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Abstract As coral reefs face warming oceans and increased coral bleaching, a whitening of the coral due to loss of microalgal endosymbionts, the possibility of evolutionary rescue offers some hope for reef persistence. In tightly linked mutualisms, evolutionary rescue may occur through evolution of the host and/or endosymbionts. Many obligate mutualisms are composed of relatively small, fast-growing symbionts with greater potential to evolve on ecologically relevant time scales than their relatively large, slower growing hosts. Numerous jellyfish species harbor closely related endosymbiont taxa to other cnidarian species such as coral, and are commonly used as a model system for investigating cnidarian mutualisms. We examined the potential for adaptation of the upside-down jellyfishCassiopea xamachanato increased temperature via evolution of its microalgal endosymbiont,Symbiodinium microadriaticum. We quantified trait variation among five algal genotypes in response to three temperatures (26 °C, 30 °C, and 32 °C) and fitness of hosts infected with each genotype. All genotypes showed positive growth rates at each temperature, but rates of respiration and photosynthesis decreased with increased temperature. Responses varied among genotypes but were unrelated to genetic similarity. The effect of temperature on asexual reproduction and the timing of development in the host also depended on the genotype of the symbiont. Natural selection could favor different algal genotypes at different temperatures, affecting host fitness. This eco-evolutionary interaction may be a critical component of understanding species resilience in increasingly stressful environments.
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This content will become publicly available on October 6, 2026
Keep Your Friends Close and Your Enemies Distant: Partner Choice Can Enable Parasite Exclusion in Endosymbiotic Coevolution
Understanding how endosymbiont–host relationships evolve to be mutually beneficial better equips us to predict the future evolutionary course of existing and nascent mutualisms. One mechanism known to influence the evolution of mutualistic endosymbiosis is partner choice, wherein hosts preferentially accept a particular class of partner. However, the extent to which adding partner choice to a system promotes the evolution of mutualism is unknown. In this work, we investigate how partner choice selectivity affects the evolutionary stability and de novo evolution of mutualism. To do so, we implemented tag (i.e. an evolvable label) matching as a mechanism for partner choice in a host–endosymbiont coevolutionary context. We then measured the levels of endosymbiotic mutualism that evolved under a range of partner choice selectivity, tag mutation rates, and endosymbiont vertical transmission rates. Our results demonstrate that tag matching can be effective as an evolvable mechanism for partner choice, due to mutualists and hosts evolving to have more similar tags than parasites and hosts. In addition, we show that partner choice can facilitate the evolution of mutualism, but its specific influence depends on the permissiveness of hosts’ mechanism for partner choice. Specifically, we found ranges of partner selectivity and tag mutation rates that enabled the de novo evolution of exclusive mutualism (i.e. parasites went completely extinct), while other selectivity and mutation rate parameterizations led to coexistence of mutualists and parasites or prevented the evolution and maintenance of mutualisms. These findings pave the way for more precisely engineering systems to promote mutualism.
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- PAR ID:
- 10649836
- Editor(s):
- Witkowski, Olaf; Adams, Alyssa M; Sinapayen, Lana; Baltieri, Manuel; Khosravy, Mahdi
- Publisher / Repository:
- Artificial Life Conference Proceedings
- Date Published:
- Page Range / eLocation ID:
- pp. 57
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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