Minority mating advantage of certain eye color mutants ofDrosophila melanogaster. IV. Female discrimination among three genotypes

It was our purpose to examine how the courtship sequence by three eye color types of males inDrosophila melanogaster might affect the experience of females in such a way as to influence mating success. Flies were mutants for a pair of alleles at thebrown locus (bw andbw ⁷⁵; 104.5 on chromosome 2) combined withscarlet (st; 44.0 on chromosome 3). Mutant red-eyed (R), orange-eyed (O), and white-eyed (W) flies were tested, mature virgin females individually in the presence of six males, either three each of two eye color types or two each of three types. About 12% of the females displayed a low threshold and mated to the first male that courted in less than 5 min. For these females and for those with a higher threshold when courted by one type of male only, R males were twice as successful as O and about four times as successful as W. For trials in which two male types courted, females tended to accept the type that was not the first to court in 62.5% of the trials with a 33 ratio of males and in 70% of the trials with a 222 ratio but one type of male not courting. When all three types of males courted at the latter ratio, females tended to discriminate against both the first type to court and the joint combination of first with second type to court, tending to mate with the third type in 47% of the trials. There was no significant association between either the second male or the second type of male to court and the type that mated. Evidence is presented that the visual component of courtship is important to persistence and efficiency but less important to initiation of courtship. The time to mating (female acceptance) is longer with increase in the number of male types courting. These results and some arguments by other authors trying to account for negative results using the same mutants are discussed. We conclude that sexual behavior is controlled by loci other than those markers determining eye colors tested, and the genetic background for the mutant phenotypes is most critical for female discrimination.     

Minority mating advantage of certain eye color mutants ofDrosophila melanogaster. III. Female discrimination and genetic background

A repetition of certain experiments done 2 years previously with two eye color mutants,brown andscarlet, inDrosophila melanogaster was undertaken to reconfirm results; however, initial tests revealed that strains or conditions had changed so that females were less discriminating. Testing was undertaken with changes in genetic background and certain laboratory conditions, with single females courted by equal numbers of two eye color types of males (3 red,R: 3 orange,O). These eye colors were produced as (1) mutants off the shelf, (2) recombinants from an outcross to a wild-type strain (CS), (3) mutants as in Experiment 1 but with male types stored either together or separately, and (4) recombinants from a double outcross of flies from Experiment 2 to hybrids from two additional wild strains,LS andOR. Experiment 4 producedR andO males that courted nearly equally (as in previous experiments), in contrast with about 70% courtship byR males in the other experiments. Females discriminated in favor of those second to court in G₀, G₁, and a repeat of G₀; however, with two generations of inbreeding, discrimination by this criterion lessened to become nonsignificant. In Experiments 1 and 2,O females favored second-courting males, butR females in hose experiments and all females in Experiment 3 mated more randomly. Effects of storing males either together or separately were not significant. About 20–30% of the females (low threshold) were highly receptive immediately after first courtship. Those trials plus any in which only a single type of male courted were omitted from estimations of female discrimination; a possible bias incurred by such omission against females that might have initial preferences was found to be nonsignificant. Discriminating ability was discussed as a fitness property inDrosophila populations.This research was supported in part by National Science Foundation Grant DEB 79-03259.     

Mating patterns of differentAdh genotypes ofDrosophila melanogaster. II. Testing rare-male mating advantage

In this paper we analyze the rare-male mating advantage at theAdh locus inDrosophila melanogaster by three different statistical methods: X² test [classically applied for this kind of experiment (Ehrman, 1966; Spiess and Schwer, 1978; Markowet al., 1980)], linear regression (Adams-Duncan's test), and estimation of relative male mating success (Anderson-Browns's test). With the X² test, a rare-male SS mating advantage could be speculated in the FF vs. SS comparison, but when the other two statistical methods were applied, this effect was not evident. However, in the FF vs. SS comparison, FF males show a much greater mating success than SS males in experiments with a 11 or 19 ratio. In the FF vs. FS and FS vs. SS comparisons, differences in mating success and frequency dependent selection were not found. The fact that a rare-male mating advantage is not detected for any of theAdh genotypes seems to indicate that this type of frequency-dependent selection is not a major component of the mechanism to maintain polymorphism at theAdh locus.     

Selection for increased female sexual receptivity inRaised stocks ofDrosophila melanogaster

Two third-chromosome mutations inraised (rsd) stocks, when homozygous, cause the wings ofDrosophila melanogaster adults to be held upright. Males expressing these mutations cannot vibrate their wings to produce the courtship song, which functions to increase female receptivity to copulation. As expected,rsd males are less successful when courting wild-type females. However, females from long-establishedrsd stocks are more receptive to courtship stimuli and mate more readily with bothrsd and wild-type males than do wild-type females. Genetic analysis reveals dominant factors on the X and third chromosomes that, in combination, are responsible for the increased receptivity ofrsd females. These observations suggest that the lack of courtship song inrsd stocks, which would be expected to reduce the vigor of the stock, may have functioned as a selective force, favoring mutations that increased female receptivity. Possible consequences of selection favoring the development of differential female receptivity on speciation are discussed.     

The behavioral phenotype and mating behavior of two inbred strains ofDrosophila melanogaster

Time to copulation was measured in matings within and between two inbred Drosophilamelanogaster strains, Edinburgh (E) and 6C/L, using groups of one or five flies of each sex. The E males, which mated faster, usually mate with E females, which are less likely to be fertilized and have fewer progeny whose adult viability is lower. Although generally E males mated far faster with E females than did 6C/L males, there was no difference between the males when with 6C/L females. This need not imply any mating discrimination by E females, but only differences between the strains in the use of preening as a general repulsion movement toward other flies. It is suggested that a greater variety of behavioral and other characteristics (the behavioral phenotype) should be considered in studies of mating speed and assortative mating, especially where mating speed is being considered as a major component of fitness.This work was carried out while the author was in receipt of a University of Birmingham research fellowship and is part of a research program in psychogenetics supported by the British Medical Research Council.     

Relative male age,fertility, and competitive mating success inDrosophila melanogaster

Female choice experiments were used to investigate the effect of relative male age on mating success inD. melanogaster. Experiments were conducted with a Canton-S (CS) strain, in which two virgin males of different ages (2, 4, or 8 days old) were offered to virgin females. Older males were found to be more successful under competitive conditions. In another group of experiments, vermilion (v) males of different ages competed with CS males of different ages. The competitive success ofv males was found to increase with their relative age. Male fertility at 2, 4, and 8 days of age was documented for both male genotypes mated with CS females. CS males fathered more offspring per copulation thanv males, and the fertility of all males was found to increase with age. Discussion focuses on the changes in male mating success and fertility with age and genotype.This work was supported by NIH Grants MH 30382 and NS 15263 to T. A. M.     

Isolation ofDrosophila melanogaster mutants with a wavelength-specific alteration in their phototactic response

A method is described for the isolation ofDrosophila mutants whose positive spontaneous phototactic reaction in repeated choices between UV light (368 nm) and blue light (481 nm) tended less to the UV than that of the wild type. From those 32 strains which have been isolated up till now and which fulfill this criterion, most showed only a relatively slight deviation from normal behavior. Among those exhibiting a marked change in the choice tendency was one allele of the mutantrdgB (receptor degeneration B) and seven alleles of the mutantsevenless (receptor cell 7 missing); four other mutants belong to two complementation groups which have not been identified as yet. The method described should be suitable for detecting further mutants with defects in receptor-cell function. In addition, it should be possible to isolate mutants in which the mechanisms of wavelength-specific processing are altered.     

Asymmetric response to directional selection for licking behavior ofDrosophila melanogaster males

Selection for high and low licking rate was carried out on courting males of a cage-population ofDrosophila melanogaster for 21 generations. The males were tested against a standard female tester genotype in every generation. The low-scoring line responded linearly to selection, reaching a plateau after eight generations. The attempt to raise the licking rate above the level of the base population was not effective. The realized heritability of the L and H line over the first seven generations was 41.0 and 0.4%, respectively. From the fourth generation onward, the two lines differed significantly. Reciprocal crossing between the two lines indicated the absence of X-chromosome and maternal effects. There was no significant dominance. The selection for licking in males had no discernible effect on female sexual activity. H-line males mated significantly faster with standard females than L-line males.Preparation of this paper was facilitated by a grant from the German Scientific Research Foundation (DFG).     

The stability of the specific-mate recognition system ofDrosophila melanogaster

The present data illustrate an important characteristic of the mate recognition system of individuals ofDrosophila melanogaster. This system showed a high degree of stability, and the stability occurred even though the populations under investigation were divergent in other characteristics. We review the results of other studies of this type, discuss our results in terms of the general characteristics of specific-mate recognition systems, and account for its stability in terms of the structure of the communication system.Publication No. 15 Evolutionary Genetics Laboratory, University of Auckland.     

Influence of food on frequency-dependent sexual activity ofDrosophila Melanogaster

When two types ofDrosophila are in competition, the frequency dependence of mating successes frequently is measured by direct observation of copulating pairs in Elens-Wattiaux observation chambers, the relative frequency of both types being varied. The present experiments, concerningwhite-ebony mutants in competition with wild-type Canton-S flies, show that the presence of food in the mating chamber influences the sexual activity of flies, this influence differing in the two types when food is present. Thus, in order to have a realistic estimation of frequency dependence, it would seem prudent to conduct these experiments with food in the chamber. Three methods are used to analyze observation data:K coefficients of Petit and Ehrman, regression equations of Ayala and Campbell, and regression equations of Wattiaux and Lichtenberger. These three methods are compared and discussed.This paper is dedicated to the memory of Marcel Lichtenberger, M.D., 15 years medical missionary in China and 17 years Professor of Human Genetics at the State University of Saigon, Vietnam.     

Genotypic differences in mating success and the maintenance of the alcohol dehydrogenase polymorphism inDrosophila melanogaster: No evidence for overdominance or rare genotype mating advantage

Strains ofDrosophila melanogaster having different alcohol dehydrogenase (Adh) genotypes (FF, FS, or SS) were assembled in a mating chamber in varying ratios, and the mating successes were recorded. In experiments with a 2525 ratio, theFF males succeeded in mating more than didFS andSS males, while theFS males surpassed theSS males. As for the females,FF also surpassedSS. In experiments with a 545 or 455 ratio, some differences from the 2525 ratio occurred, but in these cases the rare genotypes were at a disadvantage. In one case, female genotypes (FF vs.SS) displayed a difference in mating latency time, but male genotypes did not. The findings did not suggest that rare genotype mating advantage and overdominance in mating success play a role in the maintenance of theAdh polymorphism.     

The effects of crowding on courtship and mating success inDrosophila melanogaster

The mating times of single males and pairs of males were increased by crowding with virgin females but only at very high densities. Mating times were decreased by the presence of a second male. Quantitative analysis of courtship showed that prestimulation of females in crowded conditions influences mating. The pattern of male courtship was highly consistent across moderate levels of crowding. This suggests thatDrosophila courtships evolved in crowded conditions.Technical assistance was supported in part by Grant GM31687, National Institutes of Health, U.S. Public Health Service.     

Genetic analysis ofDrosophila melanogaster egg insertion behavior

The tendency ofDrosophila melanogaster females to insert eggs into the substrate was analyzed by a diallel cross among five inbred lines from different geographic origins. The trait showed a great deal of additive genetic variation. The directional dominance effect was found to be large, indicating past directional selection for a strong tendency to insert eggs into the medium. Some maternal effect may also be present. Contrary to Takamura and Fuyama (Behav. Genet. 10:105–120, 1980), no relation was found between the tendency to insert eggs in the medium and the choice between a hard (paper) or soft (culture medium) oviposition surface. Lines, which did differ in the tendency to bury their eggs did not differ in the choice of oviposition site.     

The aging effect on male mating activity inDrosophila melanogaster

Noncompetitive mating activity for young (3-day) and old (28-day) Drosophila melanogaster males was measured under chromosomally homozygous and heterozygous conditions. Old males were consistently less active than young ones under both conditions. Three of 29 homozygous lines exhibited sterility due to aging. Virility at the old age did not correlate with that at the young age. Differences among homozygous lines were highly significant for old and young males, indicating a genetic basis for the trait. Individual variation in old virility was shown to be much higher than that in young males.     

Genetic and sensory aspects of mating success of phototactic strains ofDrosophila melanogaster

In female choice experiments,Drosophila melanogaster males from a selected photonegative strain show a highly significant mating advantage over males from a photopositive strain. While photonegative behavior is sex linked in this species, the X chromosome is not involved in the mating advantage seen for this strain. The degree of the photonegative male advantage changes when tests are conducted with females mutant for olfaction and auditory perception but not when females are blind.Supported by NIH Grants GM 25424 and NS 15263.     

Courtship behavior and the kinetics of mating in three lines ofDrosophila simulans and their hybrids

Mating inDrosophila is precisely characterized by an exponential phase based on second-order kinetics coupled with an initial lag phase based on zeroth-order kinetics. In this model, the two separate kinetic phases are quantified by separate parameters. Three genetically distinct lines ofDrosophila simulans differing in male and female mating propensities (measured by the relative frequencies of animals mating after a fixed interval of time) also differed sharply in both parameters of mating kinetics. One line was highly outcrossed and the other two, derivatives of the first, had been subjected to genetic drift. The lines and their F₁ hybrids were studied in no-choice mating tests with a control line to determine the two parameters describing mating kinetics and were observed in pair matings to measure four courtship traits. The two parameters of mating kinetics (L, which describes the lag phase, andK, which describes the exponential phase) and the mean percentage mating varied widely across the nine types, in both sexes. The logarithm ofL was linearly related to the percentage mating (r ²=0.732);L andK were not significantly correlated. Among female genotypes, only one courtship trait varied significantly—the latency from coconfinement of female and male to initiation of courtship; among male genotypes, the duration of the two wing displays, scissor and vibrate, varied significantly. LogK was significantly (P<0.01) correlated with the latency to courtship (r=–0.626) and with the duration of two components, orient (r=0.701) and scissor (r=0.698), whereas logL and percentage mating were not significantly correlated with components of courtship. There was evidence of inbreeding depression forL, but not forK, in both sexes of the drift lines.The research was supported in part by NSF Grant DEB 7903866 and a grant from the University of Maine and by the Computing Center of the University of Maine.     

Genetics of factors affecting the life history ofDrosophila melanogaster. III. Egg insertion behavior

A genetic analysis of two laboratory strains ofDrosophila melanogaster that displayed opposite oviposition tendencies with respect to egg insertion behavior was performed. In general, the insertion characteristic appears to be dominant over the noninsertion characteristic and is controlled by a polygenic system associated mostly with chromosomes 2 and 3. The result of this study indicate that these genes may be concentrated at the distal end of chromosome 2L and at the distal end of chromosome 3R, and their presence on both of these chromosome regions is needed to approach the full egg insertion effect, suggesting the presence of interaction among genes in these two regions.This work was supported by Research Grant AG01934 from the National Institute of Aging to Y. Hiraizumi.     

Courtship song and mating speed in hybrids betweenDrosophila melanogaster andDrosophila simulans

Courtship song and mating speed of hybrids betweenDrosophila melanogaster andD. simulans were investigated. The courtship song of hybrid males is identical to that ofD. simulans, suggesting that X chromosome determination, known from the cross betweenD. pseudoobscura andD. persimilis, is also possible here. Wingbeat frequency of hybrids is intermediate between that of the two parents, demonstrating that courtship song and wingbeat frequency are inherited independently of each other. In mating tests, hybrid males court and are accepted byD. simulans females more than hybrid females (presumably because their song is more acceptable to the former).D. melanogaster females reject hybrid males. Hybrid females acceptD. melanogaster males readily, hybrids less readily, andD. simulans least.F. v. S was supported by a scholarship from the German Academic Exchange Service.     

Foraging strategies ofDrosophila melanogaster: A chromosomal analysis

Two larval foraging strategies inDrosophila melanogaster were identified, rover and sitter. Rovers traverse a large area while feeding whereas sitters cover a small area. The difference between rovers and sitters was analyzed genetically by chromosomal substitutions between isogenic stocks. Differences in larval locomotor behavior (crawling behavior) can be attributed to the second chromosome, the rover strategy being dominant over the sitter strategy. Differences in feeding rate (shoveling behavior) are affected additively by both the second and third chromosomes. Natural populations ofDrosophila larvae were sampled three times over a 2-month period; rovers and sitters were at constant frequencies in these populations. The two foraging strategies are discussed in the light of resource utilization in environments where food is distributed continuously or discontinuously.     

Variation in courtship sounds among three geographical strains ofDrosophila mercatorum

Sound recordings of courtship inDrosophila mercatorum were analyzed with an oscilloscope. Sounds in this species consist of two kinds of pulses, referred to as the A and B sounds, respectively. These differ from each other in their oscilloscope pattern and in the behavior accompanying them. A comparative study of three strains from widely separated geographical regions (New York, El Salvador, and Hawaii) revealed significant differences among strains in the interpulse interval (ipi) of the A sound. The ipi of the B sound increased as it proceeded for New York and Hawaii males but not for males from El Salvador. These characteristics may influence mating success in interstrain corsses. The present results suggest that the first steps toward divergence in the nature of the sound are quantitative; this may affect the response threshold of the female. Genetic systems responsible for female receptivity may have been independently developed in the two sexes.This work was supported by research grants from the Ministry of Education of Japan (Nos. 034082, 312107), and was presented at the U. S.-Japan Seminar of Dynamics of Speciation in Plants and Animals, Tokyo, October 14–18, 1978.