Next Monday, Madonna will present a paper on phylogeny and global phylogeography of Angel sharks: 17 (out of 22) species in the genus Squatina. In this paper, the authors first obtained a comprehensive phylogenetic reconstruction and tested biogeographic patterns using a molecular clock. The genus was found to be monophyletic and composed of four main clades. The authors found supports for the effect of both the Thetys Sea closure and the rise of the Panamian isthmus on the diversification of the genus. Thanks Madonna.
From Stelbrink B, vonRintelen T, Cliff G, Kriwet J; Molecular Phylogenetic and Evolution (2010) 54:395-404
Title: Molecular systematics and global phylogeography of angel sharks (genus Squatina)
Abstract.
Angel sharks of the genus Squatina represent a group comprising 22 extant benthic species inhabiting continental shelves and upper slopes. In the present study, a comprehensive phylogenetic reconstruction of 17 Squatina species based on two mitochondrial markers (COI and 16S rRNA) is provided. The phylogenetic reconstructions are used to test biogeographic patterns. In addition, a molecular clock analysis is conducted to estimate divergence times of the emerged clades. All analyses show Squatina to be monophyletic. Four geographic clades are recognized, of which the Europe–North Africa–Asia clade is probably a result of the Tethys Sea closure. A second sister group relationship emerged in the analyses, including S. californica (eastern North Pacific) and S. dumeril (western North Atlantic ), probably related to the rise of the Panamanian isthmus. The molecular clock analysis show that both lineage divergences coincide with the estimated time of these two geological events.