![]() ![]() In fact, waves are not an important selective factor on the shell shape of this species because it has evolved a sufficiently powerful adhesion system to resist strong water flow irrespective of shell shape. One example is the owl limpet ( Lottia gigantea) that lives in a high energy wave environment, but has a long conical shell that is poorly designed to withstand rapid water flow. On rocky shores under heavy wave exposure, one might expect that intertidal gastropods have shell shapes that are adapted to withstand hydrodynamic stress, which constitutes a strong threat to their survival. Alternatively, it may be a by-product of adaptation at some other trait, or a consequence of a developmental constraint or plasticity, and it can prove difficult to disentangle the causative links between environment and phenotype. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist.Ī correlation between an environmental factor and a phenotypic trait is not sufficient to infer that there is local adaptation of the trait in response to that factor. Additional support came from Formas through contract 215-2012-1134 to AIL. ![]() This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.ĭata Availability: All relevant data are within the paper and its Supporting Information files.įunding: This work was performed within the Linnaeus Centre for Marine Evolutionary Biology ( ) supported by a Linnaeus-grant from the Swedish Research Councils VR ( ) and Formas ( ) grant number 217-2008-1719 to KJ. Received: SeptemAccepted: OctoPublished: October 23, 2017Ĭopyright: © 2017 Le Pennec et al. Vermeij, University of California, UNITED STATES (2017) Adaptation to dislodgement risk on wave-swept rocky shores in the snail Littorina saxatilis. This result suggests genetic control of a distinct “wave adapted” phenotype, likely to be maintained under strong divergent selection between the two adjacent habitats.Ĭitation: Le Pennec G, Butlin RK, Jonsson PR, Larsson AI, Lindborg J, Bergström E, et al. In a separate experiment, we found that snails raised in still water in a common garden showed higher resistance to water flow if originating from a wave environment than from a crab environment, and this was true both at juvenile (2 weeks) and adult (10 months) developmental stages. ![]() Snails from the wave environment were consistently more resistant to water flow than snails from the crab environment and high resistance was positively correlated with the surface area of the foot and the area of the outer aperture contour both relative to shell size, and to the extent of lateral shell compression. We sampled snails along a crab-wave transect and measured their resistance to dislodgement in a high-speed water flume with water speeds that match those of breaking waves in a range of relevant field conditions. Here, we report a test of the prediction that the wave ecotype has a higher capacity to resist water flow than the crab ecotype. This phenotypic divergence is assumed to reflect, in some part, local adaptation to wave exposure, but this hypothesis has received incomplete experimental testing. The periwinkle Littorina saxatilis has repeatedly evolved both a small, fragile and globose "wave ecotype" confined to wave-swept shores and a large, robust and elongated "crab ecotype" found in nearby crab-rich but less-exposed shores. ![]()
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