Department of Biology, University of Naples Federico II, Via Cupa Nuova Cinthia 26, 80126, Naples, Italy.
Department of Chemical Sciences, University of Naples Federico II, Via Cupa Nuova Cinthia 26, 80126, Naples, Italy.
Sci Rep. 2019 Feb 4;9(1):1288. doi: 10.1038/s41598-018-37587-3.
The Wall Gecko shows heterogeneous colour pattern, which may vary among individuals, depending on the time of day and on the habitat segregation. Nocturnal pale geckos live exclusively on walls. Diurnal dark geckos preferentially live on olive tree trunks, demonstrating an ability to change skin colour that is superior to that of the pale gecko and allows diurnal geckos becoming camouflaged on the diverse substrates occupied during the day. In our study, the nocturnal/pale/wall and diurnal/dark/trunk geckos could be considered the extremes of an ecological cline of morphological variation on which divergent selection may be acting. Combining the effect of balancing selection on nocturnal geckos and disruptive selection between two sympatric populations could lead to speciation. All geckos analysed here belong to the same species, as confirmed by genetic characterization, however diurnal and nocturnal gecko populations seem to be in an early stage of incipient speciation. These two different morphs still combine genes, as revealed by neutral genetic markers, yet they show complete separation according to the analyses of mtDNA coding genes. Experimental results show that diurnal and nocturnal geckos do not swap their niches, likely because the predation pressure causes severe selection for background matching. Genomic analysis of complete mtDNA suggests that nocturnal geckos seem to be under balancing selection perhaps due to the narrow niche in which they live, whereas the daytime population has more opportunity in fitting into the multiple available niches, and they experience positive selection. Here we hypothesize that the ecological segregation that we are witnessing between the nocturnal and diurnal geckos, can lead to a ecological speciation.
墙虎表现出不均匀的颜色图案，这种图案可能因个体而异，取决于一天中的时间和栖息地的隔离。夜行的浅色壁虎只生活在墙上。昼行的深色壁虎更喜欢生活在橄榄树干上，它们表现出的变色能力优于浅色壁虎，使昼行壁虎能够在白天栖息的多样化基质上伪装自己。在我们的研究中，夜行/浅色/墙壁虎和昼行/深色/树干壁虎可以被认为是形态变异生态梯度的极端情况，分歧选择可能正在对其起作用。结合对夜行壁虎的平衡选择和两个同域种群之间的破坏选择的影响，可能导致物种形成。所有在这里分析的壁虎都属于同一个物种，这一点得到了遗传特征的证实，然而昼行和夜行壁虎种群似乎处于物种形成的早期阶段。这两种不同的形态仍然结合了基因，这一点从中性遗传标记中可以看出，然而，根据 mtDNA 编码基因的分析，它们显示出完全的分离。实验结果表明，昼行和夜行壁虎不会交换它们的生态位，这可能是因为捕食压力导致了对背景匹配的严重选择。对完整 mtDNA 的基因组分析表明，夜行壁虎似乎受到平衡选择的影响，可能是因为它们生活的生态位狭窄，而日间种群有更多机会适应多个可用的生态位，并经历正选择。在这里，我们假设我们在夜行和昼行壁虎之间观察到的生态隔离可能导致生态物种形成。
