Abstract
The Winter Moth. (Operophtera brumata) is a common lepidopteran and a classical model species for population dynamics. It has a peculiar life cycle with both a pupal and an egg diapause. The timing of egg hatching in the Winter Moth in relation to bud-burst of Oak trees has major fitness consequences. There is strong selection on a close synchronization of egg hatching and but-burst. Despite this selection, there is large variation in the degree of synchronization, both between years and between different sites within an area (fig. 1). The within area variation in synchronization is possible due to the small-scale spatial heterogeneity in bud-burst of Oaks. The between year variation cam be attributed to the way trees and winter moth eggs respond to temperature: the date of Winter Moth egg hatching is advanced more strongly with increasing spring temperature than the date of Oak bud-burst. This results in a poor synchronization in warmer springs. We want to exploit the fact that dispersal in this species is limited and unequal between the winged males and wingless females, to study the relation between the presence of genetic variation for timing of egg-hatching and the heterogeneity of tree phenology at different scales. Our second aim is to gain a better understanding of the physiological mechanism of egg hatching (breaking of diapause and development rate) which is needed to understand why is there such a strong effect of temperature. Population number of the Winter Moth varies strongly over years and areas. Poor synchronization is a major cause of this variation. We will develop a population model including the genetic population structure, variation in diapause termination and the effect of spring temperatures on both bud burst and egg hatching. The outcome of the model will be verified by estimating population numbers.
Netherlands