Data from: Intergametophytic selfing and microgeographic genetic structure shape populations of the intertidal red seaweed Chondrus crispus

Understanding how abiotic factors influence the spatial distribution of genetic variation provides insight into microevolutionary processes. The intertidal seascape is characterized by highly heterogeneous habitats which probably influence the partitioning of genetic variation at very small scales. The effects of tidal height on genetic variation in both the haploid (gametophytes) and diploid (tetrasporophytes) stages of the red alga Chondrus crispus were studied. Fronds were sampled every 25 cm within a 5 m × 5 m grid and along a 90-m transect at two shore heights (high and low) in one intertidal site in France. The multilocus genotype of 799 fronds was determined (Nhaploid = 586; Ndiploid = 213) using eight microsatellite loci to test the following hypotheses: (i) high and low shore fronds belong to genetically differentiated populations, (ii) gene flow is restricted within the high shore habitat due to tidal-influenced isolation and (iii) significant FIS values are driven by life history characteristics. Pairwise FST estimates between high and low shore levels supported the hypothesis that high and low shore fronds were genetically differentiated. The high shore was characterized by the occurrence of within-shore genetic differentiation, reduced genetic diversity and increased levels of intergametophytic selfing, suggesting it is a marginal environment. These results suggest at fine scales within the intertidal seascape the same mechanisms as those over the species’ distributional range are at work with core and marginal population dynamics.解析非生物因子如何影响遗传变异的空间分布，可为微进化过程的研究提供关键洞察。潮间带海域生境具有高度异质性，这可能在极小空间尺度上影响遗传变异的分化格局。本研究以红藻角叉菜（Chondrus crispus）为对象，探究潮位对其单倍体（配子体，gametophytes）与二倍体（四分孢子体，tetrasporophytes）阶段遗传变异的影响。研究于法国一处潮间带采样点开展，在高低两种潮位区域内，分别采用5米×5米样方网格（采样间隔25厘米）与90米样带的方式采集红藻叶状体。本研究利用8个微卫星位点（microsatellite loci）对799份叶状体样本进行多位点基因分型（其中单倍体样本586份，二倍体样本213份），以验证以下三项假说：（1）高低潮位的叶状体分属遗传分化的种群；（2）受潮汐介导的隔离效应影响，高潮带生境内的基因流受限；（3）显著的FIS（近交系数）值由生活史特征所驱动。高低潮位间的两两FST（遗传分化系数）估计值支持了高低潮位叶状体存在遗传分化的假说。高潮带生境呈现出带内遗传分化、遗传多样性降低以及配子体自交（intergametophytic selfing）水平升高的特征，表明其属于边缘生境。本研究结果表明，在潮间带海域的精细尺度下，与物种分布全域范围内一致的作用机制正在主导核心与边缘种群的动态平衡。