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1.
Altered functional connectivity and genetic diversity of a threatened salamander in an agroecosystem
John A. Crawford William E. Peterman Andrew R. Kuhns Lori S. Eggert 《Landscape Ecology》2016,31(10):2231-2244
Context
Amphibian metapopulations have become increasingly fragmented in the Midwestern United States, with wetland-breeding salamanders being especially dependent on intact, high-quality forested landscapes. However, the degree to which amphibian populations are isolated, the factors that influence dispersal and, ultimately, functional connectivity remain areas in need of investigation.Objectives and methods
We combined population demographic and genetic approaches to assess how a landscape fragmented by agriculture influences functional connectivity and metapopulation dynamics of a locally threatened salamander (Ambystoma jeffersonianum).Results
We found that the allelic richness and heterozygosity of this species was significantly related to the level of connectivity with other occupied breeding wetlands and that decreased connectivity resulted in increased genetic differentiation. We also found that effective population size appears to be declining and, while correlative, our focal landscape has experienced significant losses of forested upland habitats and potential wetland breeding habitats over the last 200 years.Conclusions
By combining population and landscape genetic analyses with an assessment of regional wetland occupancy, our study has uniquely synthesized genetic and metapopulation processes, while also incorporating the effects of the landscape matrix on dispersal, connectivity, and population differentiation. The significant relationship between connectivity with heterozygosity, allelic richness, and genetic divergence observed in this study reinforces empirical observations of long distance dispersal and movements in ambystomatid salamanders. However, our results show that protection of core habitat around isolated wetlands may not sufficiently minimize genetic differentiation among populations and preserve critical genetic diversity that may be essential for the long-term persistence of local populations.2.
Erin L. Koen Jeff Bowman Colin J. Garroway Stephen C. Mills Paul J. Wilson 《Landscape Ecology》2012,27(1):29-43
Landscape heterogeneity can influence animal dispersal by causing a directional bias in dispersal rate, as certain landscape
configurations might promote, impede, or prevent movement and gene flow. In forested landscapes, logging operations often
contribute to heterogeneity that can reduce functional connectivity for some species. American martens (Martes americana) are one such species, as they are considered specialists of late-seral coniferous forests. We assessed marten gene flow
to test the hypothesis that habitat management has maintained landscape connectivity for martens in the managed forests of
Ontario, Canada. We genotyped 653 martens at 12 microsatellite loci, sampled from 29 sites across Ontario. We expected that
if forest management has an effect on marten gene flow, we would see a correlation between effective resistance, estimated
by circuit theory, and genetic distance, estimated by population graphs. Although we found a positive relationship between
effective resistance and genetic distance (Mantel r = 0.249, P < 0.001), marten gene flow was better described by isolation by Euclidean distance (Mantel r = 0.410, P < 0.001). Our results suggest that managed forests in Ontario are well connected for marten and neither impede nor promote
marten gene flow at the provincial scale. 相似文献
3.
Tzeidle N. Wasserman Samuel A. Cushman Michael K. Schwartz David O. Wallin 《Landscape Ecology》2010,25(10):1601-1612
Individual-based analyses relating landscape structure to genetic distances across complex landscapes enable rigorous evaluation
of multiple alternative hypotheses linking landscape structure to gene flow. We utilize two extensions to increase the rigor
of the individual-based causal modeling approach to inferring relationships between landscape patterns and gene flow processes.
First, we add a univariate scaling analysis to ensure that each landscape variable is represented in the functional form that
represents the optimal scale of its association with gene flow. Second, we use a two-step form of the causal modeling approach
to integrate model selection with null hypothesis testing in individual-based landscape genetic analysis. This series of causal
modeling indicated that gene flow in American marten in northern Idaho was primarily related to elevation, and that alternative
hypotheses involving isolation by distance, geographical barriers, effects of canopy closure, roads, tree size class and an
empirical habitat model were not supported. Gene flow in the Northern Idaho American marten population is therefore driven
by a gradient of landscape resistance that is a function of elevation, with minimum resistance to gene flow at 1500 m. 相似文献
4.
The tallgrass prairie of North America has undergone widespread habitat loss and fragmentation (<4% remains). The Flint Hills
region of Kansas and Oklahoma is the largest tallgrass prairie remaining and therefore provides an opportunity to study the
population genetic structure of grassland species in a relatively contiguous landscape and set a baseline for evaluating changes
when the habitat is fragmented. We adopted a landscape genetics approach to identify how landscape structure affected dispersal,
population genetic structure, and landscape connectivity of the Eastern Yellowbelly Racer (Coluber constrictor flaviventris) across a 13,500-km2 landscape in northeastern Kansas, USA. The racer population had high allelic diversity, high heterozygosity, and was maintaining
migration-drift equilibrium. Autocorrelation between genetic and geographic distance revealed that racers exhibited restricted
dispersal within 3 km, and isolation-by-distance. Significant isolation-by-distance occurred at broad regional scales (>100 km),
but because of sufficient gene flow between locations, we were unable to define discrete subpopulations using Bayesian clustering
analyses. Resistance distance, which considers the permeability of habitats, did not explain significant variation in genetic
distance beyond Euclidean distance alone, suggesting that racers are not currently influenced by landscape composition. In
northeastern Kansas, racers appear to be an abundant and continuously distributed snake that perceives the landscape as well
connected with no cover type currently impeding snake dispersal or gene flow. 相似文献
5.
Landscape connectivity can have profound consequences for distribution and persistence of populations and metapopulations.
Evaluating functional connectivity of a landscape for a species requires a measure of dispersal rates through landscape elements
at a spatial scale sufficient to encompass movement capabilities of individuals over the entire landscape. We evaluated functional
connectivity for a rock-dwelling mammal, the mountain vizcacha (Lagidium viscacia), in northern Patagonia. Because of the strict association of mountain vizcachas with rocks, we hypothesized that connectivity
for this species would be influenced by geology. We used molecular genetic estimates of gene flow to test spatially explicit
models of connectivity created with GIS cost-distance analysis of landscape resistance to movement. We analyzed the spatial
arrangement of cliffs with join counts and local k-function analyses. We did not capture and genotype individuals, but sampled
at the population level through non-invasive collection of feces of mountain vizcachas. The model of landscape connectivity
for mountain vizcachas based on geology was corroborated by the pattern of genetic structure, supporting the hypothesis that
functional connectivity for mountain vizcachas is influenced by geology, particularly by the distribution of appropriate volcanic
rocks. Analysis of spatial arrangement of cliffs indicated that occupied cliffs are clustered and confirmed that rivers act
as barriers to dispersal for mountain vizcachas. Our methods could be used, within certain constraints, to study functional
landscape connectivity in other organisms, and may be particularly useful for cryptic or endangered species, or those that
are difficult or expensive to capture. 相似文献
6.
Individual-based landscape genetic analyses provide empirically based models of gene flow. It would be valuable to verify
the predictions of these models using independent data of a different type. Analyses using different data sources that produce
consistent results provide strong support for the generality of the findings. Mating and dispersal movements are the mechanisms
through which gene flow operates in animal populations. The best means to verify landscape genetic predictions would be to
use movement data to independently predict landscape resistance. We used path-level, conditional logistic regression to predict
landscape resistance for American black bear (Ursus americanus) in a landscape in which previous work predicted population connectivity using individual-based landscape genetics. We found
consistent landscape factors influence genetic differentiation and movement path selection, with strong similarities between
the predicted landscape resistance surfaces. Genetic differentiation in American black bear is driven by spring movement (mating
and dispersal) in relation to residential development, roads, elevation and forest cover. Given the limited periods of the
year when gene flow events primarily occur, models of landscape connectivity should carefully consider temporal changes in
functional landscape resistance. 相似文献
7.
Bridgette E. Hagerty Kenneth E. Nussear Todd C. Esque C. Richard Tracy 《Landscape Ecology》2011,26(2):267-280
Heterogeneity in habitat often influences how organisms traverse the landscape matrix that connects populations. Understanding
landscape connectivity is important to determine the ecological processes that influence those movements, which lead to evolutionary
change due to gene flow. Here, we used landscape genetics and statistical models to evaluate hypotheses that could explain
isolation among locations of the threatened Mojave desert tortoise (Gopherus agassizii). Within a causal modeling framework, we investigated three factors that can influence landscape connectivity: geographic
distance, barriers to dispersal, and landscape friction. A statistical model of habitat suitability for the Mojave desert
tortoise, based on topography, vegetation, and climate variables, was used as a proxy for landscape friction and barriers
to dispersal. We quantified landscape friction with least-cost distances and with resistance distances among sampling locations.
A set of diagnostic partial Mantel tests statistically separated the hypotheses of potential causes of genetic isolation.
The best-supported model varied depending upon how landscape friction was quantified. Patterns of genetic structure were related
to a combination of geographic distance and barriers as defined by least-cost distances, suggesting that mountain ranges and
extremely low-elevation valleys influence connectivity at the regional scale beyond the tortoises’ ability to disperse. However,
geographic distance was the only influence detected using resistance distances, which we attributed to fundamental differences
between the two ways of quantifying friction. Landscape friction, as we measured it, did not influence the observed patterns
of genetic distances using either quantification. Barriers and distance may be more valuable predictors of observed population
structure for species like the desert tortoise, which has high dispersal capability and a long generation time. 相似文献
8.
Jeremy Larroque Sandrine Ruette Jean-Michel Vandel Sébastien Devillard 《Landscape Ecology》2016,31(3):517-531
Context
Quantifying gene flow in natural populations is a key topic in both evolutionary and conservation biology. Understanding the extent to which the landscape matrix facilitates or impedes gene flow is becoming a high priority in a context of worldwide habitat loss and fragmentation.Objectives
Unexpectedly, a lower genetic diversity and a higher genetic structure have been previously observed in the less fragmented and the most forested habitat across four pine marten (Martes martes) populations in France. Our aim was to quantify the effect of landscape on the spatial distribution of genetic diversity in two populations in contrasting habitats.Methods
We conducted an individual-based landscape genetics analysis in a highly fragmented rural plain (Bresse, n = 126) and in a highly forested (50 %) mountainous area (Ariège, n = 88) in France. We tested for isolation-by-resistance using least-cost distances and used a causal modeling approach on 16,384 landscape and 104 elevation resistance scenarios.Results
Landscape structure influenced the genetic differentiation in Bresse, with vegetation providing more genetic connectivity over the study area than open areas, while roads and human buildings showed unexpected low resistance to gene flow. In Ariège, genetic differentiation was mainly associated with changes in elevation, with an optimal elevation for gene flow of around 1700 m, likely associated with changes in vegetation structure.Conclusions
The pine marten seems to be able to cope with human-dominated landscapes and with fragmented forest landscapes, whereas elevation is the major driver of genetic differentiation in our mountainous landscape. Additionally, we highlight the importance of spatial replication in landscape genetics for deriving reliable conservation and management measures over the species distribution.9.
Context
The relative importance of habitat area and connectivity for species richness is often unknown. Connectivity effects may be confounded with area effects or they may be of minor importance as posited by the habitat-amount hypothesis.Objectives
We studied effects of habitat area and connectivity of linear landscape elements for plant species richness at plot level. We hypothesized that connectivity of linear landscape elements, assessed by resistance distance, has a positive effect on species richness beyond the effect of area and, further, that the relative importance of connectivity varies among groups of species with different habitat preferences and dispersal syndromes.Methods
We surveyed plant species richness in 50 plots (25 m2) located on open linear landscape elements (field margins, ditches) in eight study areas of 1 km2 in agricultural landscapes of Northwest Germany. We calculated the area of linear landscape elements and assessed their connectivity using resistance distance within circular buffers (500 m) around the plots. Effects of area and connectivity on species richness were modelled with generalised linear mixed models.Results
Species richness did not increase with area. Resistance distance had significant negative effects on total richness and on the richness of typical species of grasslands and wetlands. Regarding dispersal syndromes, resistance distance had negative effects on the richness of species with short-distance, long-distance and aquatic dispersal. The significant effects of resistance distance indicated that species richness increased with connectivity of the network of linear landscape elements.Conclusions
Connectivity is more important for plant species richness in linear landscape elements than area. In particular, the richness of plant species that are dispersal limited and confined to semi-natural habitats benefits from connective networks of linear landscape elements in agricultural landscapes.10.
Marleen M. P. Cobben Jana Verboom Paul F. M. Opdam Rolf F. Hoekstra René Jochem Marinus J. M. Smulders 《Landscape Ecology》2012,27(2):227-237
In response to climate change a species may move, adapt, or go extinct. For the adaptability of a population its genetic diversity
is essential, but climate change-induced range shifts can cause a loss of genetic diversity. We investigated how landscape
structure affects the level and distribution of genetic diversity in metapopulations subject to climate change-induced range
shifts. For this we used the spatially explicit, individual-based model METAPHOR which simulates metapopulation demography
and genetics under different temperature increase scenarios. The results indicated that increasing total habitat area may
enhance the maintenance of the genetic diversity in metapopulations while they are shifting their range under climate change.
However, the results also showed that a high level of total habitat area did not prevent the populations in the newly colonised
habitat area of being depleted of much of the original genetic diversity. We therefore conclude that enhancing landscape connectivity
may lead to a delayed loss of genetic diversity in metapopulations under climate change, but that additional measures would
be necessary to ensure its long-term conservation. Importantly, our simulations also show that a landscape which could be
regarded as well-structured under stable climatic conditions, may be inferior for the conservation of genetic diversity during
a range shift. This is important information for landscape management when developing strategies for the in situ conservation
of genetic variation in natural populations under climate change. 相似文献
11.
Marina Mergey Clara Bardonnet Thomas Quintaine Maxime Galan Carole Bodin Pauline Hubert Rémi Helder 《Landscape Ecology》2017,32(12):2261-2279
Context
In a global context of erosion of biodiversity, the current environmental policy in Europe is oriented towards the creation and the preservation of ecological networks for wildlife. However, most of the management guidelines arose from a structural landscape diagnostic without truly taking into consideration species’ needs.Objectives
We tested whether and how landscape elements influence the functional connectivity of landscapes for a forest specialist species, the European pine marten (Martes martes), in Northeastern France.Methods
We collected pine marten scats and tissues from 13 evenly distributed study sites across the whole study area in order to test several types of barriers such as highways, waterways, and open agricultural fields. We crossed the results of several methods: spatial autocorrelation analysis, causal modelling framework, and clustering methods.Results
The study indicates significant genetic differentiation among the sampling sites. A signal of isolation by distance was detected but disappeared after partialling out landscape or barrier resistance. The only model that was fully supported by causal modelling was the one identifying waterways as the main driver of genetic differentiation. Moreover, clustering analyses indicated the presence of genetic clusters, suggesting that pine marten spatial genetic pattern could be explained by the presence of waterways but also by their reluctance to cross open fields.Conclusions
The current ecological network could thus be improved by increasing permeability of waterways, in particular navigation canals, and by maintaining and restoring forested corridors in agricultural plains.12.
Thomas Broquet Nicolas Ray Eric Petit John M. Fryxell Françoise Burel 《Landscape Ecology》2006,21(6):877-889
Empirical studies of landscape connectivity are limited by the difficulty of directly measuring animal movement. ‘Indirect’
approaches involving genetic analyses provide a complementary tool to ‘direct’ methods such as capture–recapture or radio-tracking.
Here the effect of landscape on dispersal was investigated in a forest-dwelling species, the American marten (Martes americana) using the genetic model of isolation by distance (IBD). This model assumes isotropic dispersal in a homogeneous environment
and is characterized by increasing genetic differentiation among individuals separated by increasing geographic distances.
The effect of landscape features on this genetic pattern was used to test for a departure from spatially homogeneous dispersal.
This study was conducted on two populations in homogeneous vs. heterogeneous habitat in a harvested boreal forest in Ontario
(Canada). A pattern of IBD was evidenced in the homogeneous landscape whereas no such pattern was found in the near-by harvested
forest. To test whether landscape structure may be accountable for this difference, we used effective distances that take
into account the effect of landscape features on marten movement instead of Euclidean distances in the model of isolation
by distance. Effective distances computed using least-cost modeling were better correlated to genetic distances in both landscapes,
thereby showing that the interaction between landscape features and dispersal in Martes americana may be detected through individual-based analyses of spatial genetic structure. However, the simplifying assumptions of genetic
models and the low proportions in genetic differentiation explained by these models may limit their utility in quantifying
the effect of landscape structure. 相似文献
13.
Raquel Ribeiro Miguel A. Carretero Neftalí Sillero Gonzalo Alarcos Manuel Ortiz-Santaliestra Miguel Lizana Gustavo A. Llorente 《Landscape Ecology》2011,26(5):673-682
Landscape connectivity is a very recurrent theme in landscape ecology as it is considered pivotal for the long term conservation
of any organism’s populations. Nevertheless, this complex concept is still surrounded by uncertainty and confusion, largely
due to the separation between structural and functional connectivity. Amphibians are the most threatened vertebrates around
the globe, in Europe mostly due to habitat alteration, and to their particular life cycle. Pond breeding amphibians are considered
to be organised in metapopulations, enhancing the importance of landscape connectivity in this group of animals. We sampled
the amphibian species present in two pond groups in Central Western Spain. We applied the graph theory framework to these
two pond networks in order to determine the importance of each pond for the entire network connectivity. We related the pond
importance for connectivity with the species richness present in each pond. We tested if connectivity (partially) determined
the presence of the amphibian species sampled using logistic regression. The results show that the structural connectivity
of the pond network impacts on the amphibian species richness pattern and that the importance of the pond for the connectivity
of the network is an important factor for the presence of some species. Our results, hence, attest the importance of (structural)
landscape connectivity determining the pattern of amphibian (functional) colonization in discrete ponds. 相似文献
14.
The effects of aggregating sub-grid land surface variation on large-scale estimates of net primary production 总被引:4,自引:0,他引:4
The use of large grid cell databases (1/2° to 5°) to drive nonlinear ecosystem process models may create an incompatibility of scales which can often lead to biased outputs. Global simulations of net primary production (NPP) often assume that bias due to averaging of sub-grid variations in climate, topography, soils, and vegetation is minimal, yet the magnitude and behavior of this bias on estimates of NPP are largely unknown. The effects of averaging sub-grid land surface variations on NPP estimates were evaluated by simulating a 1° × 1° land surface area as represented by four successive levels of landscape complexity, ranging from a single computation to 8,456 computations of NPP for the study area. Averaging sub-grid cell landscape variations typical of the northern US Rocky Mountains can result in overestimates of NPP as large as 30 %. Aggregating climate within the 1° cell contributed up to 50 % of the bias to NPP estimates, while aggregating topography, soils, and vegetation was of secondary importance. Careful partitioning of complex landscapes can efficiently reduce the magnitude of this overestimation. 相似文献
15.
Linking movement behavior and fine-scale genetic structure to model landscape connectivity for bobcats (Lynx rufus) 总被引:1,自引:0,他引:1
Dawn M. Reding Samuel A. Cushman Todd E. Gosselink William R. Clark 《Landscape Ecology》2013,28(3):471-486
Spatial heterogeneity can constrain the movement of individuals and consequently genes across a landscape, influencing demographic and genetic processes. In this study, we linked information on landscape composition, movement behavior, and genetic differentiation to gain a mechanistic understanding of how spatial heterogeneity may influence movement and gene flow of bobcats in the agricultural landscape of Iowa (USA). We analyzed movement paths of 23 animals to parameterize landscape resistance surfaces, applied least cost path analysis to generate measures of effective geographic distance between DNA collection locations of 625 bobcats, and tested the correlation between genetic distance and the different models of geographic distance. We found that bobcats showed a strong preference for forest over any other habitat type, and that incorporating information on habitat composition both along the path and in the surrounding landscape provided the best model of movement. Measures of effective geographic distance were significantly correlated with genetic distance, but not once the effects of Euclidean distance were accounted for. Thus, despite the impact of habitat composition on movement behavior, we did not detect a signature of a landscape effect in genetic structure. Our results are consistent with the issue of limiting factors: the high uniformity of forest fragmentation across southern Iowa, the primary study area, results in a landscape resistance pattern virtually indistinguishable from the isolation-by-distance pattern. The northern portion of the state, however, is predicted to pose a high level of resistance to bobcat movement, which may impede the regional genetic connectivity of populations across the Midwest. 相似文献
16.
S. A. Cushman M. G. Raphael L. F. Ruggiero A. S. Shirk T. N. Wasserman E. C. O’Doherty 《Landscape Ecology》2011,26(8):1137-1149
In mobile animals, movement behavior can maximize fitness by optimizing access to critical resources and minimizing risk of
predation. We sought to evaluate several hypotheses regarding the effects of landscape structure on American marten foraging
path selection in a landscape experiencing forest perforation by patchcut logging. We hypothesized that in the uncut pre-treatment
landscape marten would choose foraging paths to maximize access to cover types that support the highest density of prey. In
contrast, in the post-treatment landscapes we hypothesized marten would choose paths primarily to avoid crossing openings,
and that this would limit their ability to optimally select paths to maximize foraging success. Our limiting factor analysis
shows that different resistant models may be supported under changing landscape conditions due to threshold effects, even
when a species’ response to landscape variables is constant. Our results support previous work showing forest harvest strongly
affects marten movement behavior. The most important result of our study, however, is that the influence of these features
changes dramatically depending on the degree to which timber harvest limits available movement paths. Marten choose foraging
paths in uncut landscapes to maximize time spent in cover types providing the highest density of prey species. In contrast,
following landscape perforation by patchcuts, marten strongly select paths to avoid crossing unforested areas. This strong
response to patch cutting reduces their ability to optimize foraging paths to vegetation type. Marten likely avoid non-forested
areas in fragmented landscapes to reduce risk of predation and to benefit thermoregulation in winter, but in doing so they
may suffer a secondary cost of decreased foraging efficiency. 相似文献
17.
The influence of landscape features on the movement of an organism between two point locations is often measured as an effective distance. Typically, raster models of landscape resistance are used to calculate effective distance. Because organisms may experience landscape heterogeneity at different scales (i.e. functional grains), using a raster with too fine or too coarse a spatial grain (i.e. analysis grain) may lead to inaccurate estimates of effective distance. We adopted a simulation approach where the true functional grain and effective distance for a theoretical organism were defined and the analysis grains of landscape connectivity models were systematically changed. We used moving windows and grains of connectivity, a recently introduced landscape graph method that uses an irregular tessellation of the resistance surface to coarsen the landscape data. We then used least-cost path metrics to measure effective distance and found that matching the functional and analysis grain sizes was most accurate at recovering the expected effective distance, affirming the importance of multi-scale analysis. Moving window scaling with a maximum function (win.max) performed well when the majority of landscape structure influencing connectivity consisted of high resistance features. Moving window scaling with a minimum function (win.min) performed well when the relevant landscape structure consisted of low resistance regions. The grains of connectivity method performed well under all scenarios, avoiding an a priori choice of window function, which may be challenging in complex landscapes. Appendices are provided that demonstrate the use of grains of connectivity models. 相似文献
18.
Although many empirical and theoretical studies have elucidated the effects of habitat fragmentation on the third trophic level, little attention has been paid to the impacts of this driver on more generalist groups of non-hymenopteran parasitoids. Here, we used the highly-diverse group of tachinid flies as an alternative model to test the effects of landscape fragmentation on insect parasitoids. Our aims were: (i) to evaluate the relative importance of habitat area and connectivity losses and their potential interaction on tachinid diversity, (ii) to test whether the effects of habitat fragmentation changes seasonally, and (iii) to further assess the effect of habitat diversity on tachinid diversity and whether different parasitoid-host associations modify the species richness response to fragmentation. In 2012 a pan-trap sampling was conducted in 18 semi-natural grasslands embedded in intensive agricultural landscapes along statistically orthogonal gradients of habitat area, connectivity and habitat diversity. We found an interaction between habitat area and connectivity indicating that tachinid abundance and species richness were more negatively affected by habitat loss in landscapes with low rather than with relatively large habitat connectivity. Although tachinid communities exhibited large within-year species turnover, we found that the effects of landscape fragmentation did not change seasonally. We found that habitat diversity and host association did not affect tachinid species diversity. Our results have important implications for biodiversity conservation as any attempts to mitigate the negative effects of habitat loss need to take the general level of habitat connectivity in the landscape into account. 相似文献
19.
Populations at the periphery of a species’ range often show reduced genetic variability within populations and increased genetic
divergence among populations compared to those at the core, but the mechanisms that give rise to this core-periphery pattern
in genetic structure can be multifaceted. Peripheral population characteristics may be a product of historical processes,
such as founder effects or population expansion, or due to the contemporary influence of landscape context on gene flow. We
sampled collared lizards (Crotaphytus collaris) at four locations within the northern Flint Hills of Kansas, which is at the northern periphery of their range, to determine
the genetic variability and extent of genetic divergence among populations for ten microsatellite loci (n = 229). We found low genetic variability (average allelic richness = 3.37 ± 0.23 SE; average heterozygosity = 0.54 ± 0.05
SE) and moderate population divergence (average FST = 0.08 ± 0.01 SE) among our sample sites relative to estimates reported in the literature at the core of the species’ range
in Texas. We also identified differences in dispersal rates among sampling locations. Gene flow within the Flint Hills was
thus greater than for other peripheral populations of collared lizards, such as the Missouri glade system where most of the
mesic grasslands have been converted to forest since the last glacial retreat, which appears to have greatly impeded gene
flow among populations. Our findings signify the importance of considering landscape context when evaluating core-peripheral
trends in genetic diversity and population structure. 相似文献
20.
Forest bird species exhibit noticeable seasonal behavioral changes that might lead to contrasting effects of landscape pattern
upon species abundance and performance. We assessed if the effect of patch and habitat attributes on the landscape use of
thorn-tailed rayaditos (Aphrastura spinicauda), a forest bird in a relict patchy forest in northern Chile, varied temporally in association with changes in the behavior
of individuals linked to breeding vs. non-breeding conditions. We also assessed the relationship between nest success and
patch and habitat attributes, as nest success might be associated to the density rayaditos during the breeding season. We
found that density of rayaditos was affected by patch size and functional connectivity but not by habitat structure and that
the magnitude of the effect of patch size was greater during the non-breeding season, thus supporting the existence of a temporally
variable effect of landscape pattern. Similarly, the nest success of rayaditos was positively affected by functional connectivity
and negatively by structural connectivity. We hypothesize that these results emerged from the interaction among territorial
behavior, resource limitation and predation risk. Despite the variable intensity of the effect of patch size upon density,
however, this landscape attribute, in addition to connectivity, is essential for the persistence of rayaditos at this relict
patchy forest landscapes. 相似文献