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.
In eusocial organisms, cooperative brood care within a colony represents a situation where the ancestral parental care duties have shifted away from the reproductive parent(s) towards their offspring. The shift to alloparental care was often instrumental in the initial emergence of eusociality, as it ultimately contributed to the establishment of the reproductive division of labour. Remarkably, eusocial taxa such as ants and termites, which still display an ancestral independent colony foundation phase, must go through an obligatory parental care period, as a temporary subsocial family unit. In termites specifically, an incipient colony inherently remains a woodroach family unit until alloparental care is established. Colony foundation success can then be limited by a series of factors that may include environmental, behavioural, symbiotic and physiological constraints. In this study, 450 incipient termite colonies ( Eusocial insect primary reproductive traits were optimized for three successive functions within the life cycle of a colony: alate dispersal (sexual reproduction), colony foundation (parental care) and colony growth (increased egg production towards colony maturity). However, results suggest that trade‐offs involving these functions appear to primarily favour dispersal ones (quantity vs. quality of alates), as founder(s) carry minimal resources and have no room for parental care inefficiency and as they then fully rely on their alloparents for further reproductive output. The transition towards alloparental care during colony foundation of eusocial insects may, therefore, reflect on the initial evolutionary transition from ancestral subsociality to eusociality.
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- PAR ID:
- 10443009
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Functional Ecology
- Volume:
- 36
- Issue:
- 12
- ISSN:
- 0269-8463
- Format(s):
- Medium: X Size: p. 3049-3059
- Size(s):
- p. 3049-3059
- Sponsoring Org:
- National Science Foundation
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