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Historical biogeography of Goniothalamus and Annonaceae tribe Annoneae: dispersal–vicariance patterns in tropical Asia and intercontinental tropical disjunctions revisited

Thomas, Daniel C., Tang, Chin Cheung, Saunders, Richard M. K.
Journal of biogeography 2017 v.44 no.12 pp. 2862-2876
Goniothalamus, Miocene epoch, ancestry, biodiversity, biogeography, fossils, models, nucleotide sequences, plastid DNA, surface water, tectonics, tropics, India, North America, Philippines
AIM: The historical biogeography of the species‐rich flowering plant genus Goniothalamus (c. 130 species) and the wider Annonaceae tribe Annoneae is investigated to evaluate hypotheses regarding the processes underlying tropical intercontinental disjunctions (‘long‐distance dispersal [LDD]’ versus ‘boreotropics’) and floristic exchange between biodiversity hotspots in tropical Asia. LOCATION: Tropics, tropical Asia. METHODS: Divergence time estimation was based on plastid DNA sequence data (c. 10 kb; 164 Annonaceae accessions, including 65 Goniothalamus species) using an uncorrelated lognormal relaxed clock model and two fossil calibrations. Likelihood ancestral range estimation was performed using dispersal‐extinction‐cladogenesis models with and without time‐stratified dispersal constraints. RESULTS: The boreotropics model incorporating high chances for intercontinental dispersal during 68–34 Ma fitted the data significantly better than LDD models enforcing low intercontinental dispersal rates. Multiple vicariance events were identified in Annoneae including at the Annoneae crown node (57–49 Ma, Africa/S+N America), and the Disepalum‐Asimina split (27–24 Ma, Asia/N America). A wide ancestral range in continental SE Asia, W and E Malesia was inferred at the Goniothalamus crown node (24–21 Ma). Several dispersal events from continental SE Asia/W Malesia were identified in the Miocene: two north‐eastwards to the Philippines, one eastwards to the Sahul Shelf and two westwards to India. MAIN CONCLUSIONS: The boreotropics hypothesis provides a well‐supported, plausible explanation for the disjunctions and dispersal–vicariance patterns in tribe Annoneae. The wide distribution inferred at the Goniothalamus crown node indicates that its ancestors already bridged the marine gap between the Sunda and Sahul Shelves by LDD or rafting on tectonic plate microfragments. Dispersal across long‐standing water bodies in Malesia occurred multiple times from the early Miocene as marine gaps decreased following tectonic plate convergence and land emergence. Substantially older crown group divergence estimates compared with previous studies indicate that hypotheses of rapid recent radiation in Goniothalamus must be rejected.