Juvenile hormone, reproduction, and worker behavior in the neotropical social waspPolistes canadensis

Abstract

Previous studies of the division of labor in colonies of eusocial Hymenoptera (wasps and bees) have led to two hypotheses regarding the evolution of juvenile hormone (JH) involvement. The novel-or single-function hypothesis proposes that the role of JH has changed from an exclusively reproductive function in primitively eusocial species (those lacking morphologically distinct queen and worker castes), to an exclusively behavioral function in highly eusocial societies (those containing morphologically distinct castes). In contrast, the split-function hypothesis proposes that JH originally functioned in the regulation of both reproduction and behavior in ancestral solitary species. Then, when reproductive and brood-care tasks came to be divided between queens and workers, the effects of JH were divided as well, with JH involved in regulation of reproductive maturation of egg-laying queens, and behavioral maturation, manifested as age-correlated changes in worker tasks, of workers. We report experiments designed to test these hypotheses. After documenting age-correlated changes in worker behavior (age polyethism) in the neotropical primitively eusocial wasp Polistes canadensis, we demonstrate that experimental application of the JH analog methoprene accelerates the onset of guarding behavior, an age-correlated task, and increases the number of foraging females; and we demonstrate that JH titers correlate with both ovarian development of queens and task differentiation in workers, as predicted by the split-function hypothesis. These findings support a view of social insect evolution that sees the contrasting worker and queen phenotypes as derived via decoupling of reproductive and brood-care components of the ancestral solitary reproductive physiology.behavioral development ͉ division of labor ͉ methoprene ͉ worker polyethism

Aversive conditioning in honey bees (Apis mellifera anatolica): a comparison of drones and workers

“…Dopamine levels in honey bees have been shown to influence associative (punishment) learning (Vergoz et al, 2007;Agarwal et al, 2011). Juvenile hormone in both males and females has been shown to work as a regulator of behavioral development (Robinson et al, 1989;Fahrbach et al, 1995;Giray and Robinson, 1996;Giray et al, 1999;Giray et al, 2005). These results suggest that the transition to more complex tasks that require learning coincides with broad expansions of neural tissue in the MB.…”

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

“…Against the background of previous studies on hormone titer and function in wasps (Röseler, 1991;O'Donnell and Jeanne, 1993;Giray et al, 2005;Tibbetts et al, 2011b), our results on the endocrine physiology of a swarm-founding epiponine species show that the endocrinology of social wasps has undergone extensive remodeling. The low JH titer of queens and developing queens in P. micans suggests that JH is not a key driver of reproduction or competition, in stark contrast to the situation in Polistes wasps (Strambi, 1990;Röseler, 1991;Tibbetts et al, 2011b).…”

“…queen), but if she disappears, former workers fighting to inherit the nest show increased JH levels . Finally, as in other hymenopteran societies (O'Donnell and Jeanne, 1993;Robinson and Vargo, 1997;Lengyel et al, 2007;Penick et al, 2011;Dolezal et al, 2012), JH appears to modulate age-related changes in worker activity, a function that is condition and context dependent in adults of Polistes (West-Eberhard, 1996;Giray et al, 2005;Shorter and Tibbetts, 2009). …”

Support for the reproductive ground plan hypothesis in a solitary bee: links between sucrose response and reproductive status

“…JH is involved in many aspects of reproductive and behavioural division of labour in eusocial bees and ants [83,84], and thus plays a key role in the major hypotheses for how these features of social life evolve [26,85,86]. Despite this, the relationship between JH, behaviour and reproductive development is virtually unknown in solitary bees (but see [44]), and inferences about how these functions have changed over the course of social evolution have necessarily been based on comparisons to distantly related insect species with life histories that do not closely resemble those of the solitary insects that gave rise to eusociality [26,83].…”