Multigenic phylogeographic divergence in the paleoendemic southern Appalachian opilionid Fumontana deprehendor Shear (Opiliones, Laniatores, Triaenonychidae)

The paleoendemic opilionid Fumontana deprehendor is restricted to a small area of mid-elevation forested habitats in the southern Blue Ridge province of the Appalachian Mountains. In a recent study we reported on the discovery of 22 new montane populations of this monotypic genus, specimens from which exhibit remarkably little morphological divergence despite their separation by intervening lowlands and large riverine barriers. Here, we further explore spatial and temporal patterns of divergence in this taxon using DNA sequence data from a portion of the mitochondrial cytochrome c oxidase subunit I gene (∼1000 bp) and full-length sequences of both nuclear ribosomal internal transcribed spacer regions, including the intervening 5.8S rRNA region (∼700 bp total). Bayesian phylogenetic analyses of these independent data sets reveal congruent genealogical patterns, with all data partitioning and combination strategies consistently recovering five allopatric, geographically cohesive genetic clades. These clades show an almost complete lack of internal genetic divergence, with most individuals sharing a clade-specific, regionally widespread haplotype. The geographic distribution of these clades corresponds to patterns seen in other upland taxa of the region, possibly indicating coincident vicariance. Because of a lack of quantifiable morphological divergence and relatively modest levels of genetic divergence, we conservatively refer to the geographically cohesive genetic clades as “phylogeographic units”, although these may actually represent cryptic species. Conservation implications and the prospect for future comparative arachnid phylogeography in the southern Appalachians are discussed in light of the results presented here.