Environmental variation during ontogeny can have profound, variable effects on an organism’s phenotype, fitness, morphology, and physiological attributes. Abiotic factors such as temperature regimes and pool drying rates often have negative impacts on the developmental environments of larval amphibians. Additionally, biotic pressures from competitors, food availability, and predation risk can interact to create synergistic, additive, or antagonistic effects on larval development. Across the globe climate change is predicted to affect annual temperatures and precipitation rates, leading to warmer temperatures and drought-like conditions in many areas, leading to shorter hydroperiods of breeding pools and eliciting plastic responses of larval developmental times. Many anurans have a dual life cycle, raising the question of whether detrimental environmental conditions experienced in the aquatic stage are carried over in the terrestrial stages, and how the negative impacts on growth and survival in the larval stage impact the fitness of metamorphs in the terrestrial stage. While many studies have focused separately on the effects of pool permanency and predation risk on developmental rates and survival of larval amphibians, few have considered carryover effects from aquatic environment into the juvenile life stage. This study was designed to evaluate potential carryover effects of hydroperiod length and predation risk of aeshnid odonate larvae on wood frogs (Lithobates sylvaticus). We manipulated hydroperiod lengths in cattle tank mesocosms with and without predation cues (caged odonate larvae). During the larval stage we assessed the effects of the aquatic treatments on larval growth and development, temperature preference at 3 separate Gosner stage, and overall survival to metamorphosis. Upon metamorphosis, we assessed endurance ability at various temperatures.
Results/Conclusions
While we found no significant difference in thermal preference of tadpoles between short and long hydroperiod treatments, tadpoles from predator treatments preferred significantly different temperature regimes compared to those from non-predator treatments. Shortened hydroperiods resulted in decreased larval survival and increased developmental rates, leading to smaller sizes at metamorphosis. When combined with predation risk, shortened hydroperiods decreased overall time to metamorphosis (~5-7 days) and illicited greater variation in metamorph size (SVL), with earlier metamorphosing individuals demonstrating decreased endurance capability. Understanding how such elements experienced in the aquatic larval stage affect the fitness of juveniles post-metamorphosis is critical for evaluating demographic consequences and population-level responses to climate change, as juvenile anurans are often the population-regulating stage, and for better understanding how conditions experienced during the aquatic stage affect their physiological capacity to respond to changing environments.