Abstract
Global warming can disrupt reproduction or lead to fewer and poorer quality offspring, owing to the thermally sensitive nature of reproductive physiology. However, phenotypic plasticity may enable some animals to adjust the thermal sensitivity of reproduction to maintain performance in warmer conditions. Whether elevated temperature affects reproduction may depend on the timing of exposure to warming and the sex of the parent exposed. We exposed male and female coral reef damselfish (Acanthochromis polyacanthus) during development, reproduction or both life stages to an elevated temperature (+1.5°C) consistent with projected ocean warming and measured reproductive output and newly hatched offspring performance relative to pairs reared in a present‐day control temperature. We found female development in elevated temperature increased the probability of breeding, but reproduction ceased if warming continued to the reproductive stage, irrespective of the male's developmental experience. Females that developed in warmer conditions, but reproduced in control conditions, also produced larger eggs and hatchlings with greater yolk reserves. By contrast, male development or pairs reproducing in higher temperature produced fewer and poorer quality offspring. Such changes may be due to alterations in sex hormones or an endocrine stress response. In nature, this could mean female fish developing during a marine heatwave may have enhanced reproduction and produce higher quality offspring compared with females developing in a year of usual thermal conditions. However, male development during a heatwave would likely result in reduced reproductive output. Furthermore, the lack of reproduction from an average increase in temperature could lead to population decline. Our results demonstrate how the timing of exposure differentially influences females and males and how this translates to effects on reproduction and population sustainability in a warming world.
Highlights
Reproduction is fundamental to sustaining viable populations
| 1153 or reproductive) of exposure to a 1.5°C increase in water temperature influenced fecundity and hatchling performance in a coral reef fish, and these impacts differed depending on the sex of the parent exposed
Developmental exposure to warming by females enhanced reproduction and offspring quality, whereas developmental exposure by males reduced reproductive output. When both sexes developed in warm water, we observed a combination of the effects for male and female development
Summary
Reproduction is fundamental to sustaining viable populations. Reproductive activities generally occur within a narrow subset of the organism's entire thermal range, due to the energetic costs and physiological optimization that reproduction requires (Pörtner et al, 2006; Van Der Kraak & Pankhurst, 1997; Visser, 2008). To accurately predict responses of organisms to climate change, we require a greater understanding of how warming impacts reproduction depending on the timing of exposure and the capacity for adjustment through phenotypic plasticity While both parents contribute to offspring phenotype, mothers are generally expected to be more important due to their ability to make nongenetic contributions via provisioning or the transfer of mitochondria (Ho & Burggren, 2010; Mousseau & Fox, 1998). We hypothesized that parental developmental exposure to elevated temperature would benefit reproductive and hatchling traits, but reproduction in elevated temperature alone would result in negative effects This is because A. polyacanthus appears to have limited capacity to adjust to warming as an adult in comparison with during development (Donelson et al, 2010, 2011; Rodgers et al, 2018; Spinks et al, 2019). We expected female developmental exposure to higher temperature would have the greatest influence on reproductive traits, because of her larger initial investment (i.e., eggs), but both sexes would have a similar influence on hatchling traits since this species exhibits joint parental care
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