Short- and long-term effects of the abiotic egg environment on viability, development and vulnerability to predators of a Neotropical anuran


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1.  Environmental variation during development is common and often has long-lasting effects on phenotypes and survival. In organisms with complex life cycles, such effects may carry over from one life stage into the subsequent stages, affecting reproductive success and survival in both direct and indirect manners. Much research has focused on the transition from the larval to adult stages, but fewer studies have addressed how egg-stage variation may affect the larval stage, development to metamorphosis, and adult fitness.

2.  We assessed the short- and long-term consequences of abiotic environmental variation during egg development of the Neotropical treefrog Dendropsophus ebraccatus. Typically, D. ebraccatus eggs are oviposited terrestrially on leaves above water and hydrated by rainfall. However, at our field site in Panama ∼25% of terrestrial eggs become desiccated during development and ∼19% become submerged underwater. In addition, in unshaded ponds D. ebraccatus lays eggs directly in water. We assessed immediate and carryover effects of egg development under hydrated, desiccated and submerged conditions. We measured morphology and vulnerability to predators at hatching and at three time points during the larval period. We also measured morphology at metamorphosis.

3.  Submerged eggs hatched less developed and later and had higher baseline mortality after hatching than either hydrated or desiccated terrestrial eggs. By 10 days after hatching, the morphology of tadpoles from the three egg environments was indistinguishable. Nonetheless, the egg environment affected predation, with tadpoles from submerged eggs being least vulnerable; later in development egg environment ceased to affect vulnerability. Tadpoles from all egg environments grew to a size refuge from dragonfly nymphs, whereas vulnerability to water bugs remained constant throughout development. At metamorphosis, froglets from submerged eggs were the largest and those from hydrated eggs were the smallest.

4.  With anticipated climate change in the Neotropics, rainstorms are predicted to become more sporadic but larger when they do occur, potentially increasing the chances of both egg desiccation and flooding. The incidence of different egg environments may therefore change, potentially affecting amphibian phenotypes, interactions with predators, and survival across multiple life stages.