Costs Of Mating Research Articles

Ageing and the evolution of female resistance to remating in seed beetles

Female remating behaviour is a key mating system parameter that is predicted to evolve according to the net effect of remating on female fitness. In many taxa, females commonly resist male remating attempts because of the costs of mating. Here, we use replicated populations of the seed beetle Acanthoscelides obtectus selected for either early or late life reproduction and show that 'Early' and 'Late' females evolved different age-specific rates of remating. Early females were more likely to remate with control males as they aged, while Late females were more resistant to remating later in life. Thus, female remating rate decreases with age when direct selection on late-life fitness is operating and increases when such selection is relaxed. Our findings not only demonstrate that female resistance to remating can evolve rapidly, but also that such evolution is in accordance with the genetic interests of females.

Adaptive speciation when assortative mating is based on female preference for male marker traits

Adaptive speciation occurs when frequency-dependent ecological interactions generate conditions of disruptive selection to which lineage splitting is an adaptive response. Under such selective conditions, evolution of assortative mating mechanisms enables the break-up of the ancestral lineage into diverging and reproductively isolated descendent species. Extending previous studies, I investigate models of adaptive speciation due to the evolution of indirect assortative mating that is based on three different mating traits: the degree of assortativity, a female preference trait and a male marker trait. For speciation to occur, linkage disequilibria between different mating traits, e.g. between female preference and male marker traits, as well as between mating traits and the ecological trait, must evolve. This can lead to novel speciation scenarios, e.g. when reproductive isolation is generated by a splitting in the degree of assortativeness, with one of the emerging lineages mating assortatively, and the other one disassortatively. I investigate the effects of variation in various model parameters on the likelihood of speciation, as well as robustness of speciation to introducing costs of assortative mating. Even though in the models presented speciation requires the genetic potential for strong assortment as well as rather restrictive ecological conditions, the results show that adaptive speciation due to the evolution of assortative mating when mate choice is based on separate female preference and male marker traits is a theoretically plausible evolutionary scenario.

Adaptive plasticity of floral display size in animal-pollinated plants

Plants need not participate passively in their own mating, despite their immobility and reliance on pollen vectors. Instead, plants may respond to their recent pollination experience by adjusting the number of flowers that they display simultaneously. Such responsiveness could arise from the dependence of floral display size on the longevity of individual flowers, which varies with pollination rate in many plant species. By hand-pollinating some inflorescences, but not others, we demonstrate plasticity in display size of the orchid Satyrium longicauda. Pollination induced flower wilting, but did not affect the opening of new flowers, so that within a few days pollinated inflorescences displayed fewer flowers than unpollinated inflorescences. During subsequent exposure to intensive natural pollination, pollen removal and receipt increased proportionally with increasing display size, whereas pollen-removal failure and self-pollination accelerated. Such benefit-cost relations allow plants that adjust display size in response to the prevailing pollination rate to increase their attractiveness when pollinators are rare (large displays), or to limit mating costs when pollinators are abundant (small displays). Seen from this perspective, pollination-induced flower wilting serves the entire plant by allowing it to display the number of flowers that is appropriate for the current pollination environment.

Carotenoid availability affects the development of a colour-based mate preference and the sensory bias to which it is genetically linked

Regardless of their origins, mate preferences should, in theory, be shaped by their benefits in a mating context. Here we show that the female preference for carotenoid colouration in guppies (Poecilia reticulata) exhibits a phenotypically plastic response to carotenoid availability, confirming a key prediction of sexual selection theory. Earlier work indicated that this mate preference is genetically linked to, and may be derived from, a sensory bias that occurs in both sexes: attraction to orange objects. The original function of this sensory bias is unknown, but it may help guppies find orange-coloured fruits in the rainforest streams of Trinidad. We show that the sensory bias also exhibits a phenotypically plastic response to carotenoid availability, but only in females. The sex-specificity of this reaction norm argues against the hypothesis that it evolved in a foraging context. We infer instead that the sensory bias has been modified as a correlated effect of selection on the mate preference. These results provide a new type of support for the hypothesis that mate preferences for sexual characters evolve in response to the benefits of mate choice--the alternatives being that such preferences evolve entirely in a non-mating context or in response to the costs of mating.

The Effect of Abdominal Spines on Female Mating Frequency and Fecundity in a Water Strider

Conflict between the sexes over mating decision may result in antagonistic coevolution in structures that increase control over copulation. In Aquarius paludum both females and males have long abdominal spines. We tested the hypothesis that abdominal spines increase female ability to resist male mating attempts and reduce the costs of mating in A. paludum. We manipulated female spine length and observed female mating and egg-production rate in two different studies. We found that females with intact spines succeeded to reject male mating attempt more often than females with removed spines. Intact females also mated less often than females with removed or shortened spines. Male presence and mating rate increased female egg number. Our results thus support the hypothesis that abdominal spines help female to reject male mating attempts but contrary to predictions, we found that A. paludum females somehow benefit from multiple matings in spite of the sexual conflict.

Mating in aphidophagous ladybirds: costs and benefits

Abstract: Mating costs and benefits were studied in three aphidophagous ladybirds, viz. Cheilomenes sexmaculata, Coccinella septempunctata and Propylea dissecta by subjecting them to different numbers of matings. Longevity, fecundity and percent egg viability were regressed with number of matings to determine the costs and trade‐offs, if any. Longevity decreased with increasing number of matings in both C. sexmaculata and P. dissecta indicating a cost of mating. The lack of such a cost in C. septempunctata has been ascribed to spermatophore consumption by females of this ladybird. Both fecundity and percent egg viability increased with increasing number of matings and are probably indicative of the benefits. Short‐lived females distributed their reproduction uniformly in their lifetime while long‐lived females showed a high burst of reproductive activity followed by a gradual decline. Percent egg viability decreased after the completion of the requisite number of matings.

Sexual selection research on spiders: progress and biases

The renaissance of interest in sexual selection during the last decades has fuelled an extraordinary increase of scientific papers on the subject in spiders. Research has focused both on the process of sexual selection itself, for example on the signals and various modalities involved, and on the patterns, that is the outcome of mate choice and competition depending on certain parameters. Sexual selection has most clearly been demonstrated in cases involving visual and acoustical signals but most spiders are myopic and mute, relying rather on vibrations, chemical and tactile stimuli. This review argues that research has been biased towards modalities that are relatively easily accessible to the human observer. Circumstantial and comparative evidence indicates that sexual selection working via substrate-borne vibrations and tactile as well as chemical stimuli may be common and widespread in spiders. Pattern-oriented research has focused on several phenomena for which spiders offer excellent model objects, like sexual size dimorphism, nuptial feeding, sexual cannibalism, and sperm competition. The accumulating evidence argues for a highly complex set of explanations for seemingly uniform patterns like size dimorphism and sexual cannibalism. Sexual selection appears involved as well as natural selection and mechanisms that are adaptive in other contexts only. Sperm competition has resulted in a plethora of morphological and behavioural adaptations, and simplistic models like those linking reproductive morphology with behaviour and sperm priority patterns in a straightforward way are being replaced by complex models involving an array of parameters. Male mating costs are increasingly being documented in spiders, and sexual selection by male mate choice is discussed as a potential result. Research on sexual selection in spiders has come a long way since Darwin, whose spider examples are reanalysed in the context of contemporary knowledge, but the same biases and methodological constraints have persisted almost unchanged through the current boom of research.

Female multiple mating for fertility assurance in red flour beetles (Tribolium castaneum)

The costs of mating with multiple partners include expenditure of energy and time and a reduction in lifespan, but females of many taxa mate with several different partners shortly after their first copulation. Often it is not clear what females gain from this behaviour. In this study, we used the red flour beetle (Tribolium castaneum Herbst, 1797) to test the hypothesis that females mate with multiple males for fertility assurance because the first copulation often does not lead to offspring production. We found that the probability of producing offspring, as measured by the proportion of females that produced offspring, was not affected by multiple mating when females were mated to virgin partners. However, when females were mated to nonvirgin partners, multiple mating led to an increased probability of producing offspring. To establish the mechanism through which multiple mating enhanced the probability of producing offspring, we further investigated whether this result was observed because multiple mating provided genetically compatible sperm or because it provided sufficient sperm. Viability of larvae from multiply mated females was higher than that of larvae from singly mated females, but the total number of adult offspring produced was not significantly different between the two groups. The capacity of males to inseminate females decreased in successive matings after the initial copulation, suggesting that ineffective copulations between virgin females and nonvirgin males are likely due to male sperm depletion. Therefore, mating with multiple males increased the probability that females would produce offspring and served as fertility assurance.

Is Male Cohabitation Costly for Females of the Spider Stegodyphus lineatus (Eresidae)?

AbstractReproductive interests of females and males can vary over a number of issues, including the number of matings and the occurrence and duration of mate guarding and cohabitation. The mating system of the spider Stegodyphus lineatus (Eresidae) is characterized by an exceptional sexual conflict where males induce females to remate by committing infanticide. Females experience high costs because of this male strategy, while males benefit. During the mating season, males tend to stay with females for several days. We examined whether this male strategy of cohabitation is also disadvantageous for females of S. lineatus. A field experiment revealed that male presence in a female's nest negatively affected her body condition, whereas cohabiting males gained weight because they fed on prey caught in webs of females. As a response, females did not renew their webs when males were present. Thus, females with a cohabiting male experienced the combined cost of prey loss and loss of time available for foraging. These costs are expected to increase with every additional cohabiting male. Mated females behaved more aggressively toward males than did virgin females. This behavior may be interpreted as an adaptive response to reduce mating costs.

Male dwarf chameleons assess risk of courting large, aggressive females

Conflict between the sexes has traditionally been studied in terms of costs of mating to females and female resistance. However, courting can also be costly to males, especially when females are larger and aggressively resist copulation attempts. We examined male display intensity towards females in the Cape dwarf chameleon, Bradypodion pumilum, in which females are larger than males and very aggressive. We assessed whether aggressive female rejection imposes potential costs on males and whether males vary their display behaviour with intensity of female rejection, female size or relative size differences. Males persisted in courtship after initial female rejection in 84% of trials, and were bitten in 28% of trials. Attempted mounts were positively associated with males being bitten. Males reduced courtship with increased intensity of female rejection. Male courtship behaviour also varied with female size: males were more likely to court and approach smaller females, consistent with the hypothesis that larger females can inflict more damage. These results suggest that, in addition to assessing female willingness to mate, male dwarf chameleons may use courtship displays to assess potential costs of persistence, including costs associated with aggressive female rejection, weighed against potential reproductive pay-offs associated with forced copulation.

Why do male Callosobruchus maculatus harm their mates?

The importance of cryptic female choice, i.e. female post-copulatory influence over male reproductive success, in driving the evolution of male traits remains controversial. The main aim of this thesis was to understand the post-copulatory consequences of sexual interactions and the importance of cryptic female choice in two species of beetle.Males of the red flour beetle Tribolium castaneum use their legs to rub the lateral edges of the female elytra during mating. When manipulating female perception of this behaviour, I found that females preferentially use the sperm of males with vigorous leg rubbing when they mate with more than one male. Leg rubbing also appeared to increase female rate of oviposition. Females do not seem to gain any indirect benefits by preferring males with an intense leg rubbing behaviour since this behaviour was found to have very low narrow sense heritability and did not appear to be condition dependent in its expression.Males of the bruchid beetle Callosobruchus maculatus have spiny genitalia that harm their mates. Females kick males during copulation and when prevented from kicking, suffered reduced lifetime offspring production as a consequence of more extensive injuries. Males were not able to delay female remating, increase rate of oviposition or increase sperm precedence by inflicting relatively severe injuries to non-kicking females. Hence, the injuries appear to be side effects of male efforts to remain in copula. When copulation duration was manipulated, ejaculate size and female lifetime offspring production increased with the length of copulation. Females reduced their mating rate when they had access to water, suggesting that they obtain water from the large ejaculates and trade-off their need for additional water against the costs of mating. Males may then reduce the benefits of remating by providing their mates with a large amount of water. Females did not increase their remating propensity to avoid inbreeding when they had mated to brothers. Together, these studies reveal the complexity of sexual interactions and the importance of post-copulatory processes for the fitness of both males and females.

Male harassment of female New Zealand sea lions, Phocarctos hookeri: mortality, injury, and harassment avoidance

Sexual aggression by male pinnipeds during breeding can lead to female injury and death, affecting reproductive success, fecundity, and increasing the cost of mating for females. Thus, females that employ strategies to minimize the probability of being injured will be at an advantage. Here we investigate the extent of injuries and the number of deaths attributed to male harassment, and test the hypothesis of whether the arrival and departure behaviour of female New Zealand sea lions (Phocarctos hookeri (Gray, 1844); NZSL) at Sandy Bay, Enderby Island, the Auckland Islands, is adapted to reduce the chance of injury or death from encounters with male NZSLs. During the breeding season, harassment by non-territorial male NZSLs causes mortality in adult female NZSLs, approximately 5 in every 1000 females breeding each year. Permanent scars from male bites are observed on 84% of adult females. This mortality and visible injury rate only represents the direct impacts on female NZSL from male harassment. Indirect impacts, such as the time and energy cost of avoidance behaviour, pup separation, and pup injury and death, can have as significant long-term effects on individuals and the population. We find that male harassment can influence the behaviour of individuals in NZSL breeding harems.

The benefits of multiple mating to female seaweed flies, Coelopa frigida (Diptera: Coelpidae)

Female seaweed flies, Coelopa frigida, have the potential to benefit from mating more than once. Single matings result in low fertility so females may benefit directly from multiple copulations by sperm replenishment. A chromosomal inversion associated with larval fitness, with heterokaryotypic larvae having higher viability than homokaryotypes, means that polyandrous homokaryotypic females have a higher probability of producing genetically fit offspring than monandrous homokaryotypic females. We allowed females to mate only once, repeatedly four times to the same male, or polyandrously four times to four different males. Multiply mated and polyandrous females laid more eggs and produced more offspring than singly mated and monandrous females, respectively. Polyandrous females laid more eggs, had higher egg-to-adult survival rates and produced more offspring than repeatedly mated females. Fertility rates did not differ between treatments. The observed fitness patterns therefore resulted from increased oviposition through multiple mating per se, and a further increase in oviposition coupled with higher egg-to-adult offspring survival benefits to polyandry. Daily monitoring of individual females over their entire life spans showed that multiple copulations induced early oviposition, with polyandrous females ovipositing earlier than repeatedly mated females. Singly mated and polyandrous females incurred a longevity cost independent of egg production, whereas repeatedly mated females did not. This suggests that repeatedly mating with the same male may counteract a general cost of mating. Longevity, however, was not correlated with overall female fitness. Our data are discussed in the overall context of the seaweed fly mating system.

Sex Peptide Causes Mating Costs in Female Drosophila melanogaster

Conflicts between females and males over reproductive decisions are common . In Drosophila, as in many other organisms, there is often a conflict over how often to mate. The mating frequency that maximizes male reproductive success is higher than that which maximizes female reproductive success . In addition, frequent mating reduces female lifespan and reproductive success , a cost that is mediated by male ejaculate accessory gland proteins (Acps) . We demonstrate here that a single Acp, the sex peptide (SP or Acp70A), which decreases female receptivity and stimulates egg production in the first matings of virgin females , is a major contributor to Acp-mediated mating costs in females. Females continuously exposed to SP-deficient males (which produce no detectable SP ) had significantly higher fitness and higher lifetime reproductive success than control females. Hence, rather than benefiting both sexes, receipt of SP decreases female fitness, making SP the first identified gene that is likely to play a central role in sexual conflict.

The Indirect Benefits of Mating with Attractive Males Outweigh the Direct Costs

The fitness consequences of mate choice are a source of ongoing debate in evolutionary biology. Recent theory predicts that indirect benefits of female choice due to offspring inheriting superior genes are likely to be negated when there are direct costs associated with choice, including any costs of mating with attractive males. To estimate the fitness consequences of mating with males of varying attractiveness, we housed female house crickets, Acheta domesticus, with either attractive or unattractive males and measured a variety of direct and indirect fitness components. These fitness components were combined to give relative estimates of the number of grandchildren produced and the intrinsic rate of increase (relative net fitness). We found that females mated to attractive males incur a substantial survival cost. However, these costs are cancelled out and may be outweighed by the benefits of having offspring with elevated fitness. This benefit is due predominantly, but not exclusively, to the effect of an increase in sons' attractiveness. Our results suggest that the direct costs that females experience when mating with attractive males can be outweighed by indirect benefits. They also reveal the value of estimating the net fitness consequences of a mating strategy by including measures of offspring quality in estimates of fitness.

Hemolymph loss during nuptial feeding constrains male mating success in sagebrush crickets

Although costs of mating have been widely documented in females, intrinsic costs of copulation have been poorly documented in males, and there is little evidence that such costs constrain male mating success under natural conditions. Male sagebrush crickets, Cyphoderris strepitans, offer females an unusual somatic food gift at copulation that may constitute a significant cost of copulation: females chew on the ends of the males’ fleshy hind wings and ingest hemolymph seeping from the wounds they inflict. Previous studies have shown that once a male has mated, his probability of obtaining an additional copulation is reduced relative to that of a virgin male seeking to secure his first mating. If the future mating prospects of nonvirgin males are diminished because of the costs of copulation, this could stem either from the resources required to manufacture a new spermatophore or through the energy needed to replenish hemolymph lost through female wing-feeding. To distinguish between these two alternatives, we experimentally depleted virgin males of varying amounts hemolymph in a way that mimicked hemolymph loss of nonvirgin males, without the attendant costs of spermatophore production. After they had been treated, males were released in the field and recaptured over the course of the breeding season to monitor their mating success. Control males mated significantly sooner than did males depleted of hemolymph. We conclude, therefore, that the depletion of hemolymph that occurs through female wing feeding is sufficient by itself to diminish a nonvirgin male’s ability to secure another mating. Key words: costs of mating, Cyphoderris strepitans, mating success, nuptial food gift, sagebrush crickets, sexual selection. [Behav Ecol 15:845–849 (2004)]

Variation in harem size of red deer (Cervus elaphus L.): the effects of adult sex ratio and age‐structure

AbstractThe relationships among harem size, adult sex ratio (proportion of males > 5 years in the adult population, i.e. males > 5 years plus females > 2 years) and male age‐structure of red deer Cervus elaphus were investigated in La Petite Pierre National Reserve (PPNR) in France. We tested whether: (1) increasing adult sex ratio leads to a decrease in harem size along with an increase in the number of harems within a given rut period; (2) whether participation of sub‐adult males in mating activities increases with decreasing adult sex ratio, and as the proportion of adult males decreases. Harem size did not vary over the mating period, suggesting a high turnover of harem‐holders leading to an increase in the costs of mating for males. Harem size averaged 1.43 ± 0.91 and was lower than harem sizes typically reported for red deer (e.g. > 2.5 in Scotland and Norway). In support of the first prediction, a decrease in harem size and an increase in the total number of harems seen with an increasing sex ratio was observed (harem size = 2.08 – 1.26 [±0.43] ± (sex ratio); r2= 0.25, F1,18= 6.19, P= 0.02). Both the uniform distribution of females among harem stags and the small harem sizes observed in PPNR might concur to a smaller variance in male reproductive success than previously reported in red deer. Lastly, in partial support of the second prediction, the proportion of sub‐adult males observed during the mating season decreased with increasing adult sex ratio and with increasing proportions of adult males. Whether or not the lower proportion of sub‐adults seen when competition among mature males increases means that fewer young males mate cannot be assessed from our study.

The evolution of paternal care with overlapping broods.

Most attempts to model the evolution of parental care assume that caring and mating are mutually exclusive activities (i.e., individuals acquire and guard broods "sequentially"). However, in most fish and certain insects, males can keep mating and collecting additional eggs while continuing to guard broods obtained earlier (i.e., males guard "overlapping" broods). We present a model of parental care with overlapping broods in which males can mate and guard simultaneously, even though there is a trade-off between these two activities. Within this framework, we show that male care is favored by short female processing times and high population densities, which minimize the mating cost of care. Relatively low mortality while guarding is also important for the stability of male care. Female care, on the other hand, is favored by long female processing times and low populations densities, which lead to longer intermating intervals. Biparental care is stable only when the cost to benefit ratio of care was not biased toward either sex. We derive quantitative estimates of fitness for different strategies for two species of assassin bugs with male and female uniparental care and show that the model predicts the correct form of care for both species. We believe our model might help explain the prevalence of male uniparental care in certain taxa, such as fish.

Exploring the consequences of postmating–prezygotic interactions between the sexes

The role of male-female interactions in the divergence of postmating-prezygotic reproductive traits has recently focused on sexual conflict as the selective force. While an association between mating costs and benefits suggests that antagonistic interactions may be important, a mosaic of processes may actually mediate the evolutionary dynamics of postmating-prezygotic interactions. Our study examines the ecological relevance of mating effects on females. We test this critical but often overlooked assumption in desert Drosophila, where the species' ecology provides a framework for evaluating the evolutionary implications of such mating consequences. We show that mating has a profound impact on an ecologically critical character--desiccation resistance. To explore what selective factors might underlie the observed population differences in mating effects, we test whether trends in the data match predictions based on the species' ecology. While these preliminary data are consistent with the expectation that the mating benefits are positively correlated with environmental conditions, further examination reveals an additional unanticipated association with the reproductive environment. This unexpected association challenges existing assumptions regarding the forces driving divergence of traits involved in mating.

Mating Tactics in Response to Costs Incurred by Mating with Multiple Males in Wild Female Japanese Macaques

We investigated the costs of mating with multiple males in terms of feeding time, traveling distances, sexual proceptivity, and male aggression, for wild female (Macaca fuscata yakui) on Yakushima Island, Japan. We analyzed all-day focal sampling data from 7 females during the mating season (Sept.-Nov. 1996). On days when estrous females copulated with multiple males, they decreased their feeding time to half that of anestrous days, traveled longer distances, showed more proceptive sexual behaviors and received more aggression from subordinate males than on days when they copulated with only the 1st-ranking male. On days when females copulated with only the 1st-ranking male, they showed no difference in feeding time with that of anestrous days, and expended less effort than the above mating pattern because of short traveling distances, diminished sexual proceptivity and a lower frequency of aggression received. The results suggest that the costs of estrous vary according to female sexual proceptivity and the number and social status of mating partners. Female Japanese macaques exhibit a mixed mating strategy over prolonged estrous periods, which may provide females with opportunities to maximize the benefits of copulating with multiple males and to minimize the costs of estrus by mating with only the 1st-ranking male. During an estrous cycle, females may be adjusting efforts for reproduction and survival; i.e., mating vs. feeding.