Embryos are largely understudied in conservation physiology

This is a Preprint and has not been peer reviewed. This is version 1 of this Preprint. You must log in to post a comment. There are no comments or no comments have been made public for this article. This is a Preprint and has not been peer reviewed. This is version 1 of this Preprint. Add a Comment You must log in to post a comment. Comments There are no comments or no comments have been made public for this article. Understanding how animals respond to environmental stressors across their life cycle is essential for predicting species’ vulnerability to climate change. Here, we systematically reviewed the literature to quantify the variation in research effort on different life stages in the field of conservation physiology. Specifically, we reviewed experimental studies measuring physiological and life-history responses to climatic stressors across three scientific journals: Conservation Physiology, Journal of Thermal Biology, and Journal of Experimental Biology. Our systematic map of 1,276 studies revealed a pronounced underrepresentation of studies on embryos, representing only 8-9% of studies. This pattern was remarkably consistent across all axes considered (i.e., journals, taxonomic groups, physiological traits, and environmental stressors). We also found that 80% of studies only investigated single life stages, and over 5% of studies did not clearly report the life stage(s) used. Despite the increasing recognition of the ecological importance and sensitivity of early life stages to environmental stressors, we found no evidence that research on embryos has gained traction over the past decade (2013-2024). We argue that these ontogenetic biases likely reflect a combination of historical precedents and enduring methodological and logistical constraints that continue to shape research agendas. To build a more holistic understanding across the life cycle, we: i) call for a paradigm shift placing embryos at the center of experimental agendas, ii) outline emerging methodological advances that increase the feasibility of research on early life stages, iii) demonstrate how studies on embryos can navigate ethical considerations for animal research, iv) highlight perspectives for future evidence syntheses and study reporting, and v) promote investigations of the mechanisms underlying physiological variation across ontogeny. Closing the ontogenetic gap will be key to improving our ability to predict population-level impacts of climate change and guiding more effective conservation and management interventions. https://doi.org/10.32942/X2KP96 Biodiversity, Biology, Ecology and Evolutionary Biology, Life Sciences, Marine Biology, Physiology Life cycle, ontogeny, ontogenetic bias, embryonic, embryos, life stages, Systematic map, experimental study, conservation physiology, climate change, Literature review, reproduction, environmental stress, environmental change, global change, egg, life history, embryonic development, early-life stages, systematic review map Published: 2025-08-21 09:43 CC BY Attribution 4.0 International Data and Code Availability Statement: All data, code, and materials are freely available at https://github.com/p-pottier/Cons_phys_life_stages, and will be archived in Zenodo upon acceptance. Language: English