Taxonomic research on Epimedium sagittatum species complex and discussion

Epimedium sagittatum and its related species are the most controversially defined in Epimedium taxonomy, and are referred as E. sagittatum species complex. So far 11 taxa are included in the complex, but the taxonomical status of most species/varieties is probably open to question. New species based on a single of solely on vegetative characters are of frequent occurrence. Species based on plasticity of phenotype variation should not be regarded as good species. Based on the investigation in the herbaria, literature, and fields, we found that the morphological variations between some taxa were continuous. Thus E. sagittatum var. guizhouense and E. pudingense were treated as a synonym of E. sagittatum and E. sagittatum var. glabratum, respectively. Six taxa, namely E. coactum, E. coactum var. longtouhum, E. myrianthum var. jianheense, E. multiflorum, E. lobophyllum, and E. jingzhouense were integrated into E. myrianthum. Therefore, the taxonomic problems of E. sagittatum species complex now are back to the relationship between E. myrianthum and E. sagittatum. In morphology, E. myrianthum closely resembles E. sagittatum with only obvious difference in the form of inflorescence, and might be easily confused. Furthermore, in terms of several key taxonomic characters, there was overlapping question between the two taxa, and further research on taxonomy based on more extensive field investigation were needed. A correct species concept stems from a correct and thorough understanding of the nature of variation pattern of plants and its taxonomical value. In general, lack of scientific field investigation and morphological observation, inadequate study on variation range, variation pattern, taxonomical value, and narrow species concept are the reasons for the taxonomical difficulty to deal with.