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Abstract The extent to which populations persist under environmental stress depends on the reproductive output of individuals that survive the stress. In coral systems, corals bleach in response to stress from elevated water temperature. However, little is known of the extent to which thermal stress impairs the reproductive capacity of the survivors over the following years, limiting the capacity to predict how populations will persist in the Anthropocene.Using histology to quantify the abundance and size of oocytes and spermaries per polyp, we tested how bleaching impairs the reproductive response of the coralPocillopora meandrinaover two reproductive seasons following the 2015 mass bleaching event in the Hawaiian Islands.We found that smaller colonies not only had a greater probability of bleaching but also suffered greater reproductive impacts over a longer time. In contrast, larger colonies generated comparable reproductive output regardless of bleaching severity, although bleached colonies generated smaller oocytes the year after bleaching.These results show that reproductive impacts of bleaching are more complex and size‐specific than commonly assumed. Therefore, estimates of bleaching mortality may underestimate the true impact of thermal stress on populations, especially as populations lose larger individuals from repeated and co‐occurring stressors. A freePlain Language Summarycan be found within the Supporting Information of this article.
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This content will become publicly available on April 27, 2026
Differential effects of temperature on multiple components of fitness in a modular animal reveal how temperature affects reproductive capacity
Abstract Thermal performance curves (TPCs) are important tools for predicting the sensitivity of populations to climate change. However, the interactive ways that temperature affects multiple life‐history components lead to different fitness outcomes. These interactions are poorly understood for modular animals, especially over the lifespan of individual colonies, which limits our capacity to connect physiological and demographic responses.The goal of this study was to assess and compare the relationships between temperature and different life‐history components in a modular animal to reveal the mechanisms underlying TPCs for fitness.We reared replicated clones of the marine bryozoanBugula neritinaacross a thermal gradient (16 values) ranging from 23 to 32°C, which reflected the upper thermal range of seasonal variation in the field. TPCs were constructed for survival (measured as zooids states within a colony), growth rate, development to reproductive maturity and reproductive capacity, which were measured over much of the realized lifespan expected under field conditions (~30 days).The effect of temperature was more acute on zooid states rather than whole‐colony survival, and increased temperature increased the frequency of polypide regression. Most colonies reached reproductive maturity up to ~30°C, but growth rate and reproduction decreased at temperatures beyond ~25°C. The decline in reproductive capacity over temperatures above ~25°C was then due to the decline in the production of zooids capable of brooding embryos and zooids transitioning to regressed states up until about 30°C and transitioning to dead state beyond that.Higher temperatures are often considered to affect reproduction by interfering with gametogenesis and post‐zygotic pathways, but in modular animals, changes in growth rate and module states could indirectly cause temperature sensitivity of reproduction. Our study has implications for the role of temperature in driving the sampled population's dynamics by setting the number of generations that occur during the time window when temperatures are conducive to reproduction. Our results also have implications for the generality and predictability of temperature on population persistence across unitary and modular animals. Read the freePlain Language Summaryfor this article on the Journal blog.
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- Award ID(s):
- 1948788
- PAR ID:
- 10585627
- Publisher / Repository:
- John Wiley & Sons Ltd
- Date Published:
- Journal Name:
- Functional Ecology
- ISSN:
- 0269-8463
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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