Abstract
Landscape genetic studies offer a fine-scale understanding of how habitat heterogeneity influences population genetic structure. We examined population genetic structure and conducted a landscape genetic analysis for the endangered Central American Squirrel Monkey (Saimiri oerstedii) that lives in the fragmented, human-modified habitats of the Central Pacific region of Costa Rica. We analyzed non-invasively collected fecal samples from 244 individuals from 14 groups for 16 microsatellite markers. We found two geographically separate genetic clusters in the Central Pacific region with evidence of recent gene flow among them. We also found significant differentiation among groups of S. o. citrinellus using pairwise FST comparisons. These groups are in fragments of secondary forest separated by unsuitable “matrix” habitats such as cattle pasture, commercial African oil palm plantations, and human residential areas. We used an individual-based landscape genetic approach to measure spatial patterns of genetic variance while taking into account landscape heterogeneity. We found that large, commercial oil palm plantations represent moderate barriers to gene flow between populations, but cattle pastures, rivers, and residential areas do not. However, the influence of oil palm plantations on genetic variance was diminished when we restricted analyses to within population pairs, suggesting that their effect is scale-dependent and manifests during longer dispersal events among populations. We show that when landscape genetic methods are applied rigorously and at the right scale, they are sensitive enough to track population processes even in species with long, overlapping generations such as primates. Thus landscape genetic approaches are extremely valuable for the conservation management of a diverse array of endangered species in heterogeneous, human-modified habitats. Our results also stress the importance of explicitly considering the heterogeneity of matrix habitats in landscape genetic studies, instead of assuming that all matrix habitats have a uniform effect on population genetic processes.
Highlights
Many species exist in spatially structured populations linked by dispersal and gene flow, which can influence evolutionary, demographic, and ecological processes
We examined genetic structure in S. o. citrinellus microsatellite data with pairwise tests for differentiation among groups and populations using F-statistics [64] calculated with Weir and Cockerham’s [65] estimators in FSTAT v 2.9 [66], for 10,000 randomizations not assuming Hardy-Weinberg equilibrium (HWE)
Population Genetic Structure Clustering analysis and F-statistics revealed that S. o. citrinellus are structured into two genetically distinct populations, an eastern and a western population
Summary
Many species exist in spatially structured populations linked by dispersal and gene flow, which can influence evolutionary, demographic, and ecological processes. Landscape genetic approaches are increasingly used to understand the influence of landscape characteristics on population genetic structure and dispersal patterns [4,5,6,7]. These emerging approaches combine population genetics, spatial statistics, and landscape ecology to measure the effects of landscape features on gene flow [8,9,10]. Many recent landscape genetic studies of birds, herpetofauna, terrestrial mammals, and primates found that geographic distances incorporating a cost to particular landscape features showed a stronger correlation to genetic distances than straight-line Euclidean distances between sampled individuals [11,12,13,14,15,16,17]
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