Range expansion during the Pleistocene drove morphological radiation of the fir genus (Abies, Pinaceae) in the Qinghai-Tibet Plateau and Himalayas

Abstract

Range expansion caused by climate oscillations in the past probably promoted morphological radiation in a few plant groups. In this study, we aim to test this hypothesis through phylogeographical analysis of the cold-tolerant fir genus (Abies) in the Qinghai-Tibet Plateau (QTP) and Himalayas, where it comprises 12 described species. We examined sequence variation in two maternally inherited mitochondrial (mt) DNA fragments (nad5-4 and nad7-1) and two paternally inherited plastid DNA fragments (trnS-G and trnL-F) for 733 individuals from 75 populations of the species in a monophyletic group. Only six mtDNA haplotypes were recovered, but five were shared between multiple species and one occurred at a high frequency, providing strong evidence of range expansion. Forty-three plastid DNA haplotypes were detected, 19 of which were shared between species and three occurred at high frequency. Network, mismatch and Bayesian skyline plot analyses of all plastid DNA haplotypes from this clade clearly suggested range expansion. This expansion was dated as having occurred during the longest and most extensive glaciation in the Pleistocene. Our results therefore supported the range expansion hypothesis for this clade of Abies during the Pleistocene; expansion probably drove the morphological radiation of the clade in the QTP and Himalayas, although it remains unclear whether the different morphotypes should be acknowledged as independent, reproductively isolated species. (C) 2015 The Linnean Society of London.