A multi-locus phylogeny for the Diamesinae (Chironomidae: Diptera) provides new insights into evolution of an amphitropical clade

Abstract

Diamesinae is a subfamily of Chironomidae, whose species live in cold lotic or oligotrophic lentic habitats with global distribution excepting Antarctica. The cool stenothermic ecology of nearly all diamesines produces a typical amphitropical pattern of absence at tropical latitudes, except at high elevation. Recent attention has focused on the species discovery, while evolutionary relationships at the generic and tribal level have remained inadequately understood. Current classification implies analogous evolutionary diversification in each hemisphere (boreal and austral). To test this concept, we used six genetic markers (18S, 28S, CAD1, COI-5p, COI-3p and COII) and fossil calibrations to produce a well-supported and resolved time-calibrated phylogeny of the subfamily. Austral and boreal diamesines indeed are reciprocally monophyletic lineages, with estimated Jurassic divergence (130-196, 164 Ma). The boreal Protanypodini, previously understood to be a tribe within Diamesinae, is excluded and elevated here to subfamily rank as Protanypodinae stat. nov. Ancestral austral diamesines probably originated in South America and successively reached New Zealand, Australia and South Africa during the Cretaceous-Paleogene. The Holarctic tribes Diamesini and Boreoheptagyiini probably originated in the Eastern Palaearctic with further dispersal/vicariance into the Western Palaearctic, Nearctic, East, and very likely dispersed southwards to montane East Africa and Borneo.