Data from: Genetic differentiation and phylogeographical structure of the Brachionus calyciflorus complex in eastern China

Spatio-temporal patterns and processes of genetic differentiation in passively dispersing zooplankton are drawing much attention from both ecologists and evolutionary biologists. Two opposite phylogeographical scenarios have already been demonstrated in rotifers, which consist of high levels of genetic differentiation among populations even on small geographical scales on the one hand, and the traditionally known cosmopolitanism that is associated with high levels of gene flow and long-distance dispersal via diapausing stages on the other hand. Here we analyzed the population genetic structure and the phylogeography of the Brachionus calyciflorus species complex in eastern China. By screening a total of 318 individuals from ten locations along a 2320 km gradient and analyzing samples from two growing seasons, we aimed at focusing on both small- and large-scale patterns. We identified eight cryptic species, and verified species status of two of these by sexual reproduction tests. Samples in summer and winter yielded different cryptic species. The distribution patterns of these genetically distinct cryptic species were diverse across eastern China, from full cosmopolitanism to local endemism. The two most abundant cryptic species BcWIII and BcSW both showed a pattern of strong genetic differentiation among populations and no significant isolation-by-distance. Long-distance colonization, secondary contact and recent range expansion are probably responsible for the indistinct pattern of isolation-by-distance. Our results suggest that geographical distance is more important than temporal segregation across seasons in explaining population differentiation and the occurrence of cryptic species. We explain the current phylogeographical structure in the B. calyciflorus species complex by a combination of recent population expansion, restricted gene flow, priority effects and long-distance colonization.被动扩散型浮游动物（passively dispersing zooplankton）的遗传分化时空格局与过程，一直是生态学家与进化生物学家广泛关注的核心议题。目前学界已在轮虫（rotifers）中证实两类截然相反的系统地理学（phylogeography）情景：其一，即便在极小地理尺度下，种群间仍存在极高水平的遗传分化；其二，传统认知中的广布性特性——该特性与高水平基因流（gene flow）及通过滞育阶段（diapausing stages）实现的长距离扩散密切相关。本研究针对中国东部的萼花臂尾轮虫（Brachionus calyciflorus）物种复合体开展种群遗传结构与系统地理学分析：我们共筛查了沿2320公里梯度分布的10个采样点的318个个体，并结合两个生长季的样本展开分析，以期同时解析小尺度与大尺度的种群格局。研究共鉴定出8个隐存种（cryptic species），其中2个通过有性生殖（sexual reproduction）实验验证了其物种地位。夏季与冬季的样本分别对应不同的隐存种。这些遗传分化显著的隐存种在中国东部的分布格局呈现显著多样性，覆盖从完全广布到局地特有的全部类型。两个丰度最高的隐存种BcWIII与BcSW均表现出种群间强烈遗传分化，但未检测到显著的距离隔离（isolation-by-distance）模式。长距离定殖、二次接触与近期的分布范围扩张，可能是导致距离隔离模式不显著的关键驱动因素。本研究结果表明，相较于季节间的时间隔离，地理距离对种群分化与隐存种的出现具有更强的解释力。本研究通过整合近期种群扩张、受限基因流（restricted gene flow）、优先效应（priority effects）与长距离定殖等机制，阐释了萼花臂尾轮虫物种复合体当前的系统地理学结构。