Phylogenetics of the endemic genus Stemonoporus Thw. (Dipterocarpaceae)

Abstract

Stemonoporus Thw. is the most species-rich (27 species) endemic dipterocarp genus in Sri Lanka. All its members are categorized as highly threatened or threatened in the IUCN Red Data Book. The existing classifications of the genus are primarily based on traditional taxonomic methods using a limited number of collected material and sometimes mainly on herbarium specimens. A recent study carried out in order to evaluate the species limits of Stemonoporus strengthens its position as the most species-rich endemic dipterocarp genus in Sri Lanka. However, there are no phylogenetic studies being carried out on this important genus. The aim of the study was to construct the phylogeny of the genus Stemonoporus, using morphological and phytochemical data. Specimens of all representative taxa were sampled from different geographical locations. A total of 170 specimens were collected and six individuals per taxon were examined. Cladistic analysis was performed based on morphological and phytochemical data extracted from specimens collected from different geographical locations and herbarium specimens. Combined analysis of morphological and phytochemical data suggests that all the species except for Stemonoporus wightii form a monophyletic group with strong bootstrap support of 82%. The strict consensus tree of the combined analysis identifies eight monophyletic groups within the genus Stemonoporus. S. wightii was resolved as the basal taxon of the genus. The identified 27 species are supported as monophyletic groups.