1. In eusocial organisms, cooperative brood care within a colony represents a situation where the ancestral parental care duties have shifted away from the reproductive parent(s) towards their own offspring. The shift to alloparental care was often instrumental in the initial emergence of eusociality, as it ultimately contributed to the establishment of reproductive division of labor.
2. Remarkably, eusocial taxa such as ants and termites, which still display an ancestral independent colony foundation phase, must go through an obligatory parental care period, as a temporary subsocial family unit. In termites specifically, an incipient colony inherently remains a woodroach family unit until alloparental care is established. Colony foundation success can then be limited by a series of factors that may include environmental, behavioral, symbiotic, and physiological constraints.
3. In this study, 450 incipient termite colonies (Coptotermes gestroi) were established to investigate the timing of physiological changes in founders during the transition from biparental to alloparental care. Results showed that the finite initial internal nutritional resources that alates carry during the dispersal flight are a primary limiting factor for successful colony establishment. The Coptotermes queen and king must rapidly establish (< 150 d) their first cohort of offspring to reach alloparental care or simply run out of resources and die. Alates, therefore, carry just enough internal resources to produce the first few alloparents (< 15 workers) to prime the system toward colony ergonomic growth, with a definitive shift to solely reproductive functions.
4. Eusocial insect primary reproductive traits were optimized for three successive functions within the life cycle of a colony: alate dispersal (sexual reproduction), colony foundation (parental care), and colony growth (increased egg production toward colony maturity). However, results suggest that trade-offs involving these functions appear to primarily favor dispersal ones (quantity vs. quality of alates), as founder(s) carry minimal resources and have no room for parental care inefficiency, and as they then fully rely on their alloparents for further reproductive output.

The transition toward alloparental care during colony foundation of eusocial insects may therefore reflect on the initial evolutionary transition from ancestral subsociality to eusociality.

See M&M in original article.

Excel file for raw data, and PDF for R analysis output and supplementary figure SF1