by William C. Roberts and Otto Mackensen
U.S.D.A., Agr. Res. Adm., Bureau of Entomology and Plant Quarantine*
(*In cooperation with the Wisconsin Agricultural Experiment Station and Louisiana State University.)
Within recent years the technique of artificial insemination has been improved and used successfully in experiments on bee breeding. Thus a major barrier in our efforts to produce better breeds of bees has been successfully hurdled.
Readers of the bee journals now find advertisements telling them that improved hybrid bees are available. Since these are said to be superior to existing races or strains, the wide-awake beekeeper will want to know how they are produced.
This is the first of a series of articles on the use of controlled breeding to improve honey bees. This article discusses the relationship of bee breeding to animal breeding in general. Articles on heredity and variation, sex determination and bee breeding, inbred and hybrid bees, and production of hybrid queens will follow.
I – Bee Breeding and Animal Breeding
Almost everything that we eat or wear is the product of our domesticated plants and animals. Most of these living forms have been cared for and propagated by man since long before the beginning of written history. Domestication implies several things, no one of which is sufficient to define it completely. It usually means tameness; but individual bears, lions, or even snakes can be tamed, and few of us would call them domesticated animals. Domestication further implies bringing the growth and reproduction of the plant or animal at least partly under man’s control, but certain pigeons and geese usually choose their own mates and accept no others. Man uses domesticated animals or their products for his own advantage, and he usually keeps them in or near his dwelling. From the variable wild species man has, by selection and reproduction, developed individuals that suit his purpose.
Breeding and selection have therefore led to the establishment of types or varieties useful to man. Selection for usefulness and survival under man’s care has frequently resuited in varieties incapable of survival without man’s care. Man did not create these genetic forms. By controlled breeding and selection he merely succeeded in putting together or fixing these varieties from the genetic variability that existed in their wild ancestors.
The honey bee has a definite place in our modern world. Its products of honey and wax are useful to man, although perhaps not essential to all men. However, the pollination activities of bees affect the lives of most of the people of the world. Although we may never succeed in taming the honey bee or in getting it to change its mating habits, it seems evident that the definition of domestication is sufficiently broad to include this most useful insect. The ways and means of improving the economic value of honey bees by controlling their growth and reproduction will be discussed in this article.
The breeder of animals must decide which animals shall produce the next generation. His choice is determined by his knowledge of the variability that exists in the potential breeding population and the usefulness that he desires in the succeeding generations. The variability in the breeding population is due in part to differences in inherited factors and also in part to differences in environment. A knowledge of the science of heredity should make it easier to choose intelligently among the many animals in the potential breeding population.
Because of the social nature of the honey bee, the colony is the unit upon which selection must be based for most economically important characteristics. The individuals of a colony consist of a queen and her worker and drone offspring. The queen is mated before she begins egg laying, and her mate is thus the father of the workers in the hive. She may have more than one mate, and therefore the genetic variability of the colony may be due to several individuals. Each of these individuals can be influenced by environmental factors that are not always easy to evaluate. The bee breeders’ problems in properly evaluating the genetic and environmental factors affecting each individual colony are much more difficult than those of other animal or plant breeders.
Although honey bees have been propagated by man for 5,000 years or more, there is little evidence that much progress in bee breeding has been made. No superior breeds of bees have been established. The species has been subdivided into races, and all these races show considerable variability. Apparently they are the product of many generations of random matings within populations that have been partially isolated by geographic barriers. Man may have had some influence in fixing these races by selection that altered the frequency of certain inherited factors.
The aim of the bee breeder is to produce better or more profitable bees. This may mean more honey per colony or it may mean more efficient pollinators. The breeder must work with the reproductive individuals that are available. Since colonies of bees differ in many characteristics, the breeder has variability from which to select. This variability may be due to both genetic and environmental factors. The successful bee breeder must observe his colonies closely so that he can make proper allowances for environmental factors affecting the genetic variability in his breeding stocks.
His next problem is to mate the breeding individuals so as to obtain genetic improvement. From the variable colonies he attempts to unite the genes (the genetic factors) for good qualities from many stocks into one line or breed while eliminating inferior or less desirable qualities. In order to succeed he must have some knowledge of the science of heredity. Geneticists have accomplished this with many plants and animals, and therefore it is possible with bees.
Since the honey bee is an animal, it would appear that animal breeding methods should be used. The honey bee, however, is quite different from the economically important animals. Its method of reproduction is in a sense more like some plants. We shall attempt to describe these differences and likenesses and show how they affect methods of bee breeding.
The science of heredity is relatively new, having only become recognized as a science in the 20th century. Yet a great amount of real progress through selective breeding was accomplished in most of our economically important plants and animals long before Mendel, the father of genetics, was born. Most every breed of horses, cattle, hogs and chickens used in the United States today was established before the 20th century. Yet even today there are no fixed breeds of bees – we still have only races.
Let us review a few of the methods employed in the establishment of improved breeds of livestock. The fundamental biological principles of inheritance are the same whether we are breeding plants or animals. Therefore, much about bee genetics can be learned by studying the genetics of other animals and plants.
All our domestic animals except the guinea and the turkey originated and were domesticated in prehistoric times in the Old World. Most domestication evidently occurred in central or western Asia, although some is believed to have taken place in Europe, Egypt, India and China. It is still disputed whether most animals descended from a single wild species or from two or more species.
Early naturalists supposed that species were fixed and had no genetic variability. However, modern geneticists have shown that wild populations of one species of animal were not genetically uniform. They have also shown that selected breeding within these wild populations, with their existing genetic variability, can produce distinctly contrasting races or breeds within a few generations.
It seems probable that all the races of bees, as we know them today, developed from a single wild species of honey bee. In time they became dispersed over a large part of the Old World and were somewhat isolated into many small groups. There was, of course, some interbreeding between groups, but geographical barriers prevented a great many matings between groups. As a result a certain amount of inbreeding took place within each geographic group. By mutations, natural selection, and perhaps some human intervention in selection, the bees within each geographic area became different from those in other areas.
The bees from the various areas are called races. Probably the most geographically isolated race of bees is the Caucasian. A Russian author who studied this race in its native home divided it into six separate varieties. These varieties ranged in color from the banded appearance of the Italian to completely black. Other genetic characteristics within this and other races of bees are equally variable. The bees of one race are fertile when crossed with those of another race.
Wild cattle, horses, and hogs were also variable animals. The recognized breeds of these animals were developed by selected breeding of outstanding individuals from variable populations. The history of the formation of the beef breeds of cattle that originated in the British Isles is typical of successful animal-breeding methods.
History tells us that migrating people and invading armies usually carried with them much livestock from their native lands. Migrations were slow, and the stocks mingled with and interbred with stocks present in the countries through which they passed. It is not known just how many and what kinds of cattle were introduced into the British Isles throughout the ages. However, it is known that the Norsemen and the Dutch carried cattle into the British Isles, and it is suspected that the Romans and the Normans also brought in some cattle. These cattle interbred with the cattle of the islands, and a great amount of genetic variability existed in these stocks before the formation of the breeds that we know today as Hereford, Shorthorn, and Aberdeen-Angus.
About the beginning of the 18th century the common lands of Great Britain were enclosed so that the intermingling of stocks on a wide scale was stopped. The cattle population was thus broken up into small groups and inbreeding within groups was the result. About this time the cities began to grow and a demand for meat developed. Some types of cattle were more useful for this purpose than others, and breeders attempted to produce these meat-type cattle. A few breeders gathered together some of the best of the desired type into one or a few herds. There followed years of rather intense inbreeding between these selected animals and their descendants. Very little outside breeding stock was permitted to enter these herds. After several generations the cattle within these herds were uniform and were distinct from the other animals in the community. Every recognized breed of cattle has arisen from the concentration of the genes (blood) of one or a few animals of greater than ordinary merit.
Breeds have developed in a similar manner among other types of livestock. The Poland China hog was evolved or originated in Butler and Warren counties in southwestern Ohio. The exact combination of breeds or types that resulted in this hog is not clear. Prior to 1830 there existed in this area a number of types, among which were the Bedfordshire, Byfield, Russian, and Big China. Some Berkshire blood was introduced in 1835 and some Irish Glazier blood in 1839. There was intermixing of these breeds without a definite plan for 20 years or more. In 1870 the Warren County hog was black and white spotted. It was regarded as a breed in 1872 and was given the name “Poland China.” The diverse races of swine from which this breed was found could hardly have come together anywhere on earth without the aid of man. From this heterogeneous mixture the breed arose by inbreeding of selected sires.
Why have not bee breeders done the same thing with bees? Many diverse races and strains from all areas of the world have been brought into the United States. There is thus great genetic variability in our bees. When we look around we find outstanding individuals (colonies). We have seen that successful breeders of other animals succeeded in establishing superior breeds of animals by inbreeding and selecting from among outstanding individuals and their descendants.
Bee breeders did try methods used by breeders of other animals but they did not succeed. It is true that they could not control matings so successfully as other animal breeders, but this was not the major cause of their failure. Studies indicate that a major cause for this failure was a lack of knowledge of sex determination in honey bees. Its importance to bee breeding will be explained in a later section.
Reprinted from AMERICAN BEE JOURNAL
Volume 91 No. 7, pages 292-294, July 1951