The Fecundity-Longevity Trade-Off in a Clonal Eusocial Insect: In Isolation, Subordinate Workers Match Dominants in Reproduction.

AbstractReproductive division of labor (DOL) is key to the ecological success of eusocial insects such as ants, termites, and honeybees, in which queens reproduce while workers perform nonreproductive tasks. DOL is often associated with a shift in the fecundity-longevity trade-off, with queens outliving nonreproductive workers. In most species, reproductive and nonreproductive individuals differ significantly (e.g., in ontogeny or morphology), which may contribute to this phenomenon. In contrast, in the ant Platythyrea punctata, females are clonally identical, and socially dominant workers produce female offspring from unfertilized eggs by thelytokous parthenogenesis. We investigated whether all workers-that is, dominants and subordinates-reproduce when given the opportunity. We formed dyads of workers of the same age and allowed them to establish rank orders. We then investigated their reproductive performance in isolation. We found that nearly 88% of workers regardless of social rank activated their ovaries in isolation. However, of the 12% that never laid eggs, a higher proportion were previously classified as subordinates than as dominants. This suggests that reproductive ability may differ among workers. Isolated subordinates that were reproductively active matched isolated dominants in their egg-laying rate, with no apparent trade-off between fecundity and longevity. Reproductive costs, likely related to the use of physiological or energetic resources, were evident for both workers in isolation, as egg-laying rates declined over time in the absence of supportive workers. These results highlight the complex interplay between reproduction, longevity, and social status in eusocial insects and provide insights into how eusociality has shaped aging and life history evolution.