (domesticus clade E and castaneus clade HG2) at opposite ends of the country; (b) multiple later invasions by domesticus clades E and F accompanying the post-1840 development of New Zealand port facilities in the central regions, plus limited local incursions by domesticus clades A, B, C and D1; (c) a separate invasion of Chatham I. by castaneus clade HG2; (d) previously undescribed New Zealand haplotypes, potentially the products of localised indigenous mutation, and (e) hybridisation between different lineages.
... If animals are found after the eradication, samples can then be analysed and microsatellites compared with the original population. This technique may enable determination of whether animals evaded eradication efforts, were introduced, or a combination of these (Abdelkrim et al. 2007). Further, DNA analysis can be used to identify individual animals, their sex and determine parent-offspring relationships, which may be important in some situations when dealing with the last animals (Forsyth et al. 2005). ...
... If animals are found after the eradication, samples can then be analysed and microsatellites compared with the original population. This technique may enable determination of whether animals evaded eradication efforts, were introduced, or a combination of these (Abdelkrim et al. 2007). Further, DNA analysis can be used to identify individual animals, their sex and determine parent-offspring relationships, which may be important in some situations when dealing with the last animals (Forsyth et al. 2005). ...
... In addition, vacant territories resulting from local culling operations could rapidly be recolonized during juvenile dispersal . Sparing even a few individuals could lead to a high failure probability of an eradication project (Abdelkrim et al., 2007). ...
Invasive species represent a major threat to biodiversity and are significant component of human-caused global environmental change. The rate of introduction of exotic species dramatically increases during the last decades. The American mink (Mustela vison) was introduced in Europe in the 1920s for the purpose of fur farming. Escapes from farms, or deliberately released animals, have lead to the establishment of feral populations in many areas, and represent a major threat to native fauna. The aim of this thesis was to understand the population dynamics of feral mink populations in Brittany, Western France, in order to draw better control strategies. Firstly, we investigated the population distribution and density, and demographic data to improve our understanding of the population functionment. We concluded than the mink population of Brittany was an invasive population. Then, we implement an experimental design to assess the impact of feral mink on native fauna. This study highlighted that the effects of alien predators could be difficult to measure in the short term. Finally, we investigated the genetic variability and population structure of feral and farmed mink from Brittany as well as mink from other European countries and from North America. A strong genetic structure and the presence of admixture areas were detected in Brittany. The insights of those results for the understanding of the population dynamics of feral American mink are discussed, as well as their consequences for control strategies
... Second, spatial genetic structure can be used to evaluate the success of an eradication operation, by establishing the source (either survivor or reinvader) of individuals caught after the campaign (e.g. Abdelkrim et al. 2005; Abdelkrim et al. 2007; Berry and Kirkwood 2010; Russell et al. 2010; Veale et al. 2013). When reinvasion is detected, the origin and possible invasion route is also ascertainable from this information. ...
Context Effective design of conservation management programs for long-term population control requires an accurate definition of the spatial extent of populations, along with a proper understanding of the ways that landscape patchiness influences demography and dispersal within these populations. Aims In the present study, genetic techniques are used to describe the population genetic structure and connectivity of invasive stoats (Mustela erminea) across the Auckland region, New Zealand, so as to assist planning for mainland stoat control, and define potential future eradication units. Methods A sample of stoats from across the region (n=120), was genotyped at 17 microsatellite loci, and a combination of clustering, genetic population assignment and various migration estimation methods were applied to these data. Key results Moderate population structure was observed (F-ST=0.03-0.21), with five geographic populations defined by genetic clustering. Almost all individuals were correctly assigned to the location of origin, and recent migration rates among forest patches were found to be low. Conclusions It is possible to define the origin of stoats at this regional scale using genetic measures. From this, we show that the stoat incursion on Rangitoto Island that occurred post-eradication in 2010 probably came from East Auckland (P<0.0001), whereas the 2014 stoat incursion on Motutapu Island probably originated from a population linked to the Waitakeres. Also, the Waiheke Island stoat population has minimal connection to all other populations and it is therefore a potential eradication unit. Implications The low migration rates among forest patches indicated that if thorough control is imposed on a discrete forest patch, reinvasion from other forest patches will be relatively low. Importantly, for stoat control in the region, the isolation of the Waiheke Island stoat population means that eradication here is likely to be feasible with low reinvasion pressure.
... Biological invasions are currently one of the major threats to biodiversity worldwide (Vitousek et al. 1996;Alonso et al. 2001;Richardson 2011), and identifying the factors that explain dispersal patterns of invasive species within non-native regions becomes a central issue for conservation biology, emergence of novel diseases and eradication programs (Abdelkrim et al. 2007;Estoup and Guillemaud, 2010). Invasive species arrive to non-native habitats following human commercial routes, deliberated or unconscious human mediated introductions, or through the breakdown of historical barrier to dispersal due to climate changes (Cadotte et al. 2006;Nentwig 2007;Richardson 2011). ...
The cactus moth, Cactoblastis cactorum mainly distributed throughout central and northeastern Argentina was intentionally introduced in the Caribbean region in 1957 as a biological control agent of cacti species of the genus Opuntia. This moth invaded during the last 20–30 years the North American continent, threatening the major center of biodiversity of native Opuntia species. Although human induced and natural dispersal have been invocated to explain its expansion in the non-native distribution range, there is still no evidence to support natural dispersal. In particular, hurricanes are one of the major environmental factors affecting species dispersal in the region. In this study we used mitochondrial DNA to examine whether the spatial distribution of haplotype variation of C. cactorum is at least partially explained by hurricane trajectories within the Caribbean region. DNA sequences for the mitochondrial gene cytochrome oxidase I were obtained for a sample of 110 individuals from the Antillean islands. This information was combined with existing sequences in the GenBank for the same gene for the Caribbean and Florida (N = 132 sequences). Genetic diversity descriptors, a haplotypic network, a spatial analyses of molecular variance and a landscape genetic analysis of migration conditioned by hurricane tracks were conducted to test our hypothesis. Our results revealed a significant spatial grouping of haplotypes consistent with the more frequent hurricane trajectories in the Caribbean region. Significant isolation by distance conditioned by hurricane tracks was detected. Populations of Florida were genetically closer to those of Cuba than to the rest of the population sampled. Within the region, Cuba appears as a reservoir of genetic diversity increasing the risk of invasion to Mexico and the US. Despite commercial transportation of Opuntia promoted dispersal to Florida, our results support the hypothesis that natural disturbances such as hurricanes played a role dispersing this invasive insect. Future conservation programs of North American Opuntia species requires taking into account hurricane mediated dispersal events and permanent whole regional monitoring and international control policies to prevent future range expansions of C. cactorum.
... Comparable patterns have been noted elsewhere: in the sub-Antarctic, a genetic study of the invasive house mouse (Mus musculus domesticus) demonstrated that the first colonists of an island rapidly dominate and apparently prevent any secondary invasions by conspecifics; later waves of invasion are only possible on islands not already colonized by the pest (Hardouin et al. 2010). Elsewhere, genetic research on eradication of rats (Rattus rattus) from islands in the French Carribean showed that some preeradication populations were genetically distinct from individuals found on the islands post-eradication, again suggesting reinvasion may have been directly facilitated by removal of the previously existing population (Abdelkrim et al. 2007). This 'release and reinvasion' process has thus been demonstrated to operate in similar ways both within species and among closely-related species that presumable utilise similar resources. ...
Molecular analyses are frequently used to assess biological gene flow and dispersal, yet recent data suggest that the operation of density-dependent priority effects often leads to underestimation of species movement patterns and associated invasive potential. Although individual movement is broadly considered to promote connectivity among populations, emerging genetic evidence on a range of scales indicates that it often fails to do so; instead, it can be a strategy that allows first colonizers to wedge a ‘foot in the door’ when new space becomes available. Founding lineages can then rapidly dominate, blocking colonization by later arrivals; subsequent invasion opportunities may be contingent on the extirpation of locals. Many contemporary studies, however, ignore the role of such density-dependent priority effects, and thus fail to assess major differences between movement and establishment. Understanding the role of these processes in the successful establishment of dispersing organisms is critical if we are to predict distributional range shifts and deal with invasive pest species.
... Genetic data is a useful tool for distinguishing between the two main reasons for eradication failure: survival of some individuals or re-colonisation after eradication efforts (e.g. Abdelkrim et al. 2007). More data is needed on the distribution and abundance of tilapia lineages across Australia to explore the stability of populations through time and possible hybrid vigour that may be linked to invasion potential. ...
Understanding dispersal routes of invasive species is essential to their control. Tilapiine fish species are
archetypal invaders of freshwater habitats. They were first reported from Australia in the 1970’s and
have spread rapidly. Incursion into Australia’s largest inland catchment, the Murray Darling Basin, may
threaten its largely endemic freshwater fauna. Direct (spatial and temporal distribution) and indirect
(genetic data from eight microsatellite loci and mitochondrial DNA sequence) information was used to
subjectively construct invasion scenarios. Specifically, we tested the expectation that tilapias have been
translocated between freshwater catchments presumably as a consequence of their popularity as bait for
angling, display in aquariums and for the table. Five cross-catchment translocation events were inferred
involving dispersal across distances up to 300 km. Translocation was not rampant, however, as genetic
distinctiveness among catchments was observed. Tilapia in eastern Australia had genetic affinities to
Oreochromis spirulus, O. hornourum urolepis and O. aureus, beyond their expected affinity to O.
mossambicus. Some individuals had admixed genomes suggesting on-going hybridisation between
lineages. Other individuals had zero nuclear genetic diversity at eight microsatellite loci demonstrating the tolerance to severe inbreeding. There was evidence of temporal instability in the composition of
populations; for example, in an artificial dam in the south (Tingalpa Weir) one genetic lineage appeared
to have replaced another over a period of approximately twenty years. Authorities have clear rationale
to more strictly enforce regulations that prohibit possession of this species (dead or alive), and a
window of opportunity for effective action given that translocation, while occurring, is currently not
rife.
... Genotyping of individuals provides information on parent-offspring relationships and thus data on the connectivity and structure of the population (Pontier et al. 2005). This helps to ensure biosecurity by providing managers with the ability to determine possible survivors or new colonists after an eradication attempt (Abdelkrim et al. 2007). We genotyped feral cats on Dirk Hartog Island at 3 sites as well as populations from the 2 main potential access points from the mainland using mitochondrial DNA and 10 microsatellite loci. ...
Invasive predators have a major impact on endemic island species; therefore, information about invasion dynamics are essential for implementing successful control measures. The introduction of feral cats onto Dirk Hartog Island, Western Australia, has had devastating effects, with presumably 10 of 13 native terrestrial mammal species being lost because of predation. Detailed records of historical introduction events were lacking; therefore, we analyzed genetic variation of the current population to gain information about past invasion dynamics and current gene-flow patterns. We analyzed the genetic structure and diversity of feral cats on the island and 2 mainland populations (Peron Peninsula and Steep Point). Analysis of mitochondrial DNA (ND5 and ND6) showed 2 primary haplotypes that we attribute to 2 main introduction events. Pairwise values indicated high connectivity on the island but some isolation to the mainland populations. Mitochondrial and nuclear data showed no evidence for genetic differentiation of island and mainland populations; however, kinship analyses rejected evidence for on-going immigration of members of the current cat populations. Overall, our data suggested that gene flow following the main introduction events ceased some years ago. Because current island populations appear to be reproductively isolated from mainland populations, a sufficiently large-scale eradication measure might successfully diminish feral cat populations long-term. © 2014 The Wildlife Society.
Humans and wildlife experience complex interactions in urban ecosystems, favoring the presence of commensal species, among which invasive species are particularly successful. Rodents are the main vertebrate group introduced to oceanic islands, where the invasion process and dispersal patterns strongly influence their evolutionary and genetic patterns. We evaluated the house mouse Mus musculus and the black rat Rattus rattus on Cozumel island, Mexico. We assessed genetic diversity and structure, connectivity, gene flow, relatedness and bottleneck signals based on microsatellite loci. Our findings show that the constant introduction of individuals of different origins to the island promotes high allelic diversity and the effective establishment of migrants. We identified a clear genetic structure and low connectivity for the two species, tightly linked with anthropogenic and urban features. Moreover, we found M. musculus has a particularly restricted distribution within the city of San Miguel Cozumel, whilst its genetic structure is associated with the historical human population growth pulses accompanying the urbanization of the city. At the fine-scale genetic level, the main urban drivers of connectivity of the house mouse were both the impervious land surfaces, i.e. the urban landscape, and the informal commerce across the city (a proxy of resources availability). Chances of a secondary invasion to natural environments have been relatively low, which is crucial for the endemic taxa of the island. Nonetheless, improving urban planning to regulate future expansions of San Miguel Cozumel is of the outmost importance in order to prevent these invasive species to disperse further.
Feral and stray cats are a major threat for endemic species on Christmas Island and have been contributing to their decline. Cats were introduced to Christmas Island in 1888 and are now distributed across the whole island. We analysed the genetic population structure and diversity of feral and stray cats on Christmas Island to evaluate connectivity across the island and the possibility of discernible populations that could be targeted separately. Results indicate no differentiated population structure across the island, with cats facing no habitat obstacles to reduce their dispersal abilities across the island. We found high kin structure, suggesting individuals breeding successfully on the whole island. With the management of domestic and feral/stray cats since 2010, removal efforts targeting the whole island have successfully reduced the effective population size of feral/stray cats in the last five years. We suggest the use of various management techniques to facilitate future removal efforts, especially in areas on the island that are difficult to access.
Elton featured isolated islands as particularly devastated by invasions, focusing on Easter Island, the Tristan da Cunha group, the Hawaiian chain, and New Zealand. Had he completed a second edition, he would have noted even greater impacts at least for Tristan de Cunha and Hawaii, as he had notes from publications on invasion impacts there from 1959 through 1970.
Invasions of alien species on islands cause serious deleterious effects on native species through predation and competition often to the point of extinction. Where eradication is not possible ongoing control programs are the only alternative. Following control efforts there are risks of both recolonisation from survivors and reinvasion from neighbouring populations. Successful pest control efforts at such sites depend heavily on two rules of eradication: (1) individuals have to be removed faster than the growth rate and (2) reinvasion must be close to zero. We used a small near-shore island as a ‘microcosm’ to test whether both these rules could be met. We applied a molecular genetic approach to assess genetic differentiation of a ship rat (Rattus rattus) population on a nearshore island with the adjacent mainland population and investigated metapopulation dynamics and pest control success. Tissue samples from Goat Island, New Zealand, from three consecutive years were genotyped at 14 microsatellite loci and compared with the mainland populations. We showed moderate genetic differentiation between the two populations despite their close proximity and demonstrated that rats were neither being removed faster than they bred nor was reinvasion able to be managed close to zero. Furthermore, population reduction on the island counter-productively facilitated establishment by invading rats. These results have important implications for interpreting the relative roles of recolonization versus reinvasion following pest control operations. To properly manage invasive species at such sites, control must have the intensity of eradication efforts, and reinvasion must be managed both pre departure and post arrival.
Background
The introduction of northern snakehead ( Channa argus ; Anabantiformes: Channidae) and their subsequent expansion is one of many problematic biological invasions in the United States. This harmful aquatic invasive species has become established in various parts of the eastern United States, including the Potomac River basin, and has recently become established in the Mississippi River basin in Arkansas. Effective management of C. argus and prevention of its further spread depends upon knowledge of current population structure in the United States.
Methods
Novel methods for invasive species using whole genomic scans provide unprecedented levels of data, which are able to investigate fine scale differences between and within populations of organisms. In this study, we utilize 2b-RAD genomic sequencing to recover 1,007 single-nucleotide polymorphism (SNP) loci from genomic DNA extracted from 165 C. argus individuals: 147 individuals sampled along the East Coast of the United States and 18 individuals sampled throughout Arkansas.
Results
Analysis of those SNP loci help to resolve existing population structure and recover five genetically distinct populations of C. argus in the United States. Additionally, information from the SNP loci enable us to begin to calculate the long-term effective population size ranges of this harmful aquatic invasive species. We estimate long-term N e to be 1,840,000–18,400,000 for the Upper Hudson River basin, 4,537,500–45,375,000 for the Lower Hudson River basin, 3,422,500–34,225,000 for the Potomac River basin, 2,715,000–7,150,000 for Philadelphia, and 2,580,000–25,800,000 for Arkansas populations.
Discussion and Conclusions
This work provides evidence for the presence of more genetic populations than previously estimated and estimates population size, showing the invasive potential of C. argus in the United States. The valuable information gained from this study will allow effective management of the existing populations to avoid expansion and possibly enable future eradication efforts.
The brushtail possum (Trichosurus vulpecula) is a widespread introduced pest in New Zealand. Some hair and faecal remains suspected to be from a possum were found on a vehicle transport barge in port at Great Barrier Island in the Hauraki Gulf (North Island, New Zealand), an island that has historically remained possum free. So that appropriate action could be taken, we used forensic genetics to confirm the species, number, and sex of the individuals that may have disembarked at the island. We concluded that forensic samples were attributable to a single male possum that did not disembark on the island, hence no eradication response was put in place. This case study illustrates how forensic DNA analysis of wildlife remains can assist in the response to a potentially disastrous invasive event by providing information in a timely and cost-effective manner.
Are concepts related to biological invasions in terrestrial ecosystems relevant to marine ecosystems? To address this question we start with a definition of "biological invasion" and some observations that show that this question is of more than academic interest. Several results are presented that show why scientists should consider biological invasions as experiments and should collaborate with managers to develop effective management procedures. Likewise, several results from "pure" science have been highly useful for conservation managers.
As the most species-rich and biologically eclectic of all social insects, ants present considerable challenges to the process of cataloguing and understanding their remarkable diversity. Substantial progress has been made in recent years, however, in identifying the major clades of ants and in clarifying their evolutionary history. We now have a higher classification of ants in which most of the subfamilies and tribes appear to be monophyletic and well diagnosed, with a few notable exceptions. Uncertainty persists regarding the phylogenetic relationships among old lineages at the base of the ant tree and concerning the time frame of ant evolution. The specieslevel taxonomy of ants has advanced more fitfully, and ant ecologists have an extensive but far-from-complete set of resources for identifying ant species. Ongoing and sustained effort is needed in the area of species discovery and delimitation, and in the delivery of this information to potential users.
The lack of biological knowledge of many invasive species remains as one of the greatest impediments to their management. Here I detail targeted research into the biology of the yellow crazy ant
Anoplolepis gracilipes
within northern Australia and detail how such knowledge can be used to improve the management outcomes for this species. I quantified nest location and density in three habitats, worker activity over 24 h, infestation expansion rate, seasonal variation of worker abundance and the timing of production of sexuals. Nests were predominantly (up to 68%) located at the bases of large trees, indicating that search efforts should focus around tree bases. Nest density was one nest per 22, 7.1 and 6.3 m
2
in the three habitats, respectively. These data form the baselines for quantifying treatment efficacy and set sampling densities for post-treatment assessments. Most (60%) nests were underground, predominantly (89%) occurring in an open area rather than underneath a rock or log. Some seasonality was evident for nests within leaf litter, with most (83%) occurring during the ‘wet season’ (October–March). Of the underground nests, most were shallow, with 44% being less than 10 cm deep, and 67% being less than 20 cm deep. Such nest location and density information serves many management purposes, for improving detection, mapping and post-treatment assessments, and also provided strong evidence that carbohydrate supply was a major driver of
A. gracilipes
populations. Just over half of the nests (56%) contained queens. Of the 62 underground nests containing queens, most queens (80%) were located at the deepest chamber. When queens were present, most often (38%) only one queen was present, the most being 16. Queen number per nest was the lowest in July and August just prior to the emergence of virgin queens in September, with queen numbers then remaining steadily high until April. Nothing is known for any ant species about how the queen number per nest/colony affects treatment efficacy, but further research would no doubt yield important breakthroughs for treating ants. Activity occurred predominantly nocturnally, ceasing during mid-day. These activity data determined the critical threshold above which work must be conducted to be considered reliable, and also suggests that treatments are best applied in the afternoon. Total brood production peaked in February and was the lowest around August and September. These abundance data form the baselines for quantifying treatment efficacy, and may have implications for treatment efficacy. Males were found every month, predominantly between August and November. Queen pupae were found in September. The reproductive timing of sexuals determines the treatment schedule. Targeted, site-specific research such as that described here should be an integral part of any eradication program for invasive species to design knowledge-based treatment protocols and determine assessment benchmarks.
The present-day distribution of ants reflects the influence of geography, geology, and climate on the origin, diversification, and spread of a lineage. Though the process is complex and often difficult to reconstruct for a given taxon, two important overall patterns emerge: taxa are neither randomly nor uniformly distributed across the earth, and endemic taxa are clustered in particular regions. The greatest ant diversity and endemicity are found in the tropics and the Gondwanaland fragments of South America, Africa, and Australia. Lines of inquiry that combine exhaustive inventories, taxonomic revisions, and phylogenetics will enable a more rigorous approach to the study of biogeography. Islands offer a model system to explore these questions. Due to their range in size, origin, degree of isolation, and habitat types, the south-west Indian Ocean islands are an ideal model system to explore the relative impact of biogeographic factors on species diversity.
Eradication of invasive species is an important component for species conservation and ecosystem restoration. Success of eradications is dependent on knowledge of population connectivity in order to determine reinvasion pathways, and hence populations requiring simultaneous eradication (eradication units). The common brushtail possum (Trichosurus vulpecula) was introduced into New Zealand from Australia and Tasmania, and now occupies a wide range of habitats across the majority of New Zealand. Possums are one of the most destructive invaders within New Zealand, with extensive control operations occurring throughout the country. Understanding the population connectivity of possums on mainland New Zealand (North and South Islands) will enhance the success of planned eradications. We examined the genetic population structure of invasive possums to identify gene flow, thus reinvasion pathways, between seven populations around Dunedin and on the Otago Peninsula where eradication of possums is occurring. Genetic variation at 12 microsatellite loci was comparable between all sampled populations and exhibited a significant isolation by distance pattern. Bayesian clustering methods supported the existence of two population clusters, indicating the presence of a reinvasion pathway onto the Otago Peninsula from urban areas at the Southern end of the Peninsula. To avoid recolonisation, all possums on the Otago Peninsula should be eradicated simultaneously, with the implementation and ongoing maintenance and monitoring of an urban buffer zone. We recommend pre-eradication genetic analyses be adopted by all pest managers to define appropriate eradication units, thereby maximising eradication success and avoiding costly failures.
Detecting bottlenecks or population declines
We use population genetics theory and computer simulations to demonstrate that population bottlenecks cause a characteristic mode-shift distortion in the distribution of allele frequencies at selectively neutral loci. Bottlenecks cause alleles at low frequency (< 0.1) to become less abundant than alleles in one or more intermediate allele frequency class (e.g., 0.1-0.2). This distortion is transient and likely to be detectable for only a few dozen generations. Consequently only recent bottlenecks are likely to be detected by tests for distortions in distributions of allele frequencies. We illustrate and evaluate a qualitative graphical method for detecting a bottleneck-induced distortion of allele frequency distributions. The simple novel method requires no information on historical population sizes or levels of genetic variation; it requires only samples of 5 to 20 polymorphic loci and approximately 30 individuals. The graphical method often differentiates between empirical datasets from bottlenecked and nonbottlenecked natural populations. Computer simulations show that the graphical method is likely (P > .80) to detect an allele frequency distortion after a bottleneck of < or = 20 breeding individuals when 8 to 10 polymorphic microsatellite loci are analyzed.
Au cours de ces cinq derniers siècles, suite à la levée des barrières biogéographiques, un grand nombre d’espèces végétales et animales a été introduit par l’homme, volontairement ou non, dans la quasi totalité des écosystèmes du globe. La plupart de ces introductions ont été des échecs et la majorité des succès est réputée ne pas poser de problèmes. Cependant, certaines introductions réussies sont à l’origine de pertes économiques importantes et de graves atteintes à la diversité biologique.
Les écosystèmes insulaires, abritant des communautés animales et végétales peu diversifiées par rapport aux milieux continentaux, souvent disharmoniques et caractérisées par de forts taux d’endémisme, sont particulièrement vulnérables aux introductions d’espèces. Dès les années soixante, l’essentiel des éradications d’espèces introduites, en particulier de mammifères, a été réalisé dans les îles compte tenu de leur superficie souvent réduite, favorable à l’expérimentation, et de leur grand intérêt écologique. À partir de l’expérience acquise lors de l’élimination du Surmulot de dix îles des côtes bretonnes (1994-1996) et du Lapin de trois îles de l’Archipel de Kerguelen (1992-1999), cet article propose une démarche d’aide à la décision et à la réalisation technique d’éradications de Mammifères introduits en milieux insulaires.
Successful eradication of the introduced and invasive brown treesnake (Boiga irregularis) from two 1 ha areas on Guam led us to suggest that the snakes could be eradicated from large nature reserves if immigration of snakes from adjoining areas could be eliminated or greatly reduced with perimeter snake barriers. Practical problems encoun-tered in the design of snake barriers on Guam include the extraordinary climbing abilities of brown treesnakes, high levels of rat damage to chewable barrier surfaces in snake-reduced areas, and frequent and destructive cyclonic storms. Four successful snake barrier designs have been developed, and one 23 ha site on Guam has been largely trapped out following erection of a snake fence around the perimeter. Unresolved problems include the failure to capture all snakes within the 23 ha exclosure, and the fragility and high maintenance requirements of low-cost barriers. Our attempt to use brown treesnake traps for control of introduced wolf snakes (Lycodon aulicus) on Ile aux Aigrettes, Mauritius was unsuccessful, possibly due to low snake densities, size selectivity of the traps, or seasonal cessation of feeding activity.
Microsatellite markers of the poly (CA) type in common carp (Cyprinus carpio L.) are described. Clones containing a (CA) repeat were isolated from a common carp genomic library and sequenced. The number of repeats found was high compared to mammals but comparable with other teleost fishes. Classification of the repeats (perfect, imperfect and compound) are compared with the Atlantic cod (Gadus morhua L.), rainbow trout (Oncorhynchus mykiss), and Atlantic salmon (Salmo salar L.). A total of 41 primer sets were designed and tested for polymorphism on a test panel of eight animals (derived from outbred lines, inbred lines and gynogenetic clones). Thirty-two markers were found to be polymorphic. The heterozygosity in the outbred animals was 60·4%, 51·1% in the inbred animals and 0% in the gynogenetic clones. The average number of alleles among the eight animals was 4·7 per marker. Six markers (18·8%) gave an additional polymorphic amplification product besides the polymorphic amplification product in the expected size range. The possibility that these loci are tetraploid is discussed. The polymorphic loci described for common carp will be valuable as genetic markers for use in population, breeding, and evolutionary studies.
Abstract Thirty-eight new microsatellite markers were developed for genome mapping and population genetics studies in rainbow trout (Oncorhynchus mykiss). The amount of polymorphism, percentage of heterozygosity and ability of each marker to amplify genomic DNA from other salmonids were recorded. Five markers were observed to be duplicated in the rainbow trout genome by containing more than one allele in homozygous (clonal) fish.
Over the last four decades the eradication of rats from islands around New Zealand has moved from accidental eradication following the exploratory use of baits for rat control to carefully planned complex eradications of rats and cats (Felis catus) on large islands. Introduced rodents have now been eradicated from more than 90 islands. Of these successful campaigns, those on Breaksea Island, the Mercury Islands, Kapiti Island, and Tuhua Island are used here as case studies because they represent milestones for techniques used or results achieved. Successful methods used on islands range from bait stations and silos serviced on foot to aerial spread by helicopters using satellite navigation systems. The development of these methods has benefited from adaptive management. By applying lessons learned from previous operations the size, complexity, and cost effectiveness of the campaigns has gradually increased. The islands now permanently cleared of introduced rodents are being used for restoration of island‐seabird systems and recovery of threatened species such as large flightless invertebrates, lizards, tuatara, forest birds, and some species of plants. The most ambitious campaigns have been on remote subantarctic Campbell Island (11 300 ha) and warm temperate Raoul Island (2938 ha), aimed to provide long‐term benefits for endemic plant and animal species including land and seabirds. Other islands that could benefit from rat removal are close inshore and within the natural dispersal range of rats and stoats (Mustela erminea). Priorities for future development therefore include more effective methods for detecting rodent invasions, especially ship rats (Rattus rattus) and mice (Mus musculus), broader community involvement in invasion prevention, and improved understanding of reinvasion risk management.
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A new Bayesian method that uses individual multilocus genotypes to estimate rates of recent immigration (over the last several generations) among populations is presented. The method also estimates the posterior probability distributions of individual immigrant ancestries, population allele frequencies, population inbreeding coefficients, and other parameters of potential interest. The method is implemented in a computer program that relies on Markov chain Monte Carlo techniques to carry out the estimation of posterior probabilities. The program can be used with allozyme, microsatellite, RFLP, SNP, and other kinds of genotype data. We relax several assumptions of early methods for detecting recent immigrants, using genotype data; most significantly, we allow genotype frequencies to deviate from Hardy-Weinberg equilibrium proportions within populations. The program is demonstrated by applying it to two recently published microsatellite data sets for populations of the plant species Centaurea corymbosa and the gray wolf species Canis lupus. A computer simulation study suggests that the program can provide highly accurate estimates of migration rates and individual migrant ancestries, given sufficient genetic differentiation among populations and sufficient numbers of marker loci.
Eradication of alien species is a key conservation tool to mitigate the impacts caused by biologic inva-sions. The aim of the present paper is to review the eradications successfully completed in Europe and to discuss the main limits to a wider application of this management option in the region. On the basis of the available literature – including conference proceedings, national reports to the Bern Convention, etc. – a total of 37 eradication programmes have been recorded. Thirty-three eradications were carried out on islands and four on the mainland. The rat (Rattus spp.) has been the most common target (n ¼ 25, 67%), followed by the rabbit (n ¼ 4). In many cases, these eradications determined a significant recovery of native biodiversity. Differently to other regions of the world, no eradications of alien inverte-brates and marine organisms have been recorded; regarding invasive alien plants, it appears that only some very localized removals have been completed so far in Europe. The limited number of eradications carried out in Europe so far is probably due to the limited awareness of the public and the decision makers, the inadequacy of the legal framework, and the scarcity of resources. Synthetic guidelines for improving the ability of European states to respond to aliens incursions are presented.
During their introduction, non-native species typically undergo founder events that reduce genetic variation. To allow a high-resolution genetic investigation of introduced populations of the small Indian mongoose (Herpestes javanicus), we developed primers for nine variable microsatellite loci. Their applicability was assessed in 10 mongooses from the large Fijian population, which originated from a single pair from Calcutta, India. The number of alleles ranged from two to five per locus, possibly as a result of preservation of initial variability and in situ mutations during the rapid population expansion after introduction.
Data on eradication operations against alien mammals on New Zealand islands show that there was a substantial increase in the number of successful eradications in the 1980s and 1990s. The most significant change has been in the ability to eradicate rodents from increasingly large islands (to over 11,000ha), using aerial poisoning techniques. Based on the New Zealand experience, there are good prospects for further eradications of alien mammals from islands around the world, facilitating ecological restoration and the recovery of threatened species. However, instances of reinvasion of rats (Rattus spp.) and stoats (Mustela erminea) onto previously cleared islands illustrate the importance of prevention, effective monitoring and a fuller understanding of invasion risks.
Pest eradication is an important facet of conservation and ecological restoration and has been applied successfully to invasive rat species on offshore and oceanic islands. Successful eradication requires the definition of a target population that is of manageable size, with low recolonization risk. We applied a molecular genetic approach to the identification of populations suitable for eradication (eradication units) to provide a new tool to assist the management of brown rats Rattus norvegicus on South Georgia (Southern Ocean).
A single eradication attempt on South Georgia (4000 km ² ) would be an order of magnitude larger than any previously successful rat eradication programme (110 km ² ). However, rats are demarcated into glacially isolated populations, which could allow sequential eradication. We examined genetic variation at 18 nuclear microsatellite loci to identify gene flow between two glacially isolated rat populations. One population, Greene Peninsula (30 km ² ), was earmarked for an eradication trial.
Genetic diversity in 40 rats sampled from each population showed a pronounced level of genetic population differentiation, allowing individuals to be assigned to the correct population of origin.
Our study suggests limited or negligible gene flow between the populations and that glaciers, permanent ice and icy waters restrict rat dispersal on South Georgia. Such barriers define eradication units that, with due care, could be eradicated with low risk of recolonization, hence facilitating the removal of brown rats from South Georgia.
Synthesis and applications . We propose that the molecular definition of eradication units is a valuable approach to management as it (i) provides a temporal perspective to gene flow, which is important if dispersal events are rare; (ii) allows an eradication failure (i.e. surviving individuals) to be distinguished from a recolonization event, opening the way for adaptive management in the face of failure; and (iii) can aid the management of pest species in habitat continua by resolving meta‐population dynamics, so guiding pest eradication/control strategies. This study further illustrates the developing array of applied ecological issues in which molecular techniques can help guide management.
When a population experiences a reduction of its effective size, it generally develops a heterozygosity excess at selectively neutral loci, i.e., the heterozygosity computed from a sample of genes is larger than the heterozygosity expected from the number of alleles found in the sample if the population were at mutation drift equilibrium. The heterozygosity excess persists only a certain number of generations until a new equilibrium is established. Two statistical tests for detecting a heterozygosity excess are described. They require measurements of the number of alleles and heterozygosity at each of several loci from a population sample. The first test determines if the proportion of loci with heterozygosity excess is significantly larger than expected at equilibrium. The second test establishes if the average of standardized differences between observed and expected heterozygosities is significantly different from zero. Type I and II errors have been evaluated by computer simulations, varying sample size, number of loci, bottleneck size, time elapsed since the beginning of the bottleneck and level of variability of loci. These analyses show that the most useful markers for bottleneck detection are those evolving under the infinite allele model (IAM) and they provide guidelines for selecting sample sizes of individuals and loci. The usefulness of these tests for conservation biology is discussed.
Les 4 îlets de Sainte-Anne (Martinique, Antilles françaises) bénéficient depuis 1995 du statut de réserve naturelle en raison de l’important rôle qu’ils assument à l’échelle des Petites Antilles vis-à-vis de la nidification de 5 espèces d’oiseaux marins. Le caractère important des perturbations occasionnées par le Rat noir (Rattus rattus) sur ces populations aviennes a conduit le Parc Régional de la Martinique, gestionnaire de la réserve naturelle, à tenter l’éradication du rongeur allochtone. Un état initial, première phase de l’opération, a débuté dès 1997 sur le seul îlet Hardy par l’évaluation du succès de reproduction du Puffin d’ Audubon (Puffinus lherminieri), du Noddi brun (Anous stolidus), de la Sterne bridée (Sterna anaethetus) et du Phaéton à bec rouge (Phaethon aethereus), et s’est poursuivi en 2001-02 par l’inventaire semi-quantifié de l’herpétofaune et de la carcinofaune terrestre. Le résultat de l’opération d’éradication, conduite en novembre 1999 et fondée sur l’usage successif du piégeage non vulnérant et de la lutte chimique, a été contrôlé en janvier 2001 et en janvier 2002. Ces contrôles permettent de conclure que seule l’éradication de la population de rongeurs de l’îlet Percé est acquise. La population de l’îlet Hardy a été réduite à 3 et 28 % de son effectif initial en 2001 et 2002 respectivement. Cette réduction d’effectif a généré un accroissement du succès reproducteur du Puffin d’Audubon et du Noddi brun, le faisant passer de respectivement 0 et 5 % en 1999, à 61 et 90 % en 2000 et à 63 et 85 % en 2001. Par ailleurs l’indice d’abondance du Crabe zombi (Gecarcinus ruricola) s’est accru de 0,85 à 1,36 captures pour 100 nuits-pièges entre 1999 et 2002. La relation de cause à effet entre cet accroissement de l’indice d’abondance et la réduction d’effectif de la population de Rats noirs ne sera rigoureusement établie qu’à l’issue d’un suivi prolongé sur plusieurs années. La cause probable de l’échec de l’éradication des populations de Rats noirs de 3 des îlots traités est attribuée à l’inadéquation de l’appât toxique employé. La dernière tentative d’éradication mise en place en janvier 2002 pallie cette cause probable d’échec. Son résultat devra être établi en janvier 2003. C’est à une veille systématique des gardes et des scientifiques travaillant sur la réserve naturelle que l’on doit le diagnostic précoce de son envahissement par le Rat noir et la prise de décision rapide de son éradication selon une stratégie permettant d’en évaluer, a posteriori , l’efficacité et l’intérêt au plan de la biologie de la conservation. Déterminer l’impact d’une espèce allochtone sur le fonctionnement de son écosystème d’accueil nécessite de disposer d’inventaires systématiques détaillés, quantifiés ou semi-quantifiés, et régulièrement mis à jour, activité qui devrait s’inscrire dans la mission d’observatoire du vivant conférée par le Ministère de l’Environnement aux espaces protégés.
L’éradication simultanée de la Petite Mangouste indienne (Herpestes javanicus auropunctatus), du Rat noir (Rattus rattus) et de la Souris domestique (Mus musculus) a été tentée en mars 2001 sur l’îlet Fajou (104 ha de mangrove sur tourbe, 11 ha de formation végétale xérophile sur sol sableux), partie d’une réserve naturelle gérée par le Parc National de la Guadeloupe (Antilles françaises). Elle a fait appel à l’utilisation successive du piégeage et de la lutte chimique. Un contrôle réalisé en décembre 2001 et janvier 2002 a démontré l’échec de l’éradication du Rat noir. Une seconde opération d’éradication a été conduite en mars 2002. Elle a permis de tester diverses hypothèses destinées à expliquer l’échec de l’élimination du Rat noir lors de la première tentative et de pallier certaines imperfections techniques. Le résultat de cette seconde tentative devra être établi en 2003. Elle a permis de conclure au succès de la tentative d’éradication de la Mangouste par le seul piégeage. L’éventuel succès de l’élimination de la Souris domestique par l’action cumulée du piégeage et de la lutte chimique dès mars 2001, ne sera contrôlé qu’en 2003. L’analyse de la répartition spatiale des captures des espèces-cibles a permis de démontrer qu’elles fréquentaient préférentiellement la partie de l’île couverte de végétation xérophile. L’élimination de la Mangouste et la forte réduction de l’effectif du Rat noir sont directement corrélées à la totale cessation des destructions de nids de la Tortue imbriquée (Eretmochelys imbricata) et à une apparente colonisation de la partie sèche de l’île par le Râle gris (Rallus longirostris), cantonné auparavant à la seule mangrove. Les indices d’abondance du Râle gris et du Crabe blanc (Cardisoma guanhumi) ont augmenté à Tissue de cette opération. Seul un suivi à long terme permettra de conforter ou d’invalider la présomption de relation de cause à effet entre l’augmentation de ces indices et l’élimination des populations allochtones. De pareilles opérations de recherche et de gestion imposent un travail sur le long terme ainsi que la mobilisation de moyens techniques importants et d’un personnel qualifié. Ces conditions ont été réunies lors de la présente opération grâce au statut d’aire protégée dont bénéficie l’îlet Fajou.
We describe a model-based clustering method for using multilocus genotype data to infer population structure and assign individuals to populations. We assume a model in which there are K populations (where K may be unknown), each of which is characterized by a set of allele frequencies at each locus. Individuals in the sample are assigned (probabilistically) to populations, or jointly to two or more populations if their genotypes indicate that they are admixed. Our model does not assume a particular mutation process, and it can be applied to most of the commonly used genetic markers, provided that they are not closely linked. Applications of our method include demonstrating the presence of population structure, assigning individuals to populations, studying hybrid zones, and identifying migrants and admixed individuals. We show that the method can produce highly accurate assignments using modest numbers of loci—e.g., seven microsatellite loci in an example using genotype data from an endangered bird species. The software used for this article is available from http://www.stats.ox.ac.uk/~pritch/home.html.
In March 2001, simultaneously by trapping and chemical baits an attempt was done to eradicate the Javanese Mongoose (Herpestes javanicus), the Ship Rat (Rattus rattus) and the House Mouse (Mus domesticus) from Fajou Island (104 ha of mangrove on peat, 11 ha of dry vegetation on sandy soil), part of a natural reserve managed by the Guadeloupe National Park (French West Indies). A control in December 2001 and January 2002 revealed the failure of the Ship Rat eradication. A second eradication operation was undertaken in March 2002 in order to test hypotheses explaining this failure and put right some technical defects. Its result will not be available before 2003. However it allowed to conclude to the success of the Mongoose eradication by trapping alone but the potential success of the House Mouse eradication by trapping and poisoning in March 2001 could not yet be properly evaluated. The spatial distribution of trapping specimens of the target species showed that statistically they concentrate on the dry part of the island. The Mongoose eradication and the sharp decline of the Ship Rat population induced the disappearance of the destruction of Hawksbill Turtle (Eretmochelys imbricata) nests and the colonization of the dry part of the island by the Clapper Rail (Rallus longirostris), strictly located in the mangrove before. The abundance indices of the Clapper Rail and the terrestrial crab Cardisoma guanhumi increased. To be tested, the eventual relationships between these increases and the drop of the alien mammal populations require more data. Such operations combining research and management have to be planned in the long term with good logistical, technical and qualified human supports. All these conditions were gathered here because of the protected area status of the Fajou Island.
During the last five centuries, along with the reduction of biogeographic barriers, a great number of alien species were introduced by men, intentionally or not, in nearly all ecosystems throughout the world. Most of these introductions failed and a majority of the others didn't raise any problem. But some of them led to major economic losses and/or biological diversity reduction. The insular vegetal and animal communities are little diversified, often disharmonic, and characterized by an important rate of endemic species when compared with those of continental ecosystems. These communities are therefore particularly vulnerable to alien species. For these reasons and because of the small size of islands which allows experimental studies, most operations of eradication took place in this type of ecosystems since the 1960s, mammal species being the main target. This paper offers an approach to improve the decision and the technical implementation in view of the eradication of alien mammals on islands. These recommendations are founded on the experiences of brown rat eradication from ten Brittany Islands (1994-1996) and those of rabbit eradication from three islands of the Kerguelen Archipelago (1992-1999).
A new method called the neighbor-joining method is proposed for reconstructing phylogenetic trees from evolutionary distance data. The principle of this method is to find pairs of operational taxonomic units (OTUs [= neighbors]) that minimize the total branch length at each stage of clustering of OTUs starting with a starlike tree. The branch lengths as well as the topology of a parsimonious tree can quickly be obtained by using this method. Using computer simulation, we studied the efficiency of this method in obtaining the correct unrooted tree in comparison with that of five other tree-making methods: the unweighted pair group method of analysis, Farris's method, Sattath and Tversky's method, Li's method, and Tateno et al.'s modified Farris method. The new, neighbor-joining method and Sattath and Tversky's method are shown to be generally better than the other methods.
Since 1995, the 4 Sainte-Anne Islets were under the protected status of Natural Reserve because of the major role they play for the nesting of 2 marine bird species at the scale of the Lesser Antilles and 3 more at the scale of the Martinique Island (French West Indies). The Ship Rat (Rattus rattus) invaded these islets may be as recently as 1996 or 1997. In November 1999, an attempt to eradicate this alien species by successive trapping and poisoning was conducted by the Martinique Regional Natural Park who is in charge of the management of the natural reserve. To evaluate the impact of the management of the Ship Rat populations, breeding data for Audubon's Shearwater (Puffinus lherminieri), Brown Noddy (Anous stolidus), Bridled Tern (Sterna anaethetus), and Red-billed Tropicbird (Phaethon aethereus), were collected since 1997 solely on the Hardy Islet. A semi-quantified inventory of the herpetofauna and terrestrial carcinofauna began in 2001-02 on the same island. Controls of the eradication operation were done in January 2001 and 2002. Only the eradication of the Percé Islet Ship Rat population was verified. In 2001 and 2002, the Hardy Islet Ship Rat population size was respectively 3 and 28 % of the initial one. The decrease of the Hardy Islet Ship Rat population induced an increase of the breeding success of Audubon's Shearwater and Brown Noddy from respectively 0 and 5 % in 1999, before the eradication attempt, to 61 and 90 % in 2000 and to 63 and 85 % in 2001, after the eradication attempt. Between 1999 and 2002 the number of the terrestrial crab Gecarcinus ruricola increased from 0.85 to 1.36 for 100 traps-nights. The relationship between the increase of trapped crabs and the drop of the Ship Rat size population remains to be rigorously established by further data. The failure of the eradication of 3 island Ship Rat populations among 4 was attributed to a bad efficiency of toxic bait. A new eradication campaign took place in January 2002. Its results will not be available until 2003. The very recent diagnostic of the Ship Rat invasion and the quick decision to attempt to eradicate the rodent were the result of a peer systematic survey of these islands by scientists and wildlife rangers. Up to date quantified or half-quantified inventories of fauna and flora have to be done before eradication in order to evaluate its impact. The build-up of such inventories is clearly pointed as one of the main missions devoted to the protected areas by the French Ministry of Environment.
Herein 6 criteria are suggested for deciding if eradication is technically possible and preferable to continuing control for managing vertebrate pests. The authors assess 3 case studies against the criteria. -from Authors
In order to protect the endemic ecosystem of Raoul Island (2943 ha), a programme to eradicate alien plants commenced in 1972. Almost 30 years on it is possible that seven species have been eradicated, none of which was widespread but some of which were difficult to control. There are another 22 species on the eradication list, most of which are barely present. Seven species represent the greatest threat at present and also are the most difficult to control. These are Senna septemtrionalis, Caesalpinia decapetala, Anredera cordifolia, Psidium cattleianum, P. guajava, Olea europaea subsp. cuspidata, and Passiflora edulis. Difficulties of the programme include the rugged terrain, resistance of some species to herbicide, cryptic species, and long-lived seedbank of some species. Each year an area equivalent to one quarter of Raoul Island is grid-searched twice; this is the area where alien plants are known to be present. The remainder of the island is checked during the recreational time of staff and volunteers and occasionally by air. The alien plant eradication programme has been successful to date but still has many years to run. Changes in abundance or distribution of some alien plant species are expected as a result of the planned rat eradication in 2002 and, in anticipa-tion of the changes, a number of species have been eradicated. Maintaining search efficiency and staff morale at low alien plant densities and determining the end point of the programme will be a challenge.
Gypsy moth DNA segments containing polymorphic dinucleotide repeats were sought for future studies regarding paternity and sperm precedence. Three microsatellite DNA loci were amplified by three sets of primers. These loci were sufficiently polymorphic to be used for paternity tests. The allele types observed were different among the three local populations.
Using a unique data set on eradication attempts by the California Department of Food and Agriculture on 18 species and 53 separate infestations targeted for eradication in the period 1972-2000, we show that professional eradi-cation of exotic weed infestations smaller than one hectare is usually possible. In addition, about 1/3 of infestations between 1 ha and 100 ha and 1/4 of infestations between 101 and 1000 ha have been eradicated. However, costs of eradication projects increase dramatically. With a realistic amount of resources, it is very unlikely that infestations larger than 1000 ha can be eradicated. Early detection of the presence of an invasive taxon can make the difference between being able to employ offensive strategies (eradication), and the necessity of retreating to a defensive strategy that usually means an infinite financial commitment. Nevertheless, depending on the potential impact of individual weedy species, even infestations larger than 1000 hectares should be targeted for eradication effort or, at least, substantial reduction and containment. If an exotic weed is already widespread, then species-specific biological control may be the only long-term effective method able to suppress its abundance over large areas.
The Chinese mitten crab, Eriocheir sinensis is an important human food source in Asia and causes considerable ecological and economical damage as a recent invader of North America and Europe. Here we report the isolation and characterization of 12 highly polymorphic microsatellite loci for E. sinensis. The number of observed alleles per locus ranged from 7 to 40 and the observed heterozygosity from 0.50 to 0.95. These markers should prove a useful tool to investigate the colonization process and its evolutionary implications.
We document the isolation and characterization of 27 microsatellite DNA markers for nutria, or coypu (Myocastor coypus), an invasive rodent introduced to North America as a domestic furbearer. Markers revealed moderate levels of diversity (averaging 5.0 alleles/locus) and heterozygosity (averaging 46%). Genotypic frequencies at 25 of 27 (93%) markers conformed to Hardy–Weinberg equilibrium expectations and no linkage disequilibrium was observed in a M. coypus collection (N = 64) from Maryland, USA. We believe this suite of markers to yield sufficient diversity to resolve patterns of effective migration among subpopulations, breeding structure, and demographics. This information can be instrumental to eradication programs that attempt to prevent recolonization among subpopulations.
The geographical range of the red squirrel ( Sciurus vulgaris ) in Britain has decreased substantially since the introduction of the American grey squirrel ( S. carolinensis ). We have developed 21 novel, polymorphic microsatellite markers for S. vulgaris to enable analysis of population genetic structure in this species. All 21 markers amplify well, and are generally polymorphic in S. carolinensis , allowing a comparison of population structure of both the introduced and native squirrel species.
Keywords:Linepithema humile;microsatellites;population structure;social insects
Microsatellite-enriched genomic libraries were obtained from the whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) using a magnetic/biotin capture of repetitive sequences. Ten dinucleotide markers were successfully isolated and characterized from these libraries. Variability was assessed in six populations of B. tabaci collected from different localities of the island of Crete, Greece. The number of alleles per locus in approximately 105 individuals screened across populations ranged from two to 13. Averaged observed heterozygosity over the six populations ranged from 0.001 to 0.58.
Here we describe 32 di-, tri- and tetranucleotide microsatellite loci isolated by PIMA, a polymerase chain reaction (PCR)-based procedure, for the common snook (Centropomus undecimalis). Five loci were monomorphic, and the remaining loci averaged 6.7 alleles per locus in a sample of 45 common snook. For polymorphic loci, expected heterozygosities ranged from 0.02 to 0.91 (mean = 0.538). Significant departures from Hardy–Weinberg equilibrium expectations occurred in two loci. Exact tests for genotype disequilibrium gave evidence for linkage at one pair of loci. Many cross-species primer assays yielded PCR fragments of the expected size for 11 species of Centropomus and two species of the confamilial genus Lates.
The Aedes scutellaris complex of mosquitoes contains the most important vectors of lymphatic filariasis in the South Pacific region, particularly Aedes polynesiensis. Six microsatellite loci were isolated and characterized from this species; all were polymorphic and appear to be useful markers for population studies. Five of the primer pairs also amplified homologous products from three other species in the A. scutellaris group and from the important dengue vector Aedes albopictus.
In molecular ecology the analysis of large microsatellite data sets is becoming increasingly popular. Here we introduce a new software tool, which is specifically designed to facilitate the analysis of large microsatellite data sets. All common microsatellite summary statistics and distances can be calculated. Furthermore, the microsatellite analyser (msa) software offers an improved method to deal with inbred samples (such as Drosophila isofemale lines). Executables are available for Windows and Macintosh computers.
Comparing available paleontological, archaeological, historical, and former distributional data with cur-rent natural history and distributions demonstrated a turnover in the French vertebrate fauna during the Holocene (subdivided into seven sub-periods). To this end, a network of 53 specialists gleaned infor-mation from more than 1300 documents, the majority never cited before in the academic literature. The designation of 699 species as native, vanished, or non-indigenous in France or in one or more of its bio-geographical entities during the Holocene period was investigated. Among these 699 species, 585 were found to belong to one or more of these categories. Among the 154 species that fit the definition of non-indigenous, 86 species were new species for France during the Holocene. Fifty-one that were autochthonous vanished from France during this period. Among these 51 species, 10 (two birds and eight mammals) are now globally extinct. During the last 11 millennia, the turnover in the French verte-brate fauna yielded a net gain of 35 species. On a taxon-by-taxon basis, there was a gain in the sizes of the ichthyofauna (19 : 27%), the avifauna (10 : 3%) and the herpetofauna (7 : 9%) and a loss in the mammalian fauna ()1 : 1%). Values of a per-century invasion index were less than 1 between 9200 BC and 1600 AD but increased dramatically after this date. An exponential model fits the trajectory of this index well, reaching the value of 132 invasions per century for the last sub-period, which encompasses 1945–2002. Currently, the local ecological and economic impacts of populations of 116 species (75% of the 154 that satisfied the criteria for non-indigenous) are undocumented, and the non-indigenous popula-tions of 107 vertebrate species (69%) are unmanaged. The delay in assessing the ecological and economi-cal impact of non-indigenous species, which is related to a lack of interest of French academic scientists in the Science and Action programmes, prevents the public from becoming informed and hinders the debates needed to construct a global strategy. For such a strategy to be effective, it will have to be elab-orated at a more global scale than in just France – definitely at least in Europe.
Understanding the spatial structure of populations is important in developing effective management strategies for feral and invasive species, such as feral pigs Sus scrofa . World‐wide, feral pigs can act as ‘triple threat’ pests, impacting upon biodiversity, agricultural production and public health; in Australia they are a significant vertebrate pest. We utilized a molecular approach to investigate the structure of populations of feral pigs in south‐western Australia. These approaches have been underutilized in pest management.
Using 14 highly polymorphic microsatellite markers from 276 adult pigs, we identified eight inferred ( K = 8) pig populations that would be difficult to define with standard ecological techniques. All populations had moderate heterozygosity ( H E = 0·680) and moderate to high levels of differentiation ( F ST = 0·118; R ST = 0·132) between populations.
The molecular approach identified feral pig groups that appeared to be acting as a source for reinvasion following control operations. It also identified populations where current control measures were less successful in reducing ‘effective population size’. Additionally, the data indicated that dispersal rates between, but not within, the inferred feral pig populations were relatively low.
The potential for the spread of directly transmitted wildlife diseases between the pig populations studied was low. However, under some circumstances, such as within major river catchments, the role of feral pigs in the transmission of endemic or exotic diseases is likely to be high.
Synthesis and applications. A molecular‐based approach allowed us to determine the genetic structure and dispersal patterns of a cryptic, destructive and invasive vertebrate pest. Our results indicated that the feral pig populations studied were unlikely to be acting as closed populations and, importantly, it identified where movement between groups was likely to occur. This should lead to more informed decisions for managing the potential risk posed by feral species, such as pigs, in the transmission of wildlife diseases. The suggested technique could help in understanding the dynamics of many other free‐ranging pest animal populations.