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WEAK CROSSABILITY BARRIER BUT STRONG JUVENILE SELECTION SUPPORTS ECOLOGICAL SPECIATION OF THE HYBRID PINE PINUS DENSATA ON THE TIBETAN PLATEAU
Author(s) -
Zhao Wei,
Meng Jingxiang,
Wang Baosheng,
Zhang Lisha,
Xu Yulan,
Zeng QingYin,
Li Yue,
Mao JianFeng,
Wang XiaoRu
Publication year - 2014
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/evo.12496
Subject(s) - biology , reproductive isolation , introgression , ecology , genetic algorithm , ecological speciation , habitat , hybrid , local adaptation , adaptation (eye) , evolutionary biology , range (aeronautics) , incipient speciation , ecological selection , selection (genetic algorithm) , botany , population , genetic variation , gene flow , genetics , demography , materials science , neuroscience , artificial intelligence , sociology , computer science , composite material , gene
Determining how a new hybrid lineage can achieve reproductive isolation is a key to understanding the process and mechanisms of homoploid hybrid speciation. Here, we evaluated the degree and nature of reproductive isolation between the ecologically successful hybrid species Pinus densata and its parental species P. tabuliformis and P. yunnanensis . We performed interspecific crosses among the three species to assess their crossability. We then conducted reciprocal transplantation experiments to evaluate their fitness differentiation, and to examine how natural populations representing different directions of introgression differ in adaptation. The crossing experiments revealed weak genetic barriers among the species. The transplantation trials showed manifest evidence of local adaptation as the three species all performed best in their native habitats. Pinus densata populations from the western edge of its distribution have evolved a strong local adaptation to the specific habitat in that range; populations representing different directions of introgressants with the two parental species all showed fitness disadvantages in this P. densata habitat. These observations illustrate that premating isolation through selection against immigrants from other habitat types or postzygotic isolation through selection against backcrosses between the three species is strong. Thus, ecological selection in combination with endogenous components and geographic isolation has likely played a significant role in the speciation of P. densata .