Molecular Ecology and Evolution Laboratory, Department of Biological Science, Sangji University, Wonju, South Korea.
Korean Entomological Institute, College of Life Sciences and Biotechnology, Korea University, Seoul, South Korea.
BMC Evol Biol. 2018 Apr 11;18(1):52. doi: 10.1186/s12862-018-1171-8.
Life history characteristics are considered important factors influencing the evolutionary processes of natural populations, including the patterns of population genetic structure of a species. The sister species Cottus hangiongensis and C. koreanus are small bottom-dwelling freshwater sculpin fishes from South Korea that display marked life history divergence but are morphologically nearly indistinguishable. Cottus hangiongensis evolved an 'amphidromous' life history with a post-hatching pelagic larval phase. They spawn many small eggs in the low reaches of rivers, and hatched larvae migrate to the sea before returning to grow to maturity in the river mouth. In contrast, C. koreanus evolved a 'fluvial' landlocked type with benthic larvae. They release a smaller number of larger eggs, and the larvae undergo direct development, remaining benthic in the upstream rivers throughout their entire lives. We tested whether there were differences in patterns and levels of within-population genetic diversities and spatial population structure between the two closely related Korean sculpins using mitochondrial DNA control region sequences and seven nuclear microsatellite loci.
The combined analyses of both marker sets revealed that C. hangiongensis harboured considerably higher levels of within-population genetic diversities (e.g. haplotype/allelic richness, heterozygosities) than C. koreanus. In contrast, the fluvial sculpin exhibited noticeably more spatial population structure than did the amphidromous sculpin, as suggested by pairwise F statistics. The finding that C. hangiongensis individuals comprised a single random mating population across the east-flowing river basins in the Korean Peninsula, whereas C. koreanus individuals comprised genetically discrete individual populations, was further supported by an individual-based Bayesian population assignment and also factorial correspondence analyses.
The higher genetic diversity, but lower population structure, of the amphidromous sculpin relative to the fluvial sculpin may have resulted from its greater larval dispersal and also possibly, higher fecundity accompanied by an amphidromous life history. Hence, we conclude that contrasting early life histories - including the presence or absence of the pelagic larval phase - may have led to divergent patterns of within-population genetic diversities and spatial population structure between the sister Cottus species following speciation from a common ancestor of marine sculpin.
生活史特征被认为是影响自然种群进化过程的重要因素，包括物种的种群遗传结构模式。韩国的姊妹种中华细须鮠和朝鲜细须鮠是小型底栖淡水鮠鱼，它们具有明显的生活史分化，但在形态上几乎无法区分。中华细须鮠进化出一种“洄游”的生活史，具有孵化后的浮游幼体阶段。它们在河流下游产下许多小卵，孵化后的幼鱼迁移到海洋，然后返回河口生长成熟。相比之下，朝鲜细须鮠进化出一种“内陆河流型”的有底栖幼体。它们释放数量较少但较大的卵，幼鱼直接发育，在整个生命周期中都保持底栖状态。我们使用线粒体 DNA 控制区序列和 7 个核微卫星基因座，测试了这两个密切相关的韩国鮠鱼的种群内遗传多样性的模式和水平以及空间种群结构是否存在差异。
两种标记物的联合分析表明，中华细须鮠的种群内遗传多样性水平（如单倍型/等位基因丰富度、杂合度）显著高于朝鲜细须鮠。相比之下，洄游鮠的空间种群结构明显比内陆河流型鮠更明显，这一点可以从成对 F 统计数据中看出。个体基于贝叶斯种群分配和因子对应分析的结果进一步支持了这一发现，即中华细须鮠个体在朝鲜半岛向东流动的河流流域中构成了一个单一的随机交配种群，而朝鲜细须鮠个体则构成了遗传上不同的个体种群。
与内陆河流型鮠相比，洄游鮠的遗传多样性更高，但种群结构更低，这可能是由于其幼体扩散更大，以及可能伴随着洄游生活史的更高繁殖力所致。因此，我们得出结论，对比鲜明的早期生活史——包括是否存在浮游幼体阶段——可能导致了姊妹种细须鮠在从共同的海洋鮠祖先分化后，种群内遗传多样性和空间种群结构模式的分歧。
