Data from: Phylogeography of the prickly sculpin (Cottus asper) in north-western North America reveals parallel phenotypic evolution across multiple coastal–inland colonizations

Aim: Glacial cycles during the Pleistocene may have frequently contributed to parallel evolution of phenotypes across independently evolving genetic lineages associated with separate glacial refugia. Previous studies based on morphology suggested that the prickly sculpin (Cottus asper) survived the Last Glacial Maximum (LGM) in southern coastal and inland refugia, favouring allopatric divergence between coastal and inland prickling phenotypes, which vary in the degree to which spine-like scales cover the body of the fish. Herein, we aimed to test whether parallel evolution across multiple genetic lineages rather than a single-lineage origin of highly prickled inland sculpins could serve as an explanation for the biogeographical distribution of prickling phenotypes. Location: North-western North America, Southeast Alaska and Canada (British Columbia). Methods: We used data from mitochondrial haplotypes and 19 microsatellite loci to identify distinct genetic lineages as a basis to interpret patterns of phenotypic evolution. Results: The occurrence of multiple mtDNA groups suggests that highly prickled inland phenotypes comprise more than one genetic lineage. Both mtDNA and microsatellite data are consistent with post-glacial dispersal along the coast and repeated coastal to inland colonization events, as opposed to inland dispersal of a single lineage from a southern refugium to northern regions. Main conclusions: Our results suggest that highly prickled inland phenotypes evolved repeatedly following multiple inland colonization events, probably via coastal rivers. The prickly sculpin therefore provides an example of recent (post-glacial) parallel evolution, potentially facilitated by standing genetic variation already present in the ancestral coastal populations.

研究目的：更新世（Pleistocene）冰期或曾频繁推动与独立冰期避难所相关的不同演化遗传支系间出现表型平行演化。此前基于形态学的研究表明，多棘杜父鱼（Cottus asper）在末次冰盛期（Last Glacial Maximum, LGM）期间存活于南部沿海与内陆避难所，支持沿海与内陆棘状表型间的异域分化——这类表型的差异体现为鱼体覆盖的棘状鳞片程度各不相同。本研究旨在验证：高度棘化的内陆杜父鱼表型究竟是源自多个遗传支系的平行演化，还是单一遗传支系的起源，以此解释棘状表型的生物地理分布格局。
研究区域：北美西北部、阿拉斯加东南部及加拿大不列颠哥伦比亚省。
研究方法：本研究利用线粒体单倍型与19个微卫星（microsatellite）位点的数据，识别不同的遗传支系，以此解析表型演化模式。
研究结果：多个线粒体DNA（mtDNA）类群的存在表明，高度棘化的内陆表型包含不止一个遗传支系。线粒体DNA与微卫星数据均支持冰期后沿海扩散、多次沿海至内陆定殖的演化模式，而非单一遗传支系从南部避难所向北部区域的内陆扩散。
主要结论：本研究结果显示，高度棘化的内陆表型是在多次内陆定殖事件后重复演化而来的，定殖路径大概率经由沿海河流。因此，多棘杜父鱼可作为近期（冰期后）平行演化的实例，其演化过程或得益于祖先沿海种群中已存在的现有遗传变异（standing genetic variation）。