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.

阐明非生物因子如何影响遗传变异的空间分布，有助于解析微观进化过程。潮间带滨海景观以生境高度异质性为典型特征，该特征极可能在极小空间尺度上影响遗传变异的分区模式。本研究以红藻皱波角叉菜（Chondrus crispus）为研究对象，探讨了潮位对其单倍体（haploid）配子体（gametophytes）阶段与二倍体（diploid）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，在高潮位与低潮位两个潮区中，分别采用5米×5米样方内每25厘米间隔采样，以及沿90米样带采样的方案，共采集叶状体（fronds）样本799份（其中单倍体样本586份，二倍体样本213份）。本研究利用8个微卫星位点（microsatellite loci）对所有样本进行多位点基因分型，以此验证三项假说：（1）高潮位与低潮位的藻体分属遗传分化的种群；（2）受潮汐介导的隔离效应影响，高潮位生境内的基因流受限；（3）显著的近交系数（FIS）值由物种的生活史特征所驱动。高低潮位之间的成对FST（遗传分化系数）估计值支持了"高低潮位藻体存在遗传分化"的假说。高潮位生境表现为岸内遗传分化显著、遗传多样性降低以及配子体间自交水平升高的特征，表明该生境属于边缘环境。本研究结果表明，在潮间带滨海景观的精细尺度下，与物种分布范围尺度上相同的演化机制仍在发挥作用，核心与边缘种群的动态模式亦遵循此规律。