Consequences of a poecilogonous life history for genetic structure in coastal populations of the polychaete Streblospio benedicti

In many species, alternative developmental pathways lead to the production of two distinct phenotypes, promoting the evolution of morphological novelty and diversification. Offspring type in marine invertebrates influences transport time by ocean currents, which dictate dispersal potential and gene flow, and thus has sweeping evolutionary effects on the potential for local adaptation and on rates of speciation, extinction, and molecular evolution. Here we use the polychaete Streblospio benedicti to investigate the effects of dimorphic offspring type on gene flow and genetic structure in coastal populations. We use 84 single nucleotide polymorphism (SNP) markers for this species to assay populations on the East and West Coasts of the United States. Using these markers we found that in their native East Coast distribution, populations of S. benedicti have high population genetic structure, but this structure is associated primarily with geographic separation rather than developmental differences. Interestingly, very little genetic differentiation is recovered between individuals of different development types when they occur in the same or nearby populations, further supporting that this is a true case of poecilogony. In addition, we were able to demonstrate that the recently introduced West Coast populations (~100ya) likely originated from a lecithotrophic population near Delaware.

在众多物种中，异型发育途径可催生两种截然不同的表型，进而推动形态创新与物种多样化的演化进程。海洋无脊椎动物的幼体类型会影响洋流介导的幼体运输时长，而该时长直接决定种群的扩散潜力与基因流，因此对局部适应潜力、物种形成速率、灭绝速率与分子进化速率均具有广泛的进化效应。本研究以多毛纲物种本尼节蜢（Streblospio benedicti）为研究对象，探讨其二态性幼体类型对美国东西海岸沿岸种群基因流与遗传结构的影响。本研究采用该物种的84个单核苷酸多态性（Single Nucleotide Polymorphism，SNP）标记，对美国东西海岸的沿岸种群开展基因分型检测。基于上述标记，本研究发现，在其原生分布的东海岸区域，本尼节蜢种群的遗传结构分化程度较高，但该结构主要与地理隔离相关，而非发育差异。值得注意的是，当不同发育类型的个体栖息于同一种群或邻近种群时，二者之间几乎未检测到遗传分化，这进一步证实该物种属于真正的多型幼体发育（poecilogony）案例。此外，本研究还证实，距今约100年前引入的西海岸种群，其起源大概率为特拉华州附近的卵黄营养型种群。