Predator-prey interactions often vary on the basis of the traits of the individual predators and prey involved. Here we examine whether the multidimensional behavioral diversity of predator groups shapes prey mortality rates and selection on prey behavior. We ran individual sea stars (Pisaster ochraceus) through three behavioral assays to characterize individuals’ behavioral phenotype along three axes. We then created groups that varied in the volume of behavioral space that they occupied. We further manipulated the ability of predators to interact with one another physically via the addition of barriers. Prey snails (Chlorostome funebralis) were also run through an assay to evaluate their predator avoidance behavior before their use in mesocosm experiments. We then subjected pools of prey to predator groups and recorded the number of prey consumed and their behavioral phenotypes. We found that predator-predator interactions changed survival selection on prey traits: when predators were prevented from interacting, more fearful snails had higher survival rates, whereas prey fearfulness had no effect on survival when predators were free to interact. We also found that groups of predators that occupied a larger volume in behavioral trait space consumed 35% more prey snails than homogeneous predator groups. Finally, we found that behavioral hypervolumes were better predictors of prey survival rates than single behavioral traits or other multivariate statistics (i.e., principal component analysis). Taken together, predator-predator interactions and multidimensional behavioral diversity determine prey survival rates and selection on prey traits in this system.

The initial stages of a disease outbreak can determine the magnitude of the ensuing epidemic. Though rarely tested in unison, two factors with important consequences for the transmission dynamics of infectious agents are the collective traits of the susceptible population and the individual traits of the index case (i.e. 'patient zero'). Here, we test whether the personality composition of a social group can explain horizontal transmission dynamics of cuticular bacteria using the social spider Stegodyphus dumicola. We exposed focal spiders of known behavioural phenotypes with a GFP-transformed cuticular bacterium (Pantoea sp.) and placed them in groups of 10 susceptible individuals (i.e. those with no experience with this bacterium). We measured bacterial transmission to groups composed of either all shy spiders, 10% bold spiders or 40% bold spiders. We found that colonies with 40% bold spiders experienced over twice the incidence of transmission compared to colonies with just 10% bold individuals after only 24 h of interaction. Colonies of all shy spiders experienced an intermediate degree of transmission. Interestingly, we did not detect an effect of the traits of the index case on transmission. These data suggest that the phenotypic composition of the susceptible population can have a greater influence on the degree of early transmission events than the traits of the index case.

Animals send and receive signals, which are honed by evolution for detection by their intended receiver, for a variety of purposes. For signals used in mate choice, selection should favor those that are easy to detect by the receiving sex’s sensory system(s). Here we test for genetic differences affecting color vision among populations and color morphs of the polytypic poison frog, Oophaga pumilio, a species where both males and females show color-assortative behavioral biases. Opsin genes, expressed in rod and cone cells in the retina, play an important role in the tuning of color vision. We therefore hypothesized that the frog’s behavioral biases may be underlain by differences in the expression or sequences of these genes. To test this, we compared closely related populations of O. pumilio containing red and green morphs to test for convergence in opsin expression and sequence by color. We also compared opsins in sympatric morphs from two polymorphic regions with those of neighboring monomorphic populations to test for differences that would confer improved color discrimination in the polymorphic area. We found no significant differences in opsin expression among red and green populations nor among frogs from one polymorphic (red/blue) zone. However, consistent with our predictions for greater color discrimination, we found greater RH1 expression in frogs from a second polymorphic (red/yellow) region. We found several opsin sequence variants that showed no clear association with color morph, though some mutations were only found in polymorphic populations and some mutations should have significant impacts on color vision in affected individuals. Overall, we found limited evidence that differences in color vision have evolved among distinctly colored O. pumilio populations, though the variation we observed within populations does suggest that the raw material needed for selection to act on color vision is present.