Diversification across an altitudinal gradient in the Tiny Greenbul (Phyllastrephus debilis) from the Eastern Arc Mountains of Africa

BMC Evolutionary Biology

Research Article

Jon Fjeldså¹  Rauri CK Bowie²  Jérôme Fuchs³ 

[1] Centre of Macroecology, Evolution and Climate, Zoological Museum, University of Copenhagen, Universitetsparken 15, DK-2100, Copenhagen, Denmark;Museum of Vertebrate Zoology and Department of Integrative Biology, University of California, 3101 Valley Life Science Building, 94720-3160, Berkeley, CA, USA;DST/NRF Centre of Excellence at the Percy FitzPatrick Institute, University of Cape Town, 7701, Rondebosch, South Africa;Museum of Vertebrate Zoology and Department of Integrative Biology, University of California, 3101 Valley Life Science Building, 94720-3160, Berkeley, CA, USA;DST/NRF Centre of Excellence at the Percy FitzPatrick Institute, University of Cape Town, 7701, Rondebosch, South Africa;California Academy of Sciences, 55 Music Concourse Drive, 94118, San Francisco, CA, USA;

关键词: Altitudinal Gradient;    Secondary Contact;    Disruptive Selection;    Bayesian Skyline Plot;    Lowland Population;   

DOI  :  10.1186/1471-2148-11-117

 received in 2010-09-21, accepted in 2011-05-03,  发布年份 2011

来源: Springer

【 摘 要 】

BackgroundThe Eastern Arc Mountains of Africa have become one of the focal systems with which to explore the patterns and mechanisms of diversification among montane species and populations. One unresolved question is the extent to which populations inhabiting montane forest interact with those of adjacent lowland forest abutting the coast of eastern Africa. The Tiny Greenbul (Phyllastephus debilis) represents the only described bird species within the Eastern Arc/coastal forest mosaic, which is polytypic across an altitudinal gradient: the subspecies albigula (green head) is distributed in the montane Usambara and Nguru Mountains whereas the subspecies rabai (grey head) is found in Tanzanian lowland and foothill forest. Using a combination of morphological and genetic data, we aim to establish if the pattern of morphological differentiation in the Tiny Greenbul (Phyllastrephus debilis) is the result of disruptive selection along an altitudinal gradient or a consequence of secondary contact following population expansion of two differentiated lineages.ResultsWe found significant biometric differences between the lowland (rabai) and montane (albigula) populations in Tanzania. The differences in shape are coupled with discrete differences in the coloration of the underparts. Using multi-locus data gathered from 124 individuals, we show that lowland and montane birds form two distinct genetic lineages. The divergence between the two forms occurred between 2.4 and 3.1 Myrs ago.Our coalescent analyses suggest that limited gene flow, mostly from the subspecies rabai to albigula, is taking place at three mid-altitude localities, where lowland and montane rainforest directly abut. The extent of this introgression appears to be limited and is likely a consequence of the recent expansion of rabai further inland.ConclusionThe clear altitudinal segregation in morphology found within the Tiny Greenbul is the result of secondary contact of two highly differentiated lineages rather than disruptive selection in plumage pattern across an altitudinal gradient. Based on our results, we recommend albigula be elevated to species rank.

【 授权许可】

CC BY   
© Fuchs et al; licensee BioMed Central Ltd. 2011