Latitudinal differences in the circadian system of Nasonia vitripennis

Abstract

Daily and seasonal environmental changes are initiated by gradual variation of temperature and day length, following different patterns across a latitudinal cline. These recurring events are predictable by an adaptive circadian clock. The circadian clock times molecular, physiological and behavioural processes in near all organism on a daily and annual bases and can synchronise to the environment, mainly by light. The circadian core clock mechanism is conserved through various organisms like bacteria, insects and mammals. Strategies how the circadian and annual timing system interact to anticipate to different environment and its specific conditions are divers and species specific. With this thesis we have investigated the circadian clock of Nasonia vitripennis, a small cosmopolitan parasitoid wasp. Our interest was the ability of the circadian clock to adapt to different environments and day lengths (as at different latitudes) and the mechanism that drives this adaptation and seasonal timing. For this purpose we performed comparative studies between two European Nasonia lines, one from Finland and one from France. Our results let us assume that probably a natural mutation of a specific clock gene leads to a longer internal period in the northern Nasonia which allows them to enter diapause (= dormancy) earlier in the year so they can survive the harsher winter condition in polar regions. Additionally, in order to enable daily circadian adaptation, it seems that the northern line is more sensitive to light, resulting in a daily reset of the internal clock by light.