The effect of resource limitation on the temperature-dependence of mosquito population fitness

Abstract

Laboratory-derived temperature-dependencies of life history traits are increasingly being used to make mechanistic predictions for how climatic warming will affect the abundance of disease vectors. These laboratory data are typically from populations reared on optimal resource supply, even though natural populations are expected to experience fluctuations in resource availability.Using laboratory experiments and stage-structured population projection modelling, here we ask how resource limitation affects temperature-dependence of life history traits and emergent fitness of a principal arbovirus vector, Aedes aegypti, across a temperature range it typically experiences (22–32°C).We show that low-resource supply significantly depresses the vector’s maximal population growth rate (rmax) across the entire temperature range and causes it to peak at a lower temperature, than under high-resource supply. This difference is driven by the fact that resource limitation significantly increases juvenile mortality, slows development, and reduces lifespan and size at maturity (which then decreases fecundity in adults). These results show that resource supply can significantly affect the temperature-dependence of population-level fitness of disease vectors by modifying the thermal responses of underlying traits.Our study suggests that by ignoring resource limitation, projections of vector abundance and disease transmission based on laboratory studies are likely to substantially underestimate the effect of temperature on development time and juvenile survival, and overestimate the effect of temperature on lifespan, size and fecundity.Our results provide compelling evidence for future studies to consider resource supply when making predictions about the effects of climate and habitat change on disease vectors. More generally, our results point at the need to consider the effects of resource limitation on temperature-dependence of life history traits to further advance Ecological Metabolic Theory and improve its utility for predicting the responses of holometabolous insects to climate change.

The effect of resource depletion on the thermal response of mosquito population fitness

“…This increased juvenile survival at 26°C, leading to increased fitness as greater numbers of individuals could contribute to population growth through reproductive output. This is consistent with general studies of ectotherm fitness Coutinho 2013, Huey andBerrigan 2001), including mosquitoes (Huxley et al 2020). This key finding implies that predictions about the effect of climatic warming on ectotherms, including disease vectors and transmission (which are generally from populations under high-or optima resource supply) likely underestimate the effect of temperature on development time and juvenile survival, and overestimate effects of temperature on lifespan and fecundity.…”

“…However, none of these studies have considered environmental temperature. On the other hand, studies that have considered temperature have not considered resource depletion (Huxley et al 2020), or how the effects of temperature and resource availability together affect fitness through traits (Couret et al 2014, Padmanabha et al 2012. As such, our study addresses an important gap by showing that the interactive effects of temperature and resource depletion should also be considered in studies of ectotherm population dynamics.…”

“… Coutinho 2013, Huey andBerrigan 2001), including mosquitoes(Huxley et al 2020). This key finding implies that predictions about the effect of climatic warming on ectotherms, including disease vectors and transmission (which are generally from populations under high-or optima resource supply) likely underestimate the effect of temperature on development time and juvenile survival, and overestimate effects of temperature on lifespan and fecundity.…”

Competition in depleting resource environments shapes the thermal response of population fitness in a disease vector

“…However, recent studies suggest that many predictions of how vector populations will respond to climatic warming are likely to be biased. For example, when food is supplied at a constant rate, low resource availability in the larval stage can have a significant negative effect on temperature-trait relationships (Couret et al 2014;Barreaux et al 2018;Huxley et al 2021). In particular, our recent work (Huxley et al 2021) has shown that low-resource supply, through its adverse impact on juvenile traits, can significantly depress population fitness and decrease its predicted peak temperature.…”

“…For example, when food is supplied at a constant rate, low resource availability in the larval stage can have a significant negative effect on temperature-trait relationships (Couret et al 2014;Barreaux et al 2018;Huxley et al 2021). In particular, our recent work (Huxley et al 2021) has shown that low-resource supply, through its adverse impact on juvenile traits, can significantly depress population fitness and decrease its predicted peak temperature. Despite such advances, resources in natural habitats are not constant and, in many, or arguably even most cases, deplete over time (Ostfeld & Keesing 2000;Yang et al 2008;Beltran et al 2021).…”