Dated phylogeny and biogeography of the Eurasian Allium section Rhizirideum (Amaryllidaceae)

Abstract

Allium section Rhizirideum constitutes a group of approximately 24 species, distributed mostly in steppe areas of the Eurasian temperate zone. Its phylogenetic relationships are therefore relevant for understanding of the evolutionary and biogeographical patterns of the Eurasian steppes. Based upon DNA sequences from two plastid regions (trnQ-rps16 and trnL-rpl32) and the internal transcribed spacer region of nuclear ribosomal DNA, the phylogenetic relationships in Allium section Rhizirideum are investigated by using maximum parsimony and Bayesian inference. Dated phylogenies revealed (1) that diversification started in the upper Pliocene and further speciation events occurred during the Pleistocene and (2) a clear division of the section Rhizirideum into an ``Asiatic'' and ``European'' geographical group. Nomenclature, distribution maps and identification key for all species are provided. Origin and diversification within this section thus reflect the development and history of the modern Eurasian steppe.