Phenotypic plasticity in two marine snails: constraints superseding life history

Abstract

In organisms encountering predictable environments, fixed development is expected, whereas in organisms that cannot predict their future environment, phenotypic plasticity would be optimal to increase local adaptation. To test this prediction we experimentally compared phenotypic plasticity in two rocky‐shore snail species; Littorina saxatilis releasing miniature snails on the shore, and Littorina littorea releasing drifting larvae settling on various shores, expecting L. littorea to show more phenotypic plasticity than L. saxatilis. We compared magnitude and direction of vectors of phenotypic difference in juvenile shell traits after 3 months exposure to different stimuli simulating sheltered and crab‐rich shores, or wave‐exposed and crab‐free shores. Both species showed similar direction and magnitude of vectors of phenotypic difference with minor differences only between ecotypes of the nondispersing species, indicating that plasticity is an evolving trait in L. saxatilis. The lack of a strong plastic response in L. littorea might be explained by limits rather than costs to plasticity.

Long-term exposure to elevated pCO2 more than warming modifies early-life shell growth in a temperate gastropod

“…Younger shells of both control pCO 2 treatments were most antithetic to one another while in the older groups it were shells from ambient pCO 2 combined with elevated temperature, as well as shells from elevated temperature combined with ambient temperature treatments. Gastropod morphology varies with environmental pressures such as predation, wave action and desiccation, substrate, CaCO 3 and O 2 concentration and temperature (Langerhans and Dewitt, 2002;Hollander et al, 2006;Queiroga et al, 2011). Although water chemistry, pH, and temperature have also been known to affect molluscs' shell shapes (Melatunan et al, 2013), the main factors influencing gastropods seem to be more of a more mechanical nature, namely predation and wave pressure (Queiroga et al, 2011;Langerhans and Dewitt, 2002).…”

What can aquatic gastropods tell us about phenotypic plasticity? A review and meta-analysis

“…Plastic shell responses are not limited to shell thickening via increased calcium carbonate deposition, and both marine and freshwater gastropods are capable of plastically altering different aspects of their shell shape (for example, aspect ratio; DeWitt, 1998;Hollander et al, 2006;Bourdeau, 2009). Altering shell shape may not require additional investment in shell deposition, just re-allocation of shell material to different shell locations, which could allow for the development of adaptive shell forms without the necessity for increased shell deposition in calcium-limited habitats.…”

“…Further, marine species with benthic development may disperse widely via rafting on seaweeds (Highsmith, 1985;Martel and Chia, 1991;Donald et al, 2011). It is becoming increasingly clear that direct developing species with low dispersal capacity can display strong plastic responses, whereas planktonic developers with high dispersal capacity may exhibit little or no plasticity (Behrens Yamada, 1989;Parsons, 1997;Hollander et al, 2006). Our meta-analyses support these findings and suggest that larval dispersal may not have a large role in creating the environmental heterogeneity marine gastropods experience once they settle, nor in selecting for plasticity.…”

“…These plastic responses appear ubiquitous; they have been found in multiple species (for example, Appleton and Palmer, 1988;Palmer, 1990;Trussell, 1996;DeWitt, 1998;Hoverman et al, 2005;Hollander et al, 2006;Bourdeau, 2009;Brönmark et al, 2011), in species with different dispersal capabilities (for example, Behrens Yamada, 1989;Hollander et al, 2006), from different geographic locations (for example, Trussell, 2000a, b;Trussell and Smith, 2000) and in response to several predator species (for example, Hoverman and Relyea, 2007;Bourdeau, 2009). However, populations and species often differ in their degree of shell plasticity (for example, Appleton and Palmer, 1988;Palmer, 1990;Trussell, 1996;Edgell and Neufeld, 2008;Bourdeau, 2012).…”

“…However, populations and species often differ in their degree of shell plasticity (for example, Appleton and Palmer, 1988;Palmer, 1990;Trussell, 1996;Edgell and Neufeld, 2008;Bourdeau, 2012). Environmental factors other than predator cues can also modify or limit the plasticity of gastropod shell form (for example, water motion (Hollander et al, 2006;Minton et al, 2007Minton et al, , 2011Dillon et al, 2013), temperature (Melatunan et al, 2013) and calcium availability ). In the case of water temperature, thinner shells are predicted to develop in relatively cold water because the amount of calcium carbonate needed to saturate cold water is larger than that in warm water and dissolution rates increase with decreasing water temperature.…”