Multigenerational Trophic Responses to Coupled Short- and Long-term Environmental Change

The negative effects of climate change on biodiversity are already being felt on a global scale, disrupting numerous natural ecosystem services that human societies depend upon, like biological pest control, the pollination of agricultural crops and the provision of clean water and food. The vast majority of experiments investigating the impacts of climate change on biodiversity have used an indirect, "step-change" type approach, where biological responses (like maturation times) to current environmental conditions are compared simultaneously in independent experimental populations, to projected future conditions, with no gradual transition between the conditions. E.g., experiments will record how organisms behave under 20 C conditions at the same time as other organisms from the same species are exposed to 25 C. Differences in their responses are then used as evidence of how climate change will affect biodiversity. However, this approach excludes the potential for populations to adapt and evolve across multiple generations to gradual, directional environmental changes - foundational concepts in population biology. Climate change is happening gradually, albeit rapidly, over time, and while current rates are faster than historical changes, we do not expect to see an instantaneous, dramatic change in conditions in most cases. This disparity creates gaps in understanding between what these experiments predict and what is actually happening in the real world.

We will address these fundamental knowledge and evidence gaps by investigating how a moth (the 'Host' species) a pest species whose caterpillars consume and spoil stored food products worldwide (including simple grains like wheat, as well as biscuits and chocolate), and a wasp (the 'Parasitoid') that attacks and kills the moth by laying eggs in the moth's juvenile caterpillar stage, respond to long-term temperature increases across multiple generations. Parasitoids play a key role in controlling plant and animal populations across all land-based, and many aquatic, food webs, therefore understanding how they respond to climate change gives us extremely useful information that is applicable around the world. We will examine these responses in a carefully integrated system of computer models and carefully controlled laboratory experiments, in this globally important Host-Parasitoid interaction. We will assess how key biological features of the two species, such as the length of time they remain as juveniles, which is highly sensitive to temperature, affect how their population sizes change over time and whether they can continue to live together, or at least one or both species go extinct. We will test if and how these responses change under temperatures that gradually increase by either 1.5 or 3 C over 2-years, spanning ~18 Host generations. We will further increase biological realism by investigating whether short-term (daily) fluctuations around the long-term temperature trend can mask, or even reverse, the ability of these populations to adapt to climate change and coexist across multiple generations. We will apply our findings to other species and climate scenarios using mathematical models that are based on measurements from hundreds of other species, available from publicly available databases.

Our combined work enables us to move beyond describing simple climate change-biodiversity relationships in hindsight - based on data that was often collected for other reasons, by providing a deeper understanding of precisely how natural-enemy systems will respond to future climate change. This will transform our understanding of how we can predict how ecosystems will respond to future, uncertain climate change, vastly improving our understanding of major global challenges, such as pest and disease outbreaks, threats from invasive species and the accelerating loss of biodiversity.