Habitat ephemerality affects the evolution of contrasting growth strategies and cannibalism in anuran larvae

Abstract

Ephemeral streams are challenging environments for tadpoles; thus, adaptive features that increase the survival of these larvae should be favored by natural selection. In this study, we compared the adaptive growth strategies of Bombina orientalis (the oriental fire-bellied toad) tadpoles from ephemeral streams with those of such tadpoles from non-ephemeral streams. Using a common garden experiment, we tested the interactive effects of location (ephemeral vs. non-ephemeral), food availability, and growing density on larval period, weight at metamorphosis, and cannibalism. We found that tadpoles from ephemeral streams underwent a shorter larval period compared with those from non-ephemeral streams but that this difference was contingent on food availability. The observed faster growth is likely to be an adaptive response because tadpoles in ephemeral streams experience more biotic/abiotic stressors, such as desiccation risk and limited resources, compared with those in non-ephemeral streams, with their earlier metamorphosis potentially resulting in survival benefits. As a trade-off for their faster growth, tadpoles from ephemeral streams generally had a lower body weight at metamorphosis compared with those from non-ephemeral streams. We also found lower cannibalism rates among tadpoles from ephemeral streams, which can be attributed to the indirect fitness costs of cannibalizing their kin. Our study demonstrates how ephemeral habitats have affected the evolutionary change in cannibalistic behaviors in anurans and provides additional evidence that natural selection has mediated the evolution of growth strategies of tadpoles in ephemeral streams.

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

“…Indeed, in their own study, most of the newly spawned eggs were cannibalised under the presence of conspeci c tadpoles within 24 hours. Considering that (i) egg cannibalism commonly occurs in this population (Baek et al 2021;Oh et al 2021), and (ii) there were always some available pools without conspeci cs throughout the seasons, it is unclear why B. orientalis did not show any avoidance of others' juveniles. D. japonicus even preferred to lay eggs in pools with others' eggs/juveniles present.…”

“…In that case, we predict the females to avoid laying eggs in pools under low canopy covergae. However, under the direct sunlight, the water temperature can be maintained higher than those under high canopy coverage which can boost development, a favourable condition in ephemeral streams (Oh et al 2021). In the latter scenario, we predict females to selectively lay eggs in pools under higher canopy coverage.…”