Many inferences about contemporary rates of gene flow are based on the assumption that the observed genetic structure among populations is stable. Recent studies have uncovered several cases in which this assumption is tenuous. Most of those studies have focused on the effects that regular environmental fluctuations can have on genetic structure and gene flow patterns. Occasional catastrophic disturbances could also alter either the distribution of habitat or the spatial distribution of organisms in a way that affects population structure. However, evidence of such effects is sparse in the literature because it is difficult to obtain. Hurricanes, in particular, have the potential to exert dramatic effects on population structure of organisms found on islands or coral reefs or in near shore and coastal habitats. Here we draw on a historic genetic data set and new data to suggest that the genetic structure of sailfin molly (Poecilia latipinna) populations in north Florida was altered dramatically by an unusually large and uncommon type of storm surge associated with Hurricane Dennis in 2005. We compare the spatial pattern of genetic variation in these populations after Hurricane Dennis to the patterns described in an earlier study in this same area. We use comparable genetic data from another region of Florida, collected in the same two periods, to estimate the amount of change expected from typical temporal variation in population structure. The comparative natural history of sailfin mollies in these two regions indicates that the change in population structure produced by the storm surge is not the result of many local extinctions with recolonization from a few refugia but emerged from a pattern of mixing and redistribution.

Forestry practices are placing ever increasing emphasis on sustainability and the maintenance of ecological processes, biodiversity, and endangered species or populations. Balancing timber harvest and the management of imperiled species presents a particularly difficult challenge during this shift, as we often know very little about these species’ natural history and how and why silviculture practices affect their populations. Accordingly, investigation of and improvement on current management practices for threatened species is imperative. We investigated the effectiveness of habitat buffers as a management technique for the imperiled Red Hills salamander (Phaeognathus hubrichti) by combining genetic, transect, and body-condition data. We found that populations where habitat buffers have been employed have higher genetic diversity and higher population densities, and individuals have better overall body condition. These results indicate that buffering the habitat of imperiled species can be an effective management tool for terrestrial salamanders. Additionally, they provide further evidence that leaving the habitat of imperiled salamanders unbuffered can have both immediate and long-term negative impacts on populations.