Species trees, temporal divergence and historical biogeography of coastal rove beetles (Coleoptera: Staphylinidae) reveal their early Miocene origin and show that most divergence events occurred in the early Pliocene along the Pacific coasts.

Abstract

We investigated the species trees, temporal divergence and historical biogeography of Emplenota Casey and Triochara Bernhauer (ET clade hereafter), subgenera of the Aleochara coastal staphylinid beetles, to determine their place of origin. We explored a multilocus dataset to infer gene trees and species trees based on traditional concatenated and multispecies coalescent-based approaches using both model- (maximum likelihood and Bayesian) and parsimony-based methods. The multilocus dataset comprised DNA sequences from five nuclear genes (ArgK, CAD, EF1-α, wg and 28S) and three mitochondrial genes (COI, COII and 16S). *BEAST analysis according to a coalescent-based approach resolved the following phylogenetic relationships: ((A.trisulcata (A.nubis+A.zerchei)) (A.obscurella ((A.pacifica (A.curtidens + A.litoralis)) (A.hayamai (A.yamato (A.fucicola (A.segregata+A.puetzi))))))). Using a relaxed molecular clock, we reconstructed a time-calibrated phylogeny for this group. Furthermore, to account for the historical biogeography of the ET clade at the ages of major divergences, we investigated the ancestral area based on a time-calibrated phylogeny. Biogeographical analyses suggested that the ancestor of the ET clade was widely distributed along the eastern and western Palearctic and the western Nearctic coasts in the early Miocene. According to reconstruction of the ancestral area, one dispersal and three vicariance events were required, and the analyses indicated that vicariance events were important in shaping its current distribution patterns. Most of the divergence events occurred in the late Miocene and early Pliocene along the Pacific coasts, and the East Asian seacoasts harboured the most species-rich fauna, including eight of the 13 species in the ET clade.