• Energy Research

AbstractIt is unclear how sustained increases in temperature and changes in precipitation, as a result of climate change, will affect crops and their interactions with agricultural weeds, insect pests and predators, due to the difficulties in quantifying changes in such complex relationships. We simulated the combined effects of increasing temperature (by an average of 1.4°C over a growing season) and applying additional rainwater (10% of the monthly mean added weekly, 40% total) using a replicated, randomized block experiment within a wheat crop. We examined how this affected the structure of 24 quantitative replicate plant–aphid–parasitoid networks constructed using DNA‐based methods. Simulated climate warming affected species richness, significantly altered consumer–resource asymmetries and reduced network complexity. Increased temperature induced an aphid outbreak, but the parasitism rates of aphids by parasitoid wasps remained unchanged. It also drove changes in the crop, altering in particular the phenology of the wheat as well as its quality (i.e., fewer, lighter seeds). We discuss the importance of considering the wider impacts of climate change on interacting species across trophic levels in agroecosystems.

Abstract Simulated climate-warming experiments have provided important insights into the response of terrestrial ecosystems, but few have examined the impacts on agricultural insects, particularly those associated with the ecosystem service of biological pest control. Within a spring-sown wheat crop, we artificially increased temperature by 2 °C and precipitation by 10% in a short-term (April to August 2013) replicated open-field experiment and examined the impacts on coleopteran (mainly Carabidae) diversity and ‘activity-densities’. Diversity indices decreased as a result of warming but were not affected by extra precipitation. We found a significant increase in activity-densities of the four most trapped species due to warming, which was responsible for observed changes in diversity. However, Staphylinidae beetles were negatively affected by the warming treatments while other, less common species were not affected. We provide the first experimental evidence of climate-driven impacts on an important farmland insect community. We discuss the implications of our results in the context of biological control and top-down effects across trophic levels.

In order to examine the physiological capabilities of marine invertebrates in their natural environment, a series of physiological measurements were conducted on congeneric amphipod species (Genus Gammarus) distributed along a natural thermal gradient in the NE Atlantic and Arctic Oceans. This synoptic paper summarises our most recent findings by describing physiological differences within and between Gammarus species collected from the intertidal between Portugal at 38°N and Svalbard at 79°N. Two physiological variables were examined to include temperature-adaptive responses at two different levels of biological organisation: (1) whole animal responses by measuring oxygen uptake rates as a measure of metabolic rates or costs of living; and (2) molecular responses by examining sequence variation in two functional regions of the myosin heavy chain gene (loops 1 and 2) which influence muscle contractibility. Our initial observations on Gammarus species showed that physiological variation as a function of latitude was species-specific. For instance, the sub-arctic/boreal species Gammarus oceanicus did not compensate its metabolism at polar latitudes. Instead, metabolic rates declined with latitudinal changes in temperature resulting in relatively low rates of metabolism in the sub-arctic population. In contrast, the boreal and temperate species G. locusta and G. duebeni duebeni conserved metabolic rate across latitudes indicating a capacity for physiological compensation. A similar response was observed at the molecular level as sequence diversity in the loop 2 region of the myosin heavy chain gene remained unchanged with latitude in G. oceanicus but increased with latitude in G. d. duebeni which was attributed to differences in thermal habitat. Further work is required to establish whether these physiological differences involve local adaptation or are dependent on phenotypic plasticity. These findings provide valuable information on the ability of each species to adjust their physiology to maintain function despite increases in temperature due to global warming.