Phylogeography, character evolution and taxonomy of Scurrulinae (Loranthaceae): New insights into the circumscription of the genus Taxillus

Abstract

Abstract Background Exploring the relationship between parasitic plants and answering taxonomic questions are still challenging. The subtribe Scurrulinae (Loranthaceae), which has a wide distribution in Asia and Africa, provides an excellent example to illuminate this scenario. Using a comprehensive taxon sampling of the subtribe, this study focuses to infer the phylogenetic relationships within Scurrulinae, investigate the phylogeography of the subtribe, and establish a phylogenetically-based classification incorporating both molecular and morphological evidence. We conducted phylogenetic, historical biogeography, and ancestral character state reconstruction analyses of Scurrulinae based on the sequences of 6 DNA regions from 89 individuals to represent all 5 tribes of the Loranthaceae and the dataset from eleven morphological characters. Results The results strongly support the non-monophyletic of Scurrulinae, with Phyllodesmis recognized as a separate genus from its allies Taxillus and Scurrula. “Afrotaxillus” is well supported as a new genus from Africa. The mistletoe Scurrulinae originated in Asia during the Oligocene. Scurrulinae was inferred to have been widespread in Asia but did not disperse to other areas. “Afrotaxillus” was confirmed to have originated in Africa from African Loranthaceae ca. 17 Ma, and likely the genus independently evolved from Taxillus in Asia. Conclusions This study based on comprehensive taxon sampling of the subtribe Scurrulinae, strongly supports the relationship between genera. The taxonomic treatment for Phyllodesmis, Afrotaxillus were provided. The historical biogeography of mistletoe Scurrulinae was determined with origin in Asia during the Oligocene. Taxillus and Scurrula diverged during the climatic optimum in the middle Miocene. Afrotaxillus originated in Africa from African Loranthaceae. Diversification of Scurrulinae and the development of endemic species in Asia may have been supported by the fast-changing climate, including cooling, drying, and the progressive uplift of the high mountains in central Asia, especially during the late Pliocene and Pleistocene.