NSF-SNSF: Molecular Mechanism of a Life-History Tradeoff between Growth and Survival

Evolutionary adaptation often involves “fitness tradeoffs” where optimization of one trait comes at the expense of another. For example, a tradeoff between the ability to survive starvation and growth rate upon recovery has been documented in a variety of organisms. However, the molecular mechanisms that underly such tradeoffs are hardly understood despite being fundamental to evolutionary adaption.

The roundworm C. elegans is a powerful model system that experiences feast or famine in the wild, and these worms display a tradeoff between starvation survival and recovery rate. The research team has developed an innovative approach using DNA sequencing of mixed populations to measure the fitness of competing strains during starvation and recovery.

They have also developed imaging tools to precisely measure biochemical properties of these worms during starvation and recovery. These approaches will enable them to identify strains that are most fit in different evolutionary scenarios and to characterize the molecular mechanisms that support fitness. Each member of the team will engage in outreach.

Dr. Baugh will host high school students from underrepresented backgrounds in his lab during the summer as part of Duke’s Cell Biology Academy (CeBA), and he will visit Dr. Towbin to learn innovative pedagogical methods from the Pestallozzi School Camps (PSCs).

The PSCs have a similar mission to the CeBA but have been in operation much longer, and cross-participation will foster the exchange of ideas and approaches. This work will address a fundamental problem in evolutionary biology, advance state-of-the-art approaches, and engage students in research.

Evolutionary adaptation to different niches is shaped by phenotypic tradeoffs between life-history traits. Yet the proximal molecular mechanisms of life-history tradeoffs are unknown. The team proposes using the nematode C. elegans to address this knowledge gap and determine the molecular basis of a life-history tradeoff between growth and survival.

C. elegans is a powerful animal model to address the molecular mechanisms of trait evolution given its genetic tractability, well-characterized development, short lifecycle, and the availability of hundreds of genetically diverse wild strains with sequenced genomes. The central hypothesis of this proposal is that the frequency and duration of larval starvation in a niche shapes the evolution of a phenotypic tradeoff between starvation survival and recovery speed, and that molecular rates of autophagy/ribophagy impact the balance between the two.

This hypothesis will be tested using experimental evolution, genetics, proteomics, quantitative live imaging, and mathematical modeling. The goals of this proposal are to identify wild strains with different life-history strategies in response to starvation, evaluate the mechanistic contribution of autophagy and ribophagy rates to natural variation in starvation survival and recovery speed, and to identify genetic variants that influence the tradeoff between survival and recovery and the molecular mechanism affected.

Accomplishment of these goals will be impactful by illustrating the importance of a particular tradeoff to evolutionary adaptation to different niches and by linking adaptation to a particular, conserved molecular mechanism.

This collaborative U.S.-Swiss project is supported by the U.S. National Science Foundation (NSF) and the Swiss National Science Foundation (SNSF), where NSF funds the U.S. investigator and SNSF funds the partners in Switzerland.

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.