Benefits and Costs of Dominance in the Angelfish Centropyge bicolor

Social groups are often structured by dominance hierarchies in which subordinates consistently defer to dominants. High‐ranking individuals benefit by gaining inequitable access to resources, and often achieve higher reproductive success; but may also suffer costs associated with maintaining dominance. We used a large‐scale field study to investigate the benefits and costs of dominance in the angelfish Centropyge bicolor, a sequential hermaphrodite. Each haremic group contains a single linear body size‐based hierarchy with the male being most dominant, followed by several females in descending size order. Compared to their subordinate females, dominant males clearly benefited from disproportionately high spawning frequencies, but bore costs in lower foraging rates and greater aggressive defence of their large territories. Within the female hierarchy, more dominant individuals benefited from higher spawning frequencies and larger home ranges, but displayed neither higher foraging rates nor spawn order priority. However, dominance in females was also linked to aggressiveness, particularly towards immediate subordinates, suggesting that females were using energetically costly aggression to maintain their high rank. We further showed by experimentally removing dominant females that the linear hierarchy was also a social queue, with subordinates growing to inherit higher rank with its attendant benefits and costs when dominants disappeared. We suggest that in C. bicolor, the primary benefit of high rank is increased reproductive success in terms of current spawning frequency and the prospect of inheriting the male position in the near future, which may be traded off against the cost of aggressively defending rank and territory.     

Males Benefit from Mating with Outbred Females in Drosophila littoralis: Male Choice for Female Genetic Quality?

The evolution and expression of mate choice behaviour in either sex depends on the sex‐specific combination of mating costs, benefits of choice and constraints on choice. If the benefits of choice are larger for one sex, we would expect that sex to be choosier, assuming that the mating costs and constraints on choice are equal between sexes. Because deliberate inbreeding is a powerful genetic method for experimental manipulation of the quality of study organisms, we tested the effects of both male and female inbreeding on egg and offspring production in Drosophila littoralis. Female inbreeding significantly reduced offspring production (mostly due to lower egg‐to‐adult viability), whereas male inbreeding did not affect offspring production (despite a slight effect of paternal inbreeding on egg‐to‐adult viability). As inbreeding depressed female quality more than male quality, the benefits of mate choice were larger for males than for females. In mate choice experiments, inbreeding did not affect male mating success (measured as a probability to be accepted as a mate in a large group), suggesting that females did not discriminate among inbred and outbred males. In contrast, female mating success was affected by inbreeding, with outbred females having higher mating success than inbred females. This result was not explained by lower activity of inbred females. Our results show that D. littoralis males benefit from mating with outbred females of high genetic quality and suggest adaptive male mate choice for female genetic quality in this species. Thus, patterns of mating success in mate choice trials mirrored the benefits of choice: the sex that benefited more from choice (i.e. males) was more choosy.     

The Evolution of Male and Female Parental Care in Fishes

In this paper we propose an explanation for (a) the predominanceof male care in fishes, and (b) the phylogenies and transitionsthat occur among care states. We also provide a general evolutionarymodel for studying the conditions under which parental careevolves. Our conclusions are as follows: (i) Parental care hasonly one benefit, the increased survivorship of young. It may,however, have three costs: a "mating cost," an "adult survivorshipcost," and a "future fertility cost." (ii) On average, malesand females will derive the same benefit from care. They probablyalso pay the same adult survivorship cost. However, their matingcost and future fertility costs may differ, (iii) A mating costusually applies only to males. However, this cost may be reducedby male territoriality and, in some situations, be entirelyremoved. Under this condition, natural selection on presentreproductive success is equivalent for males and females, (iv)When fecundity accelerates with body size in females, whilemale mating success follows a linear relationship with bodysize, future fertility costs of parental care are greater forfemales than males. Although further tests are needed, a preliminaryanalysis suggests this often may be the case in fishes. Thus,the predominance of male parental care in fishes is not explainedby males deriving greater benefits from care, but by males payingsmaller future costs. Males thus accrue a greater net fitnessadvantage from parental care (see expressions [6] and [12]).(v) The evolution of biparental care from uniparental male caremay occur because male care selects for larger egg sizes andincreased embryo investment by females. This increases the benefitto the female of parental care, (vi) By contrast, uniparentalfemale care may originate from biparental care when males areselected to desert. This occurs when female care creates a matingcost to males. In some cases male desertion may "lock" femalesinto uniparental care. However, in many other cases femalesmay be selected to desert, giving rise to "no care." (vii) Theorigin of uniparental female care from no care is rare in externallyfertilizing fishes. This is because the benefits of care rarelyoutweigh a female's future fertility costs (expression [9]).For internally fertilizing species, however, the benefit ofcare is high whereas the cost is probably low. Most of thesespecies have evolved embryo retention, (viii) When parentalcare begins with male care and moves to biparental care, ouranalysis suggests that care evolution will include cyclicaldynamics. Parental care in some fishes may thus be seen as transitionaland changing through evolutionary time rather than as an evolutionarilystable state. In theory, "no care" may be a phylogeneticallyadvanced state.     

Incidental Sanctions and the Evolution of Direct Benefits

Recent research has shown that a variety of traits that increase male success in mating and sperm competition can impose costs on females, resulting in antagonistic coevolution between the sexes. Yet, in many animals, females are known to receive direct benefit from their mates, including many in which female multiple mating results in intense sperm competition among males. The most common explanation for the evolution of male‐provided direct benefits is pre‐mating female choice based on benefit quality. This explanation is insufficient, however, for those direct benefits that females cannot directly assess prior to mating. Given that intrasexual selection will often favor male traits that increase female mating costs, many types of direct benefits can thus be difficult to explain. In this paper, we review four additional hypotheses for the evolution of male‐provided direct benefits, and present a fifth hypothesis that has received little attention. This latter hypothesis proposes that selection often favors female reproductive tactics that are conditional upon the past costs and benefits of mating. These conditional female reproductive tactics should evolve because the quality of the benefit provided by a previous mate can change the costs and benefits of alternative reproductive decisions. Furthermore, many of the conditional reproductive tactics we might expect females to express should incidentally penalize males which provide lower quality direct benefits. These conditional reproductive tactics may thus play an important role in determining whether females incur costs or receive benefits from their mates. In addition to favoring the evolution of direct benefits, we argue that conditional female reproductive tactics may also favor reliable signaling of benefit quality. The most common explanation for reliable signaling is the handicap mechanism, which proposes that differential costs of signaling prevent low quality males from deceptively producing attractive signals. For direct benefits, however, there is a second type of deception: males which produce attractive signals and can afford to provide high quality direct benefits may choose to cheat on the advertised benefit. The handicap mechanism does nothing to prevent cheating on direct benefits by males which can afford to produce attractive signals, and is thus insufficient for ensuring reliable signaling of benefit quality. In contrast, conditional female reproductive tactics that incidentally penalize low benefit males should also penalize males which cheat on the benefits advertised by their signals.     

FEMALES RECEIVE A LIFE-SPAN BENEFIT FROM MALE EJACULATES IN A FIELD CRICKET

Abstract.— Mating has been found to be costly for females of some species because of toxic products that males transfer to females in their seminal fluid. Such mating costs seem paradoxical, particularly for species in which females mate more frequently than is necessary to fertilize their eggs. Indeed, some studies suggest that females may benefit from mating more frequently. The effect of male ejaculates on female life span and lifetime fecundity was experimentally tested in the variable field cricket, Gryllus lineaticeps. In field crickets, females will mate repeatedly with a given male and mate with multiple males. Females that were experimentally mated either repeatedly or multiply lived more than 32% longer than singly mated females. In addition, multiply mated females produced 98% more eggs than singly mated females. Because females received only sperm and seminal fluid from males in the experimental matings, these life‐span and fecundity benefits may result from beneficial seminal fluid products that males transfer to females during mating. Mating benefits rather than mating costs may be common in many animals, particularly in species where female mate choice has a larger effect on male reproductive success than does the outcome of sperm competition.     

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

Reproductive 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‐induced costs of mating for females compensated by offspring viability benefits in an insect

Sexual conflict facilitates the evolution of traits that increase the reproductive success of males at the expense of components of female fitness. Theory suggests that indirect benefits are unlikely to offset the direct costs to females from antagonistic male adaptations, but empirical studies examining the net fitness pay‐offs of the interaction between the sexes are scarce. Here, we investigate whether matings with males that invest intrinsically more into accessory gland tissue undermine female lifetime reproductive success (LRS) in the cricket Teleogryllus oceanicus. We found that females incur a longevity cost of mating that is proportional to the partner’s absolute investment into the production of accessory gland products. However, male accessory gland weight positively influences embryo survival, and harmful ejaculate‐induced effects are cancelled out when these are put in the context of female LRS. The direct costs of mating with males that sire offspring with higher viability are thus compensated by direct and possibly indirect genetic benefits in this species.     

Mate-Guarding as a Male Reproductive Tactic in <Emphasis Type="Italic">Propithecus verreauxi</Emphasis>

Sexual selection theory predicts that in group-living mammals, male reproductive tactics can lead to high reproductive skew in favor of dominant individuals. In sifakas (Propithecus verreauxi), a group-living primate with extremely seasonal reproduction, male reproductive success is highly skewed because dominant males sire almost all offspring despite a tendency toward an even adult group sex ratio. To understand the underlying behavioral mechanism resulting in this rank-related reproductive skew in male sifakas, we studied mate-guarding as a potential reproductive tactic. Behavioral observations of dominant males and adult females in combination with hormonal determination of timing of female receptivity in 9 groups at Kirindy Forest revealed that dominant males spent more time in proximity to females when they were receptive and were responsible for the maintenance of this proximity. Results also indicated that monopolization of receptive females was facilitated by both estrous asynchrony within groups and by the ability of dominant males to obtain olfactory cues as to the timing of female receptivity. Although dominant males engaging in mate-guarding are expected to experience various costs, there was no evidence for decreased foraging behavior and only a trend toward increased aggression between dominant and subordinate non-natal males within groups. Our results are in accordance with the hypothesis that dominant males use mate-guarding to monopolize receptive females and that it is one proximate mechanism that contributes to the high reproductive skew observed within the population of male sifakas at Kirindy.     

Treat ’em Mean,Keep ’em (sometimes) Keen: Evolution of Female Preferences for Dominant and Coercive Males

How should females choose their mates if choice is not completely free, but at least partly dictated by outcomes of male–male competition, or sexual coercion? This question is of central importance when evaluating the relationship between sexually antagonistic ‘chase-away’ scenarios and models of more traditional female choice. Currently, there is a mismatch between theories: indirect benefits are seen to play a role in conventional mate choice, whereas they are not predicted to have an influence on the outcome if matings impose direct costs on females. This is at odds with the idea that resistance and preference are two sides of the same coin: either leads to a subset of males enjoying enhanced mating success. In the same way as choosy females benefit from mating with sexy males if this yields sexy sons, females could benefit from being manipulated or ‘seduced’, if the manipulative or seductive ability of males is heritable. Here I build a model where male dominance (or coerciveness) improves his mating success, and this relationship can be modified by female behaviour. This clarifies the definitions of resistance and preference: resisting females diminish the benefit a male gains from being dominant, while preferences enhance this pre-existing benefit enjoyed by dominant males. In keeping with earlier theory, females may evolve to resist costly mating attempts as a counterstrategy to male traits, particularly if male dominance is environmentally rather than genetically determined. Contrary to earlier results, however, indirect benefits are also predicted to influence female mating behaviour, and if sufficiently strong, they may produce female preferences for males that harm them.     

Mating patterns in late-maturing female Mediterranean tarantulas may reflect the costs and benefits of sexual cannibalism

During courtship and mating, males of some invertebrate predators risk being killed and consumed by females, who in turn can obtain a foraging benefit from feeding on males. In these invertebrates, the sex ratio at the end of the mating season is usually female biased, probably due to sexual cannibalism and other sources of male mortality. Thus, at the end of the mating season males can be a limited resource to females as both mates and prey. Because of the high risk incurred when approaching females, males should show mate choice. To date there are little data on the costs and benefits of sexual cannibalism in natural populations. For one month we followed the mating patterns of 60 late-maturing Mediterranean tarantula, Lycosa tarentula L., females in a desert grassland population. The later a female matured, the shorter was her cohabitation time with males and the lower her probability of cohabiting with a male at all, suggesting that late-maturing females may be limited in their access to males as mates. At the end of the mating season, nonsexually cannibalistic late-maturing females also had poorer body conditions than did both sexually cannibalistic late-maturing females and early-maturing females, suggesting that late-maturing females may be also limited in their access to males as food. Females had higher mating success if they were smaller or in better condition (better fed). This pattern may reflect either male choice, or the possibility that small, well-fed females have higher mating success because they are less aggressive towards males. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.      

Why Do Dolphins Carry Sponges?

Tool use is rare in wild animals, but of widespread interest because of its relationship to animal cognition, social learning and culture. Despite such attention, quantifying the costs and benefits of tool use has been difficult, largely because if tool use occurs, all population members typically exhibit the behavior. In Shark Bay, Australia, only a subset of the bottlenose dolphin population uses marine sponges as tools, providing an opportunity to assess both proximate and ultimate costs and benefits and document patterns of transmission. We compared sponge-carrying (sponger) females to non-sponge-carrying (non-sponger) females and show that spongers were more solitary, spent more time in deep water channel habitats, dived for longer durations, and devoted more time to foraging than non-spongers; and, even with these potential proximate costs, calving success of sponger females was not significantly different from non-spongers. We also show a clear female-bias in the ontogeny of sponging. With a solitary lifestyle, specialization, and high foraging demands, spongers used tools more than any non-human animal. We suggest that the ecological, social, and developmental mechanisms involved likely (1) help explain the high intrapopulation variation in female behaviour, (2) indicate tradeoffs (e.g., time allocation) between ecological and social factors and, (3) constrain the spread of this innovation to primarily vertical transmission.     

Polyandrous females acquire indirect benefits in a nuptial feeding species

The relative force of direct and indirect selection underlying the evolution of polyandry is contentious. When females acquire direct benefits during mating, indirect benefits are often considered negligible. Although direct benefits are likely to play a prominent role in the evolution of polyandry, post‐mating selection for indirect benefits may subsequently evolve. We examined whether polyandrous females acquire indirect benefits and quantified direct and indirect effects of multiple mating on female fitness in a nuptial gift‐giving spider (Pisaura mirabilis). In this system, the food item donated by males during mating predicts direct benefits of polyandry. We compared fecundity, fertility and survival of singly mated females to that of females mated three times with the same (monogamy) or different (polyandry) males in a two‐factorial design where females were kept under high and low feeding conditions. Greater access to nutrients and sperm had surprisingly little positive effect on fitness, apart from shortening the time until oviposition. In contrast, polyandry increased female reproductive success by increasing the probability of oviposition, and egg hatching success indicating that indirect benefits arise from mating with several different mating partners rather than resources transferred by males. The evolution of polyandry in a male‐resource‐based mating system may result from exploitation of the female foraging motivation and that indirect genetic benefits are subsequently derived resulting from co‐evolutionary post‐mating processes to gain a reproductive advantage or to counter costs of mating. Importantly, indirect benefits may represent an additional explanation for the maintenance of polyandry.     

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.     

Weighing costs and benefits of mating in bushcrickets (Insecta: Orthoptera: Tettigoniidae), with an emphasis on nuptial gifts,protandry and mate density

ABSTRACT: Sexual selection is a major force driving evolution and is intertwined with ecological factors. Differential allocation of limited resources has a central role in the cost of reproduction. In this paper, I review the costs and benefits of mating in tettigoniids, focussing on nuptial gifts, their trade-off with male calling songs, protandry and how mate density influences mate choice. Tettigoniids have been widely used as model systems for studies of mating costs and benefits; they can provide useful general insights. The production and exchange of large nuptial gifts by males for mating is an important reproductive strategy in tettigoniids. As predicted by sexual selection theory spermatophylax size is condition dependent and is constrained by the need to invest in calling to attract mates also. Under some circumstances, females benefit directly from the nuptial gifts by an increase in reproductive output. However, compounds in the nuptial gift can also benefit the male by prolonging the period before the female remates. There is also a trade-off between adult male maturation and mating success. Where males mature before females (protandry) the level of protandry varies in the direction predicted by sperm competition theory; namely, early male maturation is correlated with a high level of first inseminations being reproductively successful. Lastly, mate density in bushcrickets is an important environmental factor influencing the behavioural decisions of individuals. Where mates are abundant, individuals are more choosey of mates; when they are scarce, individuals are less choosey. This review reinforces the view that tettigoniids provide excellent models to test and understand the economics of matings in both sexes.     

A sex allocation cost to polyandry in a parasitoid wasp

The costs and benefits of polyandry are central to understanding the near-ubiquity of female multiple mating. Here, we present evidence of a novel cost of polyandry: disrupted sex allocation. In Nasonia vitripennis, a species that is monandrous in the wild but engages in polyandry under laboratory culture conditions, sexual harassment during oviposition results in increased production of sons under conditions that favour female-biased sex ratios. In addition, females more likely to re-mate under harassment produce the least female-biased sex ratios, and these females are unable to mitigate this cost by increasing offspring production. Our results therefore argue that polyandry does not serve to mitigate the costs of harassment (convenience polyandry) in Nasonia. Furthermore, because males benefit from female-biased offspring sex ratios, harassment of ovipositing females also creates a novel cost of that harassment for males.     

Ecological selection and sexual dimorphism in the sooty oystercatcher,Haematopus fuliginosus

Male and female sooty oystercatchers (subspecies Haematopus fuliginosus fuliginosus; Haematopodidae) have an average difference in bill length of 19%. We studied the relationship between this sexual dimorphism and foraging ecology at coastal sites in southern New South Wales, Australia. Intersexual foraging divergence was most striking in diet, with seven prey classes eaten exclusively by one sex (male: 4, female: 3), and all shared prey classes eaten in different proportions. Intersexual diet partitioning was also observed in energetic rewards gained from foraging, with females gaining highest energetic benefits from eating ascidians and males from eating limpets. Furthermore, within the most commonly consumed prey item, limpets, females gained higher energetic benefit from eating smaller sizes while males gained greater rewards from the largest limpet sizes. Intersexual divergence was also observed in several aspects of foraging behaviour. Finally, there was a significant effect of tidal cycles upon intersexual niche partitioning in this species; the degree of diet divergence varied between tide conditions and females had a consistently more efficient dietary intake on neap tides than males. Diet divergence in the sooty oystercatcher is greater than previously observed in any oystercatcher, and is correlated with the largest sexual bill dimorphism recorded in this family. It is argued that intersexual competition between territorial pairs is operating to diverge male and female bill morphology.     

Time and energy constraints and the evolution of sexual size dimorphism — to eat or to mate?

Summary We present an empirical test of the Ghiselin—Reiss small-male hypothesis for the evolution of sexual size dimorphism (SSD). In mating systems dominated by scramble competition, where male reproductive success is a function of encounter rate with females, small males may be favoured when food is limiting because they require lower absolute amounts of food. Given a trade-off between time and energy devoted to foraging and to mate acquisition, small males should be able to devote more time to the latter. If at the same time larger females are favoured, this mechanism will contribute to the evolution of SSD and may be the major determinant of the female-biased SSDs that characterize most animal taxa. We tested this hypothesis using the water strider,Aquarius remigis (Heteroptera: Gerridae), a scramble competitor which mates many times over a prolonged mating season and which shows female-biased SSD. Laboratory experiments demonstrated that foraging success and giving up times (GUTs) are lower for males than for females during the reproductive season and that male water striders flexibly alter their time budgets under conditions of energy limitation. Controlled feeding experiments showed that male and female longevity, female fecundity and male mating success are positively related to food availability. As predicted, male body size is negatively correlated with several indices of male fitness (longevity, number of mating attempts and mating success), while female body size is positively correlated with longevity. These results are consistent with the hypothesis that scramble competition for mates favours small males in this species and provides empirical support for the Ghiselin—Reiss small-male hypothesis.     

Conflict between direct and indirect benefits of female choice in desert Drosophila

Identifying the factors that contribute to the adaptive significance of mating preferences is one major goal of evolutionary research and is largely unresolved. Both direct and indirect benefits can contribute to mate choice evolution. Failure to consider the interaction between individual consequences of mate choice may obscure the opposing effects of individual costs and benefits. We investigate direct and indirect fitness effects of female choice in a desert fly (Drosophila mojavensis), a species where mating confers resistance to desiccation stress. Females prefer males that provide a direct benefit: greater resistance to desiccation stress. Mating preferences also appear to have indirect consequences: daughters of preferred males have lower reproductive success than daughters of unpreferred males, although additional experimentation will be needed to determine if the indirect consequences of female preferences actually arise from 'sexually antagonistic' variation. Nevertheless, the results are intriguing and are consistent with the hypothesis that an interaction between direct and indirect benefits maintains sexually antagonistic variation in these desert flies: increased desiccation resistance conferred by mating might offset the cost of producing low-fecundity daughters.     

Copulation reduces male but not female longevity in Saltella sphondylli (Diptera: Sepsidae)

Mating more than once is extremely costly for females in many species, making the near ubiquity of polyandry difficult to understand. However, evidence of mating costs for males is much rarer. We investigated the effects of copulation on longevity of male and female flies (Saltella sphondylli). We also scrutinized potential fecundity and fertility benefits to females with differing mating history. Copulation per se was found to decrease the longevity of males but not that of females. However, when females were allowed to lay eggs, females that mated died earlier than virgin females, indicating costs of egg production and/or oviposition. Thus, although longevity costs of copulation are higher for males, reproduction is nevertheless costly for females. We also found no differences in fecundity or fertility relative to female mating history. Results suggest that polyandry may be driven by minor costs rather than by major benefits in this species.     

Sexual cannibalism in Nephila plumipes as a consequence of female life history strategies

The evolution of sexual cannibalism has been modelled as both an adaptive and nonadaptive female strategy. Recent evidence from several species suggests a connection between female foraging and sexual cannibalism, but the precise benefits for females have remained obscure. Here, we investigate the difference between cannibalistic and noncannibalistic female Nephila plumipes by removing the potential nutritional benefit of cannibalism. Courting and mating males that were killed by a female were immediately removed so that the female could not consume them. Nevertheless, cannibalistic females gained more mass from maturation to oviposition and produced larger first clutches than noncannibalistic females, although cannibalistic females matured at a smaller size and mass than noncannibalistic females. In juvenile instars, mass gain was generally smaller in females that moulted in a good condition but intermoult intervals were shorter. However, the time from maturity to oviposition was not shorter in females that matured in a good condition. Male behaviour did not differ according to the risk of cannibalism. We suggest that sexual cannibalism in N. plumipes is a side‐effect of an increased foraging vigour of females that matured at a smaller size and body mass. Selection pressure on males to avoid cannibalism may be weak because of limited mating opportunities.