| Diapause is an important aspect of an arthropod?s life-history and serves to survive unfavourable conditions in temperate zones. Diapause-related traits are therefore major determinants of fitness and population dynamics. Scholars often assume that diapause evolved in response to external, temporal variation in resource conditions. However, resource conditions are internally influenced by population size and by the fraction of the population that has already entered diapause. Populations also face temporal variation in predation risk. Both competition for resources and predation can be escaped from by entering diapause. To understand the evolution of diapause, the interplay between natural selection and population dynamics must be studied, because: (1) selection affects the genetic composition (of diapause traits) of the population; (2) the traits selected for affect the population dynamics, which (3) in turn affect the direction of natural selection. However, currently, such an endeavour has not been undertaken. Therefore, I propose to assess variation in diapause traits and their genetics within and between local populations of the spider mite Tetranychus urticae. In the lab, the relation between predation risk, dispersal behaviour, the dynamics and the composition of diapause-related traits of spider mite populations will be studied under controlled climatic conditions and forced population regimes. |
