International Union for the Study of Social Insects (IUSSI2018), August 5-10, 2018 in Guarujá, Brazil.

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Caste plasticity in a social wasp

Author(s):
Benjamin Aaron Taylor, Benjamin Aaron Taylor , Alessandro Cini , Max Reuter , Seirian Sumner
Institution(s):
Department of Genetics, Evolution and Environment, University College London, London, United Kingdom; Department of Genetics, Evolution and Environment, University College London, London, United Kingdom ; Department of Genetics, Evolution and Environment, University College London, London, United Kingdom; Dipartimento di Biologia, Università degli Studi di Firenze, Florence, Italy ; Department of Genetics, Evolution and Environment, University College London, London, United Kingdom ; Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
Social insect castes represent an extreme form of division of reproductive labour. The presence of specialised castes that are irreversibly determined during development greatly reduces the capacity for within-group conflict . This conflict reduction has facilitated the repeated evolution of highly derived ‘superorganismal’ traits in social insect taxa. Studying the mechanisms by which caste plasticity has been lost over evolutionary time is thus a key component to understanding the major evolutionary transition to eusociality. Simple eusocial insect societies, such as those of Polistes paper wasps, may be representative of an early stage in the transition from reproductively flexible cooperative breeding to caste-based eusociality. Dominant Polistes ‘queens’ and subordinate ‘workers’ are behaviourally distinct, resulting in an extreme division of reproductive labour within a colony. Individuals nonetheless retain caste plasticity such that a subordinate can assume a dominant position should the opportunity arise. This provides an excellent model for determining the mechanisms of caste plasticity at the transition to eusociality. Here we combine detailed behavioural, morphological and genomic data to dissect the process of ‘caste switching’ in the European paper wasp Polistes dominula in order to reveal the mechanisms of caste plasticity. We show that shifts in behaviour and reproductive development are not necessarily coupled. We also identify genes differentially expressed before, during and after the transition from subordinate to dominant, and use these to infer the cascade of molecular mechanisms that shape the shift of investment from indirect to direct fitness. We discuss our findings in the context of molecular and behavioural reprogramming. This study provides novel insights into the proximate basis of a phenotypically plastic trait that plays a key role in a major transition in evolution.
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