Abstract
Background - The genus Epimedium is well known for its ornamental representatives. However, species boundaries and evolutionary relationships within the genus remain uncertain due to several difficulties. First, potentially diagnostic characters are generally not described with enough detail, hampering linkage of specimens to recognized taxa. Second, previous molecular studies failed to gain resolution, especially within the Chinese distribution area of the genus. Nevertheless, growing scientific interest in the medicinal properties of Epimedium has prompted the need for reliable identification of species. Aims and methods - This study aims at: (1) assessing genetic diversity within Epimedium, using nuclear and chloroplast DNA sequences in combination with AFLP fingerprinting, (2) delivering a detailed description for one potentially diagnostic character, pubescence of leaflets. Key results - The DNA sequences and AFLP fingerprints resulted in an unresolved polytomy for the Chinese representatives of Epimedium. Furthermore, this study provided detailed scanning electron microscope images of four clearly distinguishable types of leaflet pubescence. Conclusions - As AFLP is considered capable of detecting rare genetic differences in groups with low sequence variation, we suggest the lack of resolution in the Chinese clade to represent a hard polytomy. This is interpreted as additional evidence for the hypothesis of a recent origin for these taxa. As this implies that several recognized species are still in the process of differentiation, these difficulties in resolving evolutionary relationships are linked to difficulties in species delimitation. Furthermore, the lack of details in some species descriptions has led to the description of new taxa based on small variations. To tackle these problems, we propose a change in view on Epimedium taxonomy. In this view, broader taxonomic entities are recognized, characterized by clearly defined characters. The four types of pubescence described in this study can serve as a first step towards this new interpretation of Epimedium taxonomy.
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