Adapting to climate change- the impact of changing daylight regimes on range shifting insect populations

Abstract

Species are shifting their ranges to higher latitudes and elevations as a response to climate change. This expansion can cause populations to encounter novel species, as well as changing the interaction strength of pre-existing associations. The following four chapters assess the impact of range expansion using evidence synthesis, in addition to lab-based experiments and population dynamic models. A meta-analysis consisting of 44 studies showed an overall negative effect of populations expand their ranges on species and community performance for both expanding and resident species, mediated by changes in inter-species interactions. This effect was driven by negative effects on species abundance, activity and diversity. A tri-trophic, multi-generational climate chamber experiment showed that different daylengths bring about a change in competitive hierarchy between aphids, with Acyrthosiphon pisum dominant at the shorter, more southern daylength of 14.5:9.5 L:D, while the other aphid Megoura viciae was dominant when exposed to the longer, more northern daylength of 22:2 L:D. This change in dominance of M. viciae was not driven directly by daylength but indirectly through daylength’s effect on A. pisum. A second set of experiments showed that longer daylengths in addition to Artificial Light At Night (ALAN) increase the attack rate of the parasitoid Aphidius megourae both over 24 hours as well as throughout its life. We then show using a simple lokta-voltera model, that this increase in attack rate causes a drop in the stability of the system causing localised extinctions and outbreaks. The final experiment empirically tested the predictions of the above lokta-voltera model. We show that longer days represented by increased parasitism rate result in increased variation in parasitoid abundance, causing a higher number and larger extremes of peaks and crashes, as well as reducing the stability of the system and increasing extinction events. These events were brought about by a higher parasitism rate on the aphid. These chapters display the importance of research into the changing dynamics of insects, and especially crop pests in response to a changing world.