Interspecific recognition based on cuticular hydrocarbons mediates reproduction control in aphids.

The preset study tested whether an aphid species can control its reproduction by recognizing the presence and density of a rival species. Acyrthosiphon pisum and Megoura crassicauda often coexist on the same leguminous plant. We established clonal colonies from each species and mixed colonies with one A. pisum and one M. crassicauda adult. There were no significant differences in the population growth patterns of the two species at 20 °C. However, mixed colonies increased faster and attained larger colony sizes than the clonal colonies. Thus, positive interspecific interactions were confirmed. A mixed colony was dominated by the members of a clone that produced a greater number of newborns in the initial stage, irrespective of the species. Thus, we confirmed the priority effect in the interspecific competition. To simulate the priority effect, 15 glass beads coated with the hexane extract of M. crassicauda aphids were attached to a cut leaf, to which one A. pisum adult was transferred. The presence of the hexane extract of M. crassicauda greatly reduced the reproductive rate of A. pisum adults. We conclude that aphids can control their reproduction by evaluating the relative density of rivals to fellow aphids based on the cuticular hydrocarbons.