Orchid phylogenomics. Diversification, evolution and systematics of the hyperdiverse subtribe Bulbophyllinae

The orchid subtribe Bulbophyllinae comprises the second largest genus of flowering plants, Bulbophyllum (ca. 2,200 species), including many threatened species. Bulbophyllum is distributed in tropical and subtropical regions worldwide, including Asia, Australasia, Africa, Madagascar and South America, with a center of diversity in Asia and Australasia. Bulbophyllum displays a striking morphological diversity in vegetative and floral characters, which renders the recognition of evolutionary relationships based on morphology difficult. Previous molecular studies mainly relied on few molecular markers with limited phylogenetic signal. Thus, evolutionary relationships within Bulbophyllum, in particular in the Asian/Australasian groups, remained largely unclear.

Bulbophyllum lilianae (sect. Adelopetalum) is an endemic rainforest epiphyte of the Australian Wet Tropics region. Photo: T. Linderhaus

This project elucidated broad-level evolutionary relationships in Bulbophyllinae based on plastome sequencing of over 500 Bulbophyllum orchids. The project thus provided a robust phylogenetic framework to re-assess taxonomic concepts for a revised classification which correctly reflects evolutionary relationships. The study provided insights into the evolution of taxonomically and ecologically significant traits in Bulbophyllum. The study allowed the reconstruction of the spatio-temporal evolution of Bulbophyllinae, showing over which evolutionary timeframes the genus and its lineages evolved and how it spread across Asia and Malesia into Australasia and the Pacific.

In Bulbophyllum gracillimum (sect. Cirrhopetalum) the fly-pollinated flowers are arranged in a semicircular pattern. Photo: T. Linderhaus