Reproduction in eusocial bees (Apidae: Apini, Meliponini)

This thesis presents some key aspects of the regulation and the mechanisms of colony reproduction in honeybees and stingless bees. Special attention is paid to key questions about how the production of males, gynes and swarms takes place, and what intranidal and extranidal factors are related to these processes. Firstly, the nest architecture and colonial characteristics were described and studied in three sympatric stingless bee species: Lisotrigona carpenteri, Trigona laeviceps and Trigona ventralis in Cucphuong forest, north Vietnam, with the first description of the nest of L. carpenteri (chapter 3). Secondly, the natural pattern of male production in Melipona favosa was investigated in Trinidad and Tobago (W.I.) and subsequently the relationship between emerging males and haploid eggs laid by laying workers was studied in the laboratory at Utrecht University. The laying workers of this species play an important role in the production of males that appears periodic (chapter 4). Thirdly, the regulation of reproductive processes such as the production of males and gynes were studies in Trigona ventralis in North Vietnam. This species produces sexuals and workers over the year although the number of sexuals was variable, depending on the availability of flowering to forage on. At the colony level, male production was periodic and occurred in distinct periods over the season. Different from the production of males, gynes were produced in low numbers. The behavioural repertoire of newly emerged gynes was described, with emphasis on the behavioural interactions between gynes and workers (chapter 5). Fourthly, in 20 colonies of Apis cerana, in northern Vietnam, observations on colony growth, on production of drones and queens, and on swarming and supersedure were related to available flowers to forage on and climatic data. In Apis cerana, the production of drones and virgin queens was restricted to two periods from March to July and from September to December. Positive correlations between available forage, colony growth and production of sexuals suggest that the synchronized production of drones and queens is defined by the forage flow into the colony. Production of reproductives is synchronized because foraging conditions are only part of the year sufficient to allow growth. Patterns in male and gyne rearing by A. cerana are similar to patterns found in Apis mellifera. Fifthly, similarities and differences in reproductive strategies between the honey bee and stingless bee species in the same habitat are compared and discussed to generalize collective evolutionary and adaptive significance in highly eusocial bees (chapter 7). Apis cerana is well adapted to exploit seasonal or temporal resources, because it responds quickly to changing environmental conditions while the stingless bees will in general flourish most in stable environments. However, some differences can be observed among sympatric stingless bee species. Species with large colonies like Trigona ventralis focus more on colony defence and growth of the colony itself. Species with small colonies like Lisotrigona carpenteri probably focus more on colonizing many new nest sites