Phylogenetics of the allodapine bee genus Braunsapis: historical biogeography and long-range dispersal over water
A previous study of the allodapine bee genus Braunsapis suggested an African origin, with dispersal events into Madagascar and Asia, and from Asia into Australia. We re-examine the phylogeny of this genus, using an expanded set of taxa from Madagascar and Malawi and additional sequence data, in order to determine the number of dispersals and the timeframe over which they occurred. Location
Africa, Madagascar, Malawi, Asia and Australia. Methods
One nuclear (EF-1α F2) and two mitochondrial (CO1 and Cyt b) gene regions were sequenced for 36 allodapine bee species (including members of the genera Braunsapis, Nasutapis, Allodape, Allodapula, and Macrogalea) and one ceratinine species (Ceratina japonica). We used Bayesian analyses to examine phylogenetic structure and a penalized likelihood approach to estimate approximate ages for key divergences in our phylogeny. Results
Our analyses indicate a tropical African origin for Braunsapis in the early Miocene followed by very early dispersal into Asia and then a subsequent dispersal, following Asian diversification, into Australia during the late Miocene. There have also been two dispersals of Braunsapis from Africa to Madagascar and this result, when combined with phylogenetic and biogeographical data for other allodapines, suggests that these bees have the ability to cross moderately large ocean expanses. These dispersals may have been aided by the West Wind Drift, but rafting across the Mozambique Channel is also possible, and could be aided by the existence of developmental stages that require minimal or no feeding and by tolerance to sea water and spume. Accumulating evidence suggests that many biogeographical patterns in the southern hemisphere may be better explained by dispersal than by Gondwanan vicariance hypotheses. Our results add to this growing body of data and raise the possibility that some puzzling trans-Indian Ocean distributions may also be explained by historical dispersal events across oceanic barriers that now seem insuperable.
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