RUI - An integrative study of covariances between behavioral and morphological life-history traits

Trade-offs are a key concept in evolutionary biology: when resources are limited, organisms must strategically allocate resources to different functions. As a result, higher investment in one trait results in lower investment in others, and the optimal allocation strategy can vary with the environment. Most studies on evolutionary trade-offs focus either on the mechanisms that result in different strategies or in their fitness consequences, rather than integrating these two questions.

The goal of this project is to investigate both causes and consequences of trade-offs using the bean beetle, Callosobruchus maculatus. A previous study by the investigator and two undergraduate researchers revealed that resource competition between juveniles leads to trade-offs between wing size and reproduction in adults. This project will explore the role of hormones during development in determining adult allocation strategies into wings versus reproduction, as well as the effects of resource allocation to immunity.

Consequences of these trade-offs will also be investigated by measuring the evolutionary fitness of individuals with different behavioral strategies. In addition to making significant contributions to our understanding of life-history trade-offs, this project will contribute to a more diverse STEM workforce through the recruitment and training of undergraduate researchers from underrepresented groups: This project will be entirely conducted by undergraduate researchers under the investigator’s supervision.

Additionally, this project will promote the integration of teaching and research through the development of inquiry-based laboratory experiments with C. maculatus for an Animal Behavior course. This classroom research experience will serve as a pipeline for undergraduates to get involved in research outside the classroom.

Trade-offs are a central concept to life-history theory, arising due to differential trait investment within an organism and resulting in negative covariances between traits. A full understanding of why trade-offs occur requires the integration of their proximate mechanisms and fitness consequences. In Callosobruchus maculatus, larval density induces differential resource allocation: High density results in the development of dispersal morphs with large, functional wings, as opposed to the short-winged flightless morphs that develop under low densities.

A previous study by the investigator and two undergraduate collaborators revealed that high-density individuals develop larger wings and smaller gonads, and larval density also affected a suite of mating behaviors in both sexes. This project will investigate the role of Juvenile Hormone in the developmental mechanisms involved in these trade-offs, as well as how sex differences and resource allocation to immunity affect overall resource allocation.

The ultimate explanations will also be investigated by measuring fitness effects of differential allocation to gonads and mating behaviors such as courtship and oviposition strategies.

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.