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.
['Krueger-Hadfield|S A|SA|', 'Roze|D|D|', 'Mauger|S|S|', 'Valero|M|M|']
D044723:Chondrus D017753:Ecosystem D005602:France D051456:Gene Flow D014644:Genetic Variation D005828:Genetics, Population D055993:Germ Cells, Plant D018895:Microsatellite Repeats D008969:Molecular Sequence Data D058885:Multilocus Sequence Typing D011003:Ploidies D011157:Population Dynamics D014872:Water Movements
intergametophytic selfing algae haploid-diploid life cycles intertidal zone mating system population genetics seascape influence