Food availability modulates temperature-dependent effects on growth, reproduction, and survival in Daphnia magna.

Gustavo S Betini,Tal Avgar,John M Fryxell,Matthew M Guzzo,Xueqi Wang

doi:10.1002/ece3.5925

Abstract

Reduced body size and accelerated life cycle due to warming are considered major ecological responses to climate change with fitness costs at the individual level. Surprisingly, we know little about how relevant ecological factors can alter these life history trade‐offs and their consequences for individual fitness. Here, we show that food modulates temperature‐dependent effects on body size in the water flea Daphnia magna and interacts with temperature to affect life history parameters. We exposed 412 individuals to a factorial manipulation of food abundance and temperature, tracked each reproductive event, and took daily measurements of body size from each individual. High temperature caused a reduction in maximum body size in both food treatments, but this effect was mediated by food abundance, such that low food conditions resulted in a reduction of 20% in maximum body size, compared with a reduction of 4% under high food conditions. High temperature resulted in an accelerated life cycle, with pronounced fitness cost at low levels of food where only a few individuals produced a clutch. These results suggest that the mechanisms affecting the trade‐off between fast growth and final body size are food‐dependent, and that the combination of low levels of food and high temperature could potentially threaten viability of ectotherms.

Highlights

Organisms are regularly exposed to several environmental stressors that can interact with each other to affect individual fitness
High temperature can lead to a decline in mean body size of a given population (Atkinson & Sibly, 1997), which has been considered a general response to global warming, especially in ectotherms (Daufresne, Lengfellner, & Sommer, 2009; Ohlberger, 2013; Sheridan & Bickford, 2011)
Many studies have demonstrated significant interactions between temperature and food stress (Cambronero et al, 2018; Heugens et al, 2001; Jackson et al, 2016; Orcutt & Porter, 1984), it is not clear whether high levels of food abundance could compensate for the negative effects of high temperature on body size imposed by an accelerated pace of life (Gardner et al, 2011) or if low levels of food could inhibit an accelerated life cycle

Summary

| INTRODUCTION

Organisms are regularly exposed to several environmental stressors that can interact with each other to affect individual fitness. Warmer temperatures can advance reproductive maturation, increase reproduction frequency and shorten life span, leading to an accelerated life cycle (Bestion, Teyssier, Richard, Clobert, & Cote, 2015) These individual effects have been shown to scale up to destabilize population dynamics and increase the risk of extinction (Bestion et al, 2015). Many studies have demonstrated significant interactions between temperature and food stress (Cambronero et al, 2018; Heugens et al, 2001; Jackson et al, 2016; Orcutt & Porter, 1984), it is not clear whether high levels of food abundance could compensate for the negative effects of high temperature on body size imposed by an accelerated pace of life (Gardner et al, 2011) or if low levels of food could inhibit an accelerated life cycle. Our dataset allowed us to investigate the combined effects of variation in temperature and/ or food abundance on adult body size and several life demographic parameters, such as size and age at first reproduction, lifetime reproductive success, and life span

| METHODS

Findings

| DISCUSSION