Co-evolution between ectoparasites and their insect hosts: a simulation study of a damselfly-water mite interaction

1. A simulation model investigating the co-evolution of water mites infesti ng their aquatic insect hosts during emergence is presented. The model is b ased on field and experimental studies of the ectoparasitic water mite Arre nurus cuspidator and the damselfly Coenagrion puella. 2. Three scenarios were studied: (1) Only the host was allowed to evolve ti ming of emergence, while the timing of the parasites' infestation opportuni ty was held constant. (2) Both host and parasite were allowed to evolve. (3 ) Only the parasite's timing was allowed to evolve, while the host was cons trained completely. 3. In the first two scenarios. parasite abundances decreased in the course of evolution and reached values well below, those found in the field, where as in the third scenario. parasite abundances were maintained at a level cl ose to that found in the field. In the second scenario (co-evolution), the host seemed to be the leader in the evolutionary race. 4. It is concluded that water mite parasitism is capable of shaping emergen ce patterns in aquatic insects and, despite the same life-cycle length for host and parasite. the parasite evolves fast enough to shape its hatching p attern to match the emergence pattern of its host.