Ovarian developmental variation in the primitively eusocial waspRopalidia marginatasuggests a gateway to worker ontogeny and the evolution of sociality

Abstract

SUMMARYSocial insects are characterized by reproductive caste differentiation of colony members into one or a small number of fertile queens and a large number of sterile workers. The evolutionary origin and maintenance of such sterile workers remains an enduring puzzle in insect sociobiology. Here, we studied ovarian development in over 600 freshly eclosed, isolated, virgin female Ropalidia marginata wasps, maintained in the laboratory. The wasps differed greatly both in the time taken to develop their ovaries and in the magnitude of ovarian development despite having similar access to resources. All females started with no ovarian development at day zero, and the percentage of individuals with at least one oocyte at any stage of development increased gradually across age, reached 100% at 100days and decreased slightly thereafter. Approximately 40% of the females failed to develop ovaries within the average ecological lifespan of the species. Age, body size and adult feeding rate, when considered together, were the most important factors governing ovarian development. We suggest that such flexibility and variation in the potential and timing of reproductive development may physiologically predispose females to accept worker roles and thus provide a gateway to worker ontogeny and the evolution of sociality.

Phylogenomic Evidence Overturns Current Conceptions of Social Evolution in Wasps (Vespidae)

“…The latter three differences are known to affect reproductive potential ( Cowan 1981 ; Markiewicz and O’Donnell 2001 ; Arrese and Soulages 2010 ; Tibbetts et al. 2011 ; Shukla et al. 2013 ; Tibbetts and Sheehan 2012 ).…”

Lipid content influences division of labour in a clonal ant

“…Judd et al, 2015;Lawson et al, 2017;Bernadou et al, 2018b). Workers hatching with high fat content may be more prone to initiate dominance interactions than leaner callows and may have a head start concerning reproduction (Shukla et al, 2013;Judd et al, 2015;Bernadou et al, 2018b). Different initial fat content might underlie the variation in reproductive performance among callows when placed into a new nest site together with older nestmates (A.B.…”

Reproductive status, endocrine physiology and chemical signaling in the Neotropical, swarm-founding eusocial wasp,Polybia micansDucke (Vespidae: Epiponini)

“…Eusocial insects within the order Hymenoptera (bees, wasps and ants) are characterized by the production of distinct phenotypes (caste polyphenism) in the female sex: the queen, the worker and often additional physiologically or morphologically specialized types within the worker caste (Wilson, 1971;Hunt, 2006;Hunt et al, 2007;Robinson, 2009;Tibbetts and Izzo, 2009;Shukla et al, 2013). In most caste-based societies the development of such specialized phenotypes is induced or at least biased in a pre-imaginal stage, where qualitative or quantitative differences in diet, pheromonal signals, mechanical stimuli or other environmental cues trigger endogenous signaling cascades toward alternative developmental trajectories (Wilson, 1971; Chavarría-Pizarro and West-Eberhard, 2010;Suryanarayanan et al, 2011;Hartfelder and Emlen, 2012;Penick and Liebig, 2012).…”