School of Life Sciences, The University of Nottingham, University Park, Nottingham, UK.
Department of Life Sciences, School of Health and Life Sciences, Whitelands College, University of Roehampton, London, UK.
Mol Biol Evol. 2023 Sep 1;40(9). doi: 10.1093/molbev/msad191.
Rapid evolution of similar phenotypes in similar environments, giving rise to in situ parallel adaptation, is an important hallmark of ecological speciation. However, what appears to be in situ adaptation can also arise by dispersal of divergent lineages from elsewhere. We test whether two contrasting phenotypes repeatedly evolved in parallel, or have a single origin, in an archetypal example of ecological adaptive radiation: benthic-limnetic three-spined stickleback (Gasterosteus aculeatus) across species pair and solitary lakes in British Columbia. We identify two genomic clusters across freshwater populations, which differ in benthic-limnetic divergent phenotypic traits and separate benthic from limnetic individuals in species pair lakes. Phylogenetic reconstruction and niche evolution modeling both suggest a single evolutionary origin for each of these clusters. We detected strong phylogenetic signal in benthic-limnetic divergent traits, suggesting that they are ancestrally retained. Accounting for ancestral state retention, we identify local adaptation of body armor due to the presence of an intraguild predator, the sculpin (Cottus asper), and environmental effects of lake depth and pH on body size. Taken together, our results imply a predominant role for retention of ancestral characteristics in driving trait distribution, with further selection imposed on some traits by environmental factors.
相似环境中相似表型的快速进化导致原地平行适应，这是生态物种形成的一个重要标志。然而，似乎原地适应也可能是由于分歧谱系的扩散从其他地方而来。我们检验了两种截然不同的表型是否在一个典型的生态适应性辐射例子中平行进化，或者有一个单一的起源：不列颠哥伦比亚省的底栖-浮游三刺鱼（Gasterosteus aculeatus）跨越物种对和独居湖泊。我们在淡水种群中鉴定出两个基因组簇，它们在底栖-浮游的不同表型特征上存在差异，并将物种对湖泊中的底栖和浮游个体分开。系统发育重建和生态位进化模型都表明，这些簇中的每一个都有一个单一的进化起源。我们在底栖-浮游的分歧特征中检测到强烈的系统发育信号，表明它们是祖先保留的。考虑到祖先状态的保留，我们发现由于内群捕食者棘鱼（Cottus asper）的存在以及湖泊深度和 pH 值对体型的环境影响，身体盔甲存在局部适应。总的来说，我们的结果意味着保留祖先特征在驱动特征分布方面起着主要作用，而一些特征则受到环境因素的进一步选择。
