Doctor of Philosophy (PhD)
Widespread bird species endemic to the lowlands of the Guineo-Congolian rainforest of Africa have traditionally been thought to lack substantial intraspecific structure. This view owes largely to their widespread distributions coupled with the absence of discrete geographic variation in plumage. In the following chapters I examine the phylogeographic patterns of three such species using a combination of molecular and morphometric data. The three species investigated are the Green Hylia (Hylia prasina), the Red-tailed Bristlebill (Bleda syndactylus), and the Yellow-whiskered Greenbul (Andropadus latirostris). Using the phylogeographic patterns from these data, I assess 1) models of rainforest species diversification, 2) current taxonomy, and 3) implications for conservation of lowland rainforests. In contrast to the lack of discrete plumage variation in these species, phylogeographic analyses reveal a high degree molecular and morphological divergence. Furthermore, general patterns of geographical structure of the mtDNA data are largely congruent among the three species. Each species has unique mtDNA haplotype groups in Liberia, Ghana, Cameroon-Gabon, Central African Republic, and the eastern Democratic Republic of Congo. Andropadus latirostris, which also occurs in montane forests, has unique haplotype groups in these montane regions. Taken together the patterns of geographic variation in molecular and morphological datasets from these three species suggest a history of allopatric divergence via genetic drift, consistent with predictions of refugial diversification. There is also some evidence for a potential role for divergent selection along a longitudinal temperature gradient in shaping the morphometric diversity in Andropadus latirostris. Despite their widespread distributions and the potential for high gene flow, these three species exhibit a remarkable level of geographic structure across the lowland rainforest. This contradicts the prevailing view of widespread lowland species as large panmictic populations. This significant geographic structure has important implications for species and habitat conservation in Africa, where lowland forest is typically viewed as a continuous block of homogeneous habitat. The implication is habitat loss in one area would not result in a substantial loss of biodiversity because many of the species are widely distributed. The geographic structure evident in these data suggests that that is not the case.
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Marks, Ben D., "Avian diversification in the afrotropics" (2008). LSU Doctoral Dissertations. 3021.
Frederick H. Sheldon