Climate warming mediates negative impacts of rapid pond drying for three amphibian species

Abstract

Abstract. Anthropogenic climate change will present both opportunities and challenges for pool-breeding amphibians. Increased water temperature and accelerated drying may directly affect larval growth, development, and survival, yet the combined effects of these processes on larvae with future climate change remain poorly understood. Increased surface temperatures are projected to warm water and decrease water inputs, leading to earlier and faster wetland drying. So it is often assumed that larvae will experience negative synergistic impacts with combined warming and drying. However, an alternative hypothesis is that warming-induced increases in metabolic rate and aquatic resource availability might compensate for faster drying rates, generating antagonistic larval responses. We conducted a mesocosm experiment to test the individual and interactive effects of pool permanency (permanent vs. temporary) and water temperature (ambient vs. þ;38C) on three anurans with fast-to-slow larval development rates (Great Basin spadefoot [Spea intermontana], Pacific chorus frog [Pseudacris regilla], and northern red-legged frog [Rana aurora]). We found that although tadpoles in warmed pools reached metamorphosis 15-17 days earlier, they did so with little cost (,2 mm) to size, likely due to greater periphyton growth in warmed pools easing drying-induced resource competition. Warming and drying combined to act antagonistically on early growth (P ¼ 0.06) and survival (P ¼ 0.06), meaning the combined impact was less than the sum of the individual impacts. Warming and drying acted additively on time to and size at metamorphosis. These nonsynergistic impacts may result from cotolerance of larvae to warming and drying, as well as warming helping to offset negative impacts of drying. Our results indicate that combined pool warming and drying may not always be harmful for larval amphibians. However, they also demonstrate that antagonistic responses are difficult to predict, which poses a challenge to proactive conservation and management. Our study highlights the importance of considering the nature of multiple stressor interactions as amphibians are exposed to an increasing number of anthropogenic threats.

Effects of hydroperiod on growth, development, survival and immune defences in a temperate amphibian

“…Our results indicate that size at and survival after metamorphosis can be negatively impacted by drying, which is also supported by previous research (Crump, ; O’Regan et al, ). Small size at metamorphosis can have long‐term negative consequences.…”

Warmer winters reduce frog fecundity and shift breeding phenology, which consequently alters larval development and metamorphic timing

“…Essentially, when wood frogs bred later, their eggs and larvae experienced warmer temperatures, and these warmer temperatures caused the tadpoles to develop more quickly (Tejedo et al, 2010). These tests often simulate the effects of climate change by experimentally increasing the temperatures experienced by larvae (Tejedo et al, 2010;Rudolf & Singh, 2013;O'regan et al, 2014). Increasing risk of frost damage may be due to increasing variance in temperature, such that warm winters are often followed by an extreme frost.…”

Compounding effects of climate change reduce population viability of a montane amphibian

“…There is some evidence that developmental rates in amphibians can increase as aquatic environments warm, compensating for increased drying rates (Newman , O'Regan et al. , Thurman and Garcia ). However, in most cases in our study system, drying occurs well before limb development in larvae (A. M. Kissel, personal observation ), and thus, increased developmental rates are unlikely to compensate for increased mortality due to pond drying.…”

“…There is evidence that increased temperatures can accelerate larval growth and metamorphosis (Newman , O'Regan et al. ), but it is unclear whether increased growth rates can compensate for increased rates of pond drying (Matthews et al. , McCaffery et al.…”