Female mate choice and mate search tactics in a sex role reversed population of the peacock blenny Salaria pavo (Risso, 1810)

Behavioural observations were carried out on a sex role reversed population of the blenny Salaria pavo to investigate possible mate choice behaviour of the females. Females mated with relatively larger males, with a larger head crest, anal gland and genital papilla, which had more eggs in their nests and that courted the female. Thus, these male traits were potentially assessed by females when choosing their mates. In order to mate, females visited one to four males (eight females spawned with the first male they had visited and eight visited more than one male). The majority of the females spawned with the last male visited but three of them returned to mate with males visited previously (two with the penultimate visited male). Additionally, the outcome of the first visit of each female depended on the quality of the males: males that were accepted on this first visit had larger head crest than rejected males. Therefore, the mate searching model that best fitted the data was a threshold tactic that allowed the searching individual to return to any potential mate visited before, i.e. that allowed for complete recall. Moreover, three females returned to mate with males rejected earlier during the search, which indicates that they lowered their thresholds. These results suggest that females use a 'one step decision' tactic to search for mates. In this tactic, females mate with males that satisfy an adjustable threshold criterion, balancing the quality of the mates expected to find in the next step of the search and the effort of finding them.     

Dynamic mate-searching tactic allows female satin bowerbirds Ptilonorhynchus violaceus to reduce searching

Females can maximize the benefits of mate choice by finding high-quality mates while using search tactics that limit the costs of searching for mates. Mate-searching models indicate that specific search tactics would best optimize this trade-off under different conditions. These models do not, however, consider that females may use information from previous years to improve mate searching and reduce search costs in subsequent years. We followed female satin bowerbirds Ptilonorhynchus violaceus during mate searching and reconstructed their search patterns. We found that females who chose very attractive males typically mated with the same male in the following year, resulting in these females sampling fewer males than those who switched mates. In contrast, females who mated with less attractive males typically rejected their previous mates and searched longer for more attractive mates in the following mating season. A potential cost to mate searching is suggested by the observed increase in the likelihood of force-copulation attempts from marauding males with increased searching. Our results suggest that by using past experiences to adjust their search tactics, females may obtain high-quality mates while limiting search costs. These results emphasize the need to consider historical effects in studies of sexual selection, especially for long-lived species with stable display sites.     

A Comparative Bayes tactic for mate assessment and choice

Models of mate choice tactics have assumed that females randomlyencounter males when collecting information and the informationis perfect. Empirical observations of four bird species showthat females selectively visit males and repeat visits to malesbefore mating. This suggests that the assumptions of previousmodels have been too restrictive. An alternative model of informationgathering and mate choice, which relaxes the assumptions ofrandom encounters and perfect information, is presented. Inthis Comparative Bayes model, the decision of when and fromwhom to collect information is made using Bayesian estimatesof each male's quality. Predictions from the model are that:(1) the occurrence of mate assessment will increase as initialuncertainty about the quality of males increases, as the costof gathering information decreases, and as the signal perceivedby the female becomes a better representation of males' actualqualities; (2) the occurrence of repeat visits to males willbe highest when signals from males are of medium reliability;and (3) the decision of which male to assess will depend onthe estimated qualities of males, prior certainty about eachmale's quality, the reliability of each male's signal, and thecosts of assessment. Simulations compare the fitness outcomesof the Comparative Bayes tactic to other mate choice tactics.The fitness from the Comparative Bayes tactic is significantlyhigher than from the fixed threshold tactic and than from thebest-of-n tactic when the cost of assessment is low. [BehavEcol 7: 451–460 (1996)]     

Female mate assessment and choice behavior affect the frequency of alternative male mating tactics

Explanations for the existence of alternative male mating tacticsfocus primarily on male–male competition. Mating systems,however, are composed of interactions both within and betweenthe sexes, and the role of female behavior in shaping male matingtactics should not be overlooked. By using a dynamic state variablegame model, I examine how female mate assessment and choicebehavior affect the frequency of alternative male mating tactics.When females can accurately assess the quality of males, onlymales with high quality are likely to be chosen as mates, andthus, lower-quality males gain little fitness from courtingfemales. This leads lower-quality males to switch to an alternativemating tactic that attempts to circumvent female mate choice.In contrast, if the abilities of females to accurately assessmales are constrained by assessment costs, imperfect information,or time constraints, or if the pool of available males is smaller,then lower-quality males are increasingly chosen as mates andthey less often use alternative mating tactics. Thus, femalebehavior shapes the frequency of alternative male mating tactics.A consequence of this game between the sexes is that male behavior(i.e., increased alternative mating tactics) decreases the benefitsfemales might otherwise gain from lower assessment costs, clearersignals of male quality, more time to choose a male, and moremales from which to choose a mate.     

Alternative mate-finding tactics in a non-territorial damselfly (Odonata: Coenagrionidae)

Males of the non-territorial damselfly Enallagma hageni have two alternative tactics for finding mates: (1) they search the banks of the pond for unmated females (searching tactic), or (2) wait at oviposition sites for females that resurface prematurely from underwater oviposition (waiting tactic). Although the searching tactic yielded more fertilizations than the waiting tactic, for time invested, the waiting tactic became increasingly successful later in the reproductive season due to changes in female oviposition behaviour. The two tactics can be maintained in the population because males can mate by the waiting tactic during the afternoon when few females are available to searchers. Among males visiting the breeding site an equal number of times, males mating by a mixture of tactics were as successful as males mating only by the main tactic. Because marked males were found to use both tactics, these behaviours are interpreted as evidence of behavioural plasticity within individuals, representing one conditional evolutionary strategy.     

Mate choice when males are in patches: optimal strategies and good rules of thumb

In standard mate-choice models, females encounter males sequentially and decide whether to inspect the quality of another male or to accept a male already inspected. What changes when males are clumped in patches and there is a significant cost to travel between patches? We use stochastic dynamic programming to derive optimum strategies under various assumptions. With zero costs to returning to a male in the current patch, the optimal strategy accepts males above a quality threshold which is constant whenever one or more males in the patch remain uninspected; this threshold drops when inspecting the last male in the patch, so returns may occur only then and are never to a male in a previously inspected patch. With non-zero within-patch return costs, such a two-threshold rule still performs extremely well, but a more gradual decline in acceptance threshold is optimal. Inability to return at all need not decrease performance by much. The acceptance threshold should also decline if it gets harder to discover the last males in a patch. Optimal strategies become more complex when mean male quality varies systematically between patches or years, and females estimate this in a Bayesian manner through inspecting male qualities. It can then be optimal to switch patch before inspecting all males on a patch, or, exceptionally, to return to an earlier patch. We compare performance of various rules of thumb in these environments and in ones without a patch structure. A two-threshold rule performs excellently, as do various simplifications of it. The best-of-N rule outperforms threshold rules only in non-patchy environments with between-year quality variation. The cutoff rule performs poorly.     

POPULATION DIVERGENCE IN SEXUAL ORNAMENTS: THE WHITE FOREHEAD PATCH OF NORWEGIAN PIED FLYCATCHERS IS SMALL AND UNSEXY

Models of sexual selection suggest that populations may easily diverge in male secondary sexual characters. Studies of a Spanish population of the pied flycatcher, Ficedula hypoleuca, and a Swedish population of the closely related collared flycatcher, F. albicollis, have indicated that the white forehead patch of males is a sexually selected trait. We studied the white forehead patch of male pied flycatchers (n = 487) in a Norwegian population over seven years. Males with large forehead patches were in general more brightly colored, but patch height was not correlated to body mass, body size, or parasite loads. Conditions during the nestling period did not seem to influence patch height as an adult. Patch height increased slightly from the first to the second year as adults, but then remained relatively constant at higher ages. Patch height was not related to survival. Year-to-year changes showed that males who increased in patch height also increased in body mass, suggesting that expression of the forehead patch may be partly condition dependent. However, changes in body mass explained only a small proportion of the variance in patch height between males. Thus, patch height would not be a good indicator of male quality. Furthermore, patch size was also not related to male ability to feed nestlings, indicating that females would not obtain direct benefits by choosing males with large patches. However, patch height could be a Fisher trait, but this requires heritability and there was no significant father-son resemblance in patch height. Comparisons of the males visited by each female during the mate sampling period indicated that chosen males did not have larger forehead patches than rejected males. Experimental manipulation of patch height did not affect male mating success. These results indicate that females do not use patch size as a mate choice cue. Finally, patch height did not predict the outcome of male contests for nestboxes, suggesting that the forehead patch is not an intrasexually selected cue of status. Norwegian pied flycatchers have smaller forehead patches than both Spanish pied flycatchers and Swedish collared flycatchers. We suggest that this pattern may be explained by the lack of sexual selection on the forehead patch in the Norwegian population as compared to the other populations, where the patch is apparently sexually selected. We discuss possible reasons for these population divergences, such as female choice on an alternative secondary sexual character (general plumage color) and speciation among Ficedula flycatchers.     

Mate inspection patterns in the female beaugregory damselfish (<Emphasis Type="Italic">Stegastes leucostictus</Emphasis>)

We observed female beaugregory damselfish (Stegastes leucostictus) as they interacted with males to see whether their movements fit the predictions of different mate-search models. We established high-quality and low-quality groups with low variance in breeding site quality and a medium-quality, high-variance breeding site group and compared focal observations of female nonforaging forays in each group. Only 8% of 137 forays monitored resulted in spawning events. Eighty-nine percent of the forays were less than 240 s and were within 7 m of the focal female’s territory. Average foray times and straight-line foray distances did not differ for females traveling between males in each group. Females entered high-quality breeding sites at a higher rate than low-quality sites and round-trip distances were also greatest in high-quality groups, indicating that females were following a more convoluted path. We interpret these results to mean that (a) female beaugregories separate the tasks of mate assessment and mate choice by conducting information-gathering forays between mating events, (b) forays are energetically costly and therefore usually short in duration and overall distance traveled, (c) information collection takes approximately the same time for high-quality and low-quality mates, but (d) females will alter their foray patterns in high-quality areas to collect additional information. These data are also consistent with the hypothesis that females optimize their search by employing a tiered process of assessment during information-gathering forays, first using an adjustable threshold to accept or reject each male based on his courtship and subsequently a fixed threshold to assess the quality of each breeding site.     

Sexual Selection on a Coloured Ornament in King Penguins

Species in which the sexes equally exhibit colourful ornaments are an issue for evolutionary theory. Among several hypotheses, sexual selection for mutual mate choice and social selection for signals of behavioural dominance are most commonly supported. We examined the previously documented sex‐similar size of yellow‐orange ear patches in the king penguin, Aptenodytes patagonicus. This species is monogamous and pairs just before reproduction. Raising a chick requires considerable effort by both parents, as they alternate care of their single offspring with foraging at sea. The size of the ear patches appears to signal aggressive territoriality in the breeding colony for both sexes. However, experiments suggest that females prefer large patch size during mate choice, and males do not prefer this trait. We tested whether the size of the coloured ear patch was influenced by sexual selection for couples that had recently paired. We used analyses of covariance to compare the size of the ear patch to a measure of body size and then tested for the difference between males and females. Males were 6.2% larger in ear patch width and 7.7% larger in ear patch area than females, and the distance between the ear patches over the head was 7.5% smaller in males, with all differences highly significant. Consequently, sexual selection appears to favour larger ear patches in males, possibly because of an excess of males that promotes female choice. Social selection also appears to favour the evolutionary maintenance of ear patches of males, and thus both types of selection may contribute to enlarged ear patches.     

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.     

Lipid economy,flight activity and reproductive behaviour in the speckled wood butterfly: on the energetic cost of territory holding

Insect flight is a highly energy demanding type of locomotion. In butterflies, males may locate females by different behavioural tactics. The tactics correspond to different flight types that, in turn, are assumed to reflect different energetic costs. Costs need to be considered to fully understand the pay‐offs of co‐existing alternative tactics relative to the environmental context and the phenotypes of the individuals. We addressed the issue in the speckled wood Pararge aegeria, in which males either adopt a territorial wait‐and‐fight tactic (i.e. territorial perching) in a sunlit patch on the forest floor, or a fly‐and‐search tactic to locate females in a wider area of the forest (i.e. patrolling). Perching corresponds to high frequency of take‐off flights and aerial combats with high levels of manoeuvrability and is assumed to be energetically more costly than longer, continuous flights at lower speed in patrollers. We tested the effect of different flight activity levels and of the behavioural tactics on lipid reserves and lipid use in males by laboratory and outdoor cage experiments. Low‐activity males that had access to honey water were capable of synthesizing lipids; their lipid reserves increased with age. The effect disappeared in males that actively flew in the outdoor cages. Lipid reserves decreased significantly faster in territorial perching males compared to non‐perching males, but resting metabolic rate did not differ between the alternative behavioural tactics. Territorial perching males had larger flight muscle ratio (i.e. thorax/body mass) than non‐perching males. We discuss the evidence of the physiological costs of perching relative to the co‐existence of perching and patrolling tactics.     

Effects of social information on life history and mating tactics of males in the orb‐web spider Argiope bruennichi

Informed mating decisions are often based on social cues providing information about prospective mating opportunities. Social information early in life can trigger developmental modifications and influence later mating decisions. A high adaptive value of such adjustments is particularly obvious in systems where potential mating rates are extremely limited and have to be carried out in a short time window. Males of the sexually cannibalistic spider Argiope bruennichi can achieve maximally two copulations which they can use for one (monogyny) or two females (bigyny). The choice between these male mating tactics should rely on female availability that males might assess through volatile sex pheromones emitted by virgin females. We predict that in response to those female cues, males of A. bruennichi should mature earlier and at a smaller body size and favor a bigynous mating tactic in comparison with controls. We sampled spiders from two areas close to the Southern and Northern species range to account for differences in mate quality and seasonality. In a fully factorial design, half of the subadult males from both areas obtained silk cues of females, while the other half remained without female exposure. Adult males were subjected to no‐choice mating tests and could either monopolize the female or leave her (bigyny). We found that Southern males matured later and at a larger size than Northern males. Regardless of their origin, males also shortened the subadult stage in response to female cues, which, however, had no effects on male body mass. Contrary to our prediction, the frequencies of mating tactics were unaffected by the treatment. We conclude that while social cues during late development elicit adaptive life history adjustments, they are less important for the adjustment of mating decisions. We suggest that male tactics mostly rely on local information at the time of mate search.     

Costs influence male mate choice in a freshwater fish

It is well known that female mate choice decisions depend on the direct costs of choosing (either because of search costs or male-imposed costs). Far less is known about how direct fitness costs affect male mate choice. We conducted an experiment to investigate male mate choice in a fish, the Pacific blue-eye (Pseudomugil signifer). Preferred females were larger, probably because larger females are also more fecund. Males, however, were consistent in their choice of female only when the costs of associating with prospective mates were equal. By contrast, males were far less consistent in their choice when made to swim against a current to remain with their initially preferred mate. Our results suggest that males may also respond adaptively to changes in the costs of choosing.     

Female ornamentation, parental quality, and competitive ability in the rock sparrow

The evolution of female ornaments is poorly understood. Recent evidence suggests not only that female ornaments may be genetic correlates of selection on males but may also have evolved through male mate choice and/or through female–female aggressive interactions. In the rock sparrow, Petronia petronia, both sexes have a carotenoid-based yellow patch that is sexually selected by both sexes. The benefits that male may gain from choosing an attractive female remain unidentified. Both parents participate in caring for the young, so there should be mutual mate choice because males and females should both benefit from choosing a good parent (good parent hypothesis; GPH). Moreover, it has already been demonstrated that the yellow patch in males is also a badge of status (armament). Therefore, the yellow patch could also serve as both ornament and armament in females (dual utility hypothesis; DUH). We investigated the hypothesis that male and female yellow patch size signals parental quality in the field. We tested by an experiment in captivity the signal function of the yellow patch in female–female aggressive interactions for access to food. Yellow patch size correlated with paternal, but not maternal, feeding rates. Thus, this study supports the hypothesis that yellow patch dimension signals male parental quality, but there is no evidence for the GPH to explain female ornamentation. In the experiment females with relatively large yellow patches had earlier access to food than those with small patches. These results seem to suggest that a sexually selected carotenoid-feather signal may be used in female–female competition, in agreement with the DUH. Males may benefit from choosing well ornamented females because these may be superior competitors.     

Alternative reproductive tactics in male freshwater fish influence the accuracy of species recognition

Sexual conflict can result in coercive mating. Because males bear low costs of heterospecific mating, coercive males may engage in misdirected mating attempts toward heterospecific females. In contrast, sexual selection through consensual mate choice can cause mate recognition cues among species to diverge, leading to more accurate species recognition. Some species show both coercive mating and mate choice‐associated courtship behaviors as male alternative reproductive tactics. We hypothesized that if the selection pressures on each tactic differ, then the accuracy of species recognition would also change depending on the mating tactic adopted. We tested this hypothesis in the guppy (Poecilia reticulata) and mosquitofish (Gambusia affinis) by a series of choice experiments. Poecilia reticulata and G. affinis males both showed imperfect species recognition and directed all components of mating behavior toward heterospecific females. They tended to direct courtship displays more frequently toward conspecific than heterospecific females. With male P. reticulata, however, accurate species recognition disappeared when they attempted coercive copulation: they directed coercions more frequently toward heterospecific females. We also found that heterospecific sexual interaction had little effect on the fecundity of gravid females, which suggests that prepregnancy interactions likely underpin the exclusion of G. affinis by P. reticulata in our region.     

What Happens after Inbreeding Avoidance? Inbreeding by Rejected Relatives and the Inclusive Fitness Benefit of Inbreeding Avoidance

Avoiding inbreeding, and therefore avoiding inbreeding depression in offspring fitness, is widely assumed to be adaptive in systems with biparental reproduction. However, inbreeding can also confer an inclusive fitness benefit stemming from increased relatedness between parents and inbred offspring. Whether or not inbreeding or avoiding inbreeding is adaptive therefore depends on a balance between inbreeding depression and increased parent-offspring relatedness. Existing models of biparental inbreeding predict threshold values of inbreeding depression above which males and females should avoid inbreeding, and predict sexual conflict over inbreeding because these thresholds diverge. However, these models implicitly assume that if a focal individual avoids inbreeding, then both it and its rejected relative will subsequently outbreed. We show that relaxing this assumption of reciprocal outbreeding, and the assumption that focal individuals are themselves outbred, can substantially alter the predicted thresholds for inbreeding avoidance for focal males. Specifically, the magnitude of inbreeding depression below which inbreeding increases a focal male’s inclusive fitness increases with increasing depression in the offspring of a focal female and her alternative mate, and it decreases with increasing relatedness between a focal male and a focal female’s alternative mate, thereby altering the predicted zone of sexual conflict. Furthermore, a focal male’s inclusive fitness gain from avoiding inbreeding is reduced by indirect opportunity costs if his rejected relative breeds with another relative of his. By demonstrating that variation in relatedness and inbreeding can affect intra- and inter-sexual conflict over inbreeding, our models lead to novel predictions for family dynamics. Specifically, parent-offspring conflict over inbreeding might depend on the alternative mates of rejected relatives, and male-male competition over inbreeding might lead to mixed inbreeding strategies. Making testable quantitative predictions regarding inbreeding strategies occurring in nature will therefore require new models that explicitly capture variation in relatedness and inbreeding among interacting population members.     

Evidence for adaptive male mate choice in the fruit fly Drosophila melanogaster

Theory predicts that males will benefit when they bias their mating effort towards females of higher reproductive potential, and that this discrimination will increase as males become more resource limited. We conducted a series of experiments to test these predictions in a laboratory population of the fruitfly, Drosophila melanogaster. In this species, courtship and copulation have significant costs to males, and females vary greatly in fecundity, which is positively associated with body size. When given a simultaneous choice between small and large virgin females, males preferentially mated with larger, more fecund, females. Moreover, after males had recently mated they showed a stronger preference for larger females. These results suggest that male D. melanogaster adaptively allocate their mating effort in response to variation in female quality and provide some of the first support for the theoretical prediction that male stringency in mate choice increases as resources become more limiting.     

Mate choice and competition in the barklouseLepinotus patruelis (Psocoptera: Trogiidae): The effect of diet quality and sex ratio

Courtship varies among individuals, partly because individuals differ in quality. To explore proximate factors affecting courtship behavior, I investigated the effect of diet quality on mate choice and competition in the barklouseLepinotus patruelis Pearman (Psocoptera: Trogiidae) in the laboratory. The effect of sex ratio on mate choice was also addressed. Some males were found to exhibit active mate choice, and rejected females in both male- and female-biased sex ratio groups, although they were more likely to do so in a female-biased sex ratio group. Diet quality affected male mate choice: males on high-quality diets were significantly more likely to reject females than males on low-quality diets. Males exhibited choice significantly more often than females, who showed no overt signs of choosiness. Both males and females competed for, access to mates: both sexes attempted to interfere with mounted pairs and females grappled. The choosiness of the male may have directly affected the incidence of female competition. The results also suggest that the patterns of mate choice inL. patruelis differ from those expected by conventional sex role theory.     

How do birds search for breeding areas at the landscape level? Interpatch movements of male ortolan buntings

Animal movements at large spatial scales are of great importance in population ecology, yet little is known due to practical problems following individuals across landscapes. We studied the whole Norwegian population of a small songbird (ortolan bunting, Emberiza hortulana ) occupying habitat patches dispersed over nearly 500 km². Movements of colour-ringed males were monitored during ten years, and extensive long-distance dispersal was recorded. More than half of all cases of breeding dispersal took place within one breeding season, and males moved up to 43 km between singing territories, using 1–22 d. Natal dispersal was usually to a habitat patch close to the natal patch, or within the natal patch if it was large. Breeding dispersal movements were often long-distance, beyond neighbouring patches, and up to 11–19 patches were overflown. Movements of at least 6–9 km across areas of unsuitable habitat occurred regularly. The number of patches visited was low (1–4) even though search costs in terms of time spent moving from one site to another were relatively low (often only a few days even for distances >10 km). Most males seemed to use a threshold tactic when choosing a patch, but returns to previously visited patches were recorded, including some cases of commuting. In conclusion, male ortolan buntings have a surprising ability to move quickly at the landscape level, and this resulted in a high connectivity of patches. We discuss our results in relation to optimal searching strategies, in particular the use of within-breeding season versus post-breeding season search, conspecific attraction and adaptive late arrival of young birds.     

The effects of body size on mate choice in a grapsid crab,Gaetice depressus (Crustacea,Decapoda)

Male and female mate choices were investigated in the grapsid crab,Gaetice depressus (Crustacea, Decapoda) in a laboratory experiment. Males mated indiscriminately with regard to the body size of the females, and frequently copulated with the first females they encountered. In contrast, females showed mate discrimination with regard to the body size of males. The females tended to sample potential mates prior to copulation, and showed both a preference for the larger males and a tendency toward the rejection of males with body sizes smaller than their own. However, they did not discriminate between two males that were either larger or smaller than they themselves. Mate choice by the females of this species is though to be based upon threshold-criterion tactics, in which the body size of the female itself is used as a threshold value.