Clonal variation in aggregation and defensive behavior in pea aphids

Abstract

The presence of several clonal lineages within a single aphid colony raises the possibility for conflict between clones over safer positions within multiclonal colonies. To study the effect of relatedness on group dynamics, we manipulated the clonal composition of pea aphid groups (2 pure clonal groups and 1 mixed group) under laboratory conditions and allowed the individuals to cluster together freely on a leaf. We found variation between the clones in both the speed at which individuals joined the group and the aggregation level, where mixed colonies showed intermediates. Experimental and simulation results showed a nonrandom distribution of aphids in mixed colonies between the center and the periphery area, suggesting that one of the clones exhibits selfish herd behavior. In a second set of experiments, aphid groups were exposed to a single parasitoid female. Interestingly, we found that aphids from pure colonies were more likely to react by falling from the plant than individuals in mixed colonies. Our results revealed unexpected kin recognition abilities by nonsocial aphids, which make aphid colony dynamics more complex than previously thought. © 2014 The Author.