ORCC: Determining the synergistic effects of global warming on tropical insect herbivore fundamental vital rates, fitness, and predation

University Of Connecticut, Storrs CT

Investigators

Abstract

Predicting how organisms will respond to novel temperatures remains one of the main conceptual challenges in ecology. Identifying the principles involved in population persistence or extinction in novel temperature environments is also an urgent conservation issue, as all organisms on earth are facing rapidly changing climates. One group of organisms facing extinctions are tropical insects. Current extinction models are based on physiological responses, which invariably overestimate thermal tolerance. To more accurately estimate organismal responses to future temperatures, this study will determine the effects of temperature on insect survival, fecundity, and the speed at which populations will grow or decline. Using a well-studied group of insect herbivores in a tropical rain forest, this proposed research will determine the synergistic effects of diet and temperature on population growth in insects with generalist and specialist diets. An even more ambitious goal of this project is to determine the indirect effects of global warming on insect herbivore fitness through interactions with predators and parasitoids. This study will improve our knowledge on how global warming will indirectly affect populations by disrupting the connections among organisms in the web of life. A broader impact of this project is the integration of concepts and discoveries in two online educational modules. These modules will be used during workshops in the field, where undergraduate students will learn concepts and explore methodologies related to the estimation of biotic responses to global warming. Despite the fact that extinction is a demographic process, our understanding of the direct consequences of global warming on insect survival, longevity, fecundity, and fitness is extremely limited. An additional complexity is that warming most likely will concomitantly affect the abundance and composition of predators and parasitoids. Young leaves of plants in the order Zingiberales – the banana-like plants – form rolled-leaf habitats, which are colonized by herbivores in the genus Cephaloleia (Chrysomelidae: Coleoptera) and their associated predators and parasitoids. This research focuses on the direct and indirect effects of warming on fitness in generalist and specialist Cephaloleia herbivores associated with Zingiberales. Using an experimental demography approach for ten insect species, this study will determine if generalist herbivores are more resilient to warming than specialists. If this scenario is true, insect communities will become dominated by generalist species. Heating experiments in the field will determine if predators are less tolerant to increasing temperatures than their prey, and if warming will generate enemy free space for herbivores. If warming reduces prey abundance, warming will generate trophic cascades. Demographic models will integrate the effects of temperature and diet on fundamental vital rates, and the effect of predation on population growth for each herbivore species. This study addresses one of the least understood effects of global warming: the role of biotic interactions in organismal responses to climate change. The resulting models will increase our predictive power to determine at which temperatures insect populations will reach tipping points to extinction. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.