Evolutionary Applications
Evolutionary Applications
3 years ago

Haemoglobin-mediated response to hyper-thermal stress in the keystone species Daphnia magna

Maria Cuenca Cambronero, Luisa Orsini, Bettina Zeis
Anthropogenic global warming has become a major geological and environmental force driving drastic changes in natural ecosystems. Due to the high thermal conductivity of water and the effects of temperature on metabolic processes, freshwater ecosystems are among the most impacted by these changes. The ability to tolerate changes in temperature may determine species long-term survival and fitness. Therefore, it is critical to identify coping mechanisms to thermal and hyper-thermal stress in aquatic organisms. A central regulatory element compensating for changes in oxygen supply and ambient temperature is the respiratory protein haemoglobin (Hb). Here, we quantify haemoglobin (Hb) plastic and evolutionary response in D. magna (sub)populations resurrected from the sedimentary archive of a lake with known history of increase in average temperature and recurrence of heat waves. By measuring constitutive changes in crude Hb protein content among (sub)populations we assessed evolution of the haemoglobin gene family in response to temperature increase. To quantify the contribution of plasticity in the response of this gene family to hyper-thermal stress, we quantified changes in Hb content in all (sub)populations under hyper-thermal stress as compared to non-stressful temperature. Further, we tested competitive abilities of genotypes as a function of their Hb content, constitutive and induced. We found that haemoglobin (Hb)-rich genotypes have superior competitive abilities as compared to Hb-poor genotypes under hyper-thermal stress after a period of acclimation. These findings suggest that whereas long-term adjustment to higher occurrence of heat waves may require a combination of plasticity and genetic adaptation, plasticity is most likely the coping mechanism to hyper-thermal stress in the short term. Our study suggests that with higher occurrence of heat waves Hb-rich genotypes may be favoured with potential long-term impact on population genetic diversity. This article is protected by copyright. All rights reserved.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/eva.12561

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