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Zosteropidae

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Old Tuesday 26th May 2020, 06:02   #101
Peter Kovalik
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Babbington, J., Boland, C.R.J., Kirwan, G.M. et al. Morphological differences between ‘Mangrove White-eye’ and montane Abyssinian White-eye (Zosterops abyssinicus arabs) in Arabia despite no differentiation in mitochondrial DNA: incipient speciation via niche divergence?. J Ornithol (2020). https://doi.org/10.1007/s10336-020-01788-3

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The Arabian population of the Abyssinian White-eye Zosterops abyssinicus arabs occurs in the Asir Mountains in southwest Saudi Arabia, the highlands of Yemen, and southwest Oman. In Saudi Arabia, a recently discovered, very small, and enigmatic population of white-eyes Zosterops sp. indet. occurs in stands of mature mangroves on the Kingdom’s southern Red Sea coast 80–100 km west of the nearest locality of Z. a. arabs in the Asir Mountains. We obtained biometric data and blood samples from individuals of both populations, in the Asir Mountains and the Red Sea mangroves, complemented by measurements from museum specimens from throughout the range of Z. a. arabs. The mangrove-dwelling white-eyes were found to differ in morphometrics and several plumage characters from montane Abyssinian White-eyes Z. a. arabs. However, no differences were revealed by one mitochondrial marker between four ‘Mangrove White-eyes’ and five Z. a. arabs from the Asir Mountains. ‘Mangrove White-eyes’ might thus represent the result of a recent colonization followed by niche divergence, and a putative case of incipient speciation in one of the fastest-radiating vertebrate lineages. A review of the scant available literature and our own surveys indicate that the ‘Mangrove White-eye’ is very scarce within a highly restricted and threatened range, and presumably at risk of extinction.
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Old Tuesday 2nd June 2020, 20:10   #102
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Maëva Gabrielli, Benoit Nabholz, Thibault Leroy, Borja Milá and Christophe Thébaud. Within-island diversification in a passerine bird. Proc Biol Sci Published:18 March 2020Article ID:20192999 https://doi.org/10.1098/rspb.2019.2999

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The presence of congeneric taxa on the same island suggests the possibility of in situ divergence, but can also result from multiple colonizations of previously diverged lineages. Here, using genome-wide data from a large population sample, we test the hypothesis that intra-island divergence explains the occurrence of four geographical forms meeting at hybrid zones in the Reunion grey white-eye (Zosterops borbonicus), a species complex endemic to the small volcanic island of Reunion. Using population genomic and phylogenetic analyses, we reconstructed the population history of the different forms. We confirmed the monophyly of the complex and found that one of the lowland forms is paraphyletic and basal relative to others, a pattern highly consistent with in situ divergence. Our results suggest initial colonization of the island through the lowlands, followed by expansion into the highlands, which led to the evolution of a distinct geographical form, genetically and ecologically different from the lowland ones. Lowland forms seem to have experienced periods of geographical isolation, but they diverged from one another by sexual selection rather than niche change. Overall, low dispersal capabilities in this island bird combined with both geographical and ecological opportunities seem to explain how divergence occurred at such a small spatial scale.
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Old Monday 15th June 2020, 16:52   #103
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Joseph D. Manthey, Carl H. Oliveros, Michael J. Andersen, Christopher E. Filardi & Robert G. Moyle. Gene flow and rapid differentiation characterize a rapid insular radiation in the southwest Pacific (Aves: Zosterops ). Evolution. First published:14 June 2020 https://doi.org/10.1111/evo.14043

Abstract:

As a dispersive lineage expands its distribution across a heterogeneous landscape, it leaves behind allopatric populations with varying degrees of geographic isolation that often differentiate rapidly. In the case of oceanic islands, even narrowly separated populations often differentiate, which seems contrary to the highly dispersive nature of the founding lineage. This pattern of highly dispersive lineages differentiating across narrow sea barriers has perplexed biologists for more than a century. We used two reduced‐representation genomic datasets to examine the diversification of a recent, rapid geographic radiation, the white‐eyes (Aves: Zosterops ) of the Solomon Islands. We incorporated methods that targeted phylogenetic structure, population structure, and explicit tests for gene flow. Both data sets showed evidence of gene flow among species, but not involving the closely spaced islands in the New Georgia Group. Instead, gene flow has occurred among the larger islands in the archipelago, including those recently connected by land bridges as well as those isolated by large expanses of deep ocean. Populations separated by shallow seas, and connected by land bridges during glacial cycles, ranged from no differentiation to both phenotypic and genomic differentiation. These complex patterns of gene flow and divergence support a model of rapid geographic radiation in which lineages differentially evolve dispersal disparity and phenotypic differences.
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