Phylogeny of Allium L. subgenus Anguinum (G. Don. ex W.D.J. Koch) N. Friesen (Amaryllidaceae)

Abstract

The disjunct distribution of the subgenus Anguinum of the genus Allium makes it a good candidate to test models of Northern hemisphere biogeography. Here we conduct phylogenetic analysis with the nuclear marker ITS and three different chloroplast markers (rps16 intron, rbcL-atpB spacer, rpl32-trnL spacer). Divergence time estimations (Beast) relying on published ITS substitution rates and ancestral range reconstructions were calculated to elucidate the biogeographical history of the subgenus. Additionally we compiled distribution maps for all species with data taken from the literature, herbariums and data from field observations. The main radiation of the subgenus took place in the last one million years and is still going on. They have their origins in the mid Miocene in East Asia and were highly influenced by the climate fluctuations in the Pliocene/Pleistocene period. Conflicting tree topologies between nuclear and cpDNA markers of Allium tricoccum Solander indicate that the species is of hybridogenous origin. Cloning the ITS sequence revealed the parental copies and confirmed our conclusion. One originated from the Eurasian and the other from the East Asian clade. We were able to show that it reached North America most likely via the Beringia around 2.5mya (95% HPD of 0.35–5.26mya). Our data suggest that Allium victorialis L. is only distributed in mountain pastures in Europe as it forms a well-supported clade in the ITS tree. In the analysis of the molecular markers we found two distinct types of Allium ochotense Prokh. and we suggest splitting the species based on Prokhanov’s (1930) proposal. Taxonomical remarks and an identification key to all species of the subgenus Anguinum is provided.