Peter Neumann

Global invasions of the western honeybee (Apis mellifera) and the consequences for biodiversity

ABSTRACT The western honeybee, Apis mellifera, has been globally transported for honey production and pollination for hundreds of years and is often kept in large numbers in beekeeping operations. Concern has been expressed that it might act as an invasive species with large impact on biodiversity. However, although the honeybee has spread into the wild and has established feral populations in Australia and the Americas, the extent to which introduced honeybees alter biodiversity remains controversial. Here we focus on the best documented cases of A. mellifera invasions and discuss the effects on biodiversity under three different conditions: 1) regions where other subspecies of A. mellifera are endemic (Europe, Africa, and western Asia), 2) regions where A. mellifera is not endemic, but other species of Apis naturally occur (central and eastern Asia), 3) regions where Apis species are not endemic (America, Australia). Although some studies show an impact on native bee survival, fecundity, or population density in response to large A. mellifera aggregations (e.g., on apiaries), there are no reports that feral honeybees caused the extinction of native bee pollinators, which are the most likely competing group of organisms. Honeybee introductions have had or still may have negative effects only within the genus Apis, primarily interfering with beekeeping activities. Although honeybee invasions seem to have had little if any effect on biodiversity of native pollinators so far, we nevertheless caution against transporting honeybees around the globe, and we particularly advise against importing foreign Apis species into tropical ecosystems.

Behavioural basis for social parasitism of Cape honeybees (Apis mellifera capensis)

Cape honeybee workers show important pre-adaptations for social parasitism and can cause the dwindling colony syndrome of host colonies. Parasitic workers may drift or actively dis- perse into host colonies. They may also join absconding swarms, which can merge with host colonies. After transmission, parasitic workers have to establish themselves in the host, which is probably pro- moted by their spatial distribution, their readiness to gain trophallactic dominance and their ability to survive worker-worker aggression. Established parasitic workers have to evade egg removal by other workers in host colonies. The resulting offspring is preferentially fed, can be expected to be highly virulent and may show different behaviour in the course of infestation. It is unknown why and how the host queen is lost. High numbers of parasitic workers are reared until the host colony dies or absconds. This offspring can infest new host colonies, thereby completing the social parasitic life cycle. Apis mellifera capensis / Apis mellifera scutellata / honeybee / social parasitism / worker repro- duction

Social encapsulation of beetle parasites by Cape honeybee colonies (Apis mellifera capensis Esch.)

Worker honeybees (Apis mellifera capensis) encapsulate the small hive beetle (Aethina tumida), a nest parasite, in propolis (tree resin collected by the bees). The encapsulation process lasts 1–4 days and the bees have a sophisticated guarding strategy for limiting the escape of beetles during encapsulation. Some encapsulated beetles died (4.9%) and a few escaped (1.6%). Encapsulation has probably evolved because the small hive beetle cannot easily be killed by the bees due to its hard exoskeleton and defensive behaviour.

Rare royal families in honeybees, Apis mellifera

The queen is the dominant female in the honeybee colony, Apis mellifera, and controls reproduction. Queen larvae are selected by the workers and are fed a special diet (royal jelly), which determines caste. Because queens mate with many males a large number of subfamilies coexist in the colony. As a consequence, there is a considerable potential for conflict among the subfamilies over queen rearing. Here we show that honeybee queens are not reared at random but are preferentially reared from rare “royal” subfamilies, which have extremely low frequencies in the colonys worker force but a high frequency in the queens reared.

Social parasitism by Cape honeybee workers in colonies of their own subspecies (Apis mellifera capensis Esch.)

Abstract.Social parasitism is widespread in the eusocial insects. Although social parasites often show a reduced worker caste, unmated workers can also parasitize colonies. Cape honeybee workers, Apis mellifera capensis, can establish themselves as social parasites in host colonies of other honeybee subspecies. However, it is unknown whether social parasitism by laying workers also occurs among Cape honeybee colonies. In order to address this question we genotyped worker offspring of six queenless A. m. capensis colonies and determined the maternity of the reproducing workers. We found that three non-nestmate workers dominated reproduction in a host colony and produced 62.5% of the progeny. Our results show that social parasitism by laying workers is a naturally occurring part of the biology of Cape honeybees. However, such social parasitism is not frequently found (6.41% of the total worker offspring) probably due to co-evolutionary processes among A. m. capensis resulting in an equilibrium between selection for reproductive dominance in workers, colony maintenance and queen adaptation.

Genetic variance of mating frequency in the honeybee (Apis mellifera L.)

Summary.The genetic variance of queen mating frequency was studied in honeybees (Apis mellifera carnica). Worker offspring (N = 966) of 28 naturally mated half sister-queens (r = 0.25) from seven unrelated breeding lines were genotyped at four DNA microsatellites. The mating frequencies of the queens were derived from the offspring genotypes. The number of observed matings per queen ranged from 10 to 28 with an average of 17.32 ± 1.10 (number of estimated matings: 24.94 ± 2.51; number of effective matings: 20.09 ± 1.73). Half-sib analyses of the breeding lines were used to estimate heritability. Heritability was h2 = 0.449 ± 0.135 for the estimated number of matings and h2 = 0.262 ± 0.103 for the number of effective males, which are both significantly different from zero. We conclude that a high genetic variance for polyandry in honeybees can be favored by balanced selection between individual queen and colony level.

Queen mating frequency in different types of honey bee mating apiaries

SUMMARYSamples of worker honey bees (Apis mellifera carnica) were taken from 29 queenright honey bee colonies. The queens of these colonies were mated at two island mating apiaries (n = 7 and n = 6), two lowland apiaries (n = 6 and n = 4), a highland mating apiary (n = 3) and on one isolated high-mountain apiary (n = 3). Genotypes of individual workers (n = 1055) were determined using four DNA microsatellite loci and the observed (no) and effective (me) numbers of matings were estimated from the worker offspring. The observed number of matings per queen ranged from 6 to 24 (me = 4.6 to 31.1). Significant differences (P < 0.05) were found between the number of matings of queens at island and mainland mating apiaries. An average of no = 13.0 ± 1.1 (me = 11.8 ± 1.2) matings for queens at the two islands and an average of no = 18.1 ± 1.1 (me = 20.4 ± 1.7) for queens at the mainland apiaries were observed. No differences in mating frequency were observed between the queens at the island locations and among the...

Laboratory rearing of small hive beetles Aethina tumida (Coleoptera, Nitidulidae)

The small hive beetle (Aethina tumida, SHB) is a common honey bee (Apis mellifera) parasite in Africa that causes little damage to strong colonies (Lundie, 1940). However, it is a serious threat in the Western Hemisphere where the beetle has been introduced recently (Elzen et al., 1999) and where host colonies lack the behavioural resistance mechanisms of African honey bees (Neumann et al., 2001). Captive breeding of this parasite is an important research technique to produce SHB under controlled conditions for experiments. Here we report on a simple technique for rearing SHB in the laboratory.

Mass production of small hive beetles (Aethina tumida, Coleoptera: Nitidulidae)

bee parasite, has recently become an invasive species causing problems for local apiculture in its new ranges (Neumann & Elzen, 2004). Captive breeding of SHB is an important research method to produce the beetles under controlled conditions for experiments. In particular during field work many SHB must be reared without sophisticated equipment in short periods of time at a low cost. Schmolke (1974) and Neumann et al. (2001) previously described captive breeding of relatively small numbers of SHB using rather elaborate techniques. Here we report on an improved and highly economical technique for the mass production of SHB.

Home-site fidelity in migratory honeybees.

Home-site fidelity is well known in migratory animals, but not in social insects. Here we show that colonies of the giant honeybee Apis dorsata are able to find the same nest location even after seasonal migration. As worker bees do not have first-hand knowledge of the old nest site, the swarms must be guided by some form of genetic mechanism.