Effects of temperature, predation risk, and resource availability on larval amphibian phenotypic plasticity and terrestrial performance
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Abstract
Aquatic ectotherms show an immense capacity to adapt to their environment in early life stages with plastic development. For example, larval amphibian development and growth rates are highly responsive to predation risk. However, growth and development rates are simultaneously constrained by resource availability and temperature. Although there is considerable work on how these factors singly alter growth and development, they are commonly experienced simultaneously within natural systems. Here, we investigate phenotypic plasticity in the face of predation risk and resource limitation across thermal regimes. Using Lithobates blairi, we conducted a 2 x 3 x 6 factorial experiment with 2 predation treatments (control & Procambarus gracilis cues), 3 resource levels (low, medium, & high), and 6 temperatures (15, 20, 22, 24, 26, 28°C). For 38 weeks, we calculated the proportion of individuals successfully reaching metamorphosis in each treatment combination, and individual development and growth rates. Additionally, we measured pre- & post-metamorphosis body length, and juvenile jumping performance to describe whether larval history has lasting effects across life stages. We found that rates of metamorphosis were highest in intermediate temperatures and observed minor interactions with predation risk and resource availability. Development and growth rates of tadpoles were temperature-dependent under high resource conditions. Predation risk and limited resources reduced the range of development and growth rates seen across temperature. Further, development and growth rates increased simultaneously with temperature, and differences in body size were only found post-metamorphosis between predation treatments. Juvenile size and performance decreased with added predation risk, and performance increased with resource availability in the absence of predator cues. Our results suggest that successful metamorphosis is largely temperature-dependent, but the breadth of plastic traits is constrained by resource availability, and consequences of predation risk may not be observed until terrestrial life stages.