Stick insect genomes reveal natural selection's role in parallel speciation

Natural selection can drive the repeated evolution of reproductive isolation, but the genomic basis of parallel speciation remains poorly understood. We analyzed whole-genome divergence between replicate pairs of stick insect populations that are adapted to different host plants and undergoing parallel speciation. We found thousands of modest-sized genomic regions of accentuated divergence between populations, most of which are unique to individual population pairs. We also detected parallel genomic divergence across population pairs involving an excess of coding genes with specific molecular functions. Regions of parallel genomic divergence in nature exhibited exceptional allele frequency changes between hosts in a field transplant experiment. The results advance understanding of biological diversification by providing convergent observational and experimental evidence for selection’s role in driving repeatable genomic divergence.

自然选择可驱动生殖隔离的重复演化，然而平行物种形成（parallel speciation）的基因组机制至今尚未得到充分阐释。本研究对适应不同寄主植物、正经历平行物种形成的多组重复竹节虫种群对之间的全基因组分化（whole-genome divergence）进行了分析。研究发现了数千个种群间分化程度显著增强的中等规模基因组区域，其中绝大多数仅为单个种群对所特有。此外，本研究还在跨种群对的平行基因组分化中检测到，相关区域显著富集了具备特定分子功能的编码基因。在野外移植实验（field transplant experiment）中，自然状态下的平行基因组分化区域在不同寄主种群间呈现出异常显著的等位基因频率变化。本研究通过提供趋同的观测与实验证据，证实了选择在推动可重复基因组分化过程中的核心作用，从而深化了学界对生物多样化进程的认知。