Integrating physiological and behavioral ecology: how limited resources and allocation trade-offs impact mate signaling

This $495,671 federal Project Grant award from the National Science Foundation's Biological Sciences program was provided to the University of South Carolina (USC) to conduct research on how limited resources and allocation trade-offs impact mate signaling in the Mormon fritillary butterfly. The work integrates physiological and behavioral ecology approaches, using both laboratory and field studies, to understand how changes in larval food availability affect the allocation of nutrients to traits supporting reproduction and survival, including egg production, fat storage, and wing pigmentation used in mate signaling.

As part of the project, USC has issued a $160,490 sub-award to the Corporation of the Rocky Mountain Biological Laboratory in Colorado to carry out the field research component. This includes quantifying differences in larval food availability and female trait allocation between lab-reared and wild populations, as well as examining how female wing color affects mate detection and attractiveness to males. The project aims to provide critical insights into how pollinator populations may respond to changes in climate and land use that impact food resources.

Abstract

Resource allocation describes how organisms budget a finite resource pool in support of crucial life activities, such as survival and reproduction. The study of this process is vital to understanding organismal biology and population dynamics. Resource allocation changes under limited food availability. Changes in weather conditions and land use affect food availability for larval insects. Little is known about the constraints and trade-offs that determine changes in allocation of nutrients acquired in the larval stage to various components of reproduction in response to such limited food availability. The proposed work explores this question, using the well-studied mormon fritillary butterfly. The results will be critical to understanding how pollinator population numbers change in response to both weather variability and directional change in climate means. The work integrates traditional physiology and behavior to yield new insights. IT also includes studies in both the laboratory and field, providing a translation between controlled studies with what actually happens in the field. In addition, to the societal importance of understanding pollinator populations, the work will also train undergraduate and graduate students working on the project and disseminate the findings more broadly via collaboration with K-12 teachers. In insects with complete metamorphosis, nutrients acquired by larvae are allocated during the pupal stage to adult morphological traits that support reproduction and survival, including eggs, STORAGE, and traits used in mate signaling. Allocation is particularly vital in species such as butterflies with incomplete adult diets, where adult feeding cannot readily supplement nitrogenous reserves. The work traces the effects of allocation of larval nutrient pools of different sizes to investment in offspring, as well as to the generation of mating signals. In so doing, IT will reveal the mechanisms underlying mating behavior and fecundity, whose inter-twined fitness effects depend on allocation. Key questions addressed include: do quantitative differences in larval food acquisition by females in the lab result in trade-offs among NITROGEN-dependent traits including oocyte number (potential reproduction), FAT body (STORAGE), and wing pigmentation (mate signaling)? Do these allocation trade-offs differ between lab-reared and field populations? How does investment in wing pigments translate to differences in wing color? How do differences in wing color translate to attractiveness of females to males? Both a common currency (NITROGEN) and fitness metrics will be assayed in the allocation work. The results will be integrated in a graphical model. The model will explore variation in trade-offs between the lab and field, and the role of food acquisition and allocation as mechanisms underlying behavior. In addition, to advancing the mechanistic understanding of pollinator populations, the project will also serve as a platform to train undergraduate and graduate students, while also disseminating the research findings via interactions with teachers and docents at the field sites. This project is jointly funded by the integrative ecological physiology program in the division of integrative and organismal systems, and the established program to stimulate competitive research (EPSCOR). 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.- subawards are planned for this award.