Seasonal changes in reproduction have been described for many taxa. As reproductive seasons progress, females often shift from greater energetic investment in many small offspring towards investing less total energy into fewer, better provisioned (i.e. larger) offspring. The underlying causes of this pattern have not been assessed in many systems. Two primary hypotheses have been proposed to explain these patterns. The first is an adaptive hypothesis from life‐history theory: early offspring have a survival advantage over those produced later. Accordingly, selection favours females that invest in offspring quantity early in the season and offspring quality later. The second hypothesis suggests these patterns are not intrinsic but result from passive responses to seasonal changes in the environment experienced by reproducing females (i.e. maternal environment). To disentangle the causes underlying this pattern, which has been reported in brown anole lizards ( In the laboratory, females increased relative effort per offspring as the reproductive season progressed; smaller eggs were laid earlier, larger eggs were laid later. Moreover, we observed significant among‐individual variation in seasonal changes in reproduction, which is necessary for traits to evolve via natural selection. Because these patterns consistently emerge under controlled laboratory conditions, they likely represent an intrinsic and potentially adaptive adjustment of reproductive effort as predicted by life‐history theory. The field study revealed similar trends, further suggesting that intrinsic patterns observed in the laboratory are strong enough to persist despite the environmental variability that characterizes natural habitats. The observed patterns are indicative of an adaptive seasonal shift in parental investment in response to a deteriorating offspring environment: allocating greater resources to late‐produced offspring likely enhances maternal fitness.
Reproduction involves considerable reorganization in an organism's physiology that incurs potential toxicity for cells (e.g., oxidative stress) and decrease in fitness. This framework has been the cornerstone of the so‐called ‘oxidative cost of reproduction’, a theory that remains controversial and relatively overlooked in non‐model ectotherms. Here, we used two complementary approaches in natural and controlled conditions to test whether altered access to climate conditions (water and temperature resources) alters oxidative status and mediates reproductive trade‐offs in viviparous populations of the common lizard ( First, we examined whether access to free‐standing water and differences in ambient temperature across 12 natural populations could be related to variation in oxidative status, reproductive effort and reproductive success. Second, we determined whether an experimental restriction to water triggers higher oxidative cost of reproduction and correlates with fitness measures (reproductive success, future survival rate and probability of future reproduction). Pregnant females exhibited higher sensitivity than males to natural or experimental limitations in temperature and water access. That is, in restricted environments, pregnant females with higher reproductive effort exhibited stronger oxidative damage despite enhanced non‐enzymatic antioxidant capacity. Enhanced antioxidant defensive capacity in pregnant females was positively correlated with higher reproductive success, whereas elevated oxidative damage negatively correlated with offspring annual survival. Altogether, our results revealed a context‐dependent oxidative cost of reproduction that was concomitant with a conflict in water demand from offspring. These new insights should be critical for understanding ectotherm responses to heat waves and summer droughts that are increasing in frequency and duration.
A free
- NSF-PAR ID:
- 10458869
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Functional Ecology
- Volume:
- 34
- Issue:
- 2
- ISSN:
- 0269-8463
- Page Range / eLocation ID:
- p. 475-485
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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A free
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