ABSTRACT
Understanding thermal performance at life stages that limit persistence is necessary to predict responses to climate change, especially for ectotherms whose fitness (survival and reproduction) depends on environmental temperature. Ectotherms often undergo stage-specific changes in size, complexity and duration that are predicted to modify thermal performance. Yet performance is mostly explored for adults, while performance at earlier stages that typically limit persistence remains poorly understood. Here, we experimentally isolate thermal performance curves at fertilization, embryo development and larval development stages in an aquatic ectotherm whose early planktonic stages (gametes, embryos and larvae) govern adult abundances and dynamics. Unlike previous studies based on short-term exposures, responses with unclear links to fitness or proxies in lieu of explicit curve descriptors (thermal optima, limits and breadth), we measured performance as successful completion of each stage after exposure throughout, and at temperatures that explicitly capture curve descriptors at all stages. Formal comparisons of descriptors using a combination of generalized linear mixed modelling and parametric bootstrapping reveal important differences among life stages. Thermal performance differs significantly from fertilization to embryo development (with thermal optimum declining by ∼2°C, thermal limits shifting inwards by ∼8–10°C and thermal breadth narrowing by ∼10°C), while performance declines independently of temperature thereafter. Our comparisons show that thermal performance at one life stage can misrepresent performance at others, and point to gains in complexity during embryogenesis, rather than subsequent gains in size or duration of exposure, as a key driver of thermal sensitivity in early life.
Footnotes
Competing interest
The authors declare no competing or financial interests.
Author contributions
Conceptualization: A.P.R., C.M.S., K.M.; Methodology: A.P.R., C.M.S., K.M.; Validation: A.P.R.; Formal analysis: A.P.R., K.M.; Investigation: A.P.R.; Resources: A.P.R., C.M.S., K.M.; Data curation: A.P.R.; Writing - original draft: A.P.R.; Writing - review & editing: A.P.R., C.M.S., K.M.; Visualization: K.M.; Supervision: C.M.S., K.M.; Project administration: A.P.R.; Funding acquisition: A.P.R., C.M.S., K.M.
Funding
This research was supported by a Holsworth Wildlife Research Endowment awarded to A.P.R., and by grants and fellowships awarded under the Australian Research Council’s Discovery Scheme to K.M. and C.M.S.
Data availability
Data have been deposited in the Dryad Digital Repository (Rebolledo et al., 2020): https://doi.org/10.5061/dryad.5dv41ns4z.
Supplementary information
Supplementary information available online at https://jeb.biologists.org/lookup/doi/10.1242/jeb.233254.supplemental
- Received July 15, 2020.
- Accepted October 9, 2020.
- © 2020. Published by The Company of Biologists Ltd
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