The ecology and evolution of male reproductive behaviour in the bees and wasps

Abstract

Males of aculeate Hymenoptera differ in the behavioural adaptations employed to locate and secure mates. The ecological and evolutionary bases of these differences are explored in this paper. Male bees and wasps search for females by patrolling widely within emergence-nesting areas or within patches of flowers attractive to conspecific females, or by waiting at landmarks, at specific emergence sites, or at nests. Nest dispersion, flower distribution, the type of female mating system and the nature of male-male competition appear to be key factors in determining the mate-locating behaviour of'males. Of special interest in multiple-mating by females, which may be an evolutionary response to the costs of attempting to resist copulation in certain situations. When polyandry occurs, males are under selection pressure to be the last male to copulate with a female prior to oviposition if sperm precedence occurs. In species in which females mate just once, a selective premium is placed on being the first male to reach a virgin female. In either case, because receptive females are a limited resource, there is intense competition among males for access to the resource. The density of competitor males may play an important role in determining whether holding a relatively restricted territory is preferable to the strategy of patrolling widely at various sites which may have females. Territoriality is practiced by males of several species of aculeate Hymenoptera when the number of male competitors is relatively few in number and the distribution of emergence sites or foraging areas of females is clumped in space.

The pollination potential of free-foraging bumblebee (Bombus spp.) males (Hymenoptera: Apidae)

“…Indeed, the learning capacity of honeybee (A. mellifera) drones (Benatar, et al 1995) was shown to be similar to that of workers despite drones, being fed by workers in the colony, are not foraging on flowers. Alcock, et al (1978) pointed out, males of several Apoidea species are attracted by flowers that are also highly attractive to females (including gynes) and visits to particular flowers may enhance their chances to encounter a mate by visiting these flowers. However, with an elaborate and costly pre-mating behaviour in form of patrolling (Alcock, et al 1978;Eickwort and Ginsberg 1980) it is unlikely that flowers are chosen to increase queen encounter rates.…”

“…Males, in contrast, visit flowers only for their own energy demands and typically spend most of the day patrolling (Svensson 1979;Goulson 2003). They preferentially forage early in the morning and late in the afternoon (Svensson 1979;Alcock, et al 1978;Eickwort and Ginsberg 1980), which may result in fewer flower visits per day than for foragers. Nevertheless, a mean of over 10,000 pollen grains per individual male should be sufficient to facilitate pollination in most plants.…”

“…In contrast to the vast number of studies conducted on foraging behaviour of bumblebee workers (Heinrich 1976;Pyke 1978;Cartar and Dill 1990;Chittka, et al 1997;Goulson, et al 1997;Osborne, et al 2008;Wolf and Moritz 2008), male bumblebees have been addressed only rarely in this context. Although the patrolling behaviour of bumblebee males was already recognized by Darwin (1886), studies on males focus almost exclusively on reproductive physiology (Alcock, et al 1978;Eickwort and Ginsberg 1980;Duvoisin, et al 1999) with few exceptions addressing foraging and flower visitation (Ranta and Lundberg 1981;Bertsch 1984;Ostervik, et al 2010). Indeed, apart from recent work on two species of orchid (Ophrys normanii and Ophrys chestermanii), which are pollinated by males of the cuckoo-bumblebee Bombus (Psithyrus) vestalis (Gögler, et al 2009) and insightful lab-experiments on male Bombus impatiens (Ostervik, et al 2010), we are not aware of any report on the potential impact of free-flying bumblebee males on pollination.…”

“…While establishing and monitoring their patrol routes to attract receptive queens (Darwin 1886;Haas 1949;Svensson 1979;Alcock, et al 1978;Eickwort and Ginsberg 1980;Bergman and Bergström 1996;Ayasse, et al 2001), the males also need to visit flowers to fuel this energetically expensive behaviour (Svensson 1979). Pollen deposited on the males' body while foraging on a flower may be transferred to the next flower visited on the foraging bout.…”

Pre-copulatory courtship behavior in a solitary bee, Nomia triangulifera Vachal (Hymenoptera: Halictidae)

“…Most studies to date have reported little or no pre-copulatory courtship behavior among bees (eg Batra, 1966;Barrows, 1975;Alcock et al, 1978;Triplett and Gittins, 1988;. Nomia (Epinomia) triangulifera Vachal, reported on here, seems unusual because of its extremely complex pre-copulatory courtship behavior, combined with structural modifications.…”