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Location of Crotalus horridus hibernacula and roads in four regions of New York State (CH, Chemung County; BM, Bear Mountain; AD, Adirondacks; SF, Sterling Forest). Hibernacula assigned to the same genetic deme in our Bayesian assignment analyses are encircled by dashed lines. The thickness of dotted lines corresponds to higher levels of population connectivity as measured by pairwise FST. Thus, line thickness is inverse to FST value: populations with higher FST values are connected by thinner lines.
Source publication
Anthropogenic habitat modification often creates barriers to animal movement, transforming formerly contiguous habitat into a patchwork of habitat islands with low connectivity. Roadways are a feature of most landscapes that can act as barriers or filters to migration among local populations. Even small and recently constructed roads can have a sig...
Contexts in source publication
Context 1
... collected tissue samples, including some shed skins, from 131 individuals from five hibernacula and used the 373 samples from the 14 hibernacula included in Clark et al. (2008). The five new sites were within 3 km of the original hibernacula, but in each case they were iso- lated from other sites by a roadway (Fig. 1). We geno- typed all samples at nine microsatellite loci ( Villarreal et al. 1996;Holycross et al. 2002). Sample sizes from our five new sites were comparable to those sampled previ- ously (Table 1). Procedures for sample collection, DNA extraction, polymerase chain reactions, and genotyping are described in Clark et al. (2008). The 19 ...
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... Procedures for sample collection, DNA extraction, polymerase chain reactions, and genotyping are described in Clark et al. (2008). The 19 hibernacula included in this study were in four different regions of New York (U.S.A.): six in the Adirondack region (AD), five in Sterling Forest (SF), six in Bear Mountain (BM), and two in Chemung County (CH) (Fig. ...
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... identified the average annual daily traffic (AADT) volume of all roads in our study areas with data provided by the New York State Department of Transportation. We classified roads as either minor (AADT < 3,000) or major (AADT > 10,000) barriers ( Fig. 1). All focal roads were paved for motorized traffic in the late 1920s or early 1930s; thus, they may have been barriers to rattlesnake populations for approximately 80-90 years. Roads were not associated with any major natural bar- riers (e.g., mountains, rivers, ridges) that could act as barriers to snake movement ( Clark et al. 2008). ...
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... from hibernac- ula south of the road showed high levels of admixture between clusters 1 and 2 (Table 3, mean percent mem- bership Q values), whereas the hibernaculum to the north of the road assigned to an independent genetic cluster (Fig. 3). The hibernaculum north of the road showed the highest proportion of cluster membership within AD, de- spite its close geographic proximity to W-07 south of the Proportion of genetic cluster or deme membership, Q, of individuals from each hibernaculum (Hib) in each cluster (1-4) defined by STRUCTURE with all regions analyzed separately. ...
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... which are separated by a major road, formed separate demes with very low levels of admixture (Table 3; Fig. 3). Over all four regions and 19 hibernacula, none of the genetic clusters identified by Bayesian assignment tests spanned either major or minor roads; hibernacula belong- ing to the same genetic deme were always on the same side of a road (Fig. 1). Genetic clusters not separated by roads showed more admixture than those separated by minor roads, which in turn showed more admixture than those separated by major roads (Fig. 3). Individuals from genetic clusters not separated by roads showed an aver- age membership with neighboring clusters of Q = 0.25 (SD 0.25), whereas this ...
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Citations
... It is noteworthy that using RCM and D PCA genetic distance, the best-supported model included Land use and Human density, suggesting the putative influences of anthrophonic factors may also be a profound factor that shapes the movement of leopard cats, as revealed in the studies of other felids (Hartmann et al. 2013). Linear features such as paved roads and highways are artificial structures known to have a significant impact on gene flow in many species (Clark et al. 2010;Kuehn et al. 2007;Robinson et al. 2012), and highways have been identified as physical barriers that impede movement and lead to a decline in genetic diversity (Epps & Keyghobadi 2015). Huge artificial linear features may also act as behavioural barriers (Kimmig et al. 2020;Laundré et al. 2010). ...
Context
Elucidating how demography and contemporary landscape features regulate functional connectivity is crucial to implementing effective conservation strategies. We assessed the impacts of landscape features on the genetic variation of a locally endangered carnivore, the leopard cat ( Prionailurus bengalensis ) in Taiwan.
Objectives
We aim to evaluate the association between genetic structure and landscape features. We further predicted the changes in genetic diversity and suitable habitats in the future.
Methods
We genotyped 184 leopard cats in western Taiwan using 12 nuclear microsatellites and a mitochondrial marker. We applied a landscape optimization procedure with two genetic distances to identify major genetic barriers and employed ecological niche modeling to predict the future distribution of the leopard cat.
Results
Bayesian demographic inferences revealed a dramatic population decline for all leopard cat populations in Taiwan. Genetic clustering and resistance surface modeling supported that the population connectivity was influenced by highways and high elevation. Niche modeling indicated low temperature was one of the primary factors limiting the occurrence of leopard cats that may inhibit their movement in high elevations. We predicted the suitable habitats of leopard cats would shrink northward and towards higher altitudes with rugged topography in response to global warming.
Conclusions
Our study provided genetic evidence that leopard cats in Taiwan had undergone a dramatic population decline that may be associated with anthropogenic impacts. We also inferred the anthropogenic linear feature compromised the connectivity and persistence of leopard cats in human-mediated landscapes. Our finding serves as a model for landscape genetic studies of island carnivores in subtropical regions.
... The displacement of rattlesnakes is likely to occur primarily along altitudinal gradients. Urban and agricultural development constantly alters habitat structure and acts as barriers to snake movement (Clark et al., 2010;Lomas et al., 2019;Maida et al., 2020). Recent records of C. intermedius at elevations ranging from 3,640 to 4,080 m in Abies-Pinus forests are noteworthy, considering that their altitudinal range is typically between 2,000 and 3,200 m (Serna-Lagunes et al., 2020). ...
Anthropogenic changes pose a significant threat to global biodiversity, especially in reptiles. Mexico, renowned for its diverse reptile population, is experiencing habitat disturbance and fragmentation, endangering rattlesnakes in particular due to their specific habitat requirements and limited mobility. The loss of structural connectivity further increases the risk of extinction for reptiles. Our study focuses on predicting the distribution and connectivity of nine Crotalus species in the Trans-Mexican Volcanic Belt (TMVB), using environmental modeling. We used climate models (CNRM-CM5 and MPI-ESM-LR) for the year 2050 and Representative Concentration Pathways (RCP 85) alongside changes in vegetation cover and land use. The Maxent modeling method in ENMeval helped assess distribution patterns and to identify key environmental variables influencing these species’ distributions and niche overlap. We also conducted an analysis of the structural connectivity of the different Crotalus species. Our findings indicate reductions in suitable habitats due to changes in agriculture, urbanization, and forest cover. The Maxent models showed high accuracy in predicting species distributions. The most influential variables varied among species and included forest types and climatic factors. We observed limited connectivity among small Crotalus species, although some species exhibited greater connectivity than others. Future models suggest potential distribution reductions for all species, with C. armstrongi facing the greatest reduction (78%) according to the cn85 global climate model. Protected areas do not encompass the majority of potential distribution for these small rattlesnake species. These findings highlight the urgency of conservation efforts and the need to mitigate the impacts of future environmental changes on reptile populations.
... These negative effects encompass habitat loss, landscape fragmentation, alterations in the physical and chemical environment, spread of exotic species [25][26][27], loss of biodiversity at both local and regional scales due to restricted movement between populations, increased human access to wildlife habitats, and intensification of bushmeat hunting [28][29][30][31][32]. In addition, some studies have revealed that road-induced isolation has led to reduced genetic diversity and increased genetic differentiation in snake populations (Crotalus horridus) due to interrupted seasonal migration [33]. ...
This study explored the role of the hydrological regime as a trigger factor for wildlife roadkill along a 22 km road crossing the Taim Wetland, a Ramsar site of international importance in South Brazil. The north–south crossing of BR-471, a federal highway, causes fatalities to numerous animals due to collisions with vehicles. An 11-year long-term time series study encompassing monthly roadkill incidents, water level, and rainfall was analyzed by considering three different periods related to a Wildlife Protection System (WPS): (i) 3 initial years before the WPS implementation (BWPS); (ii) 4 intermediate years after the WPS implementation (AWPS), which includes fences, fauna tunnels, cattle guard stocks, bumps, and speed control; (iii) 4 final years during partial destruction of the WPS (PDWPS). A pseudo-2D full hydrodynamic cell model was employed to fill missing water level data. The model had a good to very good performance (NSE: 0.73 to 0.87; R2: 0.79 to 0.90). The relationship between roadkill incidents and the WPS periods (BWPS, AWPS, and PDWPS) was modeled using Generalized Additive Models for Location, Scale, and Shape (GAMLSS), considering rainfall and water level as predictor variables. The analysis revealed a higher incidence of wildlife roadkill in BWPS compared to AWPS and PDWPS, suggesting the effectiveness of the implemented measures. Critical season and interplay between water levels, rainfall, and the roadkill were assessed. Mammals was the most common roadkill class identified (~92%), followed by reptiles (13%) and birds (2%), with no change in these percentual in the BWPS, AWPS, and PDWPS. Among mammals, capybara (Hydrochoerus hydrochaeris) and coypu (Myocastor coypu) were the most frequent victims (~93% of mammals). Winter, followed by autumn, recorded the highest number of roadkill incidents (>60%), and this pattern remained consistent during the three periods. While rainfall did not emerge as a determining variable for roadkill, water levels above certain thresholds (>3.3 m) drastically diminished the effectiveness of the WPS, mainly due to fauna tunnel submersion. These findings offer valuable insights for enhancing wildlife conservation strategies in this protected area by incorporating hydrological information providing a baseline for designing WPS in similar environments.
... Timber rattlesnakes are large forest-dwelling snakes native to eastern North America and reported to be declining by the IUCN Red List. While numerous studies report negative demographic and genetic responses to roads (Rudolph et al., 1999;Clark et al., 2010;Bushar et al., 2015), other researchers have reported timber rattlesnakes to use roadcuts and other open canopy habitats found along roadsides, particularly by gravid (pregnant) individuals (Brown, 1993;Reinert and Zappalorti, 1998;Anderson, 2010). The species shows stark intraspecific variation in habitat preferences, ostensibly due to their foraging and reproductive strategies that are seemingly made exclusive by thermal constraints (Gardner-Santana and Beaupre, 2009). ...
... For this reason, the benefits of the novel thermal habitats created by the ROW may outweigh the costs of lost foraging habitat. However, because the mitigation structures do not exclude rattlesnakes from the roadway nor maintain connectivity, eventual road mortality and genetic drift may detrimentally affect the rattlesnake population over time (Rudolph et al., 1999;Clark et al., 2010;Bushar et al., 2015). ...
Maintaining viable populations of large reptiles is often challenging in road fragmented landscapes. While mitigation structures can reduce impacts, few studies have investigated how mitigation success can be affected by roadside habitats. In southeast Ohio, USA, we evaluated mitigation effectiveness for state-endangered timber rattlesnakes (Crotalus horridus) at a new highway in a forested landscape. Road construction at the study site created a wide corridor of open canopy habitats (the right-of-way; ROW) containing roadcuts and stone piles. However, exclusion fencing was constructed along the forest-ROW boundary, leaving the open canopy habitats on the road-side of the fence. Over three years, we monitored 6 rattlesnakes using radiotelemetry and found that rattlesnakes repeatedly crossed the fence to access forest-edge and ROW habitats. Rattlesnakes ostensibly crossed through damaged sections of the fence. The ROW was used most intensively by gravid females (n = 2), with their core home ranges overlapping the ROW by more than 50 percent. Despite the fence crossings, all home ranges were bounded by the highway and no rattlesnake road mortality was observed. Operative temperature models revealed that the ROW provided warmer thermal regimes that were rare or unavailable in the forest. On average, field preferred gestation temperatures (Tb = 29.7°C, SD = 1.8) could be attained or exceeded for more than 5 times as many hours per day in the ROW (7.8 hours) than in the forest (1.4 hours). Habitat selection models indicated gravid females selected warmer thermal habitats that were spatially concentrated in the ROW and edge habitats, while non-gravid snakes avoided the ROW beyond the forest edge. Habitat use within the ROW was mostly limited to rocky microhabitat structures, especially riprap stone piles and subsurface rock crevices on roadcuts, which provided buffered thermal regimes with refugia from extreme temperatures during the day and warmer Te through the night. In forested landscapes, we encourage road planners to consider whether new road corridors are likely to introduce basking sites, and if so, maintain those features on the habitat-side of exclusion fencing, and consider restoring basking sites in the surrounding forest to reduce the potential for ecological trap formation.
... The effect of roads on dispersal and gene flow also varied among areas. One might expect the effect of roads to vary depending on where roads are located in the landscape, the amount of traffic the road sees and the number and type of roads in an area (Clark et al., 2010;Galpern et al., 2012;Holderegger & Wagner, 2008;McCartney-Melstad et al., 2018;Sunnucks & Balkenhol, 2015 occur. Even so, the total proportion of variance explained by roads is not much more than what is explained by distance alone, so roads are much less likely to have influence beyond the effect of distance. ...
The degree to which landscape genetics findings can be extrapolated to different areas of a species range is poorly understood. Here, we used a broadly distributed ectothermic lizard (Sceloporus occidentalis, Western Fence lizard) as a model species to evaluate the full role of topography, climate, vegetation, and roads on dispersal and genetic differentiation. We conducted landscape genetics analyses with a total of 119 individuals in five areas within the Sierra Nevada mountain range. Genetic distances calculated from thousands of ddRAD markers were used to optimize landscape resist- ance surfaces and infer the effects of landscape and topographic features on genetic connectivity. Across study areas, we found a great deal of consistency in the primary environmental gradients impacting genetic connectivity, along with some site-specific differences, and a range in the proportion of genetic variance explained by environ- mental factors across study sites. High-elevation colder areas were consistently found to be barriers to gene flow, as were areas of high ruggedness and slope. High tempera- ture seasonality and high precipitation during the winter wet season also presented a substantial barrier to gene flow in a majority of study areas. The effect of other landscape variables on genetic differentiation was more idiosyncratic and depended on specific attributes at each site. Across study areas, canyon valleys were always implicated as facilitators to dispersal and key features linking populations and main- taining genetic connectivity, though the relative importance varied in different areas. We emphasize that spatial data layers are complex and multidimensional, and careful consideration of spatial data correlation structure and robust analytic frameworks will be critical to our continued understanding of spatial genetics processes.
... In addition, it should be noted that the reason why barriers to movement are given a high position in the proposed framework lies in the fact that they represent another significant negative impact of roads on wildlife. They have serious impacts on wildlife populations, such as limiting gene flow and reducing genetic diversity for populations on opposite roadsides [18,[41][42][43][44]. Hence, it is especially valuable to further analyze the factors related to barriers to movement ( Figure 2). ...
Road mortalities caused by wildlife–vehicle collisions (WVCs) are the most obvious negative effect of roads on wildlife. Identifying the influencing factors and summarizing the spatial-temporal patterns of WVCs have been important research trends in recent decades. However, most studies have only considered a portion of the factors, and there remains a lack of a relatively complete framework, including the numerous factors of WVCs, as well as the underlying transmission mechanisms between factors. In this study, an analytical framework incorporating a wide range of previously discussed factors is constructed. The framework not only displays the possible direction of the influence of each factor on WVCs, but also summarizes some important potential explanations under some circumstances and reveals the main interactions between certain types of factors. From one perspective, the factors affecting WVCs can be divided into four categories: species characteristics, road and traffic characteristics, landscape and environmental characteristics, and driver-related factors and specific human activities. From another perspective, the factors affecting WVCs can be mainly categorized as those related to entering roads and those related to leaving roads safely. The study begins with a discussion of three important sub-frameworks: factors promoting road crossing, factors related to barriers to movement, and factors related to safe crossing. Finally, a suggestion is provided to promote the research on WVCs globally.
... bush cricket, Holzhauer et al., 2006; costal tailed frogs, Spear & Storfer, 2008; copperhead snake, Maigret et al., 2020) ranging from ~2 to 50 generations. Many studies also show that genetic divergence can develop rather quickly in response to strong barriers to gene flow (Ascensão et al., 2016;Holderegger & Di Giulio, 2010;Keller et al., 2004;Mapelli et al., 2020), and commonly, the observed genetic patterns reflect contemporary landscapes rather than historical ones (Clark et al., 2010;Crossley et al., 2019;Winiarski et al., 2020;Zellmer & Knowles, 2009). Overall, there is a clear need for studies investigating time lags in nature and discussing their implications for landscape genetic methods and biodiversity conservation (Manel & Holderegger, 2013). ...
... Current genetic variation is expected to reflect past rather than present landscapes due to time lags, that is, the time required for genetic variation to reflect the new demographic and connectivity Clark et al., 2010;Crossley et al., 2019;Winiarski et al., 2020; and time lags of ~2 to 50 generations, e.g. Holzhauer et al., 2006;Maigret et al., 2020;Spear & Storfer, 2008) and the many factors influencing them (Epps & Keyghobadi, 2015). ...
Aim
Current genetic variation and differentiation are expected to reflect the effects of past rather than present landscapes due to time lags, that is, the time necessary for genetic diversity to reach equilibrium and reflect demography. Time lags can affect our ability to infer landscape use and model connectivity and also obscure the genetic consequences of recent landscape changes. In this work, we test whether past forest cover better explains contemporary patterns of genetic differentiation in two closely related but ecologically distinct newt species—Lissotriton montandoni and L. vulgaris.
Location
Carpathian Mountains and foothills.
Methods
Genetic differentiation between populations was related to landscape resistance optimized with tools from landscape genetics, for multiple timeframes, using forest‐cover data from 1963 to 2015. Analyses were conducted for pairs of populations at distances from 1 to 50 km.
Results
We find evidence for a time lag in L. montandoni, with forest cover from 40 years ago (ca. 10 newt generations) better explaining current genetic differentiation. In L. vulgaris, current genetic differentiation was better predicted by present land‐cover models with lower resistance given to open forests. This result may reflect the generalist ecology of L. vulgaris, its lower effective population sizes and exposure to habitat destruction and fragmentation.
Main Conclusions
Our study provides evidence for time lags in L. montandoni, showing that the genetic consequences of landscape change for some species are not yet evident. Our findings highlight the interspecific variation in time lag prevalence and demonstrate that current patterns of genetic differentiation should be interpreted in the context of historical landscape changes.
... Linear features such as paved roads and highways are artificial structures known to have a significant impact on gene flow in many species (Clark et al., 2010;Kuehn et al., 2007;Robinson et al., 2012), and highways have been identified as physical barriers that impede movement and lead to a decline in genetic diversity (Epps et al., 2005). Huge artificial linear features may also act as behavioral barriers (Kimmig et al., 2020;Laundré, Hernández, & Altendorf, 2001). ...
Elucidating how demography and contemporary landscape features regulate functional connectivity and diversity is crucial to implementing effective conservation strategies, especially in highly fragmented landscapes. We analyzed the impacts of landscape features and demographic events on the dispersal and genetic structure of a locally endangered carnivore, the leopard cat (Prionailurus bengalensis), across subtropical Taiwan. We genotyped 184 samples from both human-impacted and natural habitats using 12 nuclear microsatellites and a mitochondrial marker. Bayesian analyses revealed a recent population decline within the past 200 years, and a current genetic hotspot appears to have arisen from interbreeding between previously diverged populations. Genetic clustering and resistance surface modeling support the notion that the population structure is influenced by manufactured linear and natural topographical features. We employed a landscape optimization procedure using two genetic distances to reveal that highways and elevation are the most significant barriers affecting leopard cat connectivity. Niche modeling indicated that low temperature is a primary factor limiting leopard cat occurrence, potentially explaining why their resistance to movement is positively correlated with elevation. Utilizing an ensemble approach, we predict that suitable leopard cat habitat will shrink northward and towards higher more rugged altitudes. Our study provides genetic evidence that anthropogenic landscape features compromise the connectivity and persistence of a vagile carnivore that is under severe pressure from habitat loss and human activities. Our findings serve as a model for landscape genetic studies of island carnivores in subtropical regions, aimed at understanding how manufactured landscapes affect intra-species diversity and dispersal.
... Urbanization transforms landscapes dramatically as human populations modify rural and natural environments to create densely populated settlements. Although limit gene flow (Clark et al. 2010). Urbanization not only alters habitats but also creates novel micro-environments within these urbanized areas (Hobbs et al. 2009). ...
Gopherus polyphemus (Gopher Tortoise) is a federally listed or state threatened species throughout its range due to significant declines in its populations, largely due to habitat loss and fragmentation. Many Gopher Tortoises reside on private lands in human-impacted and urbanized areas, yet the value of these populations to the conservation of the species is unclear. We conducted a radio-telemetry study on a population of Gopher Tortoises in a residential neighborhood in Cape Coral, FL, to determine if they could be benefitting from their location within an urban environment (i.e., whether or not they are “urbanophiles”). Some findings suggested that these tortoises could exist in an urban environment. There were no confirmed mortalities among the 10 tortoises in the year-long study, though 1 male dispersed from the area and later disappeared after 6 months. The mean annual home ranges (100% MCP) were 1.19 ha (min–max: 0.39–2.71 ha) for females (n = 5) and 1.13 ha (min–max: 0.51–1.72 ha) for males (n = 4), which are comparable to home-range sizes in natural habitats. However, other findings suggested that this urban landscape limited the animals. Gopher Tortoises rarely crossed roads (5% of all movements) and avoided lots with houses and associated human structures, in favor of undeveloped lots. Efforts to sustain these animals in urban environments can start implementing management strategies that integrate greenspaces within urban landscapes as an additional approach to protect this threatened species. This study suggests that adult Gopher Tortoises are adaptable and tolerant to high levles of urbanization and human disturbance, yet the degree to which tortoises can persist over time in these landscapes needs further exploration.
... A focal point of biological conservation is the impact that habitat fragmentation has on genetic diversity and population structure (Keyghobadi 2007;Clark et al. 2010;Herrmann et al. 2017). Barriers to gene flow, whether natural (e.g., Hartmann et al. 2013;Binks et al. 2019) or anthropogenic (e.g., Hartmann et al. 2013;Herrmann et al. 2017), can lead to genetic differentiation among populations, even in species with very small ranges (e.g., Quéméré et al. 2010). ...
Described in 2009, the Patch-nosed Salamander (Urspelerpes brucei) is a miniature species of lungless salamander with a geographic range of only ~ 45 km². This species is endemic to the foothills of the Appalachian Mountains in extreme northeastern Georgia and northwestern South Carolina. The Tugaloo River—a waterway of some 50 m in width that forms the political boundary between the two states—bisects the tiny range of U. brucei and likely acts as a barrier to gene flow. Using RADcap data and a suite of complementary population genomic analyses, we evaluated the role that this river and its tributaries may play in enabling and/or interrupting gene flow among populations of U. brucei, and we investigated patterns of within-population and between-population genetic variation. Our results revealed a general pattern of isolation-by-stream distance and indicated that a population separated by the Tugaloo River is moderately more differentiated than what is explainable by stream distance alone. Unique in both its physiography and geologic history, this region in which U. brucei lives also harbors more than a dozen other species of lungless salamanders. Therefore, the genetic patterns that we have elucidated may have larger implications for differentiation among populations of other species with similar dispersal abilities.
