Geographic range and habitat reconstructions shed light on palaeotropical intercontinental disjunction and regional diversification patterns in Artabotrys (Annonaceae)

Aim: The biogeographical and habitat history of the species-rich angiosperm genus Artabotrys is reconstructed to assess hypotheses relating to processes that underlie palaeotropical intercontinental disjunction (PID) and regional diversification patterns. Location: Palaeotropics. Taxon: Artabotrys (Annonaceae). Methods: Phylogenetic relationships were estimated based on 53 Artabotrys species, using four chloroplast and 10 nuclear markers (c. 15.7 kb). Divergence times were estimated using two fossil calibrations and an uncorrelated lognormal relaxed clock model. Ancestral range estimation was performed under a dispersal-extinction-cladogenesis model while ancestral habitat reconstruction was conducted using the BAYAREALIKE model. Results: Artabotrys is unequivocally monophyletic, with a species-rich main Artabotrys clade (MAC) comprising distinct African and Asian sister clades, and an early divergent grade (EDG) comprising two African species. An ancestral range in Africa is inferred, with a single dispersal to Asia. The PID at the MAC crown occurred in the Miocene. A broad habitat tolerance spanning rain forests and seasonally dry forests/savannas was inferred at the MAC stem and crown nodes. Several shifts from rain forests to seasonally dry habitats were inferred, but there is no indication of a reverse transition. Main conclusions: The most plausible explanation for the PID involves overland migration across Arabia in the Miocene, prior to subsequent climate deterioration. Long-standing differences in climatic niche may have resulted in a significant yet porous biogeographical divide at the Isthmus of Kra, but Wallace's line does not reflect differences in climatic niches. Niche conservatism is an underlying pattern in Artabotrys, with local niche shifts occurring rather recently.