title: Climate niche differentiation between two passerines despite ongoing gene flow.
abstract: Niche evolution underpins the generation and maintenance of biological diversity, but niche conservatism, in which niches remain little changed over time in closely related taxa, and the role of ecology in niche evolution are continually debated. To test whether climate niches are conserved in two closely related passerines in East Asia - the vinous-throated (Paradoxornis webbianus) and ashy-throated (P. alphonsianus) parrotbills - we established their potential allopatric and sympatric regions using ecological niche models and compared differences in their climate niches using niche overlap indices in background tests and multivariate statistical analyses. We also used polymorphism data on 44 nuclear genes to infer their divergence demography. We found that these two parrotbills occupy different climate niches, in both their allopatric and potential sympatric regions. Because the potential sympatric region is the area predicted to be suitable for both parrotbills based on the ecological niche models, it can serve as a natural common garden. Therefore, their observed niche differences in this potential sympatry were not simply rendered by phenotypic plasticity and probably had a genetic basis. Our genetic analyses revealed that the two parrotbills are not evolutionarily independent for the most recent part of their divergence history. The two parrotbills diverged c. 856,000 years ago and have had substantial gene flow since a presumed secondary contact c. 290,000 years ago. This study provides an empirical case demonstrating that climate niches may not be homogenized in nascent species in spite of substantial, ongoing gene flow, which in turn suggests a role for ecology in promoting and maintaining diversification among incipient species.
authors.affiliation: Department of Life Science, National Taiwan Normal University, Taipei, 116, Taiwan.
authors.forename: Pei-Jen L
authors.initials: PL
authors.lastname: Shaner
authors.affiliation: Department of Life Science, National Taiwan Normal University, Taipei, 116, Taiwan.
authors.forename: Tzu-Hsuan
authors.initials: TH
authors.lastname: Tsao
authors.affiliation: Department of Life Science, National Taiwan Normal University, Taipei, 116, Taiwan.
authors.forename: Rong-Chien
authors.initials: RC
authors.lastname: Lin
authors.affiliation: Ministry of Education Key Laboratory for Tropical Plant and Animal Ecology, College of Life Sciences, Hainan Normal University, Haikou, 571158, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Liang
authors.affiliation: Department of Life Science, National Taiwan Normal University, Taipei, 116, Taiwan.
authors.forename: Chia-Fen
authors.initials: CF
authors.lastname: Yeh
authors.affiliation: China State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Science, Kunming, 650223, China.
authors.forename: Xiao-Jun
authors.initials: XJ
authors.lastname: Yang
authors.affiliation: Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, 100080, China.
authors.forename: Fu-Min
authors.initials: FM
authors.lastname: Lei
authors.affiliation: College of Animal Science and Technology, Guangxi University, Nanning, 530005, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Zhou
authors.affiliation: Ministry of Education Key Laboratory for Tropical Plant and Animal Ecology, College of Life Sciences, Hainan Normal University, Haikou, 571158, China.
authors.forename: Can-Chao
authors.initials: CC
authors.lastname: Yang
authors.affiliation: Department of Zoological Museum, Institute of Ecology and Biological Resources, 18 Hoang Quoc Viet - Cau Giay, Hanoi, VietNam.
authors.forename: Le Manh
authors.initials: LM
authors.lastname: Hung
authors.affiliation: Department of Natural Resources and Environmental Studies, National Dong Hwa University, Hualien, 97401, Taiwan.
authors.forename: Yu-Cheng
authors.initials: YC
authors.lastname: Hsu
authors.affiliation: Department of Life Science, National Taiwan Normal University, Taipei, 116, Taiwan.
authors.forename: Shou-Hsien
authors.initials: SH
authors.lastname: Li
mesh_terms: D000818:Animals; D002980:Climate; D017753:Ecosystem; D005260:Female; D051456:Gene Flow; D049810:Genetic Speciation; D008297:Male; D008969:Molecular Sequence Data; D046109:Passeriformes / Q000145:classification / Q000235:genetics*; D010802:Phylogeny
keywords: divergence with gene flow; ecological niche modelling; niche evolution; parapatry; secondary contact; speciation