Sand dune speciation: Exploring the evolutionary history of Trogloderus leconte (Coleoptera: Tenebrionidae)

Many lineages of flightless darkling beetles have exploited arid habitats around the world.  From the fog-basking beetles from the Namib desert to the head-standing stink beetles in the Sonoran and Mojave deserts, tenebrionids are able to weather the hot and dry conditions they are faced with.  The monotypic North American genus Trogloderus LeConte is one such fascinating lineage found exclusively in eolian sand formations in the western United States.  Trogloderus possesses a highly plastic morphology, presumably due in large part to the disjunct geographic distribution.  The genus was last revised in 1946 where the four existing species were sunk to subspecific rank of a single, monotypic, Trogloderus costatus LeConte.  Collection of fresh material has allowed for the first molecular analysis of the group to be combined with a comprehensive morphological investigation.  The results of multiple phylogenetic analyses show that Trogloderus is in fact a derived lineage of the genus Eleodes Eschscholtz, making the current delimitation of Eleodes paraphyletic.  Phylogenetic analysis of Trogloderus is here presented, with an updated taxonomy taking into account both morphological and molecular evidence.  Biogeographic and evolutionary patterns are discussed in reference to the geological history of the sand dunes of the western United States.