Coastal exposure and artificialization: Drivers of shell shape variation in intertidal limpets

The level of exposure and the degree of coastal urbanization are key environmental and human-related factors that significantly affect the spatial distribution of species in different environments. Intertidal species show morphological adaptations to these influences, but little research has been done on how shell shape varies due to the island effect, including factors like island orientation and substrate type. This study aims to analyze the dorsal shell phenotypic variability of the limpets Patella aspera and Patella crenata, in response to island orientation (North vs. East) and different substrate types (Natural: platform and rocks; Artificial: wave breakers), on the island of Gran Canaria, using geometric morphometric analysis. Our findings support the hypothesis that these limpet species exhibit phenotypic plasticity in response to wave exposure influenced by island orientation and coastal artificialization. Oval shapes with wider and flattened shells, displaying greater shell lengths, on waveswept shores may be explained by the need for a larger foot to ensure attachment to substrate, thereby increasing resistance to dislodgement by wave action. In contrast, more rounded shapes with taller and narrower shells in sheltered environments can accommodate a smaller foot as an adaptation against thermal and desiccation stress. The substrate plays a secondary role in influencing the shell morphology, as slight variations were observed between natural and artificial substrates, particularly in body size, regardless of wave exposure. This phenotypic plasticity may lead to spatial segregation, enabling the species to exploit diverse habitats and reduce intraspecific and interspecific competition. The present study emphasizes the need to conserve intertidal species, particularly along the northern coast of Gran Canaria, by accounting for local responses, implementing targeted monitoring and protection efforts, and preserving the diverse phenotypic traits and plasticity of limpets on both protected and full-access shores amidst coastal sprawl and anthropogenic global change.