Disentangling disjunctus: an integrated analysis of the patent leather beetle, <i>Odontotaenius disjunctus</i> complex (Passalidae: Coleoptera) with the description of two new species

The categorical rank of species is the fundamental taxonomic unit in characterizing biodiversity, and the accurate identification of species-level lineages is vital to all fields of biological research. This is particularly true for conservation biology, where state and federal agencies make conservation assessments based on recognized species’ distribution, ecology, and demography. Currently, there are two species of bess beetle in the conterminous United States, <i>Odontotaenius flordianus</i> (Schuster) and <i>O. disjunctus</i> (Illeger). Phylogeographic studies have proposed that <i>O. disjunctus</i> may represent a species complex harboring cryptic diversity. This study combines multi-locus species delimitation methods and multivariate analyses of morphological characters used to distinguish <i>O. floridanus</i>, to assess species diversity within the <i>O. disjunctus</i> complex. Delimitation methods inferred four well-supported species that diverged during the Pleistocene and whose formation was driven by historical isolation associated with shifting climatic conditions. We found a correlation between increased morphological differentiation and time since divergence. We described two new species, <i>Odontotaenius jackmanicus</i> sp. nov., based on morphological and molecular characters, and the cryptic species, <i>Odontotaenius cryptodisjunctus</i> sp. nov., diagnosed exclusively on molecular characters. We propose that the morphological similarities between <i>O. disjunctus</i> and <i>O. cryptodisjunctus</i> are due to a recent speciation combined with morphological conservatism and evolutionary stasis.