Molecular phylogen-y and systematics of the highly polymorphic Rumex bucephalophorus complex (Polygonaceae)

Abstract

bstract Rumex bucephalophorus is a very polymorphic species that has been subjected to various taxonomic stud ies in which diverse infraspecific taxa have been recognised on the basis of diaspore traits. In this study we used molecular markers (ITS and AFLP) to explore this remarkable diversity, to test previous hypoth eses of classification, and attempt to explain biogeographic patterns. Results show that R. bucephalopho rus forms a monophyletic group in which diversification began around 4.2 Mya, at the end of Messinian Salinity Crisis. The two molecular markers clearly show a deep divergence separating subsp. bucephalo phorus from all other subspecific taxa, among which subsp. canariensis also constitutes a separate and well distinguishable unit. In contrast, subspecies hispanicus and subsp. gallicus constitute a monophyletic group in which three subgroups can be recognised: subsp. hispanicus, subsp. gallicus var. gallicus and subsp. gallicus var. subaegeus. However, these three subgroups are not clearly distinguished genetically or morphologically, so that in formal classification it would be preferable to treat them at the varietal level.