Data from: Cryptic species diversity and reproductive isolation among sympatric lineages of Strongylocentrotus sea urchins in the northwest Atlantic

Distinguishing between intra- and inter-specific variation in genetic studies is critical to understanding evolution because the mechanisms driving change among populations are expected to be different than those that shape reproductive isolation among lineages. Genetic studies of north Atlantic green sea urchins Strongylocentrotus droebachiensis (Müller, 1776) have detected significant population substructure and asymmetric gene flow from Europe to Atlantic Canada and interspecific hybridization between S. droebachiensis and Strongylocentrotus pallidus (Sars, 1871). However, combined with patterns of divergence at mtDNA sequences, morphological divergence at gamete traits suggests that the European and North American lineages of S. droebachiensis may be cryptic species. Here, we use a combination of cytochrome c oxidase subunit I (COI) sequences and single nucleotide polymorphisms (SNPs) to test for cryptic species within Strongylocentrotus sea urchins and hybrids between S. droebachiensis and S. pallidus populations. We detect striking patterns of habitat and reproductive isolation between two S. droebachiensis lineages, with offshore deep-water collections consisting of S. pallidus in addition to a cryptic lineage sharing genetic similarity with previously published sequences from eastern Atlantic S. droebachiensis. We detected only limited hybridization among all three lineages of sea urchins, suggesting that shared genetic differences previously reported may be a result of historical introgression or incomplete lineage sorting.在遗传学研究中区分种内变异（intra-specific variation）与种间变异（inter-specific variation）对于理解进化过程至关重要，因为驱动种群间演化变化的机制，与塑造不同谱系间生殖隔离（reproductive isolation）的机制存在本质差异。针对北大西洋绿海胆（Strongylocentrotus droebachiensis, Müller, 1776）的遗传学研究已检测到显著的种群亚结构，以及从欧洲向加拿大大西洋沿岸区域的不对称基因流（asymmetric gene flow），同时还发现了该物种与苍白球海胆（Strongylocentrotus pallidus, Sars, 1871）之间的种间杂交（interspecific hybridization）现象。然而，结合线粒体DNA（mtDNA）序列的分化模式，配子性状的形态分化提示，绿海胆的欧洲与北美谱系可能属于隐存种（cryptic species）。本研究结合细胞色素c氧化酶亚基I（cytochrome c oxidase subunit I, COI）序列与单核苷酸多态性（single nucleotide polymorphisms, SNPs）两种分子标记，对球海胆属（Strongylocentrotus）海胆内的隐存种，以及绿海胆与苍白球海胆种群间的杂交情况进行了检验。我们在两类绿海胆谱系间检测到了显著的生境与生殖隔离模式：近海深水采样样本中同时存在苍白球海胆，以及一类与已发表的东大西洋绿海胆序列遗传相似度较高的隐存谱系。本研究仅在三类海胆谱系中检测到了有限的杂交事件，这表明此前报道的共享遗传差异，可能源于历史渐渗（introgression）或不完全谱系分选（incomplete lineage sorting）。