Taxonomic recircumscriptions in the Aglaia elaeagnoidea complex (Meliaceae)

Aglaia is the most widespread and species-rich genus in Meliaceae, comprising 124 species. Aglaia elaeagnoidea has presented a longstanding dilemma for taxonomists; it is highly morphologically and ecologically variable, and has a range extending across India, Southeast Asia, Australia and islands of the western Pacific Ocean. Previous work has examined molecular variation in the eastern part of the species’ range; however, molecular variation in the western half of its distribution remained uncharacterised, precluding taxonomic resolution of the complex. In this study, we used DArT-seq analysis to investigate genetic structure in A. elaeagnoidea from India, Sri Lanka, Bangladesh, Thailand, Java and Bali. We find a strong genetic disjunction between Sri Lanka and Bangladesh, suggesting that western A. elaeagnoidea comprises two taxa. On the basis of these results, in combination with morphology and previous molecular work on eastern A. elaeagnoidea, we resolve A. elaeagnoidea into three species, retaining A. elaeagnoidea for the eastern (type) species, and reinstating A. wallichii for a species in Bangladesh, Thailand, Java and Bali, and A. roxburghiana for a species occurring in India and Sri Lanka. We provide descriptions for each taxon and a key to the species, thereby resolving a previously difficult species group in a notoriously complex genus.