Yim Kristina M, Brewer Michael S, Miller Craig T, Gillespie Rosemary G
From the Department of Molecular and Cell Biology, University of California, 142 Life Sciences Addition #3200, Berkeley, CA 94720-3200 (Yim and Miller); and the Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720-3114 (Brewer and Gillespie).
J Hered. 2014;105 Suppl 1:771-81. doi: 10.1093/jhered/esu043.
Discontinuous variation within individuals is increasingly recognized as playing a role in diversification and ecological speciation. This study is part of an effort to investigate the molecular genetic underpinnings of adaptive radiation in Hawaiian spiders (genus Tetragnatha). This radiation is found throughout the Hawaiian Islands, showing a common pattern of evolutionary progression from older to younger islands. Moreover, the species are characterized by repeated evolution of similar ecomorphs that can be recognized on the basis of color--Green, Maroon, Large Brown, and Small Brown. However, 2 species (including T. kauaiensis from Kauai) are polyphenic, changing from 1 ecomorph (Green) to another (Maroon) at a specific developmental period. The current study focuses on the age-associated color change in the early stages of the radiation to determine whether this ancestral flexibility in phenotype may have translated into diversification of more derived taxa. We conducted a comparative analysis of transcriptome data (expressed genes) from the Maroon morph of T. kauaiensis and T. perreirai (Oahu), which exhibits a single fixed ecomorph (Maroon). Over 70 million sequence reads were generated using Illumina sequencing of messenger RNA. Using reciprocal best hit BLAST searches, 9027 orthologous genes were identified, of which 32 showed signatures of positive selection between the 2 taxa and may be involved in the loss of the ancestral developmental polyphenism and associated switch to separate monophenic ecomorphs. These results provide critical groundwork that will allow us to advance our understanding of the genomic elements associated with adaptive radiations.
个体内部的不连续变异在物种分化和生态物种形成中所起的作用日益受到认可。本研究是调查夏威夷蜘蛛（长纺蛛属）适应性辐射分子遗传基础工作的一部分。这种辐射现象在整个夏威夷群岛都有发现，呈现出从较古老岛屿到较年轻岛屿的常见进化进展模式。此外，这些物种的特征是相似生态型的反复进化，可根据颜色识别为绿色、栗色、大型棕色和小型棕色。然而，有两个物种（包括考艾岛的考艾长纺蛛）具有多型现象，在特定发育阶段从一种生态型（绿色）转变为另一种（栗色）。当前研究聚焦于辐射早期与年龄相关的颜色变化，以确定这种表型上的祖先灵活性是否可能转化为更多衍生分类群的分化。我们对考艾长纺蛛栗色形态和佩雷拉长纺蛛（瓦胡岛）的转录组数据（表达基因）进行了比较分析，后者呈现单一固定的生态型（栗色）。使用信使核糖核酸的Illumina测序产生了超过7000万个序列读数。通过相互最佳匹配BLAST搜索，鉴定出9027个直系同源基因，其中32个在两个分类群之间显示出正选择的特征，可能参与了祖先发育多型现象的丧失以及向单独单型生态型的相关转变。这些结果提供了关键的基础工作，将使我们能够加深对与适应性辐射相关的基因组元件的理解。
