Apis dorsata


Apis dorsata, the rock bee or giant honey bee, is a honey bee of South and Southeast Asia. They are typically around long and nests are mainly built in exposed places far off the ground, like on tree limbs, under cliff overhangs, and under buildings. These social bees are known for their aggressive defense strategies and vicious behavior when disturbed. Though the species is not domesticated, indigenous peoples have traditionally used it as a source of honey and beeswax, a practice known as honey hunting.

Taxonomy and phylogeny

Apis dorsata belongs to the subgenus Megapis in the family Apidae. This honeybee is most closely related to A. mellifera, A. cerana, and A. florea. There are a few hypotheses as to when A. dorsata diverged from A. florea and A. cerana, as it is unclear which divergence occurred first. Currently, the consensus hypothesis provides a family tree that claims that A. dorsata diverged from both A. cerana and A. florea at the same time.

Subspecies

identifies the following subspecies:
Recent research has removed laboriosa from inclusion within A. dorsata, as a separate species, with supporting evidence including a significant region of sympatry. A. laboriosa is hardly distinct morphologically from the nominate subspecies of dorsata but has different housekeeping and swarming behavior, allowing it to survive at high altitudes. In addition, little gene flow has occurred between A. dorsata and A. laboriosa for millions of years; accordingly, some authors have previously classified it as a distinct species.
Likewise, the southeastern taxon A. d. binghami seems also to be potentially distinct. The limits of their ranges in Indochina and the possible distinctness of the geographically distant Philippines population require more study. However, the use of the taxonomic rank of "subspecies" is typical for geographically discrete populations, so the difference in opinion here is whether to recognize the rank of subspecies or not.

Description

Nests

A. dorsata differs from the other bees in its genus in nest design. Each colony consists of a single vertical comb made of workers' wax suspended from above, and the comb is typically covered by a dense mass of bees in several layers. The nests vary in size, reaching up to 1 meter. Each cell within the comb is hexagonal in shape. A. dorsata store their honey in an upper corner of the nest. The same size and type of cells are used to rear larvae. Nests are constructed in the open and in elevated locations, such as on urban buildings or tall trees. These bees rarely build nests on old or weak buildings for safety concerns. A. dorsata can form dense aggregations at one nesting site, sometimes with up to 200 colonies in one tree.
Each colony can have up to 100,000 bees and is separated by only a few centimeters from the other colonies in an aggregation. Some colonies also exhibit patterns of nest recognition, in which they return to the same nesting sites after migration.

Distribution and habitat

A. dorsata is found from the Indian subcontinent to Southeast Asia. The greatest populations of A. dorsata are found in China, Malaysia, Indonesia, India, Pakistan, and Sri Lanka. In the Philippines, which used to have one of the greatest populations of A. dorsata, the populations have now become relatively rare due to deforestation and people's "mindsets" towards the bees. They mostly reside in tall trees in dense forests, but also build nests on urban buildings. These bees are tropical and in most places, they migrate seasonally. Individual colonies migrate between nesting sites during the transition from the rainy to dry seasons and occupy each nesting site for about 3–4 months at a time. Some recent evidence indicates these bees return to the same nest site, though most, if not all, of the original workers might be replaced in the process because workers usually live for less than two months. Furthermore, these bees build small combs that serve as temporary nests during their long migrations.
In Bornean rainforests, A. koschevnikovi and A. dorsata are the only honeybees that appear frequently at flowering canopy trees or baits. Even though they share most of the same rain forest habitat, they are still able to coexist. Their difference in size and tongue length help separate their resource use.

Colony cycle

Colony initiation

There are two methods of reproductive swarming in which A. dorsata initiates new colonies, which usually occurs in October or November. The most common occurs when a queen flies away from the original nest slowly and a swarm of workers follows her. This new cluster of bees can be temporary, or they can permanently move to a new nesting site. The distance these bees travel is unknown, but some have been observed to travel about 500 meters away from the original nest. The second, rarer method is referred to as "budding." In budding, a group of workers leave the natal nest to form a new colony at a nesting site about 1 meter away from the original.
A non-reproductive method of colony initiation is absconding. Absconding refers to when an entire colony moves to a new location. As a colony is formed, multiple curtains, essentially layers, of bees are formed around the developing nest. Colony initiation is related to the migratory patterns of these bees.

Colony migration and decline

As a colony is initiated, the migration depends on foraging resources and predation risks. These bees travel to different sites depending on the blooming season of flowers. There are about 100,000 members in each colony and each colony resides in one nesting site for about 3–4 months at a time. Colonies tend to decline when resources, such as food, honey, and pollen, are depleted. Colonies decline during the rainy and summer seasons because of the instability of foraging sources due to climate change.

Behavior

Mating

Drones and the queen fly away from the nest and mate on the wing. This is called nuptial flight. The drone flights are shorter than those of other Asian honeybee species. A. dorsata flights occur around dusk for 13 minutes on average. A. dorsata exhibit high degrees of polyandry, with many drones mating with the queen. In fact, A. d. fabricius has the highest levels of polyandry among all social insects. This may be attributed to the short duration of flight times for mating. During mating, the drones fly to drone congregation areas. Because there is more genetic relatedness within aggregations and because of the short duration and distance traveled during the mating flight, each aggregation is believed to have its own drone congregation area.

Communication

A. dorsata utilizes what is known as a dance language, also known as waggle dance, to communicate the location of food sources to other bees in the colony. The dance language indicates the distance, profitability, and direction of the food source. These social bees dance in the open and their dances produce sound signals of high intensity in the air. The orientation of the dancer's body points in the direction of the food source and the frequency of the sound indicates the profitability of the food source. A. dorsata produces silent dances, which usually involve visual cues during the day. They additionally produce sound with their dances in the nighttime, as they are the only bees of its genus that exhibit nocturnal foraging activity. Furthermore, there is some evidence that A. dorsata dances for migration purposes as well. Bees that have returned from the new nesting site perform dances that alert the colony of information such as the direction of the new nesting site.

Foraging

A. dorsata foragers can travel farther than A. cerana and A. florea, which travel to a maximum of 500 meters; however, 72% of observed A. dorsata foragers traveled no more than 400 meters.

Kin selection

Worker policing

Unlike the rearing patterns of other species of the genus Apis, the worker and drone brood of A. dorsata are dispersed across in the same area and even share cells, and are not differentiated in separate locations of the nest. It would seem that worker policing makes mistakes often in correctly removing the drone brood since the drone brood are interspersed with worker brood, but every male raised comes from a queen-laid egg. Thus worker policing does indeed work within populations of these bees. Worker policing typically occurs through "egg-eating" or oophagy, but in the case of these bees, worker policing is directed at workers with ovaries since oophagy is hard to achieve, as worker-laid and queen-laid eggs are nearly identical in shape and size.

Genetic relatedness within and between aggregations

Since A. dorsata is known for its highly polyandrous activity, these bees exhibit a large number of colonies in close proximity to each other. Although the colonies within an aggregation are near each other, these colonies are not closely related. The queens of the colonies in an aggregation are not closely related, but the aggregation itself is more genetically linked than is expected by chance. Higher than expected genetic links may exist among colonies because they migrate together during their long distance migratory routes to the same nesting sites in the new location. This may also be attributed to short distance reproductive swarming methods and brief mating periods as well. Since it has been observed that rarely any queen-daughter relationships exist within aggregations, the "budding" hypothesis of colony initiation rarely occurs. Due to their long distance migratory patterns, the bees cause enough gene flow to occur between the colonies of different aggregations. There is distinct genetic differentiation between aggregations. In turn, the genetic relatedness between colonies within a single aggregation decreases.