Effect of landscape features on genetic structure of the goitered gazelle (Gazella subgutturosa) in Central Iran
Rasoul KhosraviMahmoud‐Reza HemamiMansoureh MalekianTeresa Luísa SilvaHamid Reza RezaeiJosé Carlos Brito
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Keywords:
Isolation by distance
Mantel test
Landscape connectivity
Conservation Genetics
Predicting population-level effects of landscape change depends on identifying factors that influence population connectivity in complex landscapes. However, most putative movement corridors and barriers have not been based on empirical data. In this study, we identify factors that influence connectivity by comparing patterns of genetic similarity among 146 black bears (Ursus americanus), sampled across a 3,000-km(2) study area in northern Idaho, with 110 landscape-resistance hypotheses. Genetic similarities were based on the pairwise percentage dissimilarity among all individuals based on nine microsatellite loci (average expected heterozygosity=0.79). Landscape-resistance hypotheses describe a range of potential relationships between movement cost and land cover, slope, elevation, roads, Euclidean distance, and a putative movement barrier. These hypotheses were divided into seven organizational models in which the influences of barriers, distance, and landscape features were statistically separated using partial Mantel tests. Only one of the competing organizational models was fully supported: patterns of genetic structure are primarily related to landscape gradients of land cover and elevation. The alternative landscape models, isolation by barriers and isolation by distance, are not supported. In this black bear population, gene flow is facilitated by contiguous forest cover at middle elevations.
Isolation by distance
Landscape connectivity
Land Cover
Mantel test
Geographical distance
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Human-driven habitat fragmentation leads to spatial isolation of endangered plant species increasing extinction risk. Understanding genetic variability and population structure of rare and isolated plant species is of great importance for assessing extinction risk and setting up conservation plans. Aconitum austrokoreense, an endangered and endemic species in Korea, is a perennial herb commonly used for medicinal purposes. We used five nuclear microsatellites and one chloroplast marker to investigate genetic diversity and population structure for 479 individuals of A. austrokoreense from seven populations throughout South Korea. A multivariate approach, discriminant analysis of principal components analysis, revealed broad-scale spatial patterns of A. austrokoreense populations across three major mountains that were composed of seven genetically distinct subgroups. High pairwise FST values (mean FST = 0.35; highest FST = 0.55) suggested significant differentiation among populations. Overall within population genetic variation was low. Based on Mantel test, there was significant correlation between geographical and genetic distances indicating pattern of isolation by distance. Our results suggest that A. austrokoreense populations may have undergone recent population bottlenecks. Given the limited dispersal ability of the species and ongoing habitat fragmentation, population isolation may further be exacerbated leading to increased extinction risk.
Mantel test
Isolation by distance
Population fragmentation
Habitat Fragmentation
Conservation Genetics
Extinction (optical mineralogy)
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Environmental gradients predict the genetic population structure of a coral reef fish in the R ed S ea
Abstract The relatively recent fields of terrestrial landscape and marine seascape genetics seek to identify the influence of biophysical habitat features on the spatial genetic structure of populations or individuals. Over the last few years, there has been accumulating evidence for the effect of environmental heterogeneity on patterns of gene flow and connectivity in marine systems. Here, we investigate the population genetic patterns of an anemonefish, Amphiprion bicinctus , along the Saudi Arabian coast of the Red Sea. We collected nearly one thousand samples from 19 locations, spanning approximately 1500 km, and genotyped them at 38 microsatellite loci. Patterns of gene flow appeared to follow a stepping‐stone model along the northern and central Red Sea, which was disrupted by a distinct genetic break at a latitude of approximately 19°N. The Red Sea is characterized by pronounced environmental gradients along its axis, roughly separating the northern and central from the southern basin. Using mean chlorophyll‐a concentrations as a proxy for this gradient, we ran tests of isolation by distance ( IBD , R 2 = 0.52) and isolation by environment ( IBE , R 2 = 0.64), as well as combined models using partial Mantel tests and multiple matrix regression with randomization ( MMRR ). We found that genetic structure across our sampling sites may be best explained by a combined model of IBD and IBE (Mantel: R 2 = 0.71, MMRR : R 2 = 0.86). Our results highlight the potential key role of environmental patchiness in shaping patterns of gene flow in species with pelagic larval dispersal. We support growing calls for the integration of biophysical habitat characteristics into future studies of population genetic structure.
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Isolation by distance
Mantel test
Population Genetics
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Isolation by distance
Mantel test
Landscape connectivity
Conservation Genetics
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PREMISE OF THE STUDY: Gene flow through dispersal of seeds and pollen is a fundamental determinant of spatial genetic structure (SGS) in natural populations of trees at different spatial scales. Within continuous populations, restrictions to gene flow should be manifested in a process of local genetic differentiation, known as isolation by distance. The present work examines the SGS of a Prosopis alba population in a patchy region where urban, forest, and agricultural areas coexist. The analysis discussed here expands our knowledge about the processes affecting the distribution of the genetic variability in populations of disturbed landscapes. METHODS: Three sites with different landscape and demographic characteristics were analyzed. Seven highly variable microsatellite markers were used to survey the relevance of both isolation by distance and stochastic migration in the SGS of the population. KEY RESULTS: The analyses showed that (1) the genetic similarity declined with increasing geographic distance, (2) the population may be conceived as a single genetically continuous unit showing spatial differentiation as consequence of isolation by distance, rather than a structured population following the island model, and (3) there is evidence supporting a past immigration event into one of the study sites, which promoted a local pattern of genetic structure. CONCLUSIONS: These results indicate that in spite of the population fragmentation produced by land‐use changes, P. alba maintains the genetic cohesion and a continuous genetic structure in the analyzed area.
Isolation by distance
Geographical distance
Genetic distance
Reproductive isolation
Genetic drift
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It is assumed that geographic isolation of Dendroctonus Erichson species populations or their plant hosts determines genetic structure. This structure can be analyzed with respect to the biogeographic pattern that describes the species in a region. The Trans-Mexican Volcanic Belt (TMVB) is located between the Neartic and Neotropical regions and is a center of diversification and endemism of trees in the genus Pinus L. Dendroctonus mexicanus Hopkins is polyphagous within Pinus species and has a continuous geographic distribution across the TMVB. We explored whether the population genetic structure of D. mexicanus is reflective of the distribution pattern of the Dendroctonus species that occur in the TMVB. Twelve gene loci were analyzed by isozyme electrophoresis in 17 populations found on pines from the Leiophyllae subsection. Allele frequencies, average heterozygosity, heterozygosity by locus, deviations from Hardy–Weinberg equilibrium (HWE), F-statistics among populations, and average genetic flow were calculated. Genetic structure was determined using the relationship between FST versus geographic distances among populations. Genetic relations among populations were established by neighbor-joining and principal components analysis by using Nei’s genetic distances. Dendrogram reliability was assessed by bootstrap analysis and cophenetic correlation coefficient by using the Mantel test. Results show that heterozygosity of D. mexicanus is similar to other scolytids. A high proportion of loci were out of HWE by homozygous excess, which may be explained by multiple factors. The scarce number of fixed alleles, the allele variation pattern, pairwise genetic distances, and F-statistics suggest a model of isolation by distance for D. mexicanus in the TMVB resulting from recent dispersal events.
Isolation by distance
Genetic distance
Mantel test
Geographical distance
Volcanic belt
Population Genetics
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Genetic structure of a population can be molded by the resistance of the landscape or the distance between populations that function as barriers to gene flow. We analyzed the population genetic structure of Abies religiosa on a fine spatial scale and examined isolation models by resistance and distance. We collected vegetative tissue from populations located at the altitudinal extremes of the distribution range of the species on three slopes of La Malinche National Park (LMNP) (South, North, and East) in central Mexico. Genomic DNA was obtained using the CTAB 2X method, and eight microsatellite chloroplast loci were amplified. The genetic structure was identified based on an Analysis of Molecular Variance, a Discriminant Analysis of Principal Components with cross-validation and a spatial Principal Component Analysis using the Gabriel-type connectivity network. The isolation hypotheses were evaluated by constructing partial Mantel tests using Reciprocal Causal Modeling and Maximum Likelihood Population Effects models. A genetic structure of isolation by resistance to elevation was identified, and two genetic groups were recognized: one including populations of the South slope and the other comprising populations of the North and East slopes. We detected in Abies religiosa populations of the LMNP an isolation by resistance to elevation that determines the genetic structure, and the greatest genetic exchange between groups of populations located at higher altitudes. It is suggested to promote the connectivity between slopes through assisted migration and immediately halt land-use changes, as part of the actions to preserve genetic diversity in the LMPN. This study contributes to the knowledge of the spatial genetic structure of species at risk in the Mexican temperate forest for their conservation.
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Landscape complexity provides opportunities for local adaptation and creates population genetic structure at limited geographic scales. We determined if fine-scale genetic structure was evident in a population of ringtails (Bassariscus astutus) inhabiting the Guadalupe Mountains, a small, isolated, and ecologically diverse mountain range in the southwest United States. We hypothesized that ringtails would exhibit either a genetic pattern of isolation by distance (IBD), because their small body size would most likely limit dispersal distances, or a pattern of isolation by resistance (IBR), because the topographical complexity of the mountain range would result in complex dispersal patterns. To investigate for the presence of fine-scale genetic structure in this population, we genotyped 153 ringtails at 15 microsatellite loci and described genetic structure using 2 Bayesian clustering techniques. Six genetic clusters were identified revealing complex spatial genetic structure within a localized geographic area. We used partial Mantel tests to test for a correlation between genetic distance and geographic distance or resistance distance but found no evidence for a genetic pattern related to IBD or IBR. We subsequently tested for an association between genetic structure and isolation by environment (IBE) using a discriminant function analysis and classified a high proportion of individuals (> 91%) to their observed genetic cluster based exclusively on landscape features. We also used a nonparametric, multivariate analysis of variance to further explore the role of land-cover type and found that plant association explained 26% of the genetic variation. These results suggest that IBE influences the genetic structure of ringtails at local geographic scales, a finding that deserves consideration in conservation planning.
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Geographical distance
Genetic distance
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Isolation by distance
Genetic distance
Geographical distance
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