Putting prey back together again: integrating predator-induced behavior, morphology, and life history

Abstract

The last decade has seen an explosion in the number of studies exploring predator-induced plasticity. Recently, there has been a call for more comprehensive approaches that can identify functional relationships between traits, constraints on phenotypic responses, and the cost and benefits of alternative phenotypes. In this study, we exposed Helisoma trivolvis, a freshwater snail, to a factorial combination of three resource levels and five predator environments (no predator, one or two water bugs, and one or two crayfish) and examined ten traits including behavior, morphology, and life history. Each predator induced a unique suite of behavioral and morphological responses. Snails increased near-surface habitat use with crayfish but not with water bugs. Further, crayfish induced narrow and high shells whereas water bugs induced wide shells and wide apertures. In terms of life history, both predators induced delayed reproduction and greater mass at reproduction. However, crayfish induced a greater delay in reproduction that resulted in reduced fecundity whereas water bugs did not induce differences in fecundity. Resource levels impacted the morphology of H. trivolvis; snails reared with greater resource levels produced higher shells, narrower shells, and wider apertures. Resource levels also impacted snail life history; lower resources caused longer times to reproduction and reduced fecundity. Based on an analysis of phenotypic correlations, the morphological responses to each predator most likely represent phenotypic trade-offs. Snails could either produce invasion-resistant shells for defense against water bugs or crush-resistant shells for defense against crayfish, but not both. Our use of a comprehensive approach to examine the responses of H. trivolvis has provided important information regarding the complexity of phenotypic responses to different environments, the patterns of phenotypic integration across environments, and the potential costs and benefits associated with plastic traits.

Investment in defense and cost of predator-induced defense along a resource gradient

“…Opposite patterns in growth rates, size at metamorphosis, and survival in response to (non-lethal) predators were found (Werner and Anholt 1996;DeWitt et al 1999;Van Buskirk 2002;Benard 2004;Hoverman et al 2005). Some of this variation might be due to different adaptation to various predator types and different defense strategies of prey species (Laurila et al 1998;Hoverman et al 2005). Some variation might also be explained by differences in resource availability.…”

The long-term effects of invasive signal crayfish (Pacifastacus leniusculus) on instream macroinvertebrate communities

“…Some life history characteristics may reduce predation effects and, as a consequence of their high predation risk, many gastropod species display avoidance behaviour by migrating above the waterline for several hours (Alexander and Covich, 1991;Crowl and Covich, 1990;Turner et al, 1999), whilst others demonstrate changes to their life history through enhanced growth rates and lowered reproduction rates (Hoverman et al, 2005). Under experimental conditions P.…”

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

“…Aquatic gastropods have provided some of the best examples of explicit consideration of functional correlations among plastic traits and so-called 'trait integration' (for example, DeWitt, 1998;DeWitt et al, 1999;Rundle and Brönmark, 2001;Cotton et al, 2004;Hoverman et al, 2005;Brookes and Rochette, 2007;Bourdeau, 2010). Despite this, our review revealed that other types of plastic traits (for example, behavioural, physiological and so on) were rarely included in studies of gastropod shell plasticity, and when they were functional, mechanistic or genetic correlations between them were often not analysed (but see DeWitt, 1998;DeWitt et al, 1999;Langerhans and DeWitt, 2002;Hoverman et al, 2005;Brookes and Rochette, 2007;Bourdeau, 2010;Brönmark et al, 2011). We suggest that future studies of aquatic gastropod shell plasticity should incorporate measurements of multiple morphological, physiological and behavioural traits to clarify the link between plastic responses and phenotypic expression and their associated costs.…”

“…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).…”