Oviposition strategies of amphibians in ephemeral streams: a multi-species perspective

Many amphibians are selective about where to lay eggs, as this greatly affects their offpsring’s survival. Theoretically, species sharing the same habitat are expected to experience similar selective pressures, leading to the prediction that they might share similar oviposition preferences. However, this hypothesis has not yet been tested. In this study, through an extensive field survey, we examined the oviposition site selection of four amphibian species (Rana uenoi, Hynobius quelpaertensis, Bombina orientalis, and Dryophytes japonicus) that reproduce in the same natural ephemeral stream. Our focus was on understanding how various abiotic and biotic factors influence their reproductive choices. We primarily found that drought avoidance is a universal selective pressure affecting all species, with a tendency to avoid laying eggs in smaller pools prone to drought. Species-specific responses to leaf litter and canopy coverage were observed, but none of the species' oviposition choices correlated with the quantity of stones in pools. The study also explored biotic influences, revealing species-specific trends in the selection of pools with conspecific and heterospecific juveniles, predators, and mosquito larvae, indicating a complex ecological interplay. These findings highlight the complexity of amphibian reproductive strategies, where decisions are not driven solely by a single factor such as the avoidance of predators or competitors but also by intricate assessments of multiple factors. The study highlights that amphibian oviposition in ephemeral streams is influenced by a diverse interplay of biotic and abiotic factors, essential for understanding their reproductive strategies in dynamic environments.