Niche evolution on reticulate polyploid phylogenies
Divergence between fundamental ecological niches occupied by closely related species is rare. One hypothesized exception to this is through formation of allopolyploid species. To test the prediction that allopolyploidization is coupled with fundamental niche shifts, one aspect of my research focuses on the African clawed frog genus Xenopus, whose evolution is characterized by allopolyploid speciation events interspersed with bifurcating speciation. Our ancestral niche reconstructions suggests that similar to plants, expansions and contractions around the ancestral niche are fairly common, and that niche novelty is present but rare, underscoring the contribution of polyploid speciation to rapid adaptation and novel ecological opportunity.
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Historical demography and refugial dynamics of Central and West African skinks
For decades the roles of rivers and mountains in formation of Pleistocene refugia and generation of high levels of species diversity in the tropics have been debated. These debates have largely been driven by poor pollen core records and conflicting phylogeographic data from areas likely to be impacted by refugial dynamics. Part of my research uses genome-level population demography analyses and paleo-distribution modeling to study the finer-scale effects of Pleistocene refugia on population dynamics in a widespread skink species complex, Trachylepis maculilabris in West and Central Africa.
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Phylogenetics and taxonomy of Toxicodryas snakes
Only recently has it become possible to take an integrative approach to test predictions derived from classical tropical diversification hypotheses using genomic sequencing and paleo-species distribution modeling. One recently completed project tested the predictions of the classic river, refuge, and river-refuge hypotheses on diversification in the arboreal Sub-Saharan African snake genus Toxicodryas. Our demographic analyses supported that rivers have represented strong barriers to gene flow among populations and no support for a major contraction of suitable habitat during the last glacial maximum, allowing us to reject both the refuge and river-refuge hypotheses in favor of the river barrier hypothesis.
Allen, K.E., et al. 2021. Rivers, not refugia, drove diversification in arboreal, sub-Saharan African snakes. Ecology and Evolution. 11, 6133–6152. DOI: 10.1002/ece3.7429. Greenbaum, E., et al. 2021. Night stalkers from above: A monograph of Toxicodryas tree snakes (Squamata: Colubridae) with descriptions of two new cryptic species from Central Africa. Zootaxa 4965 (1), 001–044. |
Modelling potential Pleistocene habitat corridors between Afromontane forest regions
The unusually high floral and faunal similarity between the different regions of the Afromontane archipelago has been noted by biogeographers since the late 1800s. A possible explanation for this similarity is the spread of montane habitat into the intervening lowlands during the glacial periods of the Pleistocene, allowing biotic exchange between mountain ranges. In this study, we sought to infer the existence and most likely positions of these potential habitat corridors using paleo-distribution reconstructions for sixteen Afromontane endemic tree, shrub, and bird species. We found widespread climatic suitability for our montane taxa throughout the lowlands of Central Africa during the LGM, connecting all regions of the Afromontane archipelago except the Ethiopian Highlands.
Allen, K.E., et al. 2021. Modelling potential Pleistocene habitat corridors between Afromontane forest regions. Biodiversity and Conservation 30, 2361–2375. |