Egg-laying Queens Research Articles

Reproductive Competition and the Evolution of Work Load in Social Insects

Independent studies of worker activities in colonies of social insects have shown that individuals are inactive for much of their time. Here, work load is analyzed as a heritable summary measure of individual activity, such that high work loads benefit the colony but increase the mortality rate of individuals. Thus, worker genotypes that adopt low work loads are expected to accumulate during colony growth at the expense of hard-working types if both occur in the same colony. When mature colony size is reached, this accumulation could, through nepotism, bias the production of sexuals toward the accumulated genotypes. A formal model shows that a gene coding for low levels of work load could indeed spread in a population of hard-working colonies, if colony workers are not always full sibs, that is, with polygyny or polyandry. Furthermore, the work load that is evolutionarily insensitive to slightly deviating mutants is predicted to decrease with the degree of polygyny (number of egg-laying queens), with polyandry (number of males contributing sperm), and with an increase in the degree of nepotism. Work load should also vary with ecological variables, such as the length of the colony's growth period before reproduction. To evaluate this hypothesis, several measures for work load (inactivity, self-grooming, brood care, risky tasks) are compared across species of ants. Average work load increases with reported colony size, but activity levels in colonies of monogynous and polygynous species are remarkably similar.

QUEEN NUMBER IN COLONIES OF SOCIAL HYMENOPTERA AS A KIN-SELECTED ADAPTATION.

Using a series of kin-selection models, I examine factors that favor multiple egg-laying queens (polygyny) in eusocial Hymenoptera colonies. One result is that there is a theoretical conflict of interest between the founding queens and their daughter workers over how many and which individuals should be the extra reproductives. Both castes should prefer their full sisters. Therefore, primary polygyny (multiple related foundresses) may favor queens while secondary polygyny (related queens added to mature colonies) may favor workers. Polygyny, itself, was found to be favored by high colony survivorship and low probability of queens contributing eggs to successive broods. Polygyne colonies, however, did not need to produce more offspring per brood to be selectively favored; they could be half as productive per brood as monogyne ones and still have higher lifetime fitness under some conditions. For reproductive data from eight ant species with both monogyne and polygyne colonies, the model generates results that are consistent with a kin-selection explanation of polygyny in all of them. It is proposed that queen number is an ecologically flexible trait that is influenced by a broad set of factors but is not necessarily linked to specific habitat types. Furthermore, neither polygyny nor monogyny may be reliably considered as the primitive or ancestral Hymenopteran social system. The optimal queen number within a species may evolutionarily increase or decrease, depending on the direction of environmental change.

Relatedness among queens in polygynous nests of the ant Leptothorax acervorum

One hundred and fifty one colonies of the ant L. acervorum comprising 815 queens were sampled in dry pine forest at nine sites in SE Sweden. 63% of the colonies contained more than one queen and of these 79% had more than one egg-laying (functional) queen, i.e. were polygynous. By using the electrophoretic variation at the PGI locus a high overall relatedness (0.4) among queens from the same colony was found indicating that young queens are adopted by their mother nest. No spatial microdifferentiation in allele frequencies could be detected and it thus seems that despite restricted movements of queens there is a free gene flow in the populations.

Culture of honeybee organs: Development of a new medium and the importance of tracheation

A culture system for honeybeen fat body and ovary was developed that supported optimal levels of protein synthesis by the explanted tissues. Abdominal body wall preparations of honeybee workers and queens, with adhering fat body, and ovaries of egg-laying queens were incubated in a culture medium designed to match honeybee hemolymph composition as closely as possible. Incorporation of [3H]eucine into soluble tissue proteins was measured. The new medium makes possible rates of tracer incorporation into fat body proteins that are up to three times higher than other media tested. When the tracheal system of the organs was let intact and open to the air during incubation, protein synthesis increased 17-fold (fat body) or 15-fold (ovary) as compared to preparations without open tracheas. After explantation into the medium, labeled proteins were synthesized at a highly variable rate for 10 h, probably due to wound response, and at a constant rate for the next 60 h. In contrast, ovarian protein synthesis occurred at a constant rate for at least 20 h and showed no wound response. The rate of tracer incorporation into fat body proteins was 3.2 times greater in tissues from the queen. This culture system is therefore suitable for a variety of investigations in honeybeen development and reproduction.

EFFECTS OF COLONY DIVISION ON FOUNDRESS ASSOCIATIONS IN POLISTES FUSCATUS (HYMENOPTERA: VESPIDAE)

AbstractThree colonies of Polistes fuscatus (Fabricius), each with two foundresses, were bisected during the pre-emergence stage and separated for 20 days. In the absence of the dominant, each subordinate foundrss became an egg-laying queen on her half of the nest. The dominant foundress did not exhibit superior reproductive productivity. The split colonies were reunited by placing the nests approximately 4.0 cm apart in a single nest box. Each foundress and all workers were observed tending both half-colonies, and the original dominance hierarchy was apparently restored in two of the three colonies.

Volatile communication substances in Dufour's gland of virgin females and old queens of the antFormica polyctena

Dufour's gland, which is present in worker ants ofFormica polyctena as a tiny gland emptying into the short duct from the poison reservoir, was found to be very enlarged in virgin females. In egg-laying queens the gland lobes were reduced in size to slender tubes. The glandular secretion was analyzed by capillary gas chromatography and mass spectrometry. Seventy-four percent of the gland secretion from virgin females consisted of undecane, but this compound was less than 1% in queens. Decane and nonane, making up 3.5% in virgin females, were not found in queens. About 74% of their secretion consisted of the lower hydrocarbons: tridecane, pentadecane, heptadecane, and a nonadecene with tridecane dominating to 50%. Apart from these characteristic differences, almost the same compounds were present in virgin females and queens. Thirty-three compounds were identified from the secretion of virgin females and 38 from queens. An additional compound present in trace amounts in the secretion from queens has not been identified. All the compounds were hydro-carbons with the exception of dodecanol, present in trace amounts in virgin females. The compounds are homologous series of saturated, aliphatic hydrocarbons from nonane to tricosane and corresponding series of monounsaturated and methyl-branched hydrocarbons. Geranylgeraniol and geranyl-geranyl acetate, present in worker ants together with some other alcohols and acetates, were absent in females.

Egg Production, Oviposition, and Survival of Isolated Queen Honey Bees Fed Experimental Diets123

Fertile egg-laying queen honey bees, Apis mellifera L., removed from the colonies and isolated on experimental diets of dextrose-levulose syrup, queen candy, egg albumin, pollen, fresh royal jelly, and royal jelly frozen 3–4 months, continued to expel eggs for only 48 hours, and none of the diets stimulated them to resume egglaying. When such queens were isolated and fed 5 days through screenwire by small numbers (15) of 15-day-old nurse bees feeding on the experimental diets, the subsequent autopsy revealed neither eggs in their oviducts nor ovulable-size eggs in their ovaries. However, when queens in screenwire push-in cages on wax blocks were introduced into larger cages containing 300 workers of known age (4 to 6, 9 to 11, or 14 to 16 days old, or equal numbers of each age group) and the attendants were fed 2.5% pollen in dextrose-levulose syrup (and water), the autopsied queens contained eggs after either 2 or 5 days of such treatment. Isolated queens lived significantly longer on diets of dextrose-levulose syrup, queen candy, or egg albumin than on fresh royal jelly, frozen royal jelly (3–4 months old) in dextrose-levulose syrup, or pollen in a carbohydrate mix.