How does sequential acquisition of nutritional resources modulate allocation decisions? A whole-organism perspective on life history tradeoffs

University Of Arizona, Tucson AZ

Investigators

Abstract

Nutritional resources available to organisms are often limited in nature. Resources allocated to one trait are not available to other traits resulting in resource allocation tradeoffs. Such tradeoffs are at the foundation of our understanding of the ecology and evolution of all animals and plants. However, empirical evidence for tradeoffs has been surprisingly difficult to obtain. This is in part due to challenges associated with quantifying which and how much nutrients organisms obtain, and how these nutrients are distributed across the organism’s life. This study will examine how the common cabbage-white butterfly (Pieris rapae) obtains and allocates nutrients between two critical functions, flight vs. fecundity. This research is particularly novel in taking advantage of the most recent technological advances in nutritional physiology to directly trace the effects of specific nutrient inputs (e.g., amino acids and carbohydrates), literally second by second, as this butterfly hatches, grows, disperses, and reproduces. Results of this study will help resolve one of the big mysteries in understanding tradeoffs, why don’t we always see the tradeoffs that are predicted to exist? This project will also support Insect Discovery, an established outreach program that uses insects, like the cabbage-white butterfly, to teach biology to K-12 students. Using lessons learned during the COVID-19 closure, this grant will develop online content and extend the virtual teaching experience to underserved rural and tribal schools around the state of Arizona. Resource allocation tradeoffs occur because organisms can only acquire a finite amount of resources in their lifetimes and resources allocated to one trait are not available to other traits. Because of their importance, tradeoffs have been studied for well over 50 years, leading to a fairly robust theoretical understanding. Surprisingly however, tradeoffs are often not found in nature, even when they are predicted to exist. Most studies of tradeoffs measure traits at a particular instant in time. Yet, resource acquisition and allocation is a dynamic process that occurs throughout an organism’s life cycle. It is possible that resources allocated now will only be manifested in a tradeoff later. This research will integrate approaches from nutritional ecology with cutting-edge stable isotope tracer methodologies to determine the interplay between acquisition and allocation of specific nutrients and nutrient mixtures, both within and across all life stages, to understand the decision making processes associated with an important tradeoff, flight vs. fecundity, in Pieris rapae butterflies. Specifically, this project will address: 1) Can nectar-feeding ameliorate flight-fecundity tradeoffs? 2) How do flight-fecundity tradeoffs influence the ability of females to acquire additional resources? 3) How do different resource currencies modulate the expression of a flight-fecundity tradeoff? 4) How does nutrient provisioning in eggs mediate flight fecundity tradeoffs across generations? By tracking individual nutrients throughout a complete life cycle, egg to egg, a perplexing conundrum in evolutionary biology will be addressed: why don’t we see tradeoffs among traits when they are expected? 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.