Species delimitation and diversification of the Doum palms (Hyphaene spp.)

Hyphaene is genus of coryphoid palm tree emblematic of African semi-arid/arid environments, characterised for some species, by a natural dichotomous branching pattern unique in palms. However, some aspects of this economically and ecologically important genus are poorly known. For example, questions remain concerning species delimitation and the history of diversification withing this genus. Its taxonomy was known to be particularly difficult due to the combination of intrinsic and extrinsic factors. Mainly, the highly polymorphic nature of its fruit together with scarcity of informative collections has led to a proliferation of names. Moreover, despite that two fossils anchor the diversification of the Hyphaenineae sub-tribe in the Paleogene, the timing of diversification within this genus has never been studied. To better resolve species delimitation, phylogenetic relationship and timing diversification within the Hyphaenineae clade, we are using target capture for genes that already showed efficiency in the Palm family. Our results show the presence of two clades consistent with different branching patterns. Species are well delimited genetically with few hybridizations detected. The only Indian taxa (H. dichotoma) is close to H. compressa, growing in east Africa. The diversification within the Hyphaenineae sub-tribe could be dated to the Oligocene-Miocene following the timing of expansion of arid habitats within Africa. This genetic study bring solid conclusions for the resolution of species delimitation in a taxonomically difficult genus, propose a timeline of diversification consistent with the processes of aridification in Africa and highlight the importance of the Horn of Africa for future investigations