Predation promotes diversification in the mean and variance of antipredator traits

Abstract

Abstract Predator species are separated along habitat gradients, with predation known to play an essential role in species' trait diversification. Because predator species differ dramatically in their hunting style and mode, a change in predator species will alter the mean and variance of prey's antipredator traits. Population trait variation has an impact on community ecology. It influences species' niche width and interactions in the food web. However, empirical studies on variance change by predation are scarce. In this study, we collected large numbers of the last instar Leucorrhinia pectoralis exuviae from lakes with predatory fish (fish lakes) and lakes with large invertebrate predators (dragonfly lakes) and compared their two antipredator traits (spines and body size). We found that individuals in dragonfly lakes grew shorter spines than individuals in fish lakes. Body size showed no significant difference between dragonfly‐lake individuals and fish‐lake individuals. Moreover, populations from dragonfly lakes showed a smaller variance of spine length than populations from fish lakes; while populations from dragonfly lakes had a larger variance in body size than populations from fish lakes. These results indicate that trait variance, as well as mean, is strongly modified by different predation regimes. Studying the mean and variance of traits can help to define the mode of selection forces (directional selection and stabilising selection) in nature. Moreover, dragonfly larvae might be ideal organisms for the study of phenotypic selection on quantitative traits in the wild.