A molecular investigation of the Aleocharinae (Coleoptera: Staphylinidae) phylogeny

Abstract

The subfamily Aleocharinae is a hyper-diverse group of staphylinid beetles that account for 40% of the diversity within the family Staphylinidae. These small to minute beetles are primarily dominant generalist predators in leaf litter and soil communities (Ashe, 1998). Several lineages of aleocharines have invaded and diversified in many unusual habitats such as mushroom habitats, seashore habitats, and tropical canopy habitats. These beetles are also known as the most successful group of inquilines in the nests of social insects (Seevers, 1978). At present, the aleocharine subfamily contains 52 tribes, over 1,000 genera, and about 12,000 species. Ashe (1984) considered the Aleocharinae to be "the most inadequately understood large group within the Coleoptera."

The subfamily was first shown to be monophyletic by Hammond (1975) and later by Ashe (1994) based on unique characteristics of the adeagus. In subsequent morphological phylogenetic analyses, Ashe and Newton (1993) and Ashe (2005) recovered a monophyletic 'higher' aleocharinae lineage based primarily on the presence of a tergal gland in both larvae and adults. 'Basal' lineages of aleocharine beetles do not possess this structure. Shortly there after, Haasl (unpublished thesis, 2005) recovered a monophyletic 'higher' aleocharine clade using molecular techniques.

Fragments of the 12s and 16s mithchondrial rDNA genes were sequenced and compared to investigate the phylogenetic relationships among selected tribes from within the 'higher' aleocharinae. The aim of this study is to investigate the usefulness of these two rDNA genes in resolving relationships at the tribal level, examine and improve upon some of the predominant morphological hypotheses that have been proposed for tribes in this subfamily, and further our understanding of the tribal-level relationships within this group.

Results from this study confirm that the 'higher' Aleocharinae form a monophyletic group. This study also supports the placement of the tribe Myllaenini within the 'higher' aleocharine clade. All datasets and analyses recovered a monophyletic Gyrophaenina lineage. The 12s and combined dataset hypothesized the paraphyly of the genus Gyrophaena with respect to Phanerota. There was also evidence that the genus Tachyusa and allied genera are closely related to members of the tribe Falagriini, as historically hypothesized by Bernhauer and Sheerpeltz (1926).