Reproductive isolation among species of the genus Apis

Abstract

In the 1960s, research on reproductive isolation in honeybees started with the pioneering work on Apis cerana and A. mellifera of F. Ruttner. Since then, the number of recognised Apis species increased from four to nine, and data on reproductive isolation played a key role in this development. In this paper, we discuss the behavioural mating barriers (mating season, mating place, sexual signals, daily mating periods), copulatory barriers (size, genitalia, mating sign) and physiological barriers (sperm transfer, sperm storage) and postzygotic barriers (fertilisation, development, hybrids). Allopatric A. mellifera and allopatric populations of the other species had a uniform mating period during the afternoon hours. Sympatric honeybee species were separated mainly by different daily mating periods. The mating period differed between populations of the same species from different regions. The sequence of the mating periods, however, described from Sri Lanka, Thailand and Sabah (Borneo) followed the same pattern and showed a taxonomic and size correlation: the dwarf bees (A. andreniformis and/or Apis florea) occupied the first position shortly after noon. The next mating period was occupied by cavity-dwelling bees and at sunset, A. dorsata drones flew out for mating. In addition, in the honeybee species that have been studied, various non behavioural mating barriers have been demonstrated.