Award: OCE-1459384

Worldwide, anthropogenic and natural processes are rapidly modifying patterns of environmental variation. Though less-well studied – especially in marine systems - environmental perturbations can also rapidly alter the mating systems of populations. The present project proposed to examine the roles that mating systems play in generating ecologically relevant trait variation and driving reproductive isolation in a marine snail. Mating systems vary widely among populations of snails and can be an important driver of variation in offspring size. How then do these differences influence offspring survival? Field based mark-recapture studies did not find significant differences in size among surviving snails at sites that varied widely in predation pressure, even though snails have a well-known size refugium with respect to crab predators. Several potential compensatory mechanisms emerged, such as aperture width: snails can reduce their aperture opening to decrease mortality when exposed to high densities of predators. However, as with shell size, aperture width was not a strong determinant of survival, though geographic variation in the strength of this relationship was apparent. Aperture width was significantly correlated with an individual’s behavioral response (i.e. personality). Snails with wider apertures displayed shy behavioral types and showed limited behavioral plasticity as compared to snails with narrower apertures, indicating that snails at higher risk of predation behaviorally compensate by displaying consistent predator avoidance behaviors. In addition to decreased plasticity, they also displayed higher predictability in their behavior, with lower residual variance around the reaction norm than snails with narrower apertures. Like size, individual behavioral responses varied geographically. Increasing evidence indicates that the expression of personality is contingent upon social context; group dynamics may thus be key in determining how individuals interact. When single snails were exposed to a predator, neither size nor personality influenced survival. However, in experimental predation trials, groups of shy individuals had the lowest survival, while groups of bold individuals had the highest. While mean mortality in bold snails remained unchanged across treatments, mortality in the mixed groups was strongly dependent on the presence of bold individuals. Indeed, the presence of a few bold individuals emerged as especially effective in decreasing mortality in the shy individuals. The influence of personality on survival is conditional on group personality composition, indicating that social context can greatly impact the success of its individual members. Additionally, parasite infection modified several aspects of behavior, leading to important changes in the interaction with predators. Infection status and size influenced behavioral plasticity: when individuals were uninfected, larger snails became bolder in high-risk environments while smaller snails became shier. This pattern was reversed in infected individuals: smaller snails became significantly bolder in high-risk environments and larger snails became shier. Infected individuals showed higher responsiveness overall, suggesting that infection status can, in certain cases, significantly impact an individual’s response to environmental changes. A growing number of studies on marine organisms is showing that the density, genetic composition, and trait distribution of groups of interacting conspecifics can exert strong effects on many aspects of performance. These effects of social context, often mediated by mating system variation, should be especially important in sessile or sedentary benthic marine communities, where intraspecific competition for food and space is generally intense, and mating often occurs between neighbors. By integrating insights from behavioral ecology and life-history theory, combined with genetic, field, and experimental approaches, this project generated novel insights into the role of mating system variation on the ecological and evolutionary dynamics of marine systems. This proposal has supported doctoral, masters and undergraduate students, and has provided training opportunities and applied learning experiences to military veterans, women, and students from historically underrepresented groups with a specific focus on the collection and analysis of data in molecular and evolutionary ecology. Last Modified: 03/21/2022 Submitted by: Stephanie Kamel