Cladistic analysis of Sericania (Coleoptera: Scarabaeidae: Sericini) - Implications for the evolution of the xerophilous fauna of the Himalaya

Abstract

A cladistic analysis of the species of Sericania Motschulsky, 1860, was executed using fifty-six morphological characters of adults. The monophyly of the genus is supported by the phylogenetic trees generated. Among the three major lineages indicated by the strict consensus tree the East Asian Sericania fuscolineata lineage represents the genus Sericania as defined "originally" and adopted by subsequent authors. The second, the clade Sericania nepalensis group + Sericania sp. 2, is a sister group to the S. fuscolineata clade. Both constitute a sister group to the third major lineage, the Sericania kashmirensis clade, which is endemic in the drier North-West Himalaya where it is the most diverse monophyletic group of Sericini. Provided that the stem species of the S. kashmirensis clade was xerophilous, the origin of this clade can not predate the early Miocene. Based on paleoclimatical and geological data, two competing hypotheses are proposed to explain the evolution of the xerophilous Sericania lineage: (a) a basal splitting within Sericania occurred because of the altitudinal and climatic barrier posed by the, Himalaya, which separated the xerophilous lineage in the north (Tibet) from the hygrophilous lineage in the south-east (S-slope of Himalaya/Tibet), or (b) it was a consequence of the increase in the climatic east-west contrast along the southern slope of the Himalaya, which strengthened with the onset of monsoons 8 Ma ago.