Phosphorus availability affects multiple metrics of reproductive investment in a freshwater snail

Reproduction, arguably the most important life-history trait to evolutionary fitness, demands significant resources. Reproductively mature animals must “choose” whether to reproduce or to allocate nutrients to other life-history traits. When nutrients are limited, organisms may reduce reproductive investment or even forego reproduction. We address a key knowledge gap regarding how nutrient availability affects multiple metrics of reproductive investment in female animals. Specifically, we experimentally manipulated dietary availability of phosphorus (P), a critical but often limiting nutrient, for reproductively mature Potamopyrgus antipodarum, a New Zealand freshwater snail. We quantified multiple components of reproductive fitness relative to body P content across life-history stages. Our study revealed a suite of outcomes linking key aspects of reproductive fitness to P availability suggesting the central importance of P to life-history milestones. In particular, dietary P availability altered which component of adult female condition – size vs. body P content - influenced the probability of reproduction, demonstrating the central importance of P in life-history milestones. Together, our study of P flow across the life cycle demonstrates that this frequently limiting nutrient is a major component of multiple metrics of reproductive investment in female animals.