Evolution of Forest Bitis (Macrocerastes) in Africa: Phylogeography, Population Genetics, and Potential as a Model for Batesian Mimicry
Abstract
The major biogeographical patterns characterizing the diversification of widely distributed species in the African rainforest remain poorly understood because of the low number of well-sampled studies that are focused on this region. I examine the phylogeography and population genetics of two broadly sympatric sister lineages of large African forest vipers (genus Bitis, subgenus Macrocerastes), the rhinoceros viper (B. nasicornis) and the Gaboon vipers (B. gabonica and B. rhinoceros). Despite their close relationship, these two lineages have notably different patterns of divergence in time and space. A time-calibrated phylogeny with sequence data from five genes, and population structure and PCA analyses of a SNP dataset show three major clades of B. nasicornis. Pleistocene refugia seem to play the primary role in their isolation, with the Middle Congo River playing a potentially secondary role as a biogeographic barrier. Parallel datasets and analyses examining B. gabonica and B. rhinoceros demonstrate the Dahomey Gap as the barrier dividing the two species, with little population structuring within B. rhinoceros. The Niger River was shown to isolate a highly localized and very distinctive population of B. gabonica in southwestern Nigeria from all other populations of the species. Analyses of the SNP dataset demonstrated higher nucleotide diversity in B. nasicornis than in B. gabonica, and showed no evidence of ongoing gene flow or regular hybridization between Gaboon and rhinoceros vipers, despite their occupation of similar niches (and past records of natural hybrids). The novel inclusion of Bitis heraldica in time-divergence analyses restricted the evolutionary origins of large, forest-dwelling Macrocerastes to the period after the Mid-Miocene Climatic Optimum. Finally, I propose a hypothesis of a mimicry complex comprised of B. gabonica and the toad Sclerophrys channingi as the Batesian model and mimic, respectively. Evidence for the hypothesis is supported by data from color, pattern, mensural data, natural history, and distributional data.
Subject Area
Evolution and Development|Ecology|Forestry
Recommended Citation
Vaughan, Eugene Richard, "Evolution of Forest Bitis (Macrocerastes) in Africa: Phylogeography, Population Genetics, and Potential as a Model for Batesian Mimicry" (2023). ETD Collection for University of Texas, El Paso. AAI30816044.
https://scholarworks.utep.edu/dissertations/AAI30816044