Genetic Diversity in Apis cerana*

by L R Verma

The genetic diversity of Apis mellifera has been organised into 24 subspecies having varied economic usefulness. These subspecies are adapted to wide range of ecological conditions and range from 0° at the equator to latitudes as great as 50°N and 30°S.

So far only four subspecies of Apis cerana are recognised, although there may be several more because of its wide range of geographical distribution.

One research group in the International Centre for Integrated Mountain Development (ICIMOD) has successfully identified genetic variance in morphological characters of Apis cerana subspecies in the Himalayan region. These subspecies are named Apis cerana cerana, Apis cerana himalaya, and Apis cerana indica. According to bee scientists in China, five different subspecies of Apis cerana representing different eco-geographic zones have been identified These include Apis cerana cerana, Apis cerana skorikovi, Apis cerana abaensis, Apis cerana hainanensis and Apis cerana indica.

Each subspecies has further locally adapted populations called ecotypes which differ from each other in several biological and economic characters. For example, we have successfully identified three ecotypes of subspecies Apis cerana himalaya that correspond to geographic distribution in 1) the Naga and Mizo Hills, 2) Brahmaputra Valley and Khasi Hills, and 3) the foothills of the north-east Himalayas. On similar lines, Chinese bee scientists have also classified Apis cerana cerana into five ecotypes namely, Guangdong-Guanxi type, Hunan type, Yunan type, North China type and Changbaishan type. In some parts of the Hindu Kush Himalaya, Apis cerana cerana matches the European hive bee Apis mellifera in commercial value and has spectacular potential for further genetic improvement.

STOCK IMPROVEMENT

Many of the above mentioned subspecies and ecotypes of Apis cerana are at present not economically viable. Therefore selection and breeding programmes to produce a bee suitable for intensive management is required. To achieve stock improvement, different Apis cerana subspecies and ecotypes should be accumulated at central location and superior genotypes be identified. Another important pre-requisite for stock improvement is to evolve efficient queen rearing for Apis cerana and also establish isolated mating stations for pure line breeding. The latter is essential because instrumental insemination in Apis cerana has unexpectedly turned out to be a difficult task due to very low volumes of semen ejaculated by drones.

MANAGEMENT

During the course of evolution, Apis cerana has developed certain behavioural characteristics such as frequent absconding and swarming which are essential for the survival of colonies but undesirable from a beekeeping point of view.

ABSCONDING

Our research group has identified a lack of sufficient bee flora, excessive handling, exposure of colonies to summer sunshine and incidence of sacbrood virus disease as major causes of absconding. Colony performance index (CPI) based on the number of pollen- bringing foragers can be used to predict absconding. Based on this, native bee species start showing symptoms of absconding even two weeks before, and CPI reaches zero even a week before absconding. Management practices like feeding sugar, providing shade and providing queen gates at the hive entrance significantly reduce absconding. However, colonies affected with sacbrood virus disease show such severe instinct of absconding that these may leave the hive even without the queen.

SWARMING

One of the most effective ways of reducing frequent swarming is to following selection programmes against this undesirable trait. Removal of newly constructed queen cells during the active season also helps to check swarming.

The recurrence of sacbrood virus after an earlier cycle during 1982-1986 has threatened beekeeping with Apis cerana throughout its range and is forcing beekeepers to replace it with more prolific Apis mellifera. Some colonies are still resistant to this disease and in the absence of any effective chemical control measures, a vigorous selection programme needs to be followed.

* Part of this paper was delivered by the author as Chairperson and Organiser of the Symposium entitled Apis cerana and other honey bees of Apidae, during the XIX International Congress of Entomology, Beijing, China 1992