The threatened Florida Sand Skink (Plestiodon reynoldsi) occurs on the scrub of central Florida. To understand the genetic characteristics of the Florida Sand Skink, and to learn more about the effect of fire on Florida Scrub organisms, we have conducted genetic analysis using both DNA sequences and microsatellite loci. We are pursuing three main avenues of research: (1) the phylogeographic relationship among Florida Sand Skinks from several extant scrubs, to describe the evolutionary history of the currently isolated patches and characterize historical barriers to gene flow; (2) the genetic diversity and genetic differentiation between a highly heterogeneous scrub and a more continuous scrub, to determine if fine-scale scrub heterogeneity generates greater genetic heterogeneity; and (3) the genetic diversity among multiple locations with differing time since last fire, to determine the effect of fire on local populations.
Results/Conclusions
(1) Our results identify two major restrictions to gene flow in the Florida Sand Skink’s range. One divides Florida Sand Skink on the Mt. Dora Ridge from those on the Lake Wales Ridge and appears to have been generated by a physical barrier. The other divides the Lake Wales Ridge into central and south segments. Genetic data and geography indicate that a restricted avenue for dispersal exists at this point. Our findings show that historical limits to Florida Sand Skink dispersal existed along Florida’s central highlands. (2) Comparing genetic diversity and differentiation indicates that multiple populations are present on the heterogeneous scrub, while a single population exists on the continuous scrub. Thus, Florida Sand Skinks may exist as large populations in an area, if sufficient habitat continuity exists, yet may be divided into multiple populations by heterogeneous habitat. (3) Fire alters the genetic diversity of local populations. More recently burned areas had significantly greater variance in genetic diversity estimates when compared to long unburned areas. Recently burned sites also lacked the isolation by distance observed among long unburned areas, which indicates that Florida Sand Skinks move greater distances after a fire. Analysis of samples from intermediately burned areas indicates that multiple generations may be required before local populations return to more consistent amounts of genetic diversity.