Taxonomy, classification, reconstructed phylogeny and biogeography of Nearctic species of Brychius Thomson (Coleoptera : Haliplidae)

摘要

The Nearctic species of Brychius Thomson, 1859 (Coleoptera: Haliplidae) were revised by examining adult and larval specimens. Brychius albertanus Carr 1928 is a junior subjective synonym of Brychius hornii Crotch 1873. Descriptions of adults and larvae (excluding B. pacificus), distribution data, and a key to adults are provided for all Nearctic species. From a reconstructed phylogeny of all species of Brychius, B. hornii + B. hungerfordi is the sister-group to Brychius elevatus Panzer 1794 + Brychius glabratus Villa 1833; and these combined are the sister group to Brychius pacificus Carr, 1928. Species of Brychius are hypothesized to have arisen and diversified on Laurasia during the Jurassic Period. Brychius hornii and B. hungerfordi originated in the Tertiary Period before the formation of the Rocky Mountains, ca. 50 to 100 million years ago. It is thought that vicariance has played an important role in the present distribution, where species were once widespread in cool mountainous glacial streams, then became restricted to geographically isolated regions with the retreat of the glaciers and the extinction of intervening populations.