Phylogeography of Geopsammodius Gordon and Pittino, 1992 (Coleoptera: Scarabaeidae: Aphodiinae): A radiation of endemic psammophilic beetles.

Geopsammodius Gordon and Pittino, 1992 are sand-dwelling beetles found throughout the southeastern United States, Texas, and Honduras. Their modified morphology including reduced flight wings, reduced eyes, expanded tibiae, and fused elytra suggests their evolutionary history may be closely tied to the sand dunes in which they inhabit. Here, using six genes, we reconstruct the relationships of species within the genus and members of the tribe Psammodiini. We then performed divergence time estimation in order to determine the age of the group. We recovered Parapsammodius Verdú, Stebnicka, and Galante, 2006 outside the Psammodiini indicating the need for future taxonomic revision. Within the genus Geopsammodius, we found two major clades that largely correspond with geography. The first occurring along the east coast and Gulf Coast and the second clade occurring inland in Florida and Georgia. We find that the age of Geopsammodius coincides with the formation of extensive sand dunes (20-23 MYA) suggesting that the group may have evolved concurrently with this sandy habitat.