IISER-TVM Centre for Research and Education in Ecology and Evolution (ICREEE), Indian Institute of Science Education and Research Thiruvananthapuram, Thiruvananthapuram, Kerala, India.
Department of Biology, Indian Institute of Science Education and Research, Pune, Maharashtra, India.
PLoS One. 2021 Jun 28;16(6):e0253038. doi: 10.1371/journal.pone.0253038. eCollection 2021.
When the habitat occupied by a specialist species is patchily distributed, limited gene flow between the fragmented populations may allow population differentiation and eventual speciation. 'Sky islands'-montane habitats that form terrestrial islands-have been shown to promote diversification in many taxa through this mechanism. We investigate floral variation in Impatiens lawii, a plant specialized on laterite rich rocky plateaus that form sky islands in the northern Western Ghats mountains of India. We focus on three plateaus separated from each other by ca. 7 to 17 km, and show that floral traits have diverged strongly between these populations. In contrast, floral traits have not diverged in the congeneric I. oppositifolia, which co-occurs with I. lawii in the plateaus, but is a habitat generalist that is also found in the intervening valleys. We conducted common garden experiments to test whether the differences in I. lawii are due to genetic differentiation or phenotypic plasticity. There were strong differences in floral morphology between experimental plants sourced from the three populations, and the relative divergences between population pairs mirrored that seen in the wild, indicating that the populations are genetically differentiated. Common garden experiments confirmed that there was no differentiation in I. oppositifolia. Field floral visitation surveys indicated that the observed differences in floral traits have consequences for I. lawii populations, by reducing the number of visitors and changing the relative abundance of different floral visitor groups. Our results highlight the role of habitat specialization in diversification, and corroborates the importance of sky islands as centres of diversification.
当专门物种的栖息地呈斑块状分布时，碎片化种群之间有限的基因流动可能会导致种群分化，并最终导致物种形成。“天空岛屿”——形成陆地岛屿的山地栖息地——通过这种机制已被证明促进了许多分类群的多样化。我们研究了印度西高止山脉北部的富铁岩石高原特化植物 Impatiens lawii 的花色变化。我们关注了三个彼此相隔约 7 至 17 公里的高原，并表明这些种群之间的花色特征已经强烈分化。相比之下，花色特征在同属植物 I. oppositifolia 中并没有分化，I. oppositifolia 与 I. lawii 共同出现在高原上，但它是一种栖息地广适种，也存在于高原之间的山谷中。我们进行了常规花园实验，以测试 I. lawii 的差异是否归因于遗传分化或表型可塑性。来自三个种群的实验植物在花色形态上存在强烈差异，种群对之间的相对差异与野外观察到的差异相吻合，表明种群存在遗传分化。常规花园实验证实 I. oppositifolia 没有分化。实地花卉访问调查表明，观察到的花色特征差异对 I. lawii 种群有影响，减少了访问者的数量，并改变了不同花卉访问者群体的相对丰度。我们的研究结果强调了栖息地特化在多样化中的作用，并证实了天空岛屿作为多样化中心的重要性。
