A Polymorphism Maintained by Opposite Patterns of Parasitism and Predation

Sylvain Takenouti(Ecole Polytechnique France)

6月29日 (木) 午後1:30から
理学部3号館 6階  数理生物学セミナー室


Dimorphism of the body color is a pattern of specie of pea aphids, Acyrthosiphon pisum. This polymorphism seems to be ESS (evolutionarily stable strategy). On the one hand, red aphids are the preferred preys of aphids' predator, Coccinella septempunctata, while on the other hand green ones are the aim of parasitoids, wasps Aphidius ervi. We built a model of the coevolution of three species, where preference of color of prey/host is genetically determined for predators and parasitoids, and where distribution of body color is continuous gradation between red and green. Changing the parameters of the model, we observed monomorphism, dimorphism, or trimorphism at equilibrium. We studied the transition of equilibrium between monomorphism and dimorphism. We also modified the model in order to be as close as possible to the example of pea aphids, and observed the same kind of evolution.

(From the picture by John E Losey et al., Nature,388, 269-272 (1997))