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Niche divergence promotes rapid diversification of East African sky island white-eyes (Aves: Zosteropidae).

ABSTRACT: The Eastern Afromontane biodiversity hotspot composed of highly fragmented forested highlands (sky islands) harbours exceptional diversity and endemicity, particularly within birds. 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. Here, we focus on the recent songbird genus Zosterops, represented by montane and lowland members, to test the roles of niche conservatism versus niche divergence in the diversification and colonization of East Africa's sky islands. The species-rich white-eyes are a typically homogeneous family with an exceptional colonizing ability, but in contrast to their diversity on oceanic islands, continental diversity is considered depauperate and has been largely neglected. Molecular phylogenetic analysis of ~140 taxa reveals extensive polyphyly among different montane populations of Z. poliogastrus. These larger endemic birds are shown to be more closely related to taxa with divergent habitat types, altitudinal distributions and dispersal abilities than they are to populations of restricted endemics that occur in neighbouring montane forest fragments. This repeated transition between lowland and highland habitats over time demonstrate that diversification of the focal group is explained by niche divergence. 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.

SUBMITTER: Cox SC

PROVIDER: S-EPMC4255762 | biostudies-other | 2014 Aug

REPOSITORIES: biostudies-other

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Niche divergence promotes rapid diversification of East African sky island white-eyes (Aves: Zosteropidae).

Cox Siobhan C SC Prys-Jones Robert P RP Habel Jan C JC Amakobe Bernard A BA Day Julia J JJ

Molecular ecology 20140708 16

The Eastern Afromontane biodiversity hotspot composed of highly fragmented forested highlands (sky islands) harbours exceptional diversity and endemicity, particularly within birds. 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. Here, we focus on the recent songbird genus Zosterops, represented by montane and lowland members, to test the roles of niche c ...[more]

PMID: 24954273

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Project description:BACKGROUND:Cichlids are a prime model system in evolutionary research and several of the most prominent examples of adaptive radiations are found in the East African Lakes Tanganyika, Malawi and Victoria, all part of the East African cichlid radiation (EAR). In the past, great effort has been invested in reconstructing the evolutionary and biogeographic history of cichlids (Teleostei: Cichlidae). In this study, we present new divergence age estimates for the major cichlid lineages with the main focus on the EAR based on a dataset encompassing representative taxa of almost all recognized cichlid tribes and ten mitochondrial protein genes. We have thoroughly re-evaluated both fossil and geological calibration points, and we included the recently described fossil †Tugenchromis pickfordi in the cichlid divergence age estimates. RESULTS:Our results estimate the origin of the EAR to Late Eocene/Early Oligocene (28.71?Ma; 95% HPD: 24.43-33.15?Ma). More importantly divergence ages of the most recent common ancestor (MRCA) of several Tanganyika cichlid tribes were estimated to be substantially older than the oldest estimated maximum age of the Lake Tanganyika: Trematocarini (16.13?Ma, 95% HPD: 11.89-20.46?Ma), Bathybatini (20.62?Ma, 95% HPD: 16.88-25.34?Ma), Lamprologini (15.27?Ma; 95% HPD: 12.23-18.49?Ma). The divergence age of the crown haplochromine H-lineage is estimated to 22.8?Ma (95% HPD: 14.40-26.32?Ma) and of the Lake Malawi radiation to 4.07?Ma (95% HDP: 2.93-5.26?Ma). In addition, we recovered a novel lineage within the Lamprologini tribe encompassing only Lamprologus of the lower and central Congo drainage with its divergence estimated to the Late Miocene or early Pliocene. Furthermore we recovered two novel mitochondrial haplotype lineages within the Haplochromini tribe: 'Orthochromis' indermauri and 'Haplochormis' vanheusdeni. CONCLUSIONS:Divergence time estimates of the MRCA of several Tanganyika cichlid tribes predate the age of the extant Lake Tanganyika basin, and hence are in line with the recently formulated "Melting-Pot Tanganyika" hypothesis. The radiation of the 'Lower Congo Lamprologus clade' might be linked with the Pliocene origin of the modern lower Congo rapids as has been shown for other Lower Congo cichlid assemblages. Finally, the age of origin of the Lake Malawi cichlid flock agrees well with the oldest age estimate for lacustrine conditions in Lake Malawi.

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Niche divergence promotes rapid diversification of East African sky island white-eyes (Aves: Zosteropidae).

Publications

Niche divergence promotes rapid diversification of East African sky island white-eyes (Aves: Zosteropidae).

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