Phylogeography and demographic expansion in the widely distributed horned passalus beetle, Odontotaenius disjunctus (coleoptera: Passalidae)

Abstract

Dynamic climatic oscillations during the Pleistocene had profound effects on the distribution of species across North America. Although the role of historical climate change on speciation remains controversial, the impact on genetic variation within species has been well documented. Analyses of mtDNA sequences from the cytochrome oxidase I gene (911 bp) for 115 individuals of Odontotaenius disjunctus was combined with ecological niche modelling (ENM) to infer the demographic and population differentiation scenarios under present and past conditions. We inferred three lineages that diverged during the Pleistocene and replace each other geographically across the eastern United States. One of these lineages traverses previously identified genetic barriers for terrestrial animals including the Mississippi and Apalachicola Rivers and the Appalachian Mountains. We observed overlapping ranges between two haplotype groups as well as a region of secondary contact associated with ecological transition zone in northern Florida. The two continental lineages depict a genetic signature of a recent population increase associated with expanding niche envelope, whereas the clade restricted to peninsular Florida shows stable populations in a shrinking niche envelope. Given the lack of ecological separation, overlapping distribution of haplogroups and the presence of secondary contact zones, the taxonomic status of these lineages must await robust testing using multilocus DNA data to assess species boundaries.