Mallet Bertrand, Martos Florent, Blambert Laury, Pailler Thierry, Humeau Laurence
UMR Peuplements Végétaux et Bio-Agresseurs en Milieu Tropical, Université de La Réunion, Saint-Denis, Ile de La Réunion, France.
School of Life Sciences, University of KwaZulu-Natal, Pietermaritzburg, South Africa.
PLoS One. 2014 Feb 3;9(2):e87469. doi: 10.1371/journal.pone.0087469. eCollection 2014.
Identifying factors that promote population differentiation is of interest for understanding the early stages of speciation. Gene flow among populations inhabiting different environments can be reduced by geographical distance (isolation-by-distance) or by divergent selection resulting from local adaptation (isolation-by-ecology). Few studies have investigated the influence of these factors in small oceanic islands where the influence of geographic distance is expected to be null but where habitat diversity could have a strong effect on population differentiation. In this study, we tested for the spatial divergence of phenotypes (floral morphology and floral scent) and genotypes (microsatellites) among ten populations of Jumellea rossii, an epiphytic orchid endemic to Réunion growing in three different habitats. We found a significant genetic differentiation between populations that is structured by habitat heterogeneity rather than by geographic distance between populations. These results suggest that ecological factors might reduce gene flow among populations located in different habitats. This pattern of isolation-by-habitat may be the result of both isolation-by-ecology by habitat filtering and asynchrony in flowering phenology. Furthermore, data on floral morphology match these findings, with multivariate analysis grouping populations by habitat type but could be only due to phenotypic plasticity. Indeed floral scent compounds were not significantly different between populations indicating that specific plant-pollinator mutualism does not seem to play a major role in the population differentiation of J. rossii. In conclusion, the results from our study emphasize the importance of habitat diversity of small oceanic islands as a factor of population differentiation.
识别促进种群分化的因素对于理解物种形成的早期阶段具有重要意义。居住在不同环境中的种群之间的基因流动可通过地理距离（距离隔离）或局部适应导致的趋异选择（生态隔离）而减少。很少有研究调查这些因素在小海洋岛屿中的影响，在这些岛屿中，地理距离的影响预计为零，但栖息地多样性可能对种群分化有强烈影响。在本研究中，我们测试了罗斯氏朱梅莉亚（Jumellea rossii）十个种群之间表型（花形态和花香）和基因型（微卫星）的空间差异，罗斯氏朱梅莉亚是留尼汪岛特有的一种附生兰花，生长在三种不同的栖息地。我们发现种群之间存在显著的遗传分化，这种分化是由栖息地异质性而非种群之间的地理距离构成的。这些结果表明，生态因素可能会减少位于不同栖息地的种群之间的基因流动。这种栖息地隔离模式可能是栖息地过滤导致的生态隔离和开花物候异步的结果。此外，花形态数据与这些发现相符，多变量分析按栖息地类型对种群进行分组，但这可能仅归因于表型可塑性。事实上，种群之间的花香化合物没有显著差异，这表明特定的植物 - 传粉者互利共生似乎在罗斯氏朱梅莉亚的种群分化中不发挥主要作用。总之，我们的研究结果强调了小海洋岛屿栖息地多样性作为种群分化因素的重要性。
