Thermally contingent plasticity: temperature alters expression of predator-induced colour and morphology in a Neotropical treefrog tadpole

Abstract

Summary1. Behavioural, morphological and coloration plasticity are common responses of prey to predation risk. Theory predicts that prey should respond to the relative magnitude of risk, rather than a single level of response to any risk level. In addition to conspecific and predator densities, prey growth and differentiation rates affect the duration of vulnerability to size-and stage-limited predators and therefore the relative value of defences. 2. We reared tadpoles of the Neotropical treefrog Dendropsophus ebraccatus with or without cues from a predator (Belostoma sp.) in ecologically relevant warm or cool temperatures. To track phenotypic changes, we measured morphology, tail coloration and developmental stage at three points during the larval period. 3. Cues from predators interacted with growth conditions causing tadpoles to alter their phenotype, changing only tail colour in response to predators in warm water, but both morphology and colour in cool growth conditions. Tadpoles with predators in warm water altered coloration early but converged on the morphology of predator-free controls. Water temperature alone had no effect on tadpole phenotype. 4. We demonstrate that seemingly small variation in abiotic environmental conditions can alter the expression of phenotypic plasticity, consistent with predictions about how growth rate affects risk. Predator-induced tadpole phenotypes depended on temperature, with strong expression only in temperatures that slow development. Thermal modulation of plastic responses to predators may be broadly relevant to poikilotherm development. It is important to include a range of realistic growth conditions in experiments to more fully understand the ecological and evolutionary significance of plasticity.

Artificial warming increases size at metamorphosis in plateau frogs (Rana kukunoris) in the presence of predators

“…Our result that warming facilitated growth more than development in the presence of predators is partly consistent with Touchon and Warkentin (2011), who show that warming facilitated tadpole development (but not growth) in the presence of predators, but seems contrary to established metamorphosis theories. For example, the Wilbur and Collins (1973) model predicts that increased growth rate is associated with slower development.…”

“…Moreover, our study lasted for 13 weeks, and it is one of the few experimental studies reporting warming effects on timing and size at metamorphosis of tail resorption. The two studies that explicitly addressed the interaction between predators and warming (Laurila et al 2008;Touchon and Warkentin 2011, as noted in Introduction) were accomplished within a short time (\30 days).…”

“…In a laboratory common garden experiment, Laurila et al (2008) found that the effect of predators (Aeshna dragonfly larva) on size at metamorphosis was negative in low-latitude groups of Rana temporaria but was neutral or positive in highlatitude groups. Touchon and Warkentin (2011) did not find a significant interaction between temperature and predator (Belostoma sp.) effects on development of the neotropical treefrog (Dendropsophus ebraccatus).…”

Artificial Warming Facilitates Growth but Not Survival of Plateau Frog (Rana kukunoris) Tadpoles in Presence of Gape-Limited Predatory Beetles

“…Nevertheless, our study is not the only case violating this dogma. Touchon and Warkentin [22] also found that the single warming effect on tadpole growth was not significant in Neotropical treefrog Dendropsophus ebraccatus over a three-week long experiment. Moreover, Alvarez and Nicieza [21] reported that tadpole body mass of the Iberian Painted Frogs ( Discoglossus galganoi ) varied inversely with temperature under non-limiting food availability.…”

“…For example, long-term field monitoring programs [16], [17] have revealed that tadpoles grow faster in warm years than in cold years; large spatial-scale investigations have shown that the growth rate of tadpoles progressively increases across the gradients from high to low latitudes or altitudes [18]–[20]; laboratory studies have also indicated that amphibian tadpoles grow faster at high temperatures [5], [21], [22]. Another issue is that many predator species preying on tadpoles are gape-limited killers such as diving beetles (e.g.…”