Ecology, Evolution, and Conservation of the Pine Barrens Treefrog (Hyla andersonii)

The Pine Barrens treefrog (Hyla andersonii) is restricted to three isolated (disjunct) regions in the eastern United States: New Jersey, North and South Carolina, and the Florida panhandle and southern Alabama. It is a seepage bog specialist and a species of conservation concern in each state in which it occurs. Previous work showed some differentiation among the three regions; however, these studies had small sample sizes, measured few variables, and/or did not include all three regions. Moreover, the only genetic study of H. andersonii, using allozyme data, did not resolve clear relationships among the three regions. Conservation management of this species requires a clearer understanding of how populations in these three regions may differ from one another and how populations within regions are structured. To extend previous work on this species, I measured differentiation among regions using morphometric, acoustic signal, ecological, and genetic data. I developed 15 microsatellite markers and used targeted sequence capture to collect large-scale nuclear and mitochondrial genomic data to test models of its evolutionary history. It is hypothesized that the species shifted southward during the last glacial maximum (LGM) into one or more refugia, then expanded northward as the glaciers receded. Overall I find a strikingly concordant pattern in which the first axis of variation for each of the data types distinguishes populations along a latitudinal and longitudinal gradient and the second axis distinguishes the set of populations occurring in the Carolinas (CL) from those occurring in the New Jersey (NJ) and Alabama/Florida (AF) regions. I know of no comparable data set that displays such concordance among different types of data across so large a geographic range. The overlap in trait values (i.e. exchangeability) between neighboring regions, however, is substantial in all types of data, except genetic, which supports continued consideration of this taxon as a single species. Using a phylogenetic framework with large-scale genomic data, I found that AF forms a single clade in both the nuclear and mitochondrial trees and that AF is sister to the rest of the Atlantic clade (CL, NJ). Climate models suggest that the distribution of the species has been repeatedly disjunct since at least the last interglacial, but probably even earlier given the genetic divergence time estimates. All three regions also showed little overlap in broad-scale (climate) environmental data, although niche modeling using climate data alone closely matched the known distribution. Fine-scale environmental data (abiotic and biotic) show greater overlap between CL and AF, with some divergence from NJ. I found some association of genetic and morphometric measures with ecological values, mostly for the broad-scale data. Projections for 2050 suggest habitat suitability will be greatly reduced in CL and AF, with only a small area of NJ available. Finally, I found very different patterns of population genetic structure within each region. Little evidence for isolation by distance was found for all regions, suggesting isolation via environment or other factors may be important for connectivity between populations. The results of my research can be applied to the conservation and management of H. andersonii because it is the most comprehensive study of the species using both an ecological and evolutionary perspective across different temporal and spatial scales.