Niche divergence promotes rapid diversification of East African sky island white-eyes (Aves: Zosteropidae).
Bottom Line: To explain their elevated diversity within this region, models founded on niche conservatism have been offered, although detailed phylogeographic studies are limited to a few avian lineages.Our results also highlight an underestimation of diversity compared to morphological studies that has implications for their taxonomy and conservation.Molecular dating suggests that the spatially extensive African radiation arose exceptionally rapidly (1-2.5 Ma) during the fluctuating Plio-Pleistocene climate, which may have provided the primary driver for lineage diversification.
Affiliation: Department of Genetics, Evolution and Environment, University College London, Gower Street, London, WC1E 6BT, UK; Bird Group, Department of Life Sciences, The Natural History Museum, Akeman Street, Tring, Hertfordshire, HP23 6AP, UK.Show MeSH
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Mentions: Unlike the continuous mountain ranges of the Himalayas or Andes, the EABH is composed of a chain of ancient isolated massifs (Griffiths 1993) and young volcanoes (<5 Ma e.g. Baker et al. 1971) forming sky islands (Fig.1A). Montane forests typically occur above 800 m on these isolated peaks, so that the climatic conditions and ecosystem are highly differentiated from the surrounding low altitude savannah habitats and thus form ‘ecological islands’. Previously, the montane forests formed a pan-African forest that fragmented in the Early Oligocene due to the onset of aridification (Lovett 1993; Sepulchre et al. 2006) and have therefore had a long period of isolation. The isolation of these habitats potentially allows in situ speciation events to be differentiated from colonization events, which would otherwise be much harder to identify in montane systems exhibiting higher degrees of connectivity (Voelker et al. 2010).
Affiliation: Department of Genetics, Evolution and Environment, University College London, Gower Street, London, WC1E 6BT, UK; Bird Group, Department of Life Sciences, The Natural History Museum, Akeman Street, Tring, Hertfordshire, HP23 6AP, UK.