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Biological invasions and the conservation of biodiversity
Abstract
Consideration of definitions of 'biological invasion' and 'biodiversity' shows why invasions have recently generated great interest among conservationists. Many studies show that invasion numbers have increased drastically over the last five centuries, that this exponential increase is not levelling off, and that human activities are the only reason for the phenomenon. Many mechanisms are portrayed in an evolutionary framework and their consequences for biodiversity are described at three levels of life--gene, species and ecosystem. Examples from islands show that insular ecosystems are especially prone to damage from invasions; they also serve as 'laboratories' to elucidate the nature of invasion impacts. An important management approach--eradication--is discussed. Eradicating invaders not only aids understanding of their impacts on native species but also in understanding how ecosystems function. In fact, biological invasions can be seen as 'experiments', providing a rare opportunity to help answer certain fundamental scientific questions.
... Invasive species are one of the main drivers of biodiversity loss (Courchamp et al. 2003, Pascal et al. 2010, especially in isolated ecosystems, such as islands, that have high levels of endemism (Blackburn et al. 2004). Introduced mammals, in particular, have had wide-ranging detrimental impacts on native species and human economies, and their eradication is a global conservation focus (Pitt and Witmer 2006). ...
... Il arrive que certaines de ces espèces colonisent rapidement le milieu et se maintiennent durablement dans celuici, changeant ainsi la composition des milieux pouvant engendrer un appauvrissement spécifique. On dit alors que ces espèces sont envahissantes (Pascal, et al., 2010). Ce phénomène s'est accentué depuis la révolution industrielle et l'augmentation des échanges commerciaux à l'échelle planétaire. ...
Titre : La compensation écologique : du principe de non perte nette de biodiversité à son opérationnalisation – analyse de l’action collectiveMots clés : Compensation écologique, action collective, effets spatio-temporels, Non perte nette de biodiversité.Résumé : En France la compensation écologique des impacts résiduels sur la biodiversité a pour objectif l'atteinte de la non perte nette de biodiversité. Un cadre normatif énonçant une dizaine de principes permet théoriquement d'atteindre cet objectif.Nous étudions donc la mise en œuvre de la compensation écologique à travers trois projets de LGV. Nous analysons le jeu d'acteur autour de cette mise en œuvre grâce aux théories de l'action collective, et notamment grâce au cadre analytique de la Traduction proposé par M. Callon. Cette première analyse nous permet de comprendre en quoi la compensation est un objet socio-technique. Nous mettons en évidence que de nombreux acteurs aux intérêts divergents se mobilisent pour mettre en place la compensation écologique. Nous montrons qu’il y a une tension entre la mobilisation des acteurs et les exigences écologiques, ces deux aspects ne sont pas toujours compatibles. La durée des cahiers de charges et la rétribution des propriétaires fonciers, chargés de la mise en œuvre de la compensation écologique est déterminante à la fois pour la mobilisation des humains et des nons humains (biodiversité). Nous nous interrogeons ensuite sur les effets spatiaux temporels de l’action collective et de sa capacité à tendre vers une non perte nette de biodiversité. Nous montrons que les mesures n’ont pas pu être effectives avant le démarrage des impacts. La gestion du foncier en France semble pour le moment difficilement compatible avec une mise en œuvre de la compensation non anticipée très en amont. Nous montrons que la majorité des sites de mesures de compensation sont de petites tailles, bien que des espaces de grandes tailles semblent davantage vertueux d’un point de vue écologique. Enfin nous montrons que la pérennité des mesures de compensations peut être appréhendée à différents niveaux suivant (i) le type de maîtrise foncière (acquisition, conventionnement); (ii) les contrats de mesures de compensation (durée, contenu de ces derniers – les sanctions en cas de manquement aux obligations influent sur le maintien des mesures) ; (iii) la gestion du renouvellement de ces contrats; (iv) la vocation des propriétaires des sites (une entreprises publique ou privée de construction n’a pas comme rôle au départ de conserver la biodiversité, tandis qu’une association naturaliste en a la vocation) ; (v) la pérennité des structures et les assurances quant au devenir des sites de mesures de compensation en cas de faillite; (vi) le suivi et le contrôle l’application de la compensation.
... Evolutionary origins and potential of invasive populations are open research problems at the intersection of evolutionary biology, genetics, ecology, and conservation (Lee and Gelembiuk 2008;Pascal et al. 2010;Handley et al. 2011;Bock et al. 2015). Being considered as 'natural experiments' that can improve our understanding of contemporary evolution (Colautti and Lau 2015), biological invasions provide evidence for rapid evolutionary change during relatively short periods of time (a review in Whitney and Gabler 2008), although evidence for evolutionary stasis is rather scarce (Miehls et al. 2015). ...
The sibling vole, Microtus rossiaemeridionalis, is a North Eurasian rodent that undergoes range expansion via casual introductions by humans. The documented cases of human-mediated spread of M. rossiaemeridionalis provide an opportunity to explore phenotypic consequences associated with the invasion events. We present an analysis of dental variability in two recently discovered invasive populations of M. rossiaemeridionalis in northern Asia (Surgut and Khabarovsk) and summarize the data on conspecifics within and outside the core range in order to uncover common and specific patterns of dental variation in the disjunctive invasive populations, and to consider the potential evolutionary significance of the phenotypic effects from neontological and paleontological standpoints. The analysis of morphotype dental patterns and inspection for rare traits suggest that the existence of invasive populations under conditions of isolation leads to a release of hidden phenotypic variation, which could be inferred from sharp increases in frequencies of reserve morphotypes and/or rare dental traits, and also from the presence of abnormalities. An atavistic anomaly of the third upper molars revealed in one individual in a fragmented habitat in Surgut recapitulates some features of the prismatic arrangement and occlusal pattern of extinct Mimomys-like arvicolines. All variants of released phenotypic variation in the invasive populations of M. rossiaemeridionalis under conditions of isolation could be interpreted as de-specialization of dentition. Such de-specialization appears to be maladaptive for a herbivore, though it might favor a transition to a more generalized diet and enhance the success during the transport, colonization, and establishment stages of the invasion.
... Invasive species are a main driver of global biodiversity loss (Courchamp et al. 2003;Hoffman et al. 2010;Pascal et al. 2010), and have been recognised as the biggest threat to biodiversity in the Pacific (Secretariat of the Convention on Biological Diversity 2010). Invasive species have particularly severe impacts on biodiversity in island ecosystems where there is high endemism (Blackburn et al. 2004). ...
Invasive species have been identified by the Convention on Biological Diversity as a significant threat to biodiversity. Conservation managers often lack tools for addressing uncertainty about the control intensity required to achieve cost-effective management of invasive species. We describe a modelling approach for informing the spacing of control-device lines given the availability of home-range data. To demonstrate its utility, we used data on stoats (Mustela erminea), an introduced mammalian predator responsible for the decline of endemic birds in New Zealand. We calculated home-range widths using three methods: kernels, circles and the narrowest distance across the raw point data. Using the widths from each method, we then permuted iteratively the relative location and orientation of home ranges between control-device lines, and calculated the probability of encounter with varying distances between lines. Widths across raw points gave lower estimates of the probability of encounter of device lines than kernels, while circles gave estimates that were intermediate between the two. For stoats, the simulation on point-data widths indicates that to ensure control-device lines will intersect 100% of female stoat home ranges they need to be <= 400 m apart, while the simulation on kernels and circles allowed <= 700 m. When needing to address uncertainty about the intensity of control to apply, managers should give priority to the collection of home-range data so that control-line spacing can be determined using the simulation described. If sufficient home-range data are available then simulating kernels provides better predictions, otherwise simulating the width across point data provides a conservative option when such data are insufficient.
... Researchers have often focused on the impacts of invasive species, including earthworms, on endangered and rare species (e.g., Coblentz 1990;Bohlen et al. 2004;Byers et al. 2010). However, an examination of the interactions of an invasive species with more common organisms can make experimental tests of ecological and evolutionary hypotheses regarding responses of native organisms to invasive species more logistically feasible (Pascal et al. 2010;Shine 2010). The red-backed salamander, Plethodon cinereus, is native to North America and is one of the most abundant vertebrates in eastern forests (Mitchell et al. 1997;Davic and Welsh 2004). ...
Invasive species may positively affect native organisms by providing habitat, serving as prey, or acting as an ecological substitute for a beneficial native species. I examined whether the behavioral responses to invasive earthworms of Plethodon cinereus, a woodland salamander native to eastern North America, were influenced by co-occurrence with native earthworms. Co-occurrence with native earthworms varies throughout North America because earthworms were extirpated from the northern portion of the continent during the Wisconsin Glacial Episode. Non-native earthworms have invaded most of North America, including once-glaciated areas. I compared responses to earthworms by P. cinereus from (1) historically glaciated areas with no co-occurrence (for ~7 ky) with native or invasive earthworms, (2) historically glaciated areas with recent co-occurrence (~10 years) with invasive earthworms, but no historical co-occurrence (for ~7 ky) with native earthworms, or (3) unglaciated areas with recent and historical co-occurrence with invasive and native earthworms. Salamanders from different areas did not differentiate between native (Eisenoides carolinensis or Diplocardia sp.) and invasive earthworms (Lumbricus terrestris) as prey or differentiate between their burrows. Salamander burrow use and time to first burrow use were influenced by recent or historical co-occurrence with earthworms, respectively. Salamanders with historical range overlap with native earthworms had shorter latencies to attack and handling times, and were more likely to consume earthworms. As globalization increases the frequency and impact of invasive species in native systems, we should consider the multiple ways in which invasive species interact with native communities and potential geographic variation in the responses of native organisms to invasives.
... The worldwide introduction and spread of invasive alien species (IAS) have led to important ecological consequences and are considered to be one of the major threats to biodiversity and ecosystem functioning (MA, 2005;Pascal et al., 2010). IAS have economic, environmental, social and health impacts, but often interest is limited to the economic and health impacts of IAS, while less attention is attributed to their environmental impacts (Parker et al., 1999). ...
Halyomorpha halys (Stål, 1855) (Hemiptera: Pentatomidae), the brown marmorated stink bug (BMSB), is an alien invasive pest that originated from South Asia (China, Japan, Taiwan, Korea) (Hoebeke and Carter 2003). Many studies have shown that the number of invasions by pests has increased significantly in the last 5 centuries and the reason for this situation is directly related to human activities. (Pascal, Le Guyader et al. 2010). Halyomorpha halys is considered to be a dangerous pest insect species due to economic losses in agricultural areas of the countries where it is distributed. It has been observed that the pest can have 1–2 generations per year (Rice, Bergh et al. 2014) and each egg mass contains of an average of 26 eggs and, furthermore, causes significant losses in many crops such as bean, hazelnut and pear. This study was conducted between July and August in 6 different areas and a total of 18 egg masses that were thought parasitized were collected from BMSB infested fields and kept in tubes to determine if they had parasitoids. Emerged parasitoids were fed with the honey solution and bred in tubes. The specimens were identified as Anastatus bifasciatus morphologically, however, they were sent for molecular identification to the USA, and the molecular test confirmed the identification. In this study, Anastatus bifasciatus was reported as the first parasitoid recorded on Halyomorpha halys in Turkiye.
Amaçlar
(i) İstilacı yabancı bitkiler konusunda temel kavramlar ve bu bitkilerin etkileri (Ör.; insan sağlığı, ekonomik kayıp vb.) konularında Türkiye’de sınırlı olan Türkçe kaynaklara bir katkı sunarak ilgili konuda çalışan, eğitim alan veya ilgilenen tüm paydaşların yararlanabileceği bir kaynak oluşturmak, (ii) İstilacı yabancı bitkilerin yayılımında antropojenik faktörler konusunda farkındalıkları arttırmak, (iii) İstilacı yabancı bitkilerin yönetimine yönelik ulusal çapta alınabilecek tedbirlerin ve kontrol müdahalelerinin planlanmasına katkı sağlamaktır.
Kapsam
(i) İstila kapsamındaki kavramların kullanımı konusunda öneriler, ilgili konuda rehberlik eden bazı literatürlerden (Ör.; Richardson ve ark., 2000, Pyšek ve ark., 2004) faydalanılarak sunulmuştur. (ii) yabancı bitki türlerinin yeni alanlara tanıtımı / giriş yolları ve bitki istilaları ile ilgili mekanizmalar konusu tartışılmıştır. (iii) Yabancı bitki taksonlarından kaynaklanabilecek etkiler çevresel ve sosyo-ekonomik boyutları ile ele alınmış ve istilacı yabancı bitkiler ile bu bitkilerin etkilerini önlemeye yönelik alınabilecek önlemler konusunda bazı temel öneriler paylaşılmıştır.
Purposes
(i) To create a resource that can be used by all stakeholders who work, receive training or are interested in the subject by contributing to the limited Turkish resources in Turkey on the basic concepts of invasive alien plants and their impacts (e.g. human health, economic loss, etc.).
(ii) To raise awareness of anthropogenic factors in the spread of invasive alien plants.
(iii) To contribute to the planning of national measures and control interventions for the management of invasive alien plants.
Scope
(i) Suggestions on the use of concepts within the scope of invasion were presented by making use of some guiding literature (e.g. Richardson et al., 2000, Pyšek et al., 2004).
(ii) The introduction of alien plant species into new areas/entry routes and mechanisms for plant invasion was discussed.
(iii) The impacts that may arise from alien plant taxa were discussed with their environmental and socio-economic dimensions, and some basic recommendations were shared about invasive alien plants and the measures that can be taken to prevent the impacts of these plants.
Five major interacting global forces heavily influence changed-distribution and abundance of biodiversity: (1) biological invasions, (2) overharvest, (3) changes in climate, (4) biogeochemical cycles, and (5) habitat. Modified land use, overharvest, and climate change have already affected distributions over large areas, regionally eliminating or substantially reducing natural resources such as fishing stocks, forestry trees, and traditional food plants. Further, habitat and climate change indirectly affect biodiversity patterns by their effects on invasions, biogeochemical cycles, and overharvest. Species-level biodiversity-the number of species on the planet-is unsustainable unless these impacts are ameliorated. Insufficient attention has been paid to how invasions and changed biogeochemical cycles directly affect distribution and abundance of biodiversity, as opposed to indirectly affecting biodiversity by modifying land use. Several direct, large-scale impacts of invasions and altered biogeochemical cycles on distributions and abundances of important species have been documented. These suggest that these global phenomena warrant much more research. Forestalling these global changes, or simply retarding them, has proven difficult, perhaps because of the immense scale of the enterprises causing them. However, great improvements in preventing or minimizing impacts of invasions are attainable, though we have been slow to develop effective policies and management strategies. Risk assessment procedures for planned introductions and invasion pathways are improving and can be modified to account for predicted climate and biogeochemical changes. Early warning systems, an underused tool in invasive species management, can be expanded and tied to effective rapid response procedures. Many approaches to managing established nonnative populations have produced successful control, but these successes result from projects highly tailored to particular species rather than from silver bullets that target multiple invaders simultaneously. Such successes will be possible even as other global changes proceed, so long as we remain committed to the effort. © 2012 Springer Science+Business Media, LLC. All rights reserved.
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.
Freshwaters are among the most vulnerable ecosystems regarding biological invasions. Reservoirs built after the last half century in São Paulo State have been continuously subjected to the introduction and establishment of alien species, both exotic and allochtonous. Here we present a short historical and the present status of some recent, still going on, biological invasion processes, for both, invertebrate and vertebrates, with emphasis on Tietê River basin. Among reservoir communities, the zooplankton has the lowest number of established exotic species, with 4 species: the cladocerans Ceriodaphnia dubia and Daphnia lumnholtzi, the cyclopoid copepod Mesocyclops ogunnus and the rotifer Kellikotia bostoniensis. Among the macroinvertebrate communities there is a fast ongoing invasion by three exotic species of mollusks, the Asian clam, Corbicula fluminea, the African-Asian gastropod, Melanoides tuberculata, and the golden mussel, Limnoperna fortunei, this latter a cause of greatest concern. However by far the community most affected by introduction of alien species is the ichthyofauna. In reservoirs of Tietê, Paranapanema and Rio Grande rivers, the main tributaries of the Upper Parana basin, the relative proportion of alien species vary approximately between 10 and 25% of the total number of species. Most introductions were derived from anthropic activities, either from direct local introduction, the so called peixamento or by accidental escape from nearby fish farming installations. Some species have profound effects on the structure of the fish community, as recently happened in Lobo (Broa) reservoir after the introduction of the Cichla kelberi. The African Sarotherodon niloticus and Tilapia rendalli and the allochtonous Plagioscion squamosissimus became the dominant species in many São Paulo state reservoirs. The complex interaction between biological invasions, water pollution and eutrophication, is the possible cause for many native species extinction going on in São Paulo State rivers and cascade of reservoirs. At short time and local scale, management actions are urgently required to eradicate or minimize the impact of exotic species in the reservoirs, especially in the small ones, and at longer time and larger scales, education and law enforcement are essential tools for both prevention of new introductions and management to the already existing problems.
It would be an exaggeration to argue that most invasions produce ecosystem impacts, and the term should be reserved for cases
in which many species in an ecosystem are affected. However, certain facts suggest that true ecosystem impacts are more common
than is normally assumed. First, the term “ecosystem impact” has often been reserved for cases in which the nutrient regime
or nutrient cycling is affected, whereas physical structural and other changes in ecosystems ought to be included. Second,
as with all ecology, very few systems and species have been studied relative to all those that exist, so it is likely that
many ecosystem impacts remain to be detected. Third, there are many types of impacts, many are idiosyncratic, many are subtle,
and many are indirect, so it is likely that many impacts have simply not been recognized even in studied systems. Finally,
the frequency of the lag phenomenon in invasions implies that at least some existing non-native species that are currently
having little or no impact will eventually have much greater ones. These facts suggest that, even if it would be an overstatement
to say that most invasions cause ecosystem impacts, it would not be more of an overstatement than the common assertion that
very few introduced species have any significant impact.
KeywordsFire regime–Habitat structure–Invasional meltdown–Lag time–Nutrient cycling
The Norwegian Rat (Rattus norvegicus) invaded the Trielen Island (Iroise Natural Reserve, Brittany, France) during the beginning of the XXth century and was eradicated in 1996. Breeding pairs of all terrestrial bird species were censused annually, from 1996 before the eradication operation to 2001. None of the 7 occasional breeding species (two being a priori exposed to Norwegian Rat predation) established as a regular breeder after the eradication operation. On the other hand, numbers of breeding pairs increased by a factor of 1.7 to 2.0 for the Dunnock (Prunella modularis), 2.2 to 2.7 for the Wren (Troglodytes troglodytes), and 5.5 to 7.0 for the Rock Pipit (Anthus petrosus). Many biological facts converged to identify the rodent disappearance as the major driving factor of these increases. This Norwegian Rat eradication was particularly pertinent as a biological conservation operation, because of its positive effect on the local Rock Pipit (Anthus petrosus) population as the French coast hosts near 50 % of the subspecies petrosus world population. The 2001 Trielen Island abundance index (26 to 46 breeding pairs per coastal km) was among the highest known ones for that species. The large and quick increase following the disappearance of the Norwegian Rat showed the high sensibility of the Rock Pipit to mammalian predation.
Since the beginning of the 70's, some engineers and nature conservationists have increased the experiments of ecosystems rehabilitation and creation to limit the disastrous effects of human activities characterized by a high ecological impact.
In its infancy, the scientists have neglected this field judged too "technical". The reversal of situation dates of the 80's with the emergence of a new disciplinary trend called the restoration ecology, that is conceived as a mean to connect the applied and basic scope of ecology. Then the experimental nature of these programs was emphasized.
Today, the debates between supporters and opponents of the restoration ecology are as intense as ever and deal with crucial concepts and principles in conservation biology : the key-species or perturbations roles, the relevant scale for the analysis and action, the methodology for the assessment and the monitoring, etc. These programs cause also some deontological problems dealing with the choice of the priorities and the reference systems, with the risk to be used as an alibi for destruction.
Time lags can be found throughout the invasion process, including in the arrival, establishment, and impacts of invaders. While we often lack the information necessary to generate quantitative expectations of invader performance, some types of lags are not surprising. For example, populations often grow exponentially in the early phases of invasion, and this will give rise to an inherent lag. More broadly, early rates of anthropogenic invasion were much slower than what we are now witnessing, but as the vectors of invasion have also increased dramatically over time, this early lag is not unexpected. Many other lags, however, appear dramatically prolonged, and can come to an end with changes to the invader or its environment. For example, exotics can exist in relatively low numbers for decades before exploding, or invaders can become more aggressive over time and increase their impacts on native species. Invasion-related lags are critical for our efforts to manage invaders, as they may lead us to make inaccurate assessments of the risks posed by invaders as well as miss critical windows for action. Recognition of the phenomenon of long lags before sudden changes in invader dynamics also suggests that we adopt a strict precautionary principle: we should assume that any invader has the potential for undesirable effects and that long periods of seemingly consistent behaviour can be poor predictors of what invaders will do in the future.
This paper begins with a survey of the patterns in discovering and recording species of animals and plants, from Linnaeus' time to the present. It then outlines various approaches to estimating what the total number of species on Earth might be: these approaches include extrapolation of past trends; direct assessments based on the overall fraction previously recorded among newly studied groups of tropical insects; indirect assessment derived from recent studies of arthropods in the canopies of tropical trees (giving special attention to the question of what fraction of the species found on a given host-tree are likely to be `effectively specialized' on it); and estimates inferred from theoretical and empirical patterns in speciessizes relations or in food web structure. I conclude with some remarks on the broader implications of our ignorance about how many species there are.
Sub-Antarctic islands share many similarities in their history of human interaction and impacts before the mid-twentieth century. Large impacts on land were associated with the marine exploitation industries of sealing and whaling. Their onshore activities involved consider - able construction and pollution in many accessible landing bays, inevitably destroying large areas of coastal terrestrial habitat. Consider- able transfer of nutrients to terrestrial environments will have been associated with scavengers utilising large carrion supplies. Attempted establishment of agricultural industries, particularly the introduction of grazing mammals, took place on several islands and, although rarely proving economically viable, often resulted in the long-term creation of feral populations. These were accompanied by introductions of other alien vertebrates, plants and invertebrates to most sub-Antarctic islands, although precise records of introduction events, or subsequent biological studies in this period, largely do not exist. Thus, exploitation industries in this region inevitably led to considerable alterations and impacts to terrestrial ecosystems almost from the outset of human contact with the islands. In the absence of baseline ecological and biodiversity studies, the true magnitude of many of these impacts is difficult to assess, although their legacy continues to the present day. Indeed, the almost complete removal of fur seals may have allowed coastal vegetation to become more extensive and lush than hitherto, paradoxically now regarded as "typical" and threatened by recovery of seal populations.
Sample scarcity and the need of a methodology well-suited to determination of archaeological specimens are responsible for the lack of information on the mechanism and on the ecological and anthropological conditions of the spread of the house mouse in Europe. We applied Fourier outline analysis to the lower first molars of mice from assemblages trapped in water wells from Early and Middle PPNB in Cyprus (Kissonerga–Mylouthkia). Results suggest that the house mouse was a part of the Neolithic ecological and cultural package introduced into the island by the very first agro-pastoral societies coming from the mainland.
Feral cats are directly responsible for a large percentage of global extinctions, particularly on islands. We reviewed feral cat eradication programs with the intent of providing information for future island conservation actions. Most insular cat introductions date from the nineteenth and twentieth centuries, whereas successful eradication programs have been carried out in the last 30 years, most in the last decade. Globally, feral cats have been removed from at least 48 islands: 16 in Baja California (Mexico), 10 in New Zealand, 5 in Australia, 4 in the Pacific Ocean, 4 in Seychelles, 3 in the sub-Antarctic, 3 in Macaronesia (Atlantic Ocean), 2 in Mauritius, and 1 in the Caribbean. The majority of these islands (75%; n= 36) are small (≤5 km²). The largest successful eradication campaign took place on Marion Island (290 km²), but cats have been successfully removed from only 10 islands (21%) of ≥10 km². On Cousine Island (Seychelles) cat density reached 243 cats/km², but on most islands densities did not exceed 79.2 cats/km² (n= 22; 81%). The most common methods in successful eradication programs were trapping and hunting (often with dogs; 91% from a total of 43 islands). Frequently, these methods were used together. Other methods included poisoning (1080; monofluoracetate in fish baits; n= 13; 31%), secondary poisoning from poisoned rats (n= 4; 10%), and introduction of viral disease (feline panleucopaenia; n= 2; 5%). Impacts from cat predation and, more recently, the benefits of cat eradications have been increasingly documented. These impacts and benefits, combined with the continued success of eradication campaigns on larger islands, show the value and role of feral cat eradications in biodiversity conservation. However, new and more efficient techniques used in combination with current techniques will likely be needed for success on larger islands.
Introduced mammals are major drivers of extinction. Feral goats (Capra hircus) are particularly devastating to island ecosystems, causing direct and indirect impacts through overgrazing, which often results in ecosystem degradation and biodiversity loss. Removing goat populations from islands is a powerful conservation tool to prevent extinctions and restore ecosystems. Goats have been eradicated successfully from 120 islands worldwide. With newly developed technology and techniques, island size is perhaps no longer a limiting factor in the successful removal of introduced goat populations. Furthermore,. the use of global positioning systems, geographic information systems, aerial hunting by helicopter specialized bunting dogs, and Judas goats has dramatically increased efficiency and significantly reduced the duration of eradication campaigns. Intensive monitoring programs are also critical for successful eradications. Because of the presence of humans with domestic goat populations on large islands, future island conservation actions will require eradication programs that involve local island inhabitants in a collaborative approach with biologists, sociologists, and educators. Given the clear biodiversity benefits, introduced goat populations should be routinely removed from islands.
This paper provides a critical analysis of archaeological small mammal collections in the Mediterranean area, from the Late Glacial to the first centuries AD, to validate the presence/absence of the house mouse through zooarchaeological criteria. The results have been synthesized through a diachronic map, whose chronological phases are related to socio-economic and cultural human evolution. The house mouse (Mus musculus domesticus) progression in the Mediterranean begins with a quick but limited diffusion in the Eastern Mediterranean Basin achieved around the 8th millennium BC. Until the 1st millennium BC, the invasive process seems to have stopped or drastically slowed, despite the increasing opportunities of passive transport during the Bronze Age. During the 1st millennium BC, there was mass colonization by the house mouse of the entire Western Mediterranean Basin and Northern Europe. We propose to explain this chronological gap in the colonization of the Eastern and Western Mediterranean using source-sink theory considering that the western environments acted like sinks until the first millennium BC. At that time the Western Mediterranean was fully opened to Eastern influences and migrations, and the human pressures on the environment drastically increased. This may have favoured definitively the adaptation of the house mouse to the Western commensal niches. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 84, 429–445.
To forecast the potential impact of plant community and dry-stone wall restoration on an insular population of the lesser
white-toothed shrewCrocidura suaveolens Pallas, 1811, shrew and house mouseMus musculus Linnaeus, 1758 abundances were assessed in 3 anthropogenic habitats on Béniguet Island, Brittany, France, by a standardised
annual trapping system checked yearly for 9 years and in 6 “natural” habitats by trap-lines. The standardised trapping system
showed that abundances of both species fluctuated synchronously for nine years, suggesting that interactions between the species
had little impact if any on abundances. Mice were trapped in all habitats, but shrews only in “stone” habitats except for
rare occurrences in one damp depression. Ruderal habitat was rarely used by either species. Data suggest that on Béniguet
Island: (1)M. musculus is associated with anthropogenic habitats but is not as strictly tied to them as at nearby continental sites; (2)C. suaveolens is synanthropic, as has been reported in continental northern France; (3) shingle beaches and seashore food resources are
particularly important forC. suaveolens; (4) the relationship betweenC. suaveolens andM. musculus could not be determined by the experiments and, if it exists at all, appears to be more competitive than predatory. Grassland
restoration is unlikely to affect shrew populations. Dry-stone wall restoration may temporarily affect shrews but should ultimately
benefit them.
Key words
Crocidura suaveolens
-
Mus musculus
-biological invasion-conservation-habitat-island
In order to examine the dynamics and potential impact of the recently introduced sacred ibis Threskiornis aethiopicus, we review the published and unpublished data and report new information on its distribution in West European countries and particularly in France. This species, which escaped from zoos during the 1990s, is well established and has spread on the Atlantic coast and in Mediterranean region of France, with a mid-winter population reaching ca.3200 individuals in winter 2004–2005 and ca.1100 breeding pairs in spring 2005. The species has also escaped from zoological parks in Belgium, Germany, Spain, Italy and Portugal, and feral populations are established in Piedmont (Italy) and in the Canary Islands (Spain). The species dispersing ability has led to observations over hundreds of kilometres from the established colonies. We identify that in temperate habitats the sacred ibis shows a behavioural flexibility similar to that known in its tropical native range, including a large diet spectrum (insects, molluscs, refuse, bird eggs, etc.) and an ability to use various habitats (meadows, rubbish dumps, marshes, reedbeds, seashore, ploughed fields, etc.). This plasticity, the fact that predation by ibises is observed on nests of threatened bird species, and the number of potential sources of ibis in Europe (zoos) are causes of concern suggesting that precautionary measures should be taken to prevent the spread of this new alien species.
Species invasions provide numerous unplanned and frequently, but imperfectly, replicated experiments that can be used to better understand the natural world. Classic studies by Darwin, Grinnell, Elton and others on these species-invasion experiments provided invaluable insights for ecology and evolutionary biology. Recent studies of invasions have resulted in additional insights, six of which we discuss here; these insights highlight the utility of using exotic species as ‘model organisms’. We also discuss a nascent hypothesis that might provide a more general, predictive understanding of invasions and community assembly. Finally, we emphasize how the study of invasions can help to inform our understanding of applied problems, such as extinction, ecosystem function and the response of species to climate change.
The literature on effects of habitat fragmentation on biodiversity is huge. It is also very diverse, with different authors measuring fragmentation in different ways and, as a consequence, drawing different conclusions regarding both the magnitude and direction of its effects. Habitat fragmentation is usually defined as a landscape-scale process involving both habitat loss and the breaking apart of habitat. Results of empirical studies of habitat fragmentation are often difficult to interpret because (a) many researchers measure fragmentation at the patch scale, not the landscape scale and (b) most researchers measure fragmentation in ways that do not distinguish between habitat loss and habitat fragmentation per se, i.e., the breaking apart of habitat after controlling for habitat loss. Empirical studies to date suggest that habitat loss has large, consistently negative effects on biodiversity. Habitat fragmentation per se has much weaker effects on biodiversity that are at least as likely to be positive as negative. Therefore, to correctly interpret the influence of habitat fragmentation on biodiversity, the effects of these two components of fragmentation must be measured independently. More studies of the independent effects of habitat loss and fragmentation per se are needed to determine the factors that lead to positive versus negative effects of fragmentation per se. I suggest that the term "fragmentation" should be reserved for the breaking apart of habitat, independent of habitat loss.
To assess the conservation status of the world's land mammals, we compiled data on the number of total species, endemic species, recently extinct species, and currently endangered species for 155 countries. Total species richness was significantly correlated with territorial land area, whereas number of endemic species was only weakly correlated with both area and total number of species. The large amount of variation left unexplained by species-area regressions reflects the influence of other factors, such as latitude, topographic and habitat heterogeneity, and historical biogeography, on species richness and especially on patterns of endemism. Countries of particular conservation concern, because they have rich mammalian faunas containing many endemic species, are the large islands of Australia Madagascar, Indonesia and the Philippines, as well as continental Mexico. Patterns of recent extinctions and the current endangered status of species were difficult to interpret, largely because of inadequate
The Portuguese oyster Crassostrea angulata (Lamarck, 1819) was long assumed to be native to the northeastern Atlantic, however, a number of lines of evidence now indicate that it is a close relative, or identical, to the Asian Pacific oyster C. gigas (Thunberg, 1793). Three hypotheses have been proposed to explain how this strikingly disjunct geographic distribution may have come about: ancient vicariance events, recent anthropogenic introduction to Asia and recent anthropogenic introduction to Europe. We have performed a molecular phylogenetic analysis of C. angulata based on mitochondrial DNA sequence data for a 579-nucleotide fragment of cytochrome oxidase I. Our results show that Portuguese oyster haplotypes cluster robustly within a clade of Asian congeners and are closely related, but not identical, to C. gigas from Japan. The mitochondrial data are the first to show that Portuguese oysters are genetically distinct from geographically representative samples of Japanese Pacific oysters. Our phylogenetic analyses are consistent with a recent introduction of C. angulata to Europe either from a non-Japanese Asian source population or from a subsequently displaced Japanese source population. Genetic characterization of Pacific oysters throughout their Asian range is necessary to fully reveal the phylogenetic relationships among Portuguese and Pacific oysters. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/42028/1/227-131-3-497_81310497.pdf
Aim Over the next 100 years, human-driven climate change and resulting changes in species occurrences will have global impacts on biodiversity, ecosystem function, and human health. Here we examine how climate change may affect the occurrences of tick species in Africa and alter the suitability of habitat outside Africa for African ticks.
Location Africa and the world.
Methods We predicted continental and global changes in habitat suitability for each of 73 African tick species, using multiple regression models in different climate change scenarios that cover a wide range of uncertainty.
Results Global habitat suitability improves for nearly all tick species under each of a representative range of eight climate change scenarios. Depending on the scenario, African tick species experience an average increase in global habitat suitability of between 1 million and 9 million square kilometres between 1990 and 2100.
Main conclusions The potential for successful translocations of ticks and their pathogens from Africa to the rest of the world is likely to increase over the next 100 years. Although the general trend is one of range expansion, there are winners and losers among tick species in each scenario, suggesting that tick community composition will be disrupted substantially by climate change. If this is also typical of other invertebrates, then climate change will disrupt not only the geographic location of communities but also their structure. Changes in tick communities are also likely to influence tick-borne pathogens.
Human settlement of Polynesia was a major event in world prehistory. Despite the vastness of the distances covered, research suggests that prehistoric Polynesian populations maintained spheres of continuing interaction for at least some period of time in some regions. A low level of genetic variation in ancestral Polynesian populations, genetic admixture (both prehistoric and post-European contact), and severe population crashes resulting from introduction of European diseases make it difficult to trace prehistoric human mobility in the region by using only human genetic and morphological markers. We focus instead on an animal that accompanied the ancestral Polynesians on their voyages. DNA phylogenies derived from mitochondrial control-region sequences of Pacific rats (Rattus exulans) from east Polynesia are presented. A range of specific hypotheses regarding the degree of interaction within Polynesia are tested. These include the issues of multiple contacts between central east Polynesia and the geographically distinct archipelagos of New Zealand and Hawaii. Results are inconsistent with models of Pacific settlement involving substantial isolation after colonization and confirm the value of genetic studies on commensal species for elucidating the history of human settlement.
Analysis of the three most ancient Zea mays inflorescence fragments from Guilá Naquitz, Oaxaca, Mexico shows they did not disarticulate naturally, indicating that agricultural selection of domesticated teosinte was underway by 5,400 (14)C years before the present (about 4,200 dendrocalibrated years B.C.). The cooccurrence of two-ranked specimens with two rows and four rows of grain and numerous additional morphological characteristics of these specimens support hypotheses based on molecular and quantitative genetic analyses that maize evolved from teosinte. Domestication of the wild ancestor of maize occurred before the end of the 5th millennium B.C.
The first part of this paper surveys emerging pathogens of wildlife recorded on the ProMED Web site for a 2-year period between 1998 and 2000. The majority of pathogens recorded as causing disease outbreaks in wildlife were viral in origin. Anthropogenic activities caused the outbreaks in a significant majority of cases. The second part of the paper develops some matrix models for quantifying the basic reproductive number, R(0), for a variety of potential types of emergent pathogen that cause outbreaks in wildlife. These analyses emphasize the sensitivity of R(0) to heterogeneities created by either the spatial structure of the host population, or the ability of the pathogens to utilize multiple host species. At each stage we illustrate how the approach provides insight into the initial dynamics of emergent pathogens such as canine parvovirus, Lyme disease, and West Nile virus in the United States.
The invasion of ecosystems by exotic species is currently viewed as one of the most important sources of biodiversity loss. The largest part of this loss occurs on islands, where indigenous species have often evolved in the absence of strong competition, herbivory, parasitism or predation. As a result, introduced species thrive in those optimal insular ecosystems affecting their plant food, competitors or animal prey. As islands are characterised by a high rate of endemism, the impacted populations often correspond to local subspecies or even unique species. One of the most important taxa concerning biological invasions on islands is mammals. A small number of mammal species is responsible for most of the damage to invaded insular ecosystems: rats, cats, goats, rabbits, pigs and a few others. The effect of alien invasive species may be simple or very complex, especially since a large array of invasive species, mammals and others, can be present simultaneously and interact among themselves as well as with the indigenous species. In most cases, introduced species generally have a strong impact and they often are responsible for the impoverishment of the local flora and fauna. The best response to these effects is almost always to control the alien population, either by regularly reducing their numbers, or better still, by eradicating the population as a whole from the island. Several types of methods are currently used: physical (trapping, shooting), chemical (poisoning) and biological (e.g. directed use of diseases). Each has its own set of advantages and disadvantages, depending on the mammal species targeted. The best strategy is almost always to combine several methods. Whatever the strategy used, its long-term success is critically dependent on solid support from several different areas, including financial support, staff commitment, and public support, to name only a few. In many cases, the elimination of the alien invasive species is followed by a rapid and often spectacular recovery of the impacted local populations. However, in other cases, the removal of the alien is not sufficient for the damaged ecosystem to revert to its former state, and complementary actions, such as species re-introduction, are required. A third situation may be widespread: the sudden removal of the alien species may generate a further disequilibrium, resulting in further or greater damage to the ecosystem. Given the numerous and complex population interactions among island species, it is difficult to predict the outcome of the removal of key species, such as a top predator. This justifies careful pre-control study and preparation prior to initiating the eradication of an alien species, in order to avoid an ecological catastrophe. In addition, long-term monitoring ofthe post-eradication ecosystem is crucial to assess success and prevent reinvasion.
Species' invasions have long been regarded as enormously complex processes, so complex as to defy predictivity. Phases of this process, however, are emerging as highly predictable: the potential geographic course of an invasion can be anticipated with high precision based on the ecological niche characteristics of a species in its native geographic distributional area. This predictivity depends on the premise that ecological niches constitute long-term stable constraints on the potential geographic distributions of species, for which a sizeable body of evidence is accumulating. Hence, although the entire invasion process is indeed complex, the geographic course that invasions are able to take can be anticipated with considerable confidence.
Invasive plants are an economic problem and a threat to the conservation of natural systems. Escape from natural enemies might contribute to successful invasion, with most work emphasizing the role of insect herbivores; however, microbial pathogens are attracting increased attention. Soil biota in some invaded ecosystems may promote 'exotic' invasion, and plant-soil feedback processes are also important. Thus, relatively rare species native to North America consistently demonstrate negative feedbacks with soil microbes that promote biological diversity, whereas abundant exotic and native species demonstrate positive feedbacks that reduce biological diversity. Here we report that soil microbes from the home range of the invasive exotic plant Centaurea maculosa L. have stronger inhibitory effects on its growth than soil microbes from where the weed has invaded in North America. Centaurea and soil microbes participate in different plant-soil feedback processes at home compared with outside Centaurea's home range. In native European soils, Centaurea cultivates soil biota with increasingly negative effects on the weed's growth, possibly leading to its control. But in soils from North America, Centaurea cultivates soil biota with increasingly positive effects on itself, which may contribute to the success of this exotic species in North America.
The human settlement of the Pacific in general, and the origin of the Polynesians in particular, have been topics of debate for over two centuries. Polynesian origins are most immediately traced to people who arrived in the Fiji, Tonga, and Samoa region ≈3,000 B.P. and are clearly associated with the Lapita Cultural Complex. Although this scenario of the immediate origins of the Polynesians is generally accepted, the debate on the ultimate origin of the Polynesians and the Lapita cultural complex continues. Our previous research has shown that analyses of mtDNA variation in the Pacific rat (Rattus exulans), often transported as a food item in the colonizing canoes, are valuable for tracing prehistoric human migration within Polynesia. Here we present mtDNA phylogenies based on ≈240 base pairs of the d-loop from both archaeological and modern samples collected from Island Southeast Asia and the Pacific. We identify three major haplogroups, two of which occur in the Pacific. Comparing our results with Lapita models of Oceanic settlement, we are able to reject two often cited but simplistic models, finding support instead for multifaceted models incorporating a more complex view of the Lapita intrusion. This study is unique and valuable in that R. exulans is the only organism associated with the Lapita dispersal for which there are sufficient ancient and extant populations available for genetic analysis. By tracking population changes through time, we can understand more fully the settlement process and population interactions in both Near and Remote Oceania.
• Oceania
• Lapita
• prehistory
• ancient DNA
• phylogeography
Aim The use of species distribution models (SDMs) to predict biological invasions is a rapidly developing area of ecology. However, most studies investigating SDMs typically ignore prediction errors and instead focus on regions where native distributions correctly predict invaded ranges. We investigated the ecological significance of prediction errors using reciprocal comparisons between the predicted invaded and native range of the red imported fire ant (Solenopsis invicta) (hereafter called the fire ant). We questioned whether fire ants occupy similar environments in their native and introduced range, how the environments that fire ants occupy in their introduced range changed through time relative to their native range, and where fire ant propagules are likely to have originated. Location We developed models for South America and the conterminous United States (US) of America. Methods We developed models using the Genetic Algorithm for Rule-set Prediction (GARP) and 12 environmental layers. Occurrence data from the native range in South America were used to predict the introduced range in the US and vice versa. Further, time-series data recording the invasion of fire ants in the US were used to predict the native range. Results Native range occurrences under-predicted the invasive potential of fire ants, whereas occurrence data from the US over-predicted the southern boundary of the native range. Secondly, introduced fire ants initially established in environments similar to those in their native range, but subsequently invaded harsher environments. Time-series data suggest that fire ant propagules originated near the southern limit of their native range. Conclusions Our findings suggest that fire ants from a peripheral native population established in an environment similar to their native environment, and then ultimately expanded into environments in which they are not found in their native range. We argue that reciprocal comparisons between predicted native and invaded ranges will facilitate a better understanding of the biogeography of invasive and native species and of the role of SDMs in predicting future distributions.
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).
Predation at North Island Robin Petroica australis longipes and North Island Tomtit Petroica macrocephala toitoi nests was studied in New Zealand over the 1993/94 breeding season to determine impacts of predators. Infra-red, time-lapse video photography and sign left after predation were used to identify predators at nests. Accurate estimates of predation rates depended on early detection of nests. Previous studies of predation may have greatly under-estimated predation rates and therefore predation impacts. Predation was patchy and intense, resulting in failure to produce young in some territories despite up to ten nesting attempts. A maximum of 82% of nests were preyed on (n = 65; 95% confidence interval 72.4%-90%) and Ship Rats Rattus rattus were probably responsible for at least 72% (95% confidence interval 57.4%-84.4%) of predations. Nine of 24 territories lost breeding females, mainly to Ship Rats, which significantly impacted on population productivity. Ship Rat predation was equally intense at exposed and concealed nests (at the site and patch levels). Predation attributed to avian predators was strongly correlated with exposed nests (at the patch level). Restoration of New Zealand's threatened forest bird communities is dependent on a commitment to further research into the significance of different predators and predation impacts on bird populations.
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.
Although Clipperton Island has been visited by only a few ornithologists, it nevertheless has been long recognized as a haven for large numbers of oceanic birds. Clipperton is the most easterly coral atoll in the Pacific Ocean and is situated at latitude 100 18' N, longitude 1090 131' W. With reference to the American mainland, the island is approximately 600 nautical miles southwest of the Mexican state of Guerrero. The
Many European politicians, managers, and scientists believe that non-indigenous species cannot be eradicated and that attempts to do so are hazardous because of frequent undesirable results. This notion seems to be based on the view that successful eradications undertaken in many other parts of the world cannot be generalised. To allow reasoned consideration of this argument, the eradication of non-indigenous vertebrate species performed in the French territories (European and overseas) and their recorded consequences on native fauna and flora are synthesised. Nineteen vertebrate eradication attempts were recorded, with seven mammal species as the targets. Of these attempts four failed for technical reasons and one for reasons undetermined as yet. These operations took place on islands of four biogeographical areas (West-European, Mediterranean, West Indies and Indian Ocean subantarctic) except a continental one (West-European continent). Among these 19 attempts, 13 were conducted according to a global strategy that provided data on the impact of the disappearance of the non-indigenous species on several native species. This impact, never detrimental, was determined for 14 species (one mammal, nine birds, one marine turtle, one crab, one beetle, one plant). Unexpected consequences of the disappearance of the invader were recorded for four native species (29%). This result highlights the poverty of natural historical information for several taxa and the flimsiness of the empty niche concept that is often used to argue for the delay of or to prevent any action again a non-indigenous species. If French territories can be taken as an example, eradications of non-indigenous species are not impossible; a good risk assessment prevents undesirable long-term consequences for native species and several native species benefited from the disappearance of the invader. Furthermore, eradication constitutes a powerful experimental tool for ecology and natural history studies if conceived as both a management and research operation.
Warfarin bait has been used since 1986 to control introduced black rats
(Rattus rattus) in palm-seeding areas on Lord Howe
Island, New South Wales. We examined the relationship between bait use and
mouse numbers in these areas. In the first experiment, one mouse population
was manipulated by removal trapping while baiting for rats was being
undertaken. When mouse density was reduced by approximately 193
ha–1, bait consumption fell by 80.0%,
suggesting that the mice were not susceptible to warfarin and that the rat
bait may have been an important food resource for these mice. During the
second experiment, the existing rat-baiting regime was maintained in one area
but manipulated in another – bait was removed for one year then returned
during the second year. Under the existing baiting regime, mouse numbers
increased during the two-year period. The mouse population that was denied rat
bait declined to near zero after one year, then increased when bait was
reintroduced to the area, reaching densities after one year similar to those
in the area where bait had been maintained. We conclude that the mice were
resistant to warfarin, consumed most of the bait distributed to control rats,
were largely dependant on the bait as a food source, and reached high
densities in rat-control areas as a direct result of rat-baiting strategies.
The small Monte di Tuda cave is filled with a slightly disturbed, 2 m thick deposit. Very rich small vertebrate bone assemblages from barn owl pellets have been sampled extensively using special techniques to avoid contamination. Stratigraphical analysis and accelerator radiocarbon dating on the bones themselves both point to a rapid sedimentation rate during the last 2500 years, with a break in the building up of sediment between 1960 and 610bp. Multivariate analyses of the frequencies of the small mammal species show that modern species had approximately the same ecology throughout the time sequence, and give, for the first time, an idea of the ecological preferences of the extinct endemic species of Corsica. The general development of the faunal spectra shows a general increase in human impact (clearance of the vegetation), through the sediment sequence. Other multivariate analyses indicate a sequence of at least three agricultural cycles: the first one during the Early Roman period, the second one between the Late Roman period (2 –5th centuriesad) and the Pisa Peace (11 –13th centuriesad), and the last one during the 14 –19th centuriesad. The two earlier ones were mainly concerned with cereal cultivation, the later with tree cultivation. Whilst most of these cycles have only a local significance, two phenomena have a more extensive significance: (1) the immigration ofRattus rattusto Corsica and probably to the whole North-Western Mediterranean Basin, dated between the 4th –2nd centuries cal-bc; and (2) the mass extinction of the small endemic species, dating either to the Late Roman period or to the 11 –13th centuriesadand probably resulting from large scale agricultural deforestation. In addition, the small mammal assemblages recovered appear to reflect a wetter climate at both the beginning of the sediment sequence (the “small alpine glacial age ”) and at the end (14 –18th centuries: “Petit Âge Glaciaire” of Le Roy Ladurie). This paper gives an example of the importance of small mammal assemblages for reconstructing the environment in the historical period.
Every form of behaviour is shaped by trial and error. Such stepwise adaptation can occur through individual learning or through natural selection, the basis of evolution. Since the work of Maynard Smith and others, it has been realised how game theory can model this process. Evolutionary game theory replaces the static solutions of classical game theory by a dynamical approach centred not on the concept of rational players but on the population dynamics of behavioural programmes. In this book the authors investigate the nonlinear dynamics of the self-regulation of social and economic behaviour, and of the closely related interactions between species in ecological communities. Replicator equations describe how successful strategies spread and thereby create new conditions which can alter the basis of their success, i.e. to enable us to understand the strategic and genetic foundations of the endless chronicle of invasions and extinctions which punctuate evolution. In short, evolutionary game theory describes when to escalate a conflict, how to elicit cooperation, why to expect a balance of the sexes, and how to understand natural selection in mathematical terms.
It is in the nature of today's world that interventionist, rather than protectionist, management strategies are likely to be in greater demand, because an enormous area of the earth's habitable surface has already been transformed by human action. [Holdgate, M.W., 1986. Summary and conclusions: characteristics and consequences of biological invasions. In: Kornberg, H., Williamson, M.H. (Eds), Quantitative aspects of the ecology of biological invasions. The Royal Society, London, pp. 733–742]Progress with ecological restoration in New Zealand is reviewed. A useful goal for restoration is that of rebuilding, as far as possible, the evolutionary and ecological context of species in the system, i.e. reinstating earlier selection regimes. Opportunities for restoring biological components of these regimes are greater than those available for restoring physical conditions. In this country, effective ecological restoration is not possible without control or eradication of introduced mammals. Descriptive models of systems to be restored are also a necessity for achieving goals. A particular problem is that caused by past extinctions of animal species. Replacement of some extinct species, within particular trophic guilds, with ecologically appropriate and related extant species, is suggested as a possible response to this problem.
Breeding success of 5 Cory's shearwater Calonectris diomedea sub-colonies of Lavezzu Island (Lavezzi Archipelago, Corsica) was checked annually for 25 consecutive years from 1979 to 2004. Between 1989 and 1994, 4 ship rat Rattus rattus controls were performed in several sub- colonies. In November 2000, rats were eradicated from Lavezzu Island and its 16 peripheral islets (85 ha) using traps then toxic baits. We compare cost (number of person-hours required in the field) and benefit (Cory's shearwater breeding success) of control and eradication. The average breeding success doubled when rats were controlled or eradicated (0.82) compared to the situation without rat management (0.45). Moreover, the average breeding success after eradication (0.86) was signifi- cantly (11%) higher than after rat controls (0.75). Furthermore, the great variation in breeding suc- cess recorded among sub-colonies both with and without rat control declined dramatically after eradication, suggesting that rats had a major impact on breeding success. The estimated effort needed to perform eradication and checking of the permanent bait-station system during the year fol- lowing eradication was 1360 person-hours. In contrast, rat control was estimated to require 240 or 1440 person-hours per year when implemented by trained and untrained staff, respectively. Within 6 yr, eradication cost is lower than control cost performed by untrained staff and confers several eco- logical advantages on more ecosystem components than Cory's shearwater alone. Improved eradi- cation tools such as hand or aerial broadcasting of toxic baits instead of the fairly labour-intensive eradication strategy we used would dramatically increase the economic advantage of eradication vs. control. Therefore, when feasible, we recommend eradication rather than control of non-native rat populations. Nevertheless, control remains a useful management tool when eradication is not practicable.
Many invasive species cause ecological or economic damage, and the fraction of introduced species that become invasive is an important determinant of the overall costs caused by invaders. According to the widely quoted tens rule, about 10% of all introduced species establish themselves and about 10% of these established species become invasive. Global taxonomic differences in the fraction of species becoming invasive have not been described. In a global analysis of mammal and bird introductions, I show that both mammals and birds have a much higher invasion success than predicted by the tens rule, and that mammals have a significantly higher success than birds. Averaged across islands and continents, 79% of mammals and 50% of birds introduced have established themselves and 63% of mammals and 34% of birds established have become invasive. My analysis also does not support the hypothesis that islands are more susceptible to invaders than continents, as I did not find a significant relationship between invasion success and the size of the island or continent to which the species were introduced. The data set used in this study has a number of limitations, e.g. information on propagule pressure was not available at this global scale, so understanding the mechanisms behind the observed patterns has to be postponed to future studies.
Much confusion exists in the English-language literature on plant invasions concerning the terms ‘naturalized’ and ‘invasive’ and their associated concepts. Several authors have used these terms in proposing schemes for conceptualizing the sequence of events from introduction to invasion, but often imprecisely, erroneously or in contradictory ways. This greatly complicates the formulation of robust generalizations in invasion ecology.
Based on an extensive and critical survey of the literature we defined a minimum set of key terms related to a graphic scheme which conceptualizes the naturalization/invasion process. Introduction means that the plant (or its propagule) has been transported by humans across a major geographical barrier. Naturalization starts when abiotic and biotic barriers to survival are surmounted and when various barriers to regular reproduction are overcome. Invasion further requires that introduced plants produce reproductive offspring in areas distant from sites of introduction (approximate scales: > 100 m over < 50 years for taxa spreading by seeds and other propagules; > 6 m/3 years for taxa spreading by roots, rhizomes, stolons or creeping stems). Taxa that can cope with the abiotic environment and biota in the general area may invade disturbed, seminatural communities. Invasion of successionally mature, undisturbed communities usually requires that the alien taxon overcomes a different category of barriers.
We propose that the term ‘invasive’ should be used without any inference to environmental or economic impact. Terms like ‘pests’ and ‘weeds’ are suitable labels for the 50–80% of invaders that have harmful effects. About 10% of invasive plants that change the character, condition, form, or nature of ecosystems over substantial areas may be termed ‘transformers’.
Scale, the scale dependency of patterns and processes, and the ways that organisms scale their responses to these patterns and processes are central to island and landscape ecology. Here, we take a database of studies in island ecology and investigate how studies have changed over a 40-year period with respect to spatial scale and organisms studied. We demonstrate that there have been changes in the spatial scale of islands studied and that there is taxonomic bias in favour of vertebrates in island ecological studies when compared to scientific publications as a whole. We discuss how such taxonomic bias may have arisen and discuss the implications for ecology and biogeography.
Four to 10 years after the successful eradication of the Norway rat (Rattus norvegicus) from three islands of the Sept–Îles Archipelago and one in the Molène Archipelago (Brittany, France), the abundance index of the lesser white-toothed shrew (Crocidura suaveolens) increased by factors of 7–25, depending on the island and the year. Moreover, in the same region, the abundance index of the greater white-toothed shrew (Crocidura russula) on Tomé Island increased by factors of 9 and 17, one and two years after the Norway rat eradication, respectively.
The maximum variation of the abundance index for the lesser white-toothed shrew during seven years on the rat-free island of Béniguet in the same region was a factor of only 2.5. Moreover, the distribution of the lesser white-toothed shrew on Bono island, restricted before the eradication to two steep areas with few rats, increased and encompassed virtually the entire island four years after rats disappeared.
These results suggest strong detrimental interactions between the introduced Norway rat and the two Crocidura shrew species on temperate oceanic islands. However, our data do not indicate the ecological mechanisms at work in these interactions.
The main reason this shrew recovery was detected after rat eradication was the inclusion in the eradication protocol of the evaluation of impacts on the local biota of eliminating alien species. The rigor of the sampling procedure was also crucial to this discovery. This example demonstrates that an eradication operation can be extremely useful for both scientists and managers if it is planned as a research project.
The focus on place rather than space provides geography with a powerful raison d’être. As in human geography, the functional role of place is integral to the understanding of evolution, persistence and extinction of biotic taxa. This paper re-examines concepts and biogeographical evidence from a geographical rather than ecological or evolutionary perspective. Functional areography provides convincing arguments for a postmodern deconstruction of major principles of the dynamic Equilibrium Theory of Island Biogeography (ETIB). Endemic oceanic island taxa are functionally insular as a result of long-term island stability, confinement, isolation, and protection from continental invasion and disturbance. Most continental taxa persist in different, more complex and open spatial systems; their geographical place is therefore fundamentally distinct from the functional insularity of oceanic island taxa. This creates an insular-continental polarity in biogeography that is currently not reflected in conservation theory. The focus on the biogeographical place leads to the development of the eigenplace concept defined as the functional spatial complex of existence. The application of still popular ETIB concepts in conservation biology is discouraged. The author calls for the integration of functional areography into modern conservation science.
At least two amphibian and 28 reptile taxa are considered to have become extinct since 1600. Almost all of them were island forms and were heavily exploited by man until their number was so low that it no longer paid to hunt them. In connection with the exploitation of the island fauna and flora, man brought with him various domestic animals. Some of them—cats, dogs, goats and pigs—became feral thus creating, together with introduced rats and mice, another serious threat to endemic animals.The deliberate introduction of the mongoose into the many islands of the West Indies amounted to a critical threat to forms which were not affected because of their economic value. At least in one case, mongoose were introduced into an island especially on purpose to get rid of the iguana and snakes. Man has also directly affected the existence of some forms by destruction of habitat and by shooting them for ‘sport’.
Restriction fragment length polymorphisms of PCR-amplified mitochondrial DNA fragments were used to examine genetic differentiation between populations of the Portuguese oyster (Crassostrea angulata) and the Pacific oyster (Crassostrea gigas). The taxonomic status of C. angulata and C. gigas has often been questioned since no morphological or genetic differences had ever been observed between the two taxa. Samples identified as C. angulata, were collected from 16 sites located in southern Portugal and Spain and samples identified as C. gigas, from European and Asian sites. Of the six haplotypes observed, one was commonly found among oysters identified as C. gigas while another one was most frequent among oysters identified as C. angulata. Analysis of haplotype diversity among sites showed that samples originating from southern Portugal and Spain cluster with the Taiwanese sample. These results implicate Taiwan as the possible origin of European C. angulata populations. The ability to differentiate between these two previously indistinguishable taxa allowed us to identify a population in Portugal as mixed. These results open new perspectives for the study of characters previously described as varying between C. gigas and C. angulata, such as growth performance and disease susceptibility.
Human alteration of Earth is substantial and growing. Between one-third and one-half of the land surface has been transformed
by human action; the carbon dioxide concentration in the atmosphere has increased by nearly 30 percent since the beginning
of the Industrial Revolution; more atmospheric nitrogen is fixed by humanity than by all natural terrestrial sources combined;
more than half of all accessible surface fresh water is put to use by humanity; and about one-quarter of the bird species
on Earth have been driven to extinction. By these and other standards, it is clear that we live on a human-dominated planet.
A growing consensus of biologists now favors the effectiveness of long-distance dispersal as a means of populating islands. The observational and experimental bases on which this opinion rests are strong, but additional work is needed. A clear under-standing of long-distance dispersal is essential to an understanding of evolutionary trends on oceanic islands, because immigrant patterns are different from relict patterns. Since oceanic islands are short-lived, the evolutionary history of waif immigrants is also short. If a continental islands maintains long isolation, arrivals by long-distance dispersal may show evolutionary patterns more completely, as is true on New Zealand for example. The evolutionary patterns of waif biotas are influenced by isolation, by the broad range of available ecological opportunities, and, to a lesser extent, by the moderation characteristic of maritime climates. In addition to problems involved in becoming established, immigrants must overcome genetic disadvantages inherent i...