Evidence for genotypic differentiation between marine snails (Littorina sitkana) from the upper- and lower-intertidal zone in Bamfield Inlet (British Columbia, Canada)

• Published in: Journal of experimental marine biology and ecology 2014-12, Vol.461, p.389-396
• Main Authors: Botta, Amy M., Rochette, Rémy, Saunders, Gary W., Addison, Jason A., Barbeau, Myriam A.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Common garden experiment; Ecotypes; Fundamental and applied biological sciences. Psychology; Invertebrates; Littorina saxatilis; Littorina sitkana; Littorinid snail; Marine; Mollusca; Phenotypic variation; Sea water ecosystems; Shell characteristics; Synecology
• ISSN: 0022-0981; 1879-1697
• DOI: 10.1016/j.jembe.2014.08.019

Along wave-protected shores of the northeastern Pacific, the demography and life history of Littorina sitkana vary with intertidal zone, producing spatially close, but separate, “populations” (high- and low-shore). Field sampling (at multiple sites in the wave-sheltered Bamfield Inlet, B.C., Canada), a common garden experiment, and genetic analysis were used to determine if these two “populations” should be considered a panmictic population or different locally adapted populations (ecotypes). In the field, shell mass and incidence of white shells were greater for low-shore than high-shore snails, complementing other previously documented phenotypic differences (growth rate, size at sexual maturity). The common garden experiment revealed patterns of genetically-based phenotypic variation between the populations. Genetic analysis using a mitochondrial marker (COI) and a nuclear maker (APN54) did not resolve any spatial population genetic structure, but did confirm the absence of cryptic species. In the context of work on another littorinid (Littorina saxatilis), our study points to L. sitkana being an interesting species for further investigation of genetic differentiation between different populations depending on their position in the intertidal shore ecotone. •Low-shore and high-shore intertidal snails have phenotypic differences in the field.•A common garden experiment indicates a genetic basis for the phenotypic variation.•Further, this experiment detected countergradient variation in growth rate.•Genetic analysis (mtDNA and nDNA markers) confirmed the absence of cryptic species.•In sum, low-shore and high-shore snails appear to be genetically-distinct ecotypes.