Brewer Michael S, Carter Rebecca A, Croucher Peter J P, Gillespie Rosemary G
Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, 94720; Department of Biology, East Carolina University, Greenville, North Carolina, 27858.
Evolution. 2015 Jan;69(1):162-78. doi: 10.1111/evo.12563. Epub 2014 Dec 23.
Particularly intriguing examples of adaptive radiation are those in which lineages show parallel or convergent evolution, suggesting utilization of similar genetic or developmental pathways. The current study focuses on an adaptive radiation of Hawaiian "spiny-leg" spiders in which diversification is associated with repeated convergent evolution leading to similar sets of ecomorphs on each island. However, two species on the oldest islands in the archipelago exhibit variability, occurring as two different ecomorphs. More derived species on the younger islands show much less variability, any one species displaying a single ecomorph. We measured ecomorphological features within individuals over time to determine the nature of the variability. Then, using transcriptomes, we conducted lineage-based tests for selection under varying models and analyses of gene tree versus species tree incongruencies. Our results provide strong evidence that variability in color in Tetragnatha kauaiensis and T. polychromata is associated with development within individuals (polyphenism). Moreover, a total of 28 loci showed a signature of selection associated with loss of the color-changing phenotype, and 37 loci showed a signature of selection associated with the colonization of a new environment. The results illustrate how developmental polyphenism might provide an avenue for the repeated evolution of ecomorphs during adaptive radiation.
适应性辐射中特别有趣的例子是那些谱系显示出平行或趋同进化的情况，这表明利用了相似的遗传或发育途径。当前的研究聚焦于夏威夷“刺腿”蜘蛛的适应性辐射，其中物种分化与反复的趋同进化相关，导致每个岛屿上出现相似的生态形态组。然而，该群岛最古老岛屿上的两个物种表现出变异性，呈现为两种不同的生态形态。较年轻岛屿上进化程度更高的物种变异性要小得多，任何一个物种都只呈现一种生态形态。我们长期测量个体的生态形态特征以确定变异性的本质。然后，利用转录组，我们在不同模型下进行基于谱系的选择测试，并分析基因树与物种树的不一致性。我们的结果提供了有力证据，表明考艾岛长脚蛛和多色长脚蛛的颜色变异性与个体发育有关（多型现象）。此外，共有28个基因座显示出与颜色变化表型丧失相关的选择特征，37个基因座显示出与新环境定殖相关的选择特征。这些结果说明了发育多型现象可能如何为适应性辐射期间生态形态的反复进化提供一条途径。
