Differential Mating Success Research Articles

Mating behavior and male mating success in wildAnastrepha Ludens (Diptera: Tephritidae) on a field-caged host tree

Mating behavior and factors affecting mating success of males were studied using wild Anastrepha ludens on a fieldcaged host tree. The most common courtship sequence had five components: (1) male calls from the underside of a leaf, (2) female arrives to the maleoccupied leaf, (3) male orients to female and stops calling, (4) one or both approach to a face-to-face position 1–3 cm apart, and (5) male mounts female after 1–2 s. Courtship behavior was almost identical to that of laboratoryculture flies observed previously under laboratory conditions. Most malefemale encounters occurred at a height of 1–2m, well inside the outer canopy of the tree. Differential mating success by males occurred. No male mated more than once per day, owing possibly to a very short sexual activity period. Factors favoring mating success of males were survival ability and tendency to join male aggregations and to fight other males. Thorax length and age (9–11 days difference) had no effects on male copulatory success. Overall win/loss percentage was not related to mating success because the males that were most successful at mating fought mostly among themselves, driving their win/loss percentage down. However, these successful males (at mating) won most of their fights against less successful males. Results confirmed a lek mating system: males aggregated, called, and defended territories; territories did not contain femalerequired resources; and females exercised mate choice, apparently through selection of sites within leks.

EXAMINING HYPOTHESES GENERATED BY FIELD MEASURES OF SEXUAL SELECTION ON MALE LIZARDS, UTA PALMERI.

I examined sexual selection in the iguanid lizard Uta palmeri by measuring phenotypic selection in a cohort of males. Relative fitness was estimated by copulation rate from one breeding season, and I analyzed selection on five morphological traits (snout-vent length, mass, jaw length, head width, and head depth) and on male territory quality. Only territory quality and head depth were identified as direct targets of selection in a linear selection gradient analysis. Head depth was suggested to also be subject to quadratic selection. All traits exhibited significant directional selection differentials, suggesting indirect selection also was present because of the correlation of these traits with direct targets of selection. I used these results to generate hypotheses about the mechanisms of selection. For traits not identified as direct targets of selection (snout-vent length, mass, head width, jaw length), I could accept the null hypothesis of no female preference for the analyzed male traits; if these morphological traits were preferred by females in mate choice, they would have been identified as direct targets of selection. Exploring possible functional relationships within the cohort, I found that all five morphological traits contributed to explaining variation in territorial status. And in staged aggressive interactions between males that were similar in snout-vent length and mass, winning was associated only with greater head depth and not with head width or jaw length. Several possible interpretations of these results are presented. This study suggests that differential mating success arising from variation in territory quality gives rise to indirect selection on morphology. The possible mechanisms giving rise to the proposed direct selection on head depth require further study.

Factors affecting differential mating success in male crested newts, Triturus cristatus

This study investigates differences in mating success in male crested newts, Triturus cristatus. In experiments, mating success varies considerably between individual males. Male size affects mating success, but the maximal height of the male's crest is more important. Male size and crest height are correlated, but in partial correlation analysis only crest height is significantly correlated with mating success. Motivation is also an important factor in determining male mating success as males that had been isolated for a week were more successful than freshly caught males. Newts might be limited in their ability to produce spermatophores, and isolation gives the male time to produce more spermatophores. It is likely that motivational state is less important in a natural population than size and crest height, because wild males are often interrupted during courtship before spermatophore deposition and hence are highly motivated to mate.

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

In this paper we analyze the rare-male mating advantage at the Adh locus in Drosophila melanogaster by three different statistical methods: chi 2 test [classically applied for this kind of experiment (Ehrman, 1966; Spiess and Schwer, 1978; Markow et al., 1980)], linear regression (Adams-Duncan's test), and estimation of relative male mating success (Anderson-Browns's test). With the chi 2 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 1:1 or 1:9 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 the Adh genotypes seems to indicate that this type of frequency-dependent selection is not a major component of the mechanism to maintain polymorphism at the Adh locus.

Genetic differences in mating success and female choice in seaweed flies (Coelopa frigida).

An association is described in seaweed flies, Coelopa frigida, between the genotype at the alcohol dehydrogenase (Adh) locus and mating success in pairwise mating trials. Significantly higher mating success was observed in females that carried the Adh-C allele, but no association was observed between Adh genotype and male mating success. There was heterogeneity in the success of different combinations of males and females, but only when the female lacked the C allele. Analyses of video recordings indicated that C-bearing females spent longer mounted by males and that they less frequently rejected males. Evidence is presented for mate discrimination by females not carrying a C allele. The significance of there being genetic differences in both mating success and in female discrimination are discussed in the context of previous results on mating behaviour in natural populations.

Mate Choice, Mate Guarding and Other Mating Tactics in Golden Hamsters Maintained Under Seminatural Conditions

Abstract Female hamsters freely interacting with a triad of males which had established a dominance hierarchy mated first and received more ejaculates from the dominant male in 11 of 15 replicates. Continuous observations of the animals on the day preceding receptivity and the day of receptivity suggest that differential mating success of the dominant males is the result of differential behavioral responses displayed prior to onset of receptivity. The females attacked all males, however, the dominant males persisted in following and licking the female at significantly higher frequencies than the subordinate males. The females responded differentially to the dominant males by vaginal marking in response to being licked and also on day 3 of the cycle by placing a higher number of vaginal marks in and around the dominant male's home area. In nine replicates the dominant male and female slept together on day 3. In two other cases the dominant male dug open the female's burrow early on day 4. Dominant males and females became active significantly earlier than subordinate males on day 4. Thus, dominant males enhanced their chances of mating both by being active earlier and by sleeping in proximity to the female. Males cannot prevent the promiscuous female from mating with another male. However, successful males continued to follow and mount the female during the period when she is likely to accept a second male. At this time they also display a high level of attack and chases against the subordinate males plus a high frequency of flank marking in the subordinate's home areas. These behaviors suggest a mate guarding function and are consistent with protection of the male's sperm investment.

Female choice selects for male sexual tail ornaments in the monogamous swallow

Male secondary sexual ornaments are widespread among polygynous animals1 where they apparently arise through female choice and differential mating success of males2–5. Darwin1 and Fisher2 suggested that female choice should also select for extravagant male ornaments in monogamous birds because female preference for ornamented males should result in earlier breeding which would increase male reproductive success by enhancing the quality and/or the quantity of offspring raised each year. In such cases female reproductive success should be positively related to body condition6 and a heritable component of the time of breeding should be affected by stabilizing selection7. Female preferences for orna-mented males would be favoured by sexual selection because such choosy females would have a greater probability of bearing orna-mented sons with an increased chance of pairing up early. I report here that in the monogamous swallow, Hirundo rustica, males with experimentally elpngated tail ornaments obtain mates more quickly than males with shorter tails, and enjoy increased reproductive output in one breeding season. Such males are also preferred by females seeking extra-pair-bond copulations. Thus male sexual ornaments may also be maintained by female mate choice in monogamous species.

SEASONAL VARIATION IN SEXUAL SELECTION IN THE MOTTLED SCULPIN.

Seasonal variation in sexual and natural selection in male mottled sculpins (Cottus bairdi) can be evaluated by calculating selection differentials, which measure the magnitude of phenotypic change resulting from selection, and by calculating indices of the opportunity for selection, which indicate the potential for phenotypic selection in a given interval. Selection differentials are high at the beginning of the breeding season and decline throughout the breeding season. The magnitude and direction of selection differentials depend on when spawning occurs and are independent of the size or age of the females that spawn. Annual selection differentials due to differences in mating success (female choice) are nearly constant between years. Annual selection differentials associated with hatching success are variable. Opportunities for selection (I = fitness variance/[mean fitness]2 ) show clear seasonal patterns. They are highest at the beginning and at the end of the spawning season. However, this variation is dependent on the mean used to calculate I, and hence variation in I values does not indicate a significant change in the variance of male fitness.

Differential mating success in populations of seaweed flies (Coelopa frigida)

The reproductive success of seaweed flies (Coelopa frigida) was studied in natural populations. The sizes of females, both mothers and those not producing eggs, as well as of the males available to be fathers, were estimated from their wing lengths. The animals were also classified for their genotype at the alcohol dehydrogenase (Adh) locus—a polymorphic locus tightly associated with a large chromosomal inversion. The fathers' genotypes were inferred from the genotypes of the mother and her offspring. Males of different Adh genotypes had different reproductive success. Reproductive success of genotypes was negatively correlated with the mean sizes of males. Differences in the reproductive success of females could be accounted for by their differential egg laying capacity, and is probably not a consequence of their mating behaviour. The incidence of progeny with mixed paternity varied from 20 per cent initially, to about 65 per cent when the animals had been mating for 6 days. It appears from previous work that large males are more successful in laboratory trials, yet under natural conditions genotypes associated with large male size have low mating success. Ways of reconciling these results and their relevance to understanding the inversion polymorphisms are discussed.

The Significance of Antiphonal Vocalisation By the Spring Peeper, Pseudacris Crucifer (Amphibia, Anura)

Abstract1. Male spring peepers respond to acoustic interference from an encroaching conspecific with a graded behavioral sequence: they increase their call repetition rate, they emit one or more encounter calls, they entrain their calls to those of the intruder. 2. Once entrained, males continue to call synchronously for extended periods. 3. The time interval between the end of the leader's call and the beginning of the follower's call (the intraduet interval) is consistent, and is maintained despite changes in the duration or repetition rate of the leader's call. 4. Our data corroborate earlier investigators who concluded that the follower is stimulated by the onset of the leader's call, but is inhibited from calling until a fixed time interval after the leader has ceased calling. 5. Controlled discrimination tests reveal no differential mating success by the leader or the follower within a simulated duet. 6. Females exhibited a significant preference for a duet over a soloing male. 7. Although test females were able distinguish between the simultaneous broadcast of two phase-locked call sequences differing only in frequency, they did so in the absence of alternative, uncovered calls. 8. We conclude that antiphonal vocalisation functions primarily to reduce the potential for broadcast interference during the initial phase of female phonotaxis.

Satin bowerbird parasites: a test of the bright male hypothesis

The number of a common parasite (Cuclotogaster sp.) on male satin bowerbirds was related to male mating success in a test of Hamilton and Zuk's (1982) bright male hypothesis. The data do not show the expected inverse correlation between female mating preferences and the level of parasitic infection of males predicted by that model. Nearly all matings are accomplished by bower-holding males (Borgia 1985a), but the vast majority of these males were uninfected. There were large differences in mating success among the uninfected bower holders, but this could not be explained by between male differences in the level of parasitic infection. From this I conclude that levels of parasitic infection are not now an important direct cause of intermale variation in mating success. The results are, however, consistent with a hypothesis that a low level of infection is indicative of the overall healthy condition of a male. If this is true, it supports the hypothesis that the ability to hold a bower may be an indicator of male condition to females.

Variation in Population Sex Ratio and Mating Success of Asexual Lineages of Alsophila pometaria (Lepidoptera: Geometridae)

Populations of Alsophila pometaria (Harris) are largely gynogenetic and composed of asexual females that must mate with a conspecific male to reproduce. Within this asexual contingent, there are a variety of electrophoretically defined multilocus genotypes. In this study we found that populations differ in sex ratio. We also found that there is an indication of differential mating success among asexual genotypes in a population of A. pometaria.

A STATISTICAL STUDY OF MATE CHOICE: SEXUAL SELECTION IN A PLETHODONTID SALAMANDER (DESMOGNATHUS OCHROPHAEUS).

Our experiment revealed the existence of significant variation in mating success in a salamander species in which males do not provide courtship feeding, nest sites, or parental care. Differences in mating success were based on natural variation among adult males and females, rather than on traits of an artificially selected set of potential mates. Courtship encounters deliberately involved only one male and one female, thus eliminating the potentially confounding effects of male-male competition and variations in mate encounter rate. Even after eliminating these effects and random error, some females were more likely than others to elicit spermatophore deposition by a male, and some males were more likely than others to inseminate a female. Such variation among individuals represents an opportunity for sexual selection to act on phenotypic characters that affect mating success. We advocate the use of a factorial experimental design to analyze sexual selection. This approach permits the statistical evaluation of separate male and female effects, interaction between these effects, and random effects. Designs which combine the evaluations of mating success and courtship behaviors could estimate the force of sexual selection on behavior.

RARE MALE MATING ADVANTAGE: A REVIEW

Summary1. The phenomenon of frequency‐dependent selection with an advantage for the rare type over the common type is intriguing because it implies balancing selection. Thus the high level of genetic variability as found in natural populations can be explained without the necessity of considerable genetic load. Rare male mating advantage is here defined as frequency‐dependent male sexual fitness with the rare type of male favoured. Such a rare male effect has been found to be very widespread in insects, at least under laboratory conditions, but there are several problems associated with this phenomenon which will be discussed in this review.2. To determine whether male mating success is frequency‐dependent, the quantity to be considered, most appropriately, is male sexual fitness of the one type relative to the other type (KM). Other approaches are discussed and it is shown that they confound differential mating success with frequency dependence of mating success. Moreover, it is shown that Levene's indices, previously designed as a measure of differential mating success, confound mating success with assortment, making these indices less useful.3. The theoretical relationship between frequency dependence of male mating success and total sexual fitness is more complicated than would be expected beforehand. Some examples are given to clarify this issue.4. Statistical tests to determine frequency dependence of male mating success have often been carried out in the past by determining the significance of deviations from random mating for each male type frequency separately. This procedure must be considered incorrect, because a change in male mating success over frequencies has to be tested. A correct way to do this is by testing all frequencies together in one single statistic, with only a moderate assumption about the type of frequency dependence. When mating success depends on frequency in a more irregular way, alternative tests are available, in which mating success at one frequency can be tested against any other frequency.5. The rare male effect has been studied most thoroughly in Drosophila, and has been demonstrated for many Drosophila species. The effect has been demonstrated for some other insects as well, and also for vertebrates. The rare male effect has been found for types of males differing in specific genotype (visible mutants, karyotypes), genetic background and geographic origin. A rare male effect has also been demonstrated for non‐genetic properties such as temperature of rearing. Though much less common than rare male mating advantage, there are some examples of rare female mating advantage. The expression of the rare male effect may be affected by several factors, such as age of the females, temperature or experimental approach.6. Only a few studies on rare type mating advantage in Nature have been carried out, but some positive evidence is available.7. It is pointed out that mating success will be frequency‐dependent if both types of males differ pronouncedly in mating behaviour, but the nature of this frequency dependence may vary. If one type of male is more vigorous than the other type, a one‐sided rare male effect can be explained on the basis of male–male competition. Quite often, though, a two‐sided rare male effect has been found for males not greatly differing in mating behaviour or mating success. Three types of explanations are considered: (a) The females prefer to choose the rare type of male; (b) The rare type of male compensates for its rarity by becoming more sexually active; (c) No individual behaviour is altered.8. As to the question whether the rare male effect could be an artefact of the experimental setup, the following points are relevant;(a) Biases as a result of alternate marking resulting in rare male mating advantage are theoretically possible, but are shown to be unimportant in explaining the rare male effect for Drosophila.(b) An effect analogous to the effect of alternate marking due to finite sample size is conceivable, but probably less important than suggested by Bryant et al. (1980).(c) When males are not sampled randomly with respect to place in the vial, bias may be introduced, resulting in a spurious rare male effect.(d) We feel that the standpoint of Bryant et al. (1980) that there is not yet any good evidence for the existence of a rare male effect is not sustained. Positive proof in favour of the existence of the rare male effect is that the effect can be modified by changing only one factor, such as odour. The artifacts just mentioned cannot explain why a rare male effect should be present in the one but absent in the other situation.

Nonrandom mate choice by females of Drosophila pseudoobscura: a case of outbreeding avoidance?

Relative mating success of genetically different males of Drosophila pseudoobscura was measured with five female strains using an experimental set-up consisting of a mating chamber containing 20 females of one strain and a total of 20 males of two different strains. No evidence was found indicating negative assortative mating, neither of the direct type, nor of the "rare male" type. Some strains, however, displayed strong positive assortative mating, as males of the same strain as the females were significantly more successful in obtaining copulations than were males of another strain present in the mating chambers. Deviations from random mating can be interpreted as the result of some males possessing higher levels of "vigour," but an alternative explanation is favoured, one involving female choice. Experimental results do indicate that the orange-eyed mutant flies, used as one of the male strains in all experiments, did have a relatively low level of courtship vigour, but not low enough to account for more than a small fraction of the differential mating success observed in some of the experiments.

Sexual Selection in the Spring Peeper, Hyla Crucifer (Amphibia, Anura): Role of the Advertisement Call

1. The advertisement call of the spring peeper exhibits significant variation in each of the four parameters examined: intensity, duration, frequency, repetition rate. 2. In playback experiments involving calls differing in a single parameter, females exhibited preference for loud calls, calls with a rapid repetition rate and low frequency calls. 3. Although we had hypothesized that females would prefer long calls to short calls, they did not. We attribute this lack of preference to unanticipated differences in the sound envelope of the two experimental calls. 4. Non-random choice by females during playback experiments may have been in response to the conspicuousness of the male call, or to encoded clues pertaining to male fitness. 5. Call repetition rate is positively correlated with body size (snout-vent length) while frequency is negatively correlated. 6. Anuran growth is thought to be indeterminate, so that larger males are typically older males. As a consequence of having survived longer, large males may be more fit. 7. Since females exhibited a preference for call parameters which were correlated with body size, we had anticipated that large males would experience differential mating success in nature. A comparison of amplexed and non-amplexed males over a three year period revealed no intergroup size difference. 8. We conclude that while females may select calls indicative of size, and perhaps fitness, during laboratory trials, such choices are likely more difficult in an active breeding congregation where acoustical interference and competition may tend to obscure call variation. 9. Finally we report the presence of small, non-calling satellite males and suggest that their success as sexual parasites may have influenced the size relationship between amplexed and non-amplexed males in our study.

RARE MALE MATING DISADVANTAGE IN DROSOPHILA MELANOGASTER.

1. Selective mating. a. Differential mating success by one male type as compared to another. b. Differential mating success by one female type as compared to another. 2. Assortative mating. a. Positive, leading to sexual isolation. b. Negative, the tendency of unlike individuals to mate. 3. Frequency-dependent mating. a. Rare male advantage or rare female advantage. b. Rare male disadvantage or rare female disadvantage.

The Evolutionary Effects of Mate Selection

Sexual selection is the subset of natural selection that depends on differential success in obtaining mates. Differential mating success within one sex, say males, may depend on the preferences of females for certain males, on the outcome of male-male competition for females, or on some combination of both processes. The purpose of this review is to analyze the evolutionary consequences of that component of sexual selection due to mating preferences. The most important step in such an analysis is to determine which characteristics of one sex determine mating preferences in the other sex, since these characteristics will be favored by sexual selection. In the past there has been much debate over the importance of mate choice as a selection pressure, and, in fact, about whether mate choice occurs at all (32, 63, 82, 128). This controversy can perhaps be largely avoided if mate choice is clearly defined. For the purposes of this review, mate choice includes all instances where there is differential mating success in one sex due to preferences exhibited by the other sex. Under this definition, mate choice includes preferences based on characters conferring genetic benefit to the young, on phenotypic characters conferring a more immediate benefit to the chooser (such as assistance with parental care), or even on characters external to the chosen individual (such as resources it controls).

Sexual behaviour and evolution of sexual dimorphism in body size in Jaera (Isopoda Asellota)

Individuals of the genus Jaera do not mate at random. In the species from the Mediterranean group, J. italica and. J. nordmanni, large males and medium sized females are at an advantage and their sizes are positively assorted. These effects are attributable to sexual competition between males. In the Ponlo-caspian species J. istri, no advantage of large males exists, but sexual selection could be the cause for a long passive phase prior to copulation and for normalizing selection upon female size at pairing. In the Atlantic species, J. albifrons, no selection can be ascertained. Differential mating success in males appears as one of the causes of the evolution of sexual dimorphism in body size, which makes males larger, of equal size, or smaller than females according to the species. The reason for this reversal in dimorphism seems to differ in the two sexes. Sexual selection provides an explanation for the evolution of male size, while the interspecific changes in female length are more likely due to ecological factors.

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

Strains of Drosophila 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 25:25 ratio, the FF males succeeded in mating more than did FS and SS males, while the FS males surpassed the SS males. As for the females, FF also surpassed SS. In experiments with a 5:45 or 45:5 ratio, some differences from the 25:25 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 the Adh polymorphism.