Spatial and temporal patterns of genetic diversity in a fragmented and transient landscape

Abstract

Anthropogenic disturbance has the potential to influence metapopulation dynamics by altering habitat quality and connectivity. In particular, species with limited vagility and specific habitat preferences, such as the Florida scrub lizard (Sceloporus woodi), are likely to be affected by landscape-altering events. In the Ocala National Forest (ONF) of central Florida, subpopulations of Florida scrub lizards encounter cycles of fire suppression, clear-cutting, and prescribe burning that give rise to a transient landscape and potentially lead to repeated colonization and founder events. As such, Florida scrub lizards in the ONF provide an ideal opportunity in which to explore metapopulation dynamics in a transient landscape. We predict that Florida scrub lizards quickly colonize newly clear-cut patches, disperse from fire-suppressed patches as vegetation density increases, and maintain stable populations in stands consistently managed with prescribe burning. Additionally, we predict that anthropogenically-maintained sand corridors facilitate Florida scrub lizard dispersal between patches. To this end, we used microsatellite markers to quantify genetic variation among Florida scrub lizard subpopulations at two time points separated by approximately six generations because habitat turnover can obscure connectivity-occupancy relationships when analyzed with snapshot data, and spatial analyses to test correlations between landscape metrics (e.g. patch area and proximity) and genetic diversity. Microsatellite markers revealed significant and varied temporal shifts in genetic differentiation among subpopulations, which our analyses indicate are linked to changes in landscape structure. Collectively, our results suggest that the spatial distribution of suitable patches of habitat (i.e. stands of quality habitat) can influence population genetic structure, and that corridors can facilitate gene flow between subpopulations in fragmented and transient landscapes.