Eusociality is not a major evolutionary transition, and why that matters

Nonacs, P.; Denton, K. K.

doi:10.1007/s00040-023-00942-3

Cited by 2 publications

(2 citation statements)

References 86 publications

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“…This may seem obvious, but it means that although we might expect queens to use their control over offspring morphology to impose worker behaviour at a lower threshold benefit/cost ratio than the threshold at which offspring themselves would work voluntarily, worker behaviour will not evolve unless the worker's own threshold has already been reached. Thus, contrary to some previous suggestions (Michener and Brothers, 1974;Alexander 1974;Craig, 1979;Kapheim et al, 2015;Nonacs and Denton 2023), maternal manipulation of offspring morphology cannot induce helping behaviour where it was not previously present: the origin of helping is instead constrained by the productivity threshold at which offspring themselves will choose to work voluntarily. We note that in Kapheim et al's (2015) model, daughters are assumed to respond to morphological manipulation by staying at their natal nests and helping more frequently i.e.…”

Section: Discussioncontrasting

confidence: 81%

“…In the previous section, we suggested that the worker caste is less likely to be lost as it becomes more specialised. We here consider more generally what evolutionary ‘irreversibility’ means in the context of eusociality (Boomsma and Gawne, 2018; see also Nonacs and Denton 2023). If reproductives are dependent on help from a worker caste to produce reproductive offspring – for example if the life cycle requires swarm founding – then that worker caste (morphologically specialised or otherwise) cannot be lost evolutionarily following a reduction in worker productivity, without resulting in extinction (Crespi and Yanega, 1995).…”

Section: Discussionmentioning

confidence: 99%

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The evolution of morphological castes under decoupled control

Flintham

Field

2023

Preprint

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The evolution of eusociality is regarded as a major evolutionary transition, where units that previously reproduced independently function as one complex entity. Advanced eusocial societies are characterised by morphologically differentiated castes and reduced conflict. We explore conditions under which morphological castes may arise and the factors constraining their evolution. Control over offspring morphology and behaviour may often be decoupled. Queens and provisioners can influence morphology directly, through the nutrition they provide, while offspring control their own behaviour as adults. Queens and provisioners may, however, influence worker behaviour indirectly, if offspring modify their behaviour in response to their morphology. Our results suggest that the evolution of a morphologically differentiated worker caste depends on the prior presence of a behavioural caste: specialist worker morphology will be mismatched with behaviour unless some offspring already choose to work. A mother's certainty about her offspring's behaviour should also be critical -less certainty results in greater mismatch. Decoupled control is important in maintaining a worker caste, and may result in reduced or no conflict between offspring and provisioners. We also show how worker productivity in the absence of a morphological trait can affect the likelihood of that trait being favoured by natural selection.

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Section: Discussioncontrasting

confidence: 81%

Section: Discussionmentioning

confidence: 99%

The evolution of morphological castes under decoupled control

Flintham

Field

2023

Preprint

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The evolution of morphological castes under decoupled control

Flintham,

Field

2024

Journal of Evolutionary Biology

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Eusociality, where units that previously reproduced independently function as one entity, is of major interest in evolutionary biology. Obligate eusociality is characterised by morphologically differentiated castes and reduced conflict. We explore conditions under which morphological castes may arise in the Hymenoptera and factors constraining their evolution. Control over offspring morphology and behaviour seem likely to be decoupled. Provisioners (queens and workers) can influence offspring morphology directly through the nutrition they provide, while adult offspring control their own behaviour. Provisioners may, however, influence worker behaviour indirectly if offspring modify their behaviour in response to their morphology. If manipulation underlies helping, we should not see helping evolve before specialised worker morphology, yet empirical observations suggest that behavioural castes precede morphological castes. We use evolutionary invasion analyses to show how the evolution of a morphologically differentiated worker caste depends on the prior presence of a behavioural caste: specialist worker morphology will be mismatched with behaviour unless some offspring already choose to work. A mother’s certainty about her offspring’s behaviour is also critical – less certainty results in greater mismatch. We show how baseline worker productivity can affect the likelihood of a morphological trait being favoured by natural selection. We then show how under a decoupled control scenario, morphologically differentiated castes should be less and less likely to be lost as they become more specialised. We also suggest that for eusociality to be evolutionarily irreversible, workers must be unable to functionally replace reproductives and reproductives must be unable to reproduce without help from workers.

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Eusociality is not a major evolutionary transition, and why that matters

Cited by 2 publications

References 86 publications

The evolution of morphological castes under decoupled control

The evolution of morphological castes under decoupled control

The evolution of morphological castes under decoupled control

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