| 1. |
- Meng, Jingxiang, et al.
(författare)
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Adaptive Differentiation in Seedling Traits in a Hybrid Pine Species Complex, Pinus densata and Its Parental Species, on the Tibetan Plateau
- 2015
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- Evidence from molecular genetics demonstrates that Pinus densata is a natural homoploid hybrid originating from the parent species Pinus tabuliformis and Pinus yunnanensis, and ecological selection may have played a role in the speciation of Pinus densata. However, data on differentiation in adaptive traits in the species complex are scarce. In this study, we performed a common garden test on 16 seedling traits to examine the differences between Pinus densata and its parental species in a high altitude environment. We found that among the 16 analyzed traits, 15 were significantly different among the species. Pinus tabuliformis had much earlier bud set and a relatively higher bud set ratio but poorer seedling growth, and Pinus yunnanensis had opposite responses for the same traits. Pinus densata had the greatest fitness with higher viability and growth rates than the parents. The relatively high genetic contribution of seedling traits among populations suggested that within each species the evolutionary background is complex. The correlations between the seedling traits of a population within a species and the environmental factors indicated different impacts of the environment on species evolution. The winter temperature is among the most important climate factors that affected the fitness of the three pine species. Our investigation provides empirical evidence on adaptive differentiation among this pine species complex at seedling stages.
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| 2. |
- Xing, Fangqian, et al.
(författare)
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Needle morphological evidence of the homoploid hybrid origin of Pinus densata based on analysis of artificial hybrids and the putative parents, Pinus tabuliformis and Pinus yunnanensis
- 2014
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 4:10, s. 1890-1902
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Tidskriftsartikel (refereegranskat)abstract
- Genetic analyses indicate that Pinus densata is a natural homoploid hybrid originating from Pinus tabuliformis and Pinus yunnanensis. Needle morphological and anatomical features show relative species stability and can be used to identify coniferous species. Comparative analyses of these needle characteristics and phenotypic differences between the artificial hybrids, P.densata, and parental species can be used to determine the genetic and phenotypic evolutionary consequences of natural hybridization. Twelve artificial hybrid families, the two parental species, and P.densata were seeded in a high-altitude habitat in Linzhi, Tibet. The needles of artificial hybrids and the three pine species were collected, and 24 needle morphological and anatomical traits were analyzed. Based on these results, variations in 10 needle traits among artificial hybrid families and 22 traits among species and artificial hybrids were predicted and found to be under moderate genetic control. Nineteen needle traits in artificial hybrids were similar to those in P.densata and between the two parental species, P.tabuliformis and P.yunnanensis. The ratio of plants with three needle clusters in artificial hybrids was 22.92%, which was very similar to P.densata. The eight needle traits (needle length, the mean number of stomata in sections 2mm in length of the convex and flat sides of the needle, mean stomatal density, mesophyll/vascular bundle area ratio, mesophyll/resin canal area ratio, mesophyll/(resin canals and vascular bundles) area ratio, vascular bundle/resin canal area ratio) relative to physiological adaptability were similar to the artificial hybrids and P.densata. The similar needle features between the artificial hybrids and P.densata could be used to verify the homoploid hybrid origin of P.densata and helps to better understand of the hybridization roles in adaptation and speciation in plants.
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| 3. |
- Zhao, Wei, et al.
(författare)
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Weak Crossability Barrier but Strong Juvenile Selection Supports Ecological Speciation of the Hybrid Pine Pinus Densata on the Tibetan Plateau
- 2014
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Ingår i: Evolution. - : John Wiley & Sons. - 0014-3820 .- 1558-5646. ; 68:11, s. 3120-3133
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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