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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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How development and survival combine to determine the thermal sensitivity of insects
Thermal performance curves (TPCs) depict variation in vital rates in response to temperature and have been an important tool to understand ecological and evolutionary constraints on the thermal sensitivity of ectotherms. TPCs allow for the calculation of indicators of thermal tolerance, such as minimum, optimum, and maximum temperatures that allow for a given metabolic function. However, these indicators are computed using only responses from surviving individuals, which can lead to underestimation of deleterious effects of thermal stress, particularly at high temperatures. Here, we advocate for an integrative framework for assessing thermal sensitivity, which combines both vital rates and survival probabilities, and focuses on the temperature interval that allows for population persistence. Using a collated data set of Lepidopteran development rate and survival measured on the same individuals, we show that development rate is generally limiting at low temperatures, while survival is limiting at high temperatures. We also uncover differences between life stages and across latitudes, with extended survival at lower temperatures in temperate regions. Our combined performance metric demonstrates similar thermal breadth in temperate and tropical individuals, an effect that only emerges from integration of both development and survival trends. We discuss the benefits of using this framework in future predictive and management contexts.
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- PAR ID:
- 10489440
- Editor(s):
- Silva, Daniel de
- Publisher / Repository:
- Public Library of Science (PLoSOne)
- Date Published:
- Journal Name:
- PLOS ONE
- Volume:
- 19
- Issue:
- 1
- ISSN:
- 1932-6203
- Page Range / eLocation ID:
- e0291393
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1371/journal.pone.0291393
