Understanding the genomic basis of adaptation is critical for understanding evolutionary processes and predicting how species will respond to environmental change. Spinner dolphins in the eastern tropical Pacific (ETP) present a unique system for studying adaptation. Within this large geographical region are four spinner dolphin ecotypes with weak neutral genetic divergence and no obvious barriers to gene flow, but strong spatial variation in morphology, behaviour and habitat. These ecotypes have large population sizes, which could reduce the effects of drift and facilitate selection. To identify genomic regions putatively under divergent selective pressures between ecotypes, we used genome scans with 8994 RADseq single nucleotide polymorphisms (SNPs) to identify population differentiation outliers and genotype–environment association outliers. Gene ontology enrichment analyses indicated that outlier SNPs from both types of analyses were associated with multiple genes involved in social behaviour and hippocampus development, including 15 genes associated with the human social disorder autism. Evidence for divergent selection on social behaviour is supported by previous evidence that these spinner dolphin ecotypes differ in mating systems and associated social behaviours. In particular, three of the ETP ecotypes probably have a polygynous mating system characterized by strong premating competition among males, whereas the fourth ecotype probably has a polygynandrous mating system characterized by strong postmating competition such as sperm competition. Our results provide evidence that selection for social behaviour may be an evolutionary force driving diversification of spinner dolphins in the ETP, potentially as a result of divergent sexual selection associated with different mating systems. Future studies should further investigate the potential adaptive role of the candidate genes identified here, and could probably find further signatures of selection using whole genome sequence data.

中文翻译：

---

旋转选择海豚生态型的不同选择的基因组特征与社会行为相关

了解适应的基因组基础对于了解进化过程和预测物种对环境变化的反应至关重要。东部热带太平洋地区（ETP）的旋转海豚提供了一个研究适应性的独特系统。在这个较大的地理区域内，有四种旋转的海豚生态型，它们具有弱的中性遗传差异，对基因流没有明显的障碍，但是在形态，行为和栖息地方面却存在很大的空间变化。这些生态型的人口规模很大，可以减少流离失所的影响并促进选择。为了确定可能在不同生态型之间的不同选择压力下确定的基因组区域，我们使用了具有8994个RADseq单核苷酸多态性（SNP）的基因组扫描来鉴定种群分化离群点和基因型与环境关联离群点。基因本体论富集分析表明，两种分析的异常单核苷酸多态性均与参与社会行为和海马发育的多个基因相关，其中包括与人类社交障碍自闭症相关的15个基因。先前的证据表明，这些旋转的海豚生态型在交配系统和相关的社会行为方面各不相同，这证明了人们对社会行为的选择存在差异。特别是，三种ETP生态型可能具有一性交配的交配系统，其特征是雄性有较强的早熟竞争，而第四种生态型可能具有一性交配的交配系统，其特征在于强的交配后竞争，如精子竞争。我们的结果提供了证据，表明对社会行为的选择可能是驱动ETP中旋转海豚多样化的进化力量，这可能是与不同​​交配系统相关的不同性选择的结果。未来的研究应进一步研究此处鉴定的候选基因的潜在适应性作用，并可能使用全基因组序列数据找到进一步选择的特征。