Competition moderates the benefits of thermal acclimation to reproductive performance in male eastern mosquitofish

Document Type


Journal/Book Title/Conference

Proceedings of the Royal Society of London, Series B-Biological Sciences






Royal Society, The

Publication Date



temperature, beneficial acclimation hypothesis, Gambusia holbrooki

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The reproductive behaviour of the sexually coercive male eastern mosquitofish (Gambusia holbrooki) offers an excellent model system for testing the benefits of reversible thermal acclimation responses to mating success. We acclimated male mosquitofish to either 18 or 30°C (14 h light : 10 h dark) for six weeks and tested their ability to obtain coercive copulations in the presence and the absence of male–male competition. Based on the beneficial acclimation hypothesis, we predicted for both sets of experiments that 18°C acclimated males would outperform 30°C acclimated males when tested at 18°C, and vice versa when tested at 30°C. We found that copulation success was greater for acclimated than non-acclimated males at both temperatures when individual males were tested without competing males. In contrast, when males from the different acclimation treatments were competed against each other for copulations with a single female, the 30°C acclimated males were more aggressive and obtained a greater number of copulations at both test temperatures. Thus, we found a clear benefit for acclimation when fish were tested in a non-competitive environment, but acclimation to cool temperatures was associated with a decrease in aggressive behaviour that reduced mating performance at both test temperatures in a competitive environment. In contrast with the long-held assumption that reversible plasticity is beneficial, the adaptive significance of reversible physiological plasticity is affected by a variety of other ecological factors and is more complex than previously suggested.

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