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Abstract Development can play a critical role in how organisms respond to changes in the environment. Tolerance to environmental challenges can vary during ontogeny, with individual- and population-level impacts that are associated with the timing of exposure relative to the timing of vulnerability. In addition, the life history consequences of different stressors can vary with the timing of exposure to stress. Salinization of freshwater ecosystems is an emerging environmental concern, and habitat salinity can change rapidly due, for example, to storm surge, runoff of road deicing salts, and rainfall. Elevated salinity can increase the demands of osmoregulation in freshwater organisms, and amphibians are particularly at risk due to their permeable skin and, in many species, semi-aquatic life cycle. In three experiments, we manipulated timing and duration of exposure to elevated salinity during larval development of southern toad (Anaxyrus terrestris) tadpoles and examined effects on survival, larval growth, and timing of and size at metamorphosis. Survival was reduced only for tadpoles exposed to elevated salinity early in development, suggesting an increase in tolerance as development proceeds; however, we found no evidence of acclimation to elevated salinity. Two forms of developmental plasticity may help to ameliorate costs of transient salinity exposure. With early salinity exposure, the return to freshwater was accompanied by a period of rapid compensatory growth, and metamorphosis ultimately occurred at a similar age and size as freshwater controls. By contrast, salinity exposure later in development led to earlier metamorphosis at reduced size, indicating an acceleration of metamorphosis as a mechanism to escape salinity stress. Thus, the consequences of transient salinity exposure were complex and were mediated by developmental state. Salinity stress experienced early in development resulted in acute costs but little long-lasting effect on survivors, while exposures later in development resulted in sublethal effects that could influence success in subsequent life stages. Overall, our results suggest that elevated salinity is more likely to affect southern toad larvae when experienced early during larval development, but even brief sublethal exposure later in development can alter life history in ways that may impact fitness.
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Developmental Plasticity in Anurans: Meta-analysis Reveals Effects of Larval Environments on Size at Metamorphosis And Timing of Metamorphosis
Many anuran amphibians (frogs and toads) rely on aquatic habitats during their larval stage. The quality of this environment can significantly impact lifetime fitness and population dynamics. Over 450 studies have been published on environmental impacts on anuran developmental plasticity, yet we lack a synthesis of these effects across different environments. We conducted a meta-analysis and used a comparative approach to understand whether developmental plasticity in response to different larval environments produces predictable changes in metamorphic phenotypes. We analyzed data from 124 studies spanning 80 anuran species and six larval environments and showed that intraspecific variation in mass at metamorphosis and the duration of the larval period is partly explained by the type of environment experienced during the larval period. Changes in larval environments tended to reduce mass at metamorphosis relative to control conditions, with the degree of change depending on the identity and severity of environmental change. Higher temperatures and lower water levels shortened the duration of the larval period, whereas less food and higher densities increased the duration of the larval period. Phylogenetic relationships among species were not associated with interspecific variation in mass at metamorphosis plasticity or duration of the larval period plasticity. Our results provide a foundation for future studies on developmental plasticity, especially in response to global changes. This study provides motivation for additional work that links developmental plasticity with fitness consequences within and across life stages, as well as how the outcomes described here are altered in compounding environments.
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- Award ID(s):
- 2109599
- PAR ID:
- 10511773
- Publisher / Repository:
- Society for Integrative and Comparative Biology
- Date Published:
- Journal Name:
- Integrative And Comparative Biology
- Volume:
- 63
- Issue:
- 3
- ISSN:
- 1540-7063
- Page Range / eLocation ID:
- 714-729
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/icb/icad059
