Abstract
AbstractGenetic connectivity results from the dispersal and reproduction of individuals across landscapes. Mammalian populations frequently exhibit sex‐biased dispersal, but this factor has rarely been addressed in individual‐based landscape genetics research. In this study, we evaluate the effects of sex‐biased dispersal and landscape heterogeneity on genetic connectivity in a small and isolated population of fisher (Pekania pennanti). We genotyped 247 fisher samples collected across the southern Sierra Nevada Mountains of California. We tested for genetic evidence of sex‐biased dispersal using sex‐specific population structure and spatial autocorrelation analyses, and sex‐biased dispersal tests of the assignment index, FST, and FIS. We developed resistance surfaces for eight landscape features hypothesized to affect gene flow and optimized each resistance surface independently by sex. Using multiple regression of distance matrices and an information‐theoretic model selection approach, we fit models of genetic distance to landscape resistance distance separately by sex and geographic region. We found genetic evidence of sex‐biased dispersal with significant differences in FST, FIS, and spatial autocorrelation between sexes. Optimal resistance values differed by sex, and model variables, fit, and parameter estimates varied substantially both between sexes and between geographic regions. We found a stronger relationship between landscape features and genetic distance for females, the philopatric sex, than the more widely dispersing males. Our results show that landscape features influencing gene flow differed by both sex and regional heterogeneity. Conducting analyses by sex and by region allowed for the identification of landscape genetics relationships not discernible when analyzed together. Our results show that failing to account for these factors can confound results and obscure relationships between landscape features and gene flow.
Highlights
Connectivity, defined as the ability of organisms to move within and among populations, is fundamental for long-term species persistence (Lowe and Allendorf 2010)
We examine how sex-biased dispersal and landscape heterogeneity affect gene flow in a small and isolated population of fisher (Pekania pennanti) in the southern Sierra Nevada Mountains of California
Using samples from across the southern Sierra Nevada fisher population, we address the following questions: (1) Is there genetic evidence of sex-biased dispersal? (2) What landscape features influence genetic connectivity? (3) Does the influence of landscape features on gene flow vary by sex? and (4) Does the influence of landscape features on gene flow vary spatially across the study area? We investigate these questions by first testing for genetic evidence of sex-biased dispersal and employ a resistance modeling approach in which we generate resistance surfaces representing our hypothesized relationships between landscape features and gene flow
Summary
Connectivity, defined as the ability of organisms to move within and among populations, is fundamental for long-term species persistence (Lowe and Allendorf 2010). Genetic connectivity results from successful dispersal and reproduction of individuals across a landscape. Understanding the dispersal characteristics of a species and gene flow is inherently intertwined. Estimating dispersal through direct methods (e.g., mark–recapture, telemetry) is. Difficult for many species as it can be cost prohibitive over large landscapes, especially for species that are rare or difficult to detect. Direct methods cannot distinguish between movement and gene flow, in which movement is followed by successful reproduction. Genetic methods for assessing dispersal (Slatkin 1987) coupled with non-invasive genetic sampling provide a powerful, cost-effective tool for sampling individuals over large areas and improving our understanding of dispersal and gene flow
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