A scientific note on levels of polyandry of 2 queens of the Himalayan giant honeybee, Apis laboriosa

Abstract

Honeybee queens mate with more males and have the lowest coefficient of genetic relatedness among workers among all eusocial Hymenoptera (Tarpy and Nielsen, 2002). In particular, the recently discovered Asian cavity-nesting honeybee Apis nigrocincta F. Smith exhibits the highest degree of polyandry in the genus Apis L. (Palmer et al., 2001). The evolution of multiple mating by honeybee queens is central to the issue of kin selection and social evolution in the Hymenoptera. Therefore, much attention has been paid to the evolution and maintenance of multiple mating in the genus Apis in concentration with kin selection or gene diversity, for which several hypotheses have been proposed (Palmer and Oldroyd, 2000). The Himalayan giant honeybee A. laboriosa F. Smith is found in the mountainous regions of Vietnam, Bhutan, China India and Nepal. The first specimen of A. laboriosa was reported in Yunnan, China. More recently, Sakagami et al. (1980) reported that A. laboriosa shows many morphological differences from A. dorsata Fabricius. Furthermore, Underwood (1986) was the first to report on certain behaviors of A. laboriosa. Specifically, he reports that this species constructs a large single comb in an open space in high cliffs at altitudes ranging from 1200 to 3600 m, makes a seasonal migration depending on the availability of nectar and pollen resources, and tends to colonize one site in a reproductive season. However, the comparative levels of polyandry in giant honeybee colonies are unknown within the genus Apis. In the present study, we used microsatellite DNA analysis to estimate queen mating frequency and the genetic relatedness among workers of two colonies of the Himalayan giant honeybee A. laboriosa. In June of 1999, two colonies of A. laboriosa were collected by local honey hunters of Rai tribe in Sadhi Village, Nepal. These colonies had nested in the same cliff site. We were unable to obtain the queen of either colony, but we collected from 45 to 53 worker pupae from each, and these were stored at 99% ethanol until DNA extraction. We chose to sample pupae in order to avoid the problem of drifted individuals which may contaminate the result. Microsatellite DNA analysis was conducted using 4 primers designed by Estoup et al. (1994), A14, A88, A107 and B124. The levels of polyandry were calculated according to Oldroyd et al. (1996). Genotype frequency was observed at the selected four microsatellite loci with 4, 5, 3 and 5 alleles at loci A14, A88, A107 and B124, respectively. The results are given in Table I. The queen of Colony 1 was found to have mated with 23 drones and the queen of Colony 2 with 21. The number of effective matings revealed 22.12 in the Colony 1, and 17.01 in Colony 2. The genetic relatedness of nestmate workers were 0.272 in Colony 1 and 0.278 in Colony 2. Our study demonstrates that queens of two A. laboriosa colonies mate 20 times, a similar level of polyandry to that found in A. dorsata (Moritz et al., 1995; Oldroyd et al., 1996). However, the level of polyandry of A. mellifera carnica queens ranged from 6 to 24 patrilines within species (Neumann et al., 1999; Tarpy and Nielsen, 2002). It is possible that the mating frequency of A. laboriosa queens has an equally large range, but more colonies need to be analyzed to estimate more precisely the levels of polyandry in A. laboriosa.