Female Mating Frequency Research Articles

The nutritional contribution of males affects the feeding behavior and spatial distribution of females in a bruchid beetle, Bruchidius dorsalis

The relationship between the quality/quantity of male investment and the feeding behavior of females was investigated in a bruchid weevil, Bruchidius dorsalis (Fahraeus), whose males donate nutrition via seminal fluid to females. Experiments on the effect of feeding regimes of both sexes on the mating frequency of females showed that females mated at a higher frequency if given low-quality food or poor male investment. On the other hand, the experiment that examined the effect of male investment quality on female feeding behavior showed that females receiving the high-quality investment exhibited feeding behavior less often. These results suggest that male investment and feeding behavior play the same role for B. dorsalis females. These experiments also showed that there are sex-related asymmetries in mating and feeding behaviors: females mated more often but males fed more often. Moreover, a field census suggested that only males visited non-host flowers to feed on the pollen and nectar during the non-flowering period of the host plants; females always stayed on the host plants irrespective of the flowering phenology. These results suggest that in B. dorsalis courtship role reversal and sex-specific feeding modes are fairly fixed and obligatory, and that male investment, derived from sexual selection, could affect the feeding behavior and spatial distribution of both sexes, which may have far-reaching impact in various ecological contexts.

Immune investment and sperm competition in a beetle

AbstractIndividuals that invest more in immunity may not be able to invest as much in o\ther life history traits. The overall effects on fitness depend on the balance of investment in life history traits and unnecessary investment in immunity may lower fitness. Adult mealworm beetles (Tenebrio molitor L.) modulate their investment according to the perceived risk of infection as larvae; the amount of investment can be assessed by body coloration. This prophylactic investment in immunity can be used to assess the costs of investment when no immune challenge is present. Whether investment in immunity is traded off against sperm competitive ability, another important fitness trait in insects, was investigated. Males that had invested more in immunity (dark males) competed against males that had invested less (light males) for fertilization of offspring. Dark males did lose sperm precedence over time, whereas light males did not. However, this decrease in sperm offensive ability may not result in decreased fitness for darker males under normal female mating frequencies; the decrease in offspring did not occur for 1 week, but females that have constant access to males mate once a day, which would negate any long‐term effects of male mating order. Thus, prophylactic investment in immunity does not produce immediate reductions in a male's ability to gain fertilizations. The costs to immune investment may be born by other fitness traits in T. molitor.

Monandry and polyandry as alternative lifestyles in a butterfly

Butterflies show considerable variability in female mating frequency, ranging from monandrous species to females mating several times in their lifetime. Degree of polyandry also varies within species, with some females only mating once and others mating multiply. Previous studies have shown that one reason for female multiple mating is to obtain nutritious male donations that both increase the longevity of females and result in higher lifetime fecundity. Despite the presence of male nutrient donations, some females of the green-veined white butterfly (Pieridae: Pieris napi) never mate more than once. In this study, we examined this apparent paradox. We assessed to what degree polyandry is under genetic control by a full-sib analysis, and we also estimated the broad sense heritability of female lifetime fecundity in singly mated females. Both polyandry and lifetime fecundity have a genetic component. However, degree of polyandry appears to be traded off against reduced longevity when denied the opportunity to mate more than once. It is possible that female P. napi display different reproductive strategies, with some females relying on male donations to realize their potential fecundity and others relying on their own resources for egg production. In nature, polyandrous females may be prevented from mating multiply due to unfavorable weather. We discuss the possibility that the trade-off between degree of polyandry and life span when singly mated may affect the maintenance of genetic variability in female mating frequency in this species. Possible reasons for these different reproductive strategies are discussed. Copyright 2002.

Natural variation in female mating frequency in a polyandrous butterfly: effects of size and age

In the polyandrous gift-giving butterfly Pieris napi, females mature at a smaller size than males under poor food conditions, so it has been suggested that females can compensate for their smaller size through nuptial feeding. We tested this hypothesis by assessing female polyandry in relation to female size in a study of a wild bivoltine population and in a laboratory experiment. Contrary to expectation, larger females had a higher mating frequency. In the wild population female polyandry was positively correlated with size and in the laboratory experiment larger females were also more polyandrous. Hence, smaller females cannot compensate for their size by increasing their mating frequency, perhaps because the rate of spermatophore breakdown sets the limit for polyandry and larger females are able to break down the spermatophore faster. In addition, the lifetime number of matings for wild females varied between one and five. As previous studies indicate that female fitness in P.napi appears to increase monotonically with number of mates as a result of the increase in spermatophore material received, it is surprising that 12% of the wild females in the oldest age classes had mated only once and that another 35–40% had mated only twice. This apparently maladaptive behaviour is discussed in terms of sexually antagonistic coevolution and whether environmental conditions influence optimal mating frequency. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.

Sexual conflict and cooperation in butterfly reproduction: a comparative study of polyandry and female fitness.

Most butterfly species can be characterized as capital breeders, meaning that reproductive output is strongly coupled to the amount of resources they have procured during the larval stage. Accordingly, female fecundity is generally correlated with female mass, both within and across species. However, the females of some species can be partly characterized as income breeders, in the sense that their reproductive output is dependent not only on larval-derived capital but also on resources acquired during the adult stage. These adult resources can be derived from female feeding or from male-transferred nuptial gifts. Recent studies on the within-species effects of multiple matings on female fitness show that females generally gain directly from multiple matings in terms of increased lifetime offspring production. Here, we test whether the positive effects of multiple mating on female fitness also hold at a comparative level, by conducting a laboratory study of female reproductive output in eight pierid species that differ in life-time female mating frequency. Female reproductive output, measured as cumulative egg mass divided by female mass, increased significantly with polyandry (r = 0.942, p < 0.001), demonstrating that the positive effect of mating rate on female reproductive fitness also holds between species. The positive effect of male nutrient contribution is substantial, and the per capita reproductive output is more than twice as high in the most polyandrous species as in the most monandrous ones. Hence, the positive net effect of the ejaculates is highly substantial, although males and females can have sexual interests that run counter to each other, setting the stage for sexually antagonistic coevolution, so that the various component parts of the male ejaculate-sperm, nutrients, anti-aphrodisiacs, and gonadotrophic hormones-may each correspond to a separate conflict-cooperation balance between the sexes. Two scenarios for the evolution of nuptial gifts in butterflies are discussed, one arguing that variation in larval food is the underlying factor and the other arguing that sexually antagonistic coevolution is the driving force. The two views are complementary rather than mutually exclusive, although the former hypothesis predicts that variation in female mating rate depends on variation in larval food availability, whereas the latter suggests that variation in female mating rate between species results from species-specific idiosyncrasies.

Polyandry in Lepidoptera: a heritable trait in Spodoptera exigua Hübner.

The genetic basis as well as the mode of inheritance of polyandry in Spodoptera exigua Hübner was studied in the laboratory by using a simple divergent selection experiment followed by F1 reciprocal crosses, F2 and backcrosses. There was an effective response to artificial selection for high (H line) and low (L line) female mating frequency with significant separation of the lines by the second generation of selection. The mean female mating frequency in the parental generation (1.57 matings per female) reached plateaus of 2.50 and 1.25 matings per female in the H and L lines, respectively, after six generations of selection. Selection response becomes saturated at about 90% and 25% levels of polyandry (percentage females re-mating) in the H and L lines, respectively, and consequently mono- and polyandric pure strains were not obtained. Polyandry levels in offspring from the H and L lines and their hybrids in F1, F2 and backcrosses consistently indicate that female mating frequency was more or less proportional to the relative amounts of genes derived from the H and L lines. Such a clear pattern of hybrid responses, together with the gradual selective changes under artificial selection, suggests the involvement of a polygenic system. Female mating frequencies from progeny of the two reciprocal F1 crosses were not significantly different, which suggest that the trait was autosomally inherited. Moreover, female mating frequency of F1 (pooled) progeny was not significantly different from the mid-parental value, which suggest no dominance. The computation of the Cavalli's joint scaling test consistently confirmed these results yielding values of d = 0.51 +/- 0.10 and h = 0.12 +/- 0.21. The broad sense heritability estimate was H2 = 0.73. It is concluded that polyandry in S. exigua is a polygenic, autosomal heritable trait and that additive genetic variance is available for selection for female mating frequency. The implications of the genetic basis of polyandry are briefly discussed in the context of current theories about this crucial insect mating system.

Reversible frequency-dependent switches in male mate choice.

Current sexual-selection theories predict that mating should occur preferentially with the highest-quality partner, and assume that for distinguishing among potential mates the choosy sex applies an internal representation of the characteristics of the desired mate, i.e. a template. Binary choice experiments were performed to test male mate choice between two different female colour morphs in the damselfly Ischnura elegans. Choice experiments were conducted before and after an habituation period, during which males were exposed to only one female colour morph. Given the choice between the two female morphs, males did exhibit a choice for the most recently experienced female morph. This is the first evidence for a reversible switch in mate choice in a frequency-dependent way. In contrast with previous studies on mate choice, template formation in male I. elegans seems not to be based on quality. Switching mate choice in a frequency-dependent manner, choosing the most common morph, probably allows males to minimize their search efforts and to maximize fitness.

Selection on age at reproduction in Drosophila melanogaster: female mating frequency as a correlated response.

We examined the effect of selection for age at reproduction on female mating frequency and fertility in female Drosophila melanogaster. Selection for increased age at reproduction (and hence increased lifespan) resulted in higher late life female mating frequencies, while females selected for younger ages at reproduction showed increased early life mating frequencies. These results indicate that the response to selection on age at reproduction has involved changes in the scheduling of female reproductive behavior.

Mating frequency, genetic structure, and sex ratio in the intermorphic female producing ant speciesMyrmecina nipponica

Summary1.Myrmecina nipponicahas two types of colonies: a queen colony type, in which the reproductive females are queens and new colonies are made by independent founding, and an intermorphic female colony type, in which reproductive females belong to a wingless intermediate morphology between queen and worker, and where colonies multiply through colonial budding.2. The mating frequencies of reproductive females in both types indicate monoandry. The relatedness among nestmates in both types was almost 0.75, however relatedness between mother and daughter in intermorphic female colonies was slightly higher than that of queen colonies.3. The sex ratio (corrected investment female ratio) was 0.70 at the population level, suggesting that the sex ratio is controlled by workers in this species, however the ratio differed greatly between the two types of colonies. Queen colonies (n = 37) had a female‐biased sex ratio of 0.77 while intermorphic female colonies (n = 33) had a ratio of 0.56.4. Each reproductive intermorphic female was accompanied by an average of 2.9 workers (including virgin intermorphic females) in the colonial budding, and when the investment to those workers was added to the female investment, the sex ratio reached 0.81.5. The frequency distribution of sex ratio was bimodal, with many colonies producing exclusively males or females, however mean estimated relatedness within colonies was almost 0.75. These data are inconsistent with the genetic variation hypothesis, which is one of the predominant hypotheses accounting for the between‐colony variation in sex ratio.

Female mating frequencies in Bombus spp. from Central Europe

The mating frequency of females in social insects is particularly interesting, because polyandry reduces colony relatedness and increases within-colony genetic variance. It thereby affects a complex balance of benefits and costs that determine the degree of reproductive skew, sex allocation to offspring, or the opportunities for nepotism and policing strategies. Few systematic surveys of female mating frequencies exist and many are based on unreliable behavioural observation or sperm counts. Here, we report the results of a survey of mating frequencies in eight European Bombus spp. by means of highly polymorphic microsatellite loci. Only B. hypnorum was found to be multiply mated, while the pattern found in B. terrestris, B. lucorum, B. pratorum, B. lapidarius, B. sicheli, B. hortorum, and B. pascuorum was compatible with single mating. The findings are compatible with recent claims that, with some exceptions, mating frequencies of social insect females are generally low.

SELECTION ON AGE AT REPRODUCTION IN DROSOPHILA MELANOGASTER: FEMALE MATING FREQUENCY AS A CORRELATED RESPONSE

We examined the effect of selection for age at reproduction on female mating frequency and fertility in female Drosophila melanogaster. Selection for increased age at reproduction (and hence increased lifespan) resulted in higher late life female mating frequencies, while females selected for younger ages at reproduction showed increased early life mating frequencies. These results indicate that the response to selection on age at reproduction has involved changes in the scheduling of female reproductive behavior.Editor: L. Nunney

Female choice in the opportunistic mating of wild chimpanzees ( Pan troglodytes schweinfurthii ) at Mahale

For female chimpanzees (Pan troglodytes schweinfurthii) in the Mahale Mountains National Park, Tanzania, the most common mating pattern is opportunistic. In such opportunistic matings, females copulated promiscuously but not randomly. This study describes female mate choice during 1-year observation of six females who exhibited regular genital-swelling cycles. During the study period, 169 opportunistic matings and four restrictive matings were recorded over the course of 51 days. As female estrus progressed, mating frequency and the number of adult male mating partners increased, although the number of potential mating partners did not change. Criteria of female choice examined were the direction and consent/rejection of courtship, proximity maintenance, and female grooming. Adult-male courtships were successful more often than those of adolescent males. During the earlier phase of estrus, females copulated rather promiscuously with many males. But during the later phase of estrus when the likelihood of conception is expected to be highest, they copulated repeatedly with high-ranking adult males. There was a positive correlation between female grooming frequency and mating frequency when the likelihood of conception was greatest. Female chimpanzees are thought to choose high-ranking males as fathers of their offspring. Moreover, female chimpanzees may adopt one or both of two mating strategies, i.e., a many-male strategy and a best-male strategy.

Sperm Digestion and Reciprocal Sperm Transfer Can Drive Hermaphrodite Sex Allocation to Equality.

The intensity of sperm competition determines how much reproductive effort should be invested in sperm. One important factor affecting sperm competition in internally fertilizing organisms is the mating frequency of females, since it determines the extent of competition between ejaculates. In simultaneous hermaphrodites, energy spent on sperm has to be traded off against energy expended on ova production. By extending an existing model, we consider how the number of matings affects sperm competition and, thus, sex allocation in internally fertilizing simultaneous hermaphrodites. We then go on to explore the consequences of two common characteristics of hermaphroditic mating systems, namely, sperm digestion and reciprocal insemination. Since sperm digestion reduces the competitive ability of a given ejaculate, it selects for increased sperm investment. As a result, the amount of sperm digested and male allocation can enter a coevolutionary cycle in which both will increase up to the point of equal investment in male and female gametes and in high rates of digestion. Because of this high degree of sperm digestion, fitness through the male function becomes more dependent on the amount of resources invested in sperm than on the number of matings. As a result, sperm digestion reduces Bateman's principle. Hence, hermaphrodites with sperm digestion should be less likely to display traits that increase the number of matings. Once ejaculates are large and costly, animals insisting on reciprocal sperm transfer will be favored since they receive some compensation for their investment. Under reciprocity, an even higher investment in sperm is favored. This is the result of the compensation received in the form of the partner's ejaculate and a nuptial gift effect by increasing a partner's production of eggs.

Sperm Digestion and Reciprocal Sperm Transfer Can Drive Hermaphrodite Sex Allocation to Equality

The intensity of sperm competition determines how much reproductive effort should be invested in sperm. One important factor affecting sperm competition in internally fertilizing organisms is the mating frequency of females, since it determines the extent of competition between ejaculates. In simultaneous hermaphrodites, energy spent on sperm has to be traded off against energy expended on ova production. By extending an existing model, we consider how the number of matings affects sperm competition and, thus, sex allocation in internally fertilizing simultaneous hermaphrodites. We then go on to explore the consequences of two common characteristics of hermaphroditic mating systems, namely, sperm digestion and reciprocal insemination. Since sperm digestion reduces the competitive ability of a given ejaculate, it selects for increased sperm investment. As a result, the amount of sperm digested and male allocation can enter a coevolutionary cycle in which both will increase up to the point of equal investment in male and female gametes and in high rates of digestion. Because of this high degree of sperm digestion, fitness through the male function becomes more dependent on the amount of resources invested in sperm than on the number of matings. As a result, sperm digestion reduces Bateman's principle. Hence, hermaphrodites with sperm digestion should be less likely to display traits that increase the number of matings. Once ejaculates are large and costly, animals insisting on reciprocal sperm transfer will be favored since they receive some compensation for their investment. Under reciprocity, an even higher investment in sperm is favored. This is the result of the compensation received in the form of the partner's ejaculate and a nuptial gift effect by increasing a partner's production of eggs.

Experimental variation in polyandry affects parasite loads and fitness in a bumble-bee

In many species of animals, females typically mate with more than one male (polyandry). Some social insects carry this behaviour to extremes1. For example, honeybee queens mate with ten to twenty (or even more) males on their nuptial flights2. The reasons for this behaviour remain unknown, given the obvious costs of time, energy and exposure to predation. Several potential benefits of polyandry have been proposed1,3,3,4, but none are well supported yet. Here we test the hypothesis that genetic diversity among a female's offspring may offer some protection from parasitism5,6,7. We artificially inseminated queens of a bumble-bee (Bombus terrestris L.) with sperm of either low or high genetic diversity. The resulting colonies were exposed to parasitism under field conditions. High-diversity colonies had fewer parasites and showed greater reproductive success, on average, than did low-diversity colonies. We suggest that female mating frequency may be influenced in part by parasites.

Male sexual ornament size but not asymmetry reflects condition in stalk–eyed flies

Models of sexual selection predict that females use ornament size to evaluate male condition. It has also been suggested that ornament asymmetry provides females with accurate information about condition. To test these ideas we experimentally manipulated condition in the stalk-eyed fly, Cyrtodiopsis dalmanni, by varying the amount of food available to developing larvae. Males of this species have greatly exaggerated eyestalk length and females prefer to mate with males with wider eyespans. Our experiments show that male ornaments (eyestalks) display a disproportionate sensitivity to condition compared with the homologous character in females, and to non-sexual traits (wing dimensions). In contrast, in neither sex did asymmetry reflect condition either in sexual ornaments or in non-sexual traits. We conclude that ornament size is likely to play a far greater role in sexual selection as an indicator of individual condition than does asymmetry.

Somatic condition determines female mating frequency in a field population of the grasshopper Eyprepocnemis plorans

Mating pairs and nonmating individuals of the grasshopper Eyprepocnemis plorans were collected in a natural population during the 1992 season, in order to determine whether sexual preferences of males and females are correlated with various morphological and physiological characters. These included condition based on body size and somatic and gonadal weight. A comparison of frequency distributions for these characters between the two types of individuals showed that mating frequency (the probability of being sampled while mating) was independent of the characters measured in males but was highly significantly dependent on somatic condition in females. Mating females showed a better somatic condition (defined as the residuals of the regression of somatic weight on body size) than nonmating ones. The implications of this finding in shaping the polygynandrous mating system of this species are discussed.

Somatic condition determines female mating frequency in a field population of the grasshopper Eyprepocnemis plorans

Mating pairs and nonmating individuals of the grasshopper Eyprepocnemis plorans were collected in a natural population during the 1992 season, in order to determine whether sexual preferences of males and females are correlated with various morphological and physiological characters. These included condition based on body size and somatic and gonadal weight. A comparison of frequency distributions for these characters between the two types of individuals showed that mating frequency (the probability of being sampled while mating) was independent of the characters measured in males but was highly significantly dependent on somatic condition in females. Mating females showed a better somatic condition (defined as the residuals of the regression of somatic weight on body size) than nonmating ones. The implications of this finding in shaping the polygynandrous mating system of this species are discussed.

Male density, female density and inter-sexual conflict in a stream-dwelling insect

Male and female densities were experimentally manipulated to determine their effects on inter-sexual conflict over mating in the water strider, Aquarius remigis. Upon encounter, males and females engage in a pre-mating struggle. The two components of female mating behaviour were the rate of evasive behaviours displayed, termed the index of female resistance, and struggle duration. The behaviour patterns of individuals of each sex changes depending on their previous experience. Females held at the high male density performed fewer resistance behaviours during struggles and struggled longer than did females held at the low male density. Female mating frequency was positively related to male density. A measure of male behaviour (male insistence) was derived from a regression of struggle duration on the index of female resistance. Males held at the high male density had greater insistence than those held at the low male density. Female density had no effect on male insistence. Male mating frequency was not related to male or female density. Overall, male and female body length were related to neither behaviour pattern nor mating frequency, although mated males were significantly longer than unmated males at low male density. The results are consistent with the view that mating frequency depends on female resistance, which varies in response to the costs of struggling that depend upon previous male harassment. Male mating behaviour changed with male density. Males harass both males and females, but females generally stay at the edge or out of the water when males are present. Since encounter rate is consistently low, males assess their probability of mating via their encounter rate with other males. A high male density leads males to increase their effort when they do encounter a female. Female mating behaviour was not related to male phenotype, suggesting that female choice is not present in A. remigis.

Mating Success in Bactrocera cucurbitae (Diptera: Tephritidae) Under Different Rearing Densities

The mating success of mass-reared and individually marked melon flies, Bactrocera cucurbitae (Coquillett), was observed during 7 d under 2 different densities in the laboratory. Frequency distribution of mating success of individual males under the low density was clumpy, but that of males under the high density was random. This difference seemed to result from disturbance among individuals under high density, where males could not make their territories. As mating frequency of females showed random or repulsed distributions in the 2 densities, all females seemed to mate at similar frequencies. Adult size was not related to mating success in either sex under the 2 densities. The characteristics of mating success in mass-reared melon flies for sterile insect techniques were considered to be related to extremely high adult rearing density.