Classification of Strobilanthinae (Acanthaceae): Trying to classify the unclassifiable?

Strobilanthinae comprise approximately 350 species from south and southeast Asia and Melanesia. Three main classifications of Strobilanthinae have been advocated, differing markedly in the number of groups recognised, their circumscription, and the rank assigned to them. But there remains no consensus concerning the best approach to the classification of the group. To investigate this issue, a morphological cladistic analysis of the southern Indian and Sri Lankan Strobilanthinae, comprising 66 species, is described. The results of the analysis demonstrate significant limitations of all three historical approaches to the classification of the group and, furthermore, suggest that any attempt to provide an informative formal classification of Strobilanthinae will be problematic. The only satisfactory approach consistent with these results is to place all previously recognised taxa in synonymy of an expanded Strobilanthes and to recognise informally those infrageneric monophyletic groups that can be clearly diagnosed.