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Warming increases survival and asexual fitness in a facultatively sexual freshwater cnidarian with winter diapause
  • Jácint Tökölyi
Jácint Tökölyi
University of Debrecen

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Temperature is a key abiotic factor controlling population dynamics. In facultatively sexual animals inhabiting the temperate zone, temperature regulates the switch between asexual and sexual modes of reproduction, initiates growth or dormancy and acts together with photoperiod to mediate seasonal physiological transitions. Increasing temperature due to recent global warming are likely to disrupt population dynamics of facultatively sexual animals because of the strong temperature-dependence of multiple fitness components. However, the fitness consequences of warming in these animals are still poorly understood. This is unfortunate, since facultatively sexual animals – through their ability for asexual reproduction resulting in quick population growth and sexual reproduction enabling long-term persistence – are key components of freshwater ecosystems. Here, I studied the fitness effects of warming in Hydra oligactis, a freshwater cnidarian that reproduces asexually throughout most of the year but switches to sexual reproduction under decreasing temperatures. I exposed hydra polyps to simulated short summer heatwaves or long-term elevated winter temperatures. Since sexual development in this species is dependent on low temperature, I predicted reduced sexual investment (gonad production) and elevated asexual fitness (budding) in polyps exposed to higher temperatures. The results show a complex effect of warming on sexual fitness: while gonad number decreased in response to warming, polyps exposed to high winter temperature were capable of multiple rounds of gamete production. Asexual reproduction and survival rate, on the other hand, clearly increased in response to higher temperatures, especially in males. These results predict increased population growth of H. oligactis in temperate freshwater habitats, which will likely affect the population dynamics of its’ main prey (freshwater zooplankton), and through that, the whole food web.
22 Dec 2022Submitted to Ecology and Evolution
24 Dec 2022Assigned to Editor
24 Dec 2022Submission Checks Completed
10 Jan 2023Reviewer(s) Assigned
08 Mar 2023Review(s) Completed, Editorial Evaluation Pending
08 Mar 2023Editorial Decision: Revise Minor
20 Mar 20231st Revision Received
21 Mar 2023Submission Checks Completed
21 Mar 2023Assigned to Editor
21 Mar 2023Review(s) Completed, Editorial Evaluation Pending
22 Mar 2023Editorial Decision: Accept