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1.
Carnivores are often particularly sensitive to landscape fragmentation. Ecological corridors may help to connect local populations, ensuring gene flow and retaining viable meta-populations. We aimed to establish habitat suitability models for two large carnivores in Poland, the grey wolf Canis lupus Linnaeus, 1758 and the Eurasian lynx Lynx lynx Linnaeus, 1758, based on ecological niche factor analysis (ENFA). Secondly, we calculated least cost paths (LCPs) based on cost values obtained from ENFA. Thirdly, we determined structures that might act as barriers, thus diminishing the value of the corridor unless appropriate conservation measures are taken. We compared some of the results with actual dispersal data of four lynx in eastern Poland. Results indicate that both species are highly marginalised. Less habitat that is currently available in Poland is suitable for lynx than for wolves. We determined a total of 76 LCPs. Comparison of these theoretical corridors with actual dispersal routes suggests that the traits of calculated LCPs are mostly within the range of those of real routes. We highlight a variety of features that might act as barriers, such as major roads (including planned highways), urbanized areas, and large un-forested areas. We give suggestions where concerted conservation efforts (eg wildlife passages) might be particularly well-directed.  相似文献   

2.
In this article, we applied demographic and genetic approaches to assess how landscape features influence dispersal patterns and genetic structure of the common frog Rana temporaria in a landscape where anthropogenic perturbations are pervasive (urbanization and roads). We used a combination of GIS methods that integrate radiotracking and landscape configuration data, and simulation techniques in order to estimate the potential dispersal area around breeding patches. Additionally, genetic data provided indirect measures of dispersal and allowed to characterise the spatial genetic structure of ponds and the patterns of gene flow across the landscape. Although demographic simulations predicted six distinct groups of habitat patches within which movement can occur, genetic analyses suggested a different configuration. More precisely, BAPS5 spatial clustering method with ponds as the analysis unit detected five spatial clusters. Individual-based analyses were not able to detect significant genetic structure. We argue that (1) taking into account that each individual breeds in specific breeding patch allowed for better explanation of population functioning, (2) the discrepancy between direct (radiotracking) and indirect (genetic) estimates of subpopulations (breeding patches) is due to a recent landscape fragmentation (e.g. traffic increase). We discuss the future of this population in the face of increasing landscape fragmentation, focusing on the need for combining demographic and genetic approaches when evaluating the conservation status of population subjected to rapid landscape changes.  相似文献   

3.
Urban areas are highly fragmented and thereby exert strong constraints on individual dispersal. Despite this, some species manage to persist in urban areas, such as the garden snail, Cornu aspersum, which is common in cityscapes despite its low mobility. Using landscape genetic approaches, we combined study area replication and multiscale analysis to determine how landscape composition, configuration and connectivity influence snail dispersal across urban areas. At the overall landscape scale, areas with a high percentage of roads decreased genetic differentiation between populations. At the population scale, genetic differentiation was positively linked with building surface, the proportion of borders where wooded patches and roads appeared side by side and the proportion of borders combining wooded patches and other impervious areas. Analyses based on pairwise genetic distances validated the isolation‐by‐distance and isolation‐by‐resistance models for this land snail, with an equal fit to least‐cost paths and circuit‐theory‐based models. Each of the 12 landscapes analysed separately yielded specific relations to environmental features, whereas analyses integrating all replicates highlighted general common effects. Our results suggest that urban transport infrastructures facilitate passive snail dispersal. At a local scale, corresponding to active dispersal, unfavourable habitats (wooded and impervious areas) isolate populations. This work upholds the use of replicated landscapes to increase the generalizability of landscape genetics results and shows how multiscale analyses provide insight into scale‐dependent processes.  相似文献   

4.
The dispersal process is crucial in determining the fate of populations over time, but habitat fragmentation limits or prevents it. Landscape genetic is an effective tool to assess the degree to which dispersal still occurs in fragmented landscapes. The purpose of this study was to investigate the landscape determinants of genetic differentiation in the hazel dormouse (Muscardinus avellanarius), a forest-dependent species of conservation concern. By comparing subpopulations in a continuous (SLR) and a fragmented (VTH) population, we (i) searched for the presence of Isolation-by-Resistance (IBR); (ii) estimated migration rates; (iii) evaluated the degree of inbreeding and genetic drift, and searched for their landscape determinants. We found an IBR effect in VTH, which heavily hindered the dispersal process. The overall number of migrants among VTH subpopulations was very low (1 per generation, compared to 15 in SLR), although a between-patch displacement of about 4 km along a well-structured hedgerow probably occurred. The inbreeding (F?>?0.2 in most subpopulations) and the genetic drift (four out five subpopulations showed private alleles on several loci, with relatively high frequencies) are of particular concern in VTH. However, they were found to be limited in large patches or in patches connected by hedgerows with a high number of neighbouring patches. As a conservation strategy in the VTH landscape, characterized by small patches, we suggest that the dispersal process among subpopulations is enhanced to sustain a functional metapopulation. For this purpose, an effective ecological network should be created by enhancing the continuity and the internal features of hedgerows.  相似文献   

5.
In the course of their maturation, most young wolves leave their natal pack and disperse in search for mating partners, improved food availability and new territories. We investigated whether this dispersal is affected by anthropogenic infrastructure in a 5,000 km2 area of the eastern region of the Polish Carpathian Mountains occupied by wolves. A radio-collared male wolf covered 230 km while dispersing through forested hills and densely populated valleys. To test if such dispersal is common in the population we analysed by microsatellite genotyping 39 samples taken from live-trapped wolves or wolves found dead in the study area. Although the obtained genotypes were assigned to different clusters in Bayesian tests, we could not ascribe this structure to landscape features, but rather to shared ancestry of wolf individuals found in distant locations. Moreover, we could not detect a spatial genetic structure in the wolf population, indicating a random occurrence of genotypes within the study area. Observation of the dispersing wolf and the absence of spatial genetic structure imply that wolves are still able to roam the entire area despite high densities of roads and a dense human population. Thus, we concluded that the existing anthropogenic infrastructure does not restrict wolf dispersal in the area and the studied wolves represent a coherent part of the Polish Carpathian wolf population.  相似文献   

6.
张宇  李丽  张于光  李佳  薛亚东  李迪强 《生态学报》2019,39(8):2935-2945
川金丝猴湖北种群是川金丝猴分布的最东缘,现主要分布于神农架国家公园和巴东自然保护区,其作为单独的管理单元,相对较低的遗传多样性、孤立的遗传状态和较小的种群数量,使得该种群面对环境变化脆弱性高。以神农架为研究区域,首先基于物种分布模型获得川金丝猴移动的阻力图层,利用电路理论分析适宜生境连接度;其次,设置道路和旅游两个人为干扰情景,运用最小费用距离模型与电路理论模型,分析道路和旅游活动对川金丝猴移动路径以及对不同亚群内和亚群间连通性的影响;最后,利用CDPOP软件模拟道路对川金丝猴遗传多样性的影响。结果表明:(1)神农架川金丝猴适宜生境分布较集中,生境斑块间存在多个潜在扩散区域;(2)道路改变了川金丝猴往来于南北生境间的最优路径,旅游干扰对川金丝猴移动路径无明显影响,其干扰主要在于川金丝猴对其具有回避性,回避距离为100 m;(3)道路显著降低金猴岭亚群内的连通性,并显著增加了所有亚群间的移动阻力,旅游活动对亚群内和亚群间的连通性无显著影响;(4)川金丝猴种群在150年内的遗传多样性呈下降趋势,道路的影响将加剧遗传多样性下降的程度。基于以上结果本文提出了针对性的保护建议,对于该物种的保护和其他濒危物种的类似研究具有较强的参考价值和借鉴意义。  相似文献   

7.
道路对林地景观连接度的影响——以巩义市为例   总被引:1,自引:0,他引:1  
梁国付  许立民  丁圣彦 《生态学报》2014,34(16):4775-4784
基于景观连接度原理,借用景观连接度指数,在地理信息系统支持下,探讨了巩义市山区林地景观在不同距离阈值下连接度的变化,定量分析了道路对林地景观连接度的影响。结果显示,随着景观距离阈值的增大,无论是否有道路,林地景观整体可能连通性指数值都表现为逐渐增大;对林地景观连接度起"非常高"和"高"作用的林地斑块数量都比较少,但占林地总面积比例较大,面积大的林地斑块在提高景观连接度中起的作用较大;道路的分割使得林地斑块重要值降低,就单一斑块而言,随着景观距离阈值的增大,分割成的小斑块的重要值降低程度在逐渐减小。  相似文献   

8.
We investigated local gene flow in a high-density wolf (Canis lupus) population of the Italian Apennines, where no effective barrier to wolf dispersal was present. From 1998 to 2004 we examined wolf carcasses and non-invasively collected samples, focusing on three mountain districts, separated by two valleys, where wolf packs showed high spatial stability. Using nine autosomal microsatellites we successfully genotyped 177 samples, achieving the identification of 74 wolves. Genetic relatedness steeply decreased with increasing distance between sampling areas, thus suggesting that short-distance interpack migration is infrequent in this population. In addition, no individual from a central pack under intensive monitoring was sampled in the range of the surrounding packs over a 4-year period. The limited short-distance gene flow resulted in a cryptic genetic structure, which was revealed by Bayesian analysis. A different genetic cluster was found in each of the three mountain areas, and a small proportion of first-generation immigrants was detected. Overall, the present study suggests that local genetic differentiation in Italian wolves might arise from high spatial stability of packs and can be favoured by a combination of long-range dispersal, the attitude to mate between unrelated individuals and a high young mortality rate.  相似文献   

9.
Landscape features of anthropogenic or natural origin can influence organisms' dispersal patterns and the connectivity of populations. Understanding these relationships is of broad interest in ecology and evolutionary biology and provides key insights for habitat conservation planning at the landscape scale. This knowledge is germane to restoration efforts for the New England cottontail (Sylvilagus transitionalis), an early successional habitat specialist of conservation concern. We evaluated local population structure and measures of genetic diversity of a geographically isolated population of cottontails in the northeastern United States. We also conducted a multiscale landscape genetic analysis, in which we assessed genetic discontinuities relative to the landscape and developed several resistance models to test hypotheses about landscape features that promote or inhibit cottontail dispersal within and across the local populations. Bayesian clustering identified four genetically distinct populations, with very little migration among them, and additional substructure within one of those populations. These populations had private alleles, low genetic diversity, critically low effective population sizes (3.2–36.7), and evidence of recent genetic bottlenecks. Major highways and a river were found to limit cottontail dispersal and to separate populations. The habitat along roadsides, railroad beds, and utility corridors, on the other hand, was found to facilitate cottontail movement among patches. The relative importance of dispersal barriers and facilitators on gene flow varied among populations in relation to landscape composition, demonstrating the complexity and context dependency of factors influencing gene flow and highlighting the importance of replication and scale in landscape genetic studies. Our findings provide information for the design of restoration landscapes for the New England cottontail and also highlight the dual influence of roads, as both barriers and facilitators of dispersal for an early successional habitat specialist in a fragmented landscape.  相似文献   

10.
Understanding the types and magnitude of human‐caused mortality is essential for maintaining viable large carnivore populations. We used a database of cause‐specific mortality to examine how hunting regulations and landscape configurations influenced human‐caused mortality of North American gray wolves (Canis lupus). Our dataset included 21 studies that monitored the fates of 3564 wolves and reported 1442 mortalities. Human‐caused mortality accounted for 61% of mortality overall, with 23% due to illegal harvest, 16% due to legal harvest, and 12% the result of management removal. The overall proportion of anthropogenic wolf mortality was lowest in areas with an open hunting season compared to areas with a closed hunting season or mixed hunting regulations, suggesting that harvest mortality was neither fully additive nor compensatory. Proportion of mortality from management removal was reduced in areas with an open hunting season, suggesting that legal harvest may reduce human‐wolf conflicts or alternatively that areas with legal harvest have less potential for management removals (e.g., less livestock depredation). Proportion of natural habitat was negatively correlated with the proportion of anthropogenic and illegal harvest mortality. Additionally, the proportion of mortality due to illegal harvest increased with greater natural habitat fragmentation. The observed association between large patches of natural habitat and reductions in several sources of anthropogenic wolf mortality reiterate the importance of habitat preservation to maintain wolf populations. Furthermore, effective management of wolf populations via implementation of harvest may reduce conflict with humans. Effective wolf conservation will depend on holistic strategies that integrate ecological and socioeconomic factors to facilitate their long‐term coexistence with humans.  相似文献   

11.
Dispersal patterns can dictate genetic population structure and, ultimately, population resilience, through maintaining gene flow and genetic diversity. However, geographical landforms, such as peninsulas, can impact dispersal patterns and thus be a barrier to gene flow. Here, we use 13 375 genome-wide single-nucleotide polymorphisms (SNPs) to evaluate genetic population structure and infer dispersal patterns of the Western Grasswren Amytornis textilis textilis (WGW, n = 140) in the Shark Bay region of Western Australia. We found high levels of genetic divergence between subpopulations on the mainland (Hamelin) and narrow peninsula (Peron). In addition, we found evidence of further genetic sub-structuring within the Hamelin subpopulation, with individuals collected from the western and eastern regions of a conservation reserve forming separate genetic clusters. Spatial autocorrelation analysis within each subpopulation revealed significant local-scale genetic structure up to 35 km at Hamelin and 20 km at Peron. In addition, there was evidence of male philopatry in both subpopulations. Our results suggest a narrow strip of land may be acting as a geographical barrier in the WGW, limiting dispersal between a peninsula and mainland subpopulation. In addition, heterogeneous habitat within Hamelin may be restricting dispersal at the local scale. Furthermore, there is evidence to suggest that the limited gene flow is asymmetrical, with directional dispersal occurring from the bounded peninsula subpopulation to the mainland. This study highlights the genetic structure existing within and between some of the few remaining WGW subpopulations, and shows a need to place equal importance on conservation efforts to maintain them in the future.  相似文献   

12.
Salix hukaoana is an endangered riparian pioneer tree that is distributed within a restricted area of Japan. Microsatellite genetic variations and genetic structures were investigated in 80 subpopulations patchily distributed within five river basins with varying degrees of habitat fragmentation. The correlation between geographic distance and genetic distance based on the Bayesian assignment test was significant across relatively intact riparian habitats, with steeper slopes of regression for more densely grouped subpopulations, suggesting restricted gene flow. However, the correlation became less apparent with increasing spacing of the habitat patches. These contradictory results are attributed to the increased chance of long-distance dispersal of sexual propagules among more isolated habitat patches. The observed accumulation of genetic diversity with increasing distance downstream along a few, but not all, of the rivers and the results of assignment tests suggested a downstream directionality of gene flow. The results of this study illustrate the patterns of genetic diversity and contemporary dispersal of S. hukaoana, and provide important insights into understanding the gene dispersal of riparian trees and into the conservation of genetic resources for this species.  相似文献   

13.
Habitat loss and fragmentation are considered to be severe threats to biodiversity, and maintaining natural levels of landscape connectivity may be one of the best responses to these issues. Graph-based habitat availability (reachability) metrics have been shown to be an appropriate method for a multifaceted but coherent landscape connectivity assessment. These metrics can be partitioned into three commensurate fractions (intra, flux, connector) that quantify the different ways in which habitat patches contribute to the overall landscape connectivity and habitat availability. In particular, the connector fraction measures the contribution of patches to the connectivity between other habitat areas as irreplaceable connecting elements or stepping stones. Because many conservation efforts and initiatives are focused on conserving or restoring corridors and other linkages between habitat areas, it is critical to understand more thoroughly the conditions under which investing in these connecting elements is an efficient management strategy. For this purpose, we analysed the contribution of the connector fraction in different simulated habitat patterns under different levels of habitat amount and fragmentation and in natural habitats for endangered forest bird species in Catalonia (Spain). We show that a prominent role of individual stepping stone patches as irreplaceable providers of habitat connectivity and availability arises only under a relatively narrow set of conditions, characterised by low habitat amount, high habitat fragmentation and modest to intermediate species dispersal abilities. We suggest that to support connectivity-related investments, it is necessary to focus on those few species or dispersal distance ranges that are likely to be both most dependent on and most benefited by the conservation or restoration of stepping stone patches. We conclude that the total amount of reachable habitat for a particular species is rarely determined by the contribution of individual connectors as the only dominant factor. Therefore, conservationists should be cautious not to overemphasise the importance of connectivity investments and to balance them with other conservation alternatives and strategies to promote species conservation in heterogeneous landscapes.  相似文献   

14.
Functional connectivity is crucial for the persistence of a metapopulation, because migration among subpopulations enables recolonization and counteracts genetic drift, which is especially important in small subpopulations. We studied the degree and drivers of connectivity among occupied patches of a coastal dune metapopulation of the Natterjack Toad (Epidalea calamita Laurenti), on the basis of microsatellite variation. As spatial landscape heterogeneity is expected to influence dispersal and genetic structure, we analyzed which landscape features affect functional connectivity and to what extent. Sixty different landscape resistance scenarios as well as the isolation-by-distance model were compared using two landscape genetics approaches. We identified three subpopulations with unidirectional levels of gene flow among the two most geographically separated subpopulations, while inferred gene flow into the geographically intermediate subpopulation was limited. Urbanization and vegetation height negatively affected connectivity. Low estimates of genetic diversity and effective population size indicate that conservation measures in the smallest and most isolated subpopulation are required.  相似文献   

15.
Patterns of human development are shifting from concentrated housing toward sprawled housing intermixed with natural land cover, and wildlife species increasingly persist in close proximity to housing, roads, and other anthropogenic features. These associations can alter population dynamics and evolutionary trajectories. Large carnivores increasingly occupy urban peripheries, yet the ecological consequences for populations established entirely within urban and exurban landscapes are largely unknown. We applied a spatial and landscape genetics approach, using noninvasively collected genetic data, to identify differences in black bear spatial genetic patterns across a rural‐to‐urban gradient and quantify how development affects spatial genetic processes. We quantified differences in black bear dispersal, spatial genetic structure, and migration between differing levels of development within a population primarily occupying areas with >6 houses/km2 in western Connecticut. Increased development disrupted spatial genetic structure, and we found an association between increased housing densities and longer dispersal. We also found evidence that roads limited gene flow among bears in more rural areas, yet had no effect among bears in more developed ones. These results suggest dispersal behavior is condition‐dependent and indicate the potential for landscapes intermixing development and natural land cover to facilitate shifts toward increased dispersal. These changes can affect patterns of range expansion and the phenotypic and genetic composition of surrounding populations. We found evidence that subpopulations occupying more developed landscapes may be sustained by male‐biased immigration, creating potentially detrimental demographic shifts.  相似文献   

16.
The successful re‐introduction of grey wolves to the western United States is an impressive accomplishment for conservation science. However, the degree to which subpopulations are genetically structured and connected, along with the preservation of genetic variation, is an important concern for the continued viability of the metapopulation. We analysed DNA samples from 555 Northern Rocky Mountain wolves from the three recovery areas (Greater Yellowstone Area, Montana, and Idaho), including all 66 re‐introduced founders, for variation in 26 microsatellite loci over the initial 10‐year recovery period (1995–2004). The population maintained high levels of variation (HO = 0.64–0.72; allelic diversity k = 7.0–10.3) with low levels of inbreeding (FIS < 0.03) and throughout this period, the population expanded rapidly (n1995 = 101; n2004 = 846). Individual‐based Bayesian analyses revealed significant population genetic structure and identified three subpopulations coinciding with designated recovery areas. Population assignment and migrant detection were difficult because of the presence of related founders among different recovery areas and required a novel approach to determine genetically effective migration and admixture. However, by combining assignment tests, private alleles, sibship reconstruction, and field observations, we detected genetically effective dispersal among the three recovery areas. Successful conservation of Northern Rocky Mountain wolves will rely on management decisions that promote natural dispersal dynamics and minimize anthropogenic factors that reduce genetic connectivity.  相似文献   

17.
Although the mechanisms controlling gene flow among populations are particularly important for evolutionary processes, they are still poorly understood, especially in the case of large carnivoran mammals with extensive continuous distributions. We studied the question of factors affecting population genetic structure in the grey wolf, Canis lupus, one of the most mobile terrestrial carnivores. We analysed variability in mitochondrial DNA and 14 microsatellite loci for a sample of 643 individuals from 59 localities representing most of the continuous wolf range in Eastern Europe. We tested an array of geographical, historical and ecological factors to check whether they may explain genetic differentiation among local wolf populations. We showed that wolf populations in Eastern Europe displayed nonrandom spatial genetic structure in the absence of obvious physical barriers to movement. Neither topographic barriers nor past fragmentation could explain spatial genetic structure. However, we found that the genetic differentiation among local populations was correlated with climate, habitat types, and wolf diet composition. This result shows that ecological processes may strongly influence the amount of gene flow among populations. We suggest natal-habitat-biased dispersal as an underlying mechanism linking population ecology with population genetic structure.  相似文献   

18.
Habitat loss and fragmentation are widely acknowledged as the main driver of the decline of giant panda populations. The Chinese government has made great efforts to protect this charming species and has made remarkable achievements, such as population growth and habitat expansion. However, habitat fragmentation has not been reversed. Protecting giant pandas in a large spatial extent needs to identify core habitat patches and corridors connecting them. This study used an equal‐sampling multiscale random forest habitat model to predict a habitat suitability map for the giant panda. Then, we applied the resistant kernel method and factorial least‐cost path analysis to identify core habitats connected by panda dispersal and corridors among panda occurrences, respectively. Finally, we evaluated the effectiveness of current protected areas in representing core habitats and corridors. Our results showed high scale dependence of giant panda habitat selection. Giant pandas strongly respond to bamboo percentage and elevation at a relatively fine scale (1 km), whereas they respond to anthropogenic factors at a coarse scale (≥2 km). Dispersal ability has significant effects on core habitats extent and population fragmentation evaluation. Under medium and high dispersal ability scenarios (12,000 and 20,000 cost units), most giant panda habitats in the Qionglai mountain are predicted to be well connected by dispersal. The proportion of core habitats covered by protected areas varied between 38% and 43% under different dispersal ability scenarios, highlighting significant gaps in the protected area network. Similarly, only 43% of corridors that connect giant panda occurrences were protected. Our results can provide crucial information for conservation managers to develop wise strategies to safeguard the long‐term viability of the giant panda population.  相似文献   

19.
Understanding population structure is important for guiding ongoing conservation and restoration efforts. The greater sage-grouse (Centrocercus urophasianus) is a species of concern distributed across 1.2 million km2 of western North America. We genotyped 1499 greater sage-grouse from 297 leks across Montana, North Dakota and South Dakota using a 15 locus microsatellite panel, then examined spatial autocorrelation, spatial principal components analysis, and hierarchical Bayesian clustering to identify population structure. Our results show that at distances of up to ~240 km individuals exhibit greater genetic similarity than expected by chance, suggesting that the cumulative effect of short-range dispersal translates to long-range connectivity. We found two levels of hierarchical genetic subpopulation structure. These subpopulations occupy significantly different elevations and are surrounded by divergent vegetative communities with different dominant subspecies of sagebrush, each with its own chemical defense against herbivory. We propose five management groups reflective of genetic subpopulation structure. These genetic groups are largely synonymous with existing priority areas for conservation. On average, 85.8 % of individuals within each conservation priority area assign to a distinct subpopulation. Our results largely support existing management decisions regarding subpopulation boundaries.  相似文献   

20.
Metacommunity theory poses that the occurrence and abundance of species is a product of local factors, including disturbance, and regional factors, like dispersal among patches. While metacommunity ideas have been broadly tested there is relatively little work on metacommunities subject to disturbance. We focused on how localized disturbance and dispersal interact to determine species composition in metacommunities. Experiments conducted in simple two-patch habitats containing eight protozoa and rotifer species tested how dispersal altered community composition in both communities that were disturbed and communities that connected to refuge communities not subject to disturbance. While disturbance lowered population densities, in disturbed patches connected to undisturbed patches this was ameliorated by immigration. Furthermore, species with high dispersal abilities or growth rates showed the fastest post-disturbance recovery in presence of immigration. Connectivity helped to counteract the negative effect of disturbances on local populations, allowing mass-effect-driven dispersal of individuals from undisturbed to disturbed patches. In undisturbed patches, however, local population sizes were not significantly reduced by emigration. The absence of a cost of dispersal for undisturbed source populations is consistent with a lack of complex demography in our system, such as age- or sex-specific emigration. Our approach provides an improved way to separate components of population growth from organisms' movement in post-disturbance recovery of (meta)communities. Further studies are required in a variety of ecosystems to investigate the transient dynamics resulting from disturbance and dispersal.  相似文献   

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