Sectional polyphyly and morphological homoplasy in Southeast Asian Cyrtandra (Gesneriaceae): consequences for the taxonomy of a mega-diverse genus

Cyrtandra (Gesneriaceae), with over 800 species, is a mega-diverse genus which presents considerable taxonomic challenges due to its size. A well-sampled phylogeny of the genus across Southeast Asia has confirmed that all but one of the sections within Clarke’s 1883 genus-wide infrageneric classification are polyphyletic. It also shows that there are high levels of homoplasy in key morphological characters, although it is possible to use morphological characters to define clades in parts of the phylogenetic tree. There is some geographic structure in the phylogeny, but there is also evidence of dispersal between islands. A practical approach for tackling the taxonomy of Cyrtandra in the region, through phylogenetically informed taxonomic revisions of geographic areas, an approach which combines evidence from molecular, morphological and distribution data, is discussed. Completing our understanding of species diversity and delimitation in this genus will allow us to maximise the use of Cyrtandra as a tool for studying biogeography, speciation, diversification and conservation prioritisation in the rainforests of Southeast Asia.