Alternative Mating Behaviours Research Articles

Sperm allocation in relation to male–male aggression and courtship in an externally fertilizing fish, the medaka

Sperm production is physiologically costly; therefore, males that mate multiple times are expected to allocate sperm prudently to maximize their fitness. Sperm allocation theory has been widely tested in internally fertilizing animals; however, few studies have investigated whether males adjust the number of sperm released according to their premating experience and cues from rival males. Here, we investigated sperm allocation strategies in an externally fertilizing fish, the medaka, Oryzias latipes, in controlled conditions. We used three treatments: direct interaction with a rival (two males were allowed to interact directly with each other), visual cue only (presenting a male in a separate compartment) and no rivals (control). In the direct interaction treatment, two types of alternative male mating behaviour, simultaneous sperm release and postspawn sperm release, were observed. Premating experiences affected subsequent mating behaviour: males that were more aggressive and exhibited more prominent courtship behaviour mated females without any disturbance from the other males, whereas simultaneous sperm release frequently occurred when both males exhibited similar levels of aggression and courtship behaviours. We also counted the sperm released per mating from the water tank. There was no change in the number of sperm released in the presence of visual cues of competition or direct interaction with the other males before mating. However, males (focal and/or rival) released more sperm only when sperm competition was high, that is, when a rival male successfully disrupted mating before simultaneous sperm release. Our results indicate that medaka males may adjust the number of sperm released per mating in different mating environments.

Environmental influences on life history strategies in partially anadromous brown trout (Salmo trutta, Salmonidae)

AbstractThis paper reviews the life history of brown trout and factors influencing decisions to migrate. Decisions that maximize fitness appear dependent on size at age. In partly anadromous populations, individuals that attain maturity at the parr stage typically become freshwater resident. For individual fish, the life history is not genetically fixed and can be modified by the previous growth history and energetic state in early life. This phenotypic plasticity may be influenced by epigenetic modifications of the genome. Thus, factors influencing survival and growth determine life‐history decisions. These are intra‐ and interspecific competition, feeding and shelter opportunities in freshwater and salt water, temperature in alternative habitats and flow conditions in running water. Male trout exhibit alternative mating strategies and can spawn as a subordinate sneaker or a dominant competitor. Females do not exhibit alternative mating behaviour. The relationship between growth, size and reproductive success differs between sexes in that females exhibit a higher tendency to migrate than males. Southern populations are sensitive to global warming. In addition, fisheries, aquaculture with increased spreading of salmon lice, introduction of new species, weirs and river regulation, poor water quality and coastal developments all threaten trout populations. The paper summarizes life‐history data from six populations across Europe and ends by presenting new research questions and directions for future research.

Integration of Genotype, Physiological Performance, and Survival in a Lizard (Uta stansburiana) with Alternative Mating Strategies.

Covariation among behavioral and physiological traits is thought to enhance reproductive success and Darwinian fitness. Species that exhibit alternative mating strategies provide excellent opportunities to assess the relative contributions of physiological and behavioral traits to fitness. Male side-blotched lizards (Uta stansburiana) exhibit three heritable throat color morphs that are associated with alternative mating behaviors. The three morphs differ in resource holding potential, mate attraction, mate defense, and physiological performance. We examined interrelationships of body mass, stamina, field metabolic rate, growth rate, and survival to the second capture (a fitness proxy). Relationships among variables were complex, and mass, stamina, and throat color interacted to predict male survival. Our analyses suggest that male side-blotched lizards exhibit trade-offs among physiological traits related to reproductive success and survival and that differential survival for different combinations of traits has caused correlational selection, leading to adaptive integration of phenotypic traits associated with alternative mating strategies.

Dimorphic ejaculates and sperm release strategies associated with alternative mating behaviors in the squid.

Sperm competition is a powerful postcopulatory selective force influencing male adaptations associated with increasing fertilization success, and it is usually related to the evolution of different strategies of ejaculate expenditure between individuals. Ejaculates may also be influenced by additional selective pressures associated with sperm competition, such as timing between insemination and fertilization, female reproductive tract morphology, and fertilization environment. Also, males that adopt alternative mating tactics may face distinct sperm competition pressures, which may lead to the evolution of intraspecific diversity in ejaculates. In loliginid squids, males with alternative reproductive tactics (sneakers and consorts) differ not only in mating behavior, but also transfer spermatophores into two distinct sites within the female. Here, we compared structure and functioning of spermatophores between sneakers and consorts in the squid Doryteuthis plei applying microscopy techniques and in vitro experiments. Sneakers and consorts exhibit differences in spermatophore structure that lead to distinct spermatophoric reactions and spermatangium morphologies. Moreover, in sneakers, sperm release lasts longer and their sperm show an aggregative behavior not detected in consorts. Slow sperm release may be a strategy to guarantee longer sperm provision, given the wide interval between sneaker mating and egg release. For consorts, in turn, intense and quick sperm discharge may be advantageous, as timing between mating and egg-laying is relatively short. Within the complex squid mating system, factors such as (i) different fertilization sites and (ii) interval between mating and egg release may also influence sperm competition, and ultimately shape the evolution of divergent ejaculates between dimorphic males.

The Association Between Personality Traits, Morphological Traits and Alternative Mating Behaviour in Male Endler's Guppies, Poecilia wingei

AbstractAlternative mating behaviour, personality traits and morphological characters are predicted to be correlated. Bolder, larger and more colourful males are expected to preferentially court females, while shy, small and drab‐coloured individuals are predicted to sneak copulations. We used males of Endler's guppy, Poecilia wingei, to test this association over a long temporal period (hence including ontogenetic changes) and under two social environments (male‐biased and female‐biased). We found that personality traits (exploration, boldness, activity) of P. wingei males were highly repeatable across long time spans, but they were not correlated (formed no behavioural syndrome). Male age and social environment had no effect on any personality trait, despite their effects on alternative mating behaviour. Young males with higher activity levels were more likely to attempt sneaking. In older fish, there was an association between orange coloration, courtship and boldness, but this was not observed in young males. Our results suggest that alternative mating behaviour is more flexible than personality traits and is independent of them. Non‐colour‐based morphological traits (gonopodium length, body length, caudal straps length, dorsal fin length) were not correlated with any particular mating behaviour.

Hot males live fast and die young: habitat segregation, reproductive output, and lifespan of sympatric Mnais damselflies

The Japanese damselflies Mnais costalis and Mnais pruinosa show microhabitat segregation in response to forest sunlight conditions in their sympatric habitat: M. costalis prefers sunny sites while M. pruinosa prefers semi-shady sites. We tested whether sunlight conditions at territorial sites influenced reproductive output, territory occupancy, and/or reproductive lifespan of males of the two species differently. Oviposition duration of females after copulation was used as the measure of reproductive output of individual males. We recorded illuminance at each territorial site on sunny days during the behavioral observation periods. M. costalis males at sites with higher illuminance had a higher reproductive output than other territorial males, while M. pruinosa males had a relatively lower reproductive output at such sites. During a reproductive season, we performed population censuses in a 500-m area of stream, which contained at least 112 potential territorial sites. Using a fish-eye converter, we took a hemispherical photograph to estimate canopy openness as a measure of insolation at each territorial site and examined whether males incur higher survival costs by holding territories at sunnier sites. Minimum reproductive lifespan, estimated as days between the first and the last sightings, showed that M. costalis males that occupied sunnier sites had a shorter lifespan than those occupying shadier sites, while M. pruinosa males did not show such a relationship. These results suggest that microhabitat segregation of these two Mnais damselflies reflects a species difference in the tradeoff between the benefit of mating rate and cost of survival in the sun. We report a field study on the relationships among thermal environment, temperature tolerance, reproductive success, and character displacement in the mating systems of two species of territorial Mnais damselflies. Allopatric populations of these two species are forest dwellers, and males of each species show wing color polymorphism linked to alternative mating behaviors. When these species are sympatric, males lose their polymorphisms and change their habitat preferences: M. pruinosa prefers shady parts of a stream, while M. costalis prefers sunnier parts. We showed the costs and benefits of character displacement coupled to microhabitat preference shift. The findings of this study may highlight an underappreciated area of study, namely, the interplay between behavioral and physiological ecology in insects.

Dimorphic sperm-transfer strategies and alternative mating tactics in loliginid squid

Animal species usually have a single sperm-storage site in the female body, but females of the squid Heterololigo bleekeri possess two distinct sperm-storage sites simultaneously. Use of two sperm-storage sites correlates with alternative male mating behaviours: large consorts guard females and place spermatophores inside the oviduct just before spawning, whereas small ‘sneaker’ males place spermatophores on the membrane around the female’s mouth within the arm crown, where a seminal receptacle is present. Previous work showed that spermatophore and sperm morphology diverge between consort and sneaker males. Here we show novel dichotomous adaptations in the sperm-transfer strategy of males of this squid, associated with the use of two distinct sperm-storage sites on females. The spermatangia ejaculated from spermatophores were clearly dimorphic: all spermatangia ejaculated from spermatophores smaller than 12 mm from small sneaker males were drop-shaped, whereas all spermatangia from spermatophores longer than 12 mm from larger consort males were rope-shaped. In addition, the dropshaped spermatangia were distinct in having a spine on their base, which might reduce the risk of it being shed from the female’s body surface. Our findings suggest that existence of alternative spermstorage sites, and related biological and environmental factors, lead to the evolution of divergent spermtransfer strategies.

Alternative male mating behaviour in the two-spotted spider mite: dependence on age and density

Alternative male mating tactics occur in many taxa, and usually include sneaking behaviour. Typically, sneaking behaviour is expressed by less competitive males to avoid fighting over females guarded by stronger males and to increase their mating chances, but in theory it can be expressed by any male as long as it improves his future reproduction. Recently, we characterized fighting and sneaking behaviour in males of the two-spotted spider mite that guard females during their preadult moulting stage. Sneaking behaviour involves not responding to rival males to avoid eliciting attack, whereas fighting behaviour involves challenging all rivals. To understand these alternative precopulatory behaviours from a life history perspective, we investigated (1) their heritability, and how they are affected by (2) male density, (3) male age and (4) competition between males differing in age. We established genetic lines for fighting or sneaking by crossing a male that displayed fighting or sneaking behaviour with one of his daughters. In fourth-generation males from these lines, however, the proportions of fighting and sneaking behaviour were not significantly different. The frequency of sneaking behaviour increased with male density, yet decreased with male age. Old males always displayed fighting and rarely lost females they guarded to young males, whereas young fighting males lost females to old rival males more frequently than young sneaking males. Of the young fighting males that did not lose the female they guarded to old males, about 40% switched to sneaking. We conclude that alternative male mating behaviours in this mite are not maintained as a genetic polymorphism, but arise from phenotypic plasticity in response to the male's environment (male density) and its own condition (age). We hypothesize that young males opt for sneaking behaviour because fighting jeopardises their future reproduction.

The effect of social environment on alternative mating tactics in male Endler's guppy, Poecilia wingei

Variation in sexual behaviour has both genetic (no experience or social contact needed) and environmental (based on individual experience) components. Within species, males can maximize their fitness during inter- and intrasexual selection in a variety of ways. This may lead to evolution of alternative male mating behaviours resulting in a dichotomy between courting/guarding and sneaking tactics. We used Endler's guppies to investigate (1) whether individual sexually naive males have a preferred mating tactic (courting or sneaking), and (2) how male mating behaviour is affected by recent social history (male- or female-biased social environment). We found that individual males approached females by either courting or sneaking, even with no previous sexual experience. We further demonstrated that male sexual behaviour in standardized mating trials was strongly affected following exposure to a sex-biased social environment for 5 weeks. Males from female-biased social environments showed decreased mating effort overall compared to the baseline level (measured prior to assignment to a social environment treatment) but were more likely to court females rather than attempt sneak copulations. Males from male-biased social environments maintained a high level of mating effort and increased the rate of sneaking attempts compared to courtship displays. Our study highlights that both genetic and environmental sources of variation contribute to individual sexual behaviour. Current sexual behaviour was strongly modulated by recent social history, underpinning the importance of previous experience in the expression of sexual behaviour.

Contrasting Alternative Hypotheses to Explain Rut‐Induced Hypophagia in Territorial Male Chamois

AbstractMale ungulates in temperate environments often show a severe reduction in time spent foraging during the mating season. Several hypotheses have been put forward to explain this phenomenon but, so far, no study investigated the proximate mechanisms underlying rut‐induced hypophagia in ungulates using alternative mating tactics (AMTs). Between the pre‐rut and post‐rut of 2011 and 2012, we collected data on activity budgets, parasite burden and androgen levels of territorial and non‐territorial male Alpine chamois Rupicapra r. rupicapra in the Gran Paradiso National Park (Italy). We aimed to investigate whether AMTs showed similar reduction in time spent foraging during the mating period and to test the predictions underlying alternative hypotheses that may explain rut‐induced hypophagia. Only territorial males showed a significant reduction in time spent foraging during the rut; the lack of correlation between proportion of time spent foraging and androgen metabolites or parasite burden did not fully support the physiological and the parasite hypotheses, while the foraging constraint, the energy‐saving and the physical rest hypotheses could not be discounted. Territorial males decreased the time spent lying down from the pre‐rut to the rut, but not their foraging‐to‐lying‐down ratio. During the mating period, we found negative correlations between time spent foraging or lying down and time spent rutting. Our data suggest that territorial males’ behaviour is more consistent with the foraging constraint hypothesis than with the energy‐saving hypothesis previously suggested. Yet, during the rut territorial males did not maximise their foraging time, and the optimisation of their energy balance could rather depend upon feeding on relatively high‐quality plants. This suggestion – possibly named ‘forage quality hypothesis’ – now requires further investigations. This work showed that alternative mating behaviours may underlie different patterns of foraging strategies: we suggest that tests of alternative hypotheses to explain rut‐induced hypophagia within ungulate populations should not ignore the occurrence of AMTs.

Alternative phenotypes of male mating behaviour in the two-spotted spider mite

Severe intraspecific competition for mates selects for aggressive individuals but may also lead to the evolution of alternative phenotypes that do not act aggressively, yet manage to acquire matings. The two-spotted spider mite, Tetranychus urticae, shows male mate-guarding behaviour and male–male combat for available females. This may provide opportunity for weaker males to avoid fighting by adopting alternative mating behaviour such as sneaker or satellite tactics as observed in other animals. We investigated male precopulatory behaviour in the two-spotted spider mite by means of video-techniques and found three types of male mating behaviour: territorial, sneaker and opportunistic. Territorial and sneaker males associate with female teleiochrysales and spend much time guarding them. Territorial males are easily disturbed by rival males and engage themselves in fights with them. However, sneaker males are not at all disturbed by rival males, never engage in fights and, strikingly, never face attack by territorial males. Opportunistic males wander around in search of females that are in the teleiochrysalis stage but very close to or at emergence. To quickly classify any given mate-guarding male as territorial or sneaker we developed a method based on the instantaneous response of males to disturbance by a live male mounted on top of a brush. We tested this method against the response of the same males to natural disturbance by two or three other males. Because this method proved to be successful, we used it to collect territorial and sneaker males, and subjected them to morphological analysis to assess whether the various behavioural phenotypes are associated with different morphological characters. However, we found no statistical differences between territorial and sneaker males, concerning the length of the first legs, the stylets, the pedipalps or the body.Electronic supplementary materialThe online version of this article (doi:10.1007/s10493-013-9673-y) contains supplementary material, which is available to authorized users.

Effects of parental number and duration of the breeding period on the effective population size and genetic diversity of a captive population of the endangered Tokyo bitterling Tanakia tanago (Teleostei: Cyprinidae)

The maintenance of genetic diversity is one of the chief concerns in the captive breeding of endangered species. Using microsatellite and mtDNA markers, we examined the effects of two key variables (parental number and duration of breeding period) on effective population size (N(e) ) and genetic diversity of offspring in an experimental breeding program for the endangered Tokyo bitterling, Tanakia tanago. Average heterozygosity and number of alleles of offspring estimated from microsatellite data increased with parental number in a breeding aquarium, and exhibited higher values for a long breeding period treatment (9 weeks) compared with a short breeding period (3 weeks). Haplotype diversity in mtDNA of offspring decreased with the reduction in parental number, and this tendency was greater for the short breeding period treatment. Genetic estimates of N(e) obtained with two single-sample estimation methods were consistently higher for the long breeding period treatment with the same number of parental fish. Average N(e) /N ratios were ranged from 0.5 to 1.4, and were high especially in the long breeding period with small and medium parental number treatments. Our results suggest that the spawning intervals of females and alternative mating behaviors of males influence the effective size and genetic diversity of offspring in bitterling. To maintain the genetic diversity of captive T. tanago, we recommend that captive breeding programs should be conducted for a sufficiently long period with an optimal level of parental density, as well as using an adequate number of parents.

Why small males have big sperm: dimorphic squid sperm linked to alternative mating behaviours

BackgroundSperm cells are the target of strong sexual selection that may drive changes in sperm structure and function to maximize fertilisation success. Sperm evolution is regarded to be one of the major consequences of sperm competition in polyandrous species, however it can also be driven by adaptation to the environmental conditions at the site of fertilization. Strong stabilizing selection limits intra-specific variation, and therefore polymorphism, among fertile sperm (eusperm). Here we analyzed reproductive morphology differences among males employing characteristic alternative mating behaviours, and so potentially different conditions of sperm competition and fertilization environment, in the squid Loligo bleekeri.ResultsLarge consort males transfer smaller (average total length = 73 μm) sperm to a female's internal sperm storage location, inside the oviduct; whereas small sneaker males transfer larger (99 μm) sperm to an external location around the seminal receptacle near the mouth. No significant difference in swimming speed was observed between consort and sneaker sperm. Furthermore, sperm precedence in the seminal receptacle was not biased toward longer sperm, suggesting no evidence for large sperm being favoured in competition for space in the sperm storage organ among sneaker males.ConclusionsHere we report the first case, in the squid Loligo bleekeri, where distinctly dimorphic eusperm are produced by different sized males that employ alternative mating behaviours. Our results found no evidence that the distinct sperm dimorphism was driven by between- and within-tactic sperm competition. We propose that presence of alternative fertilization environments with distinct characteristics (i.e. internal or external), whether or not in combination with the effects of sperm competition, can drive the disruptive evolution of sperm size.

The impact of extra-pair mating behavior on hybridization and genetic introgression

Hybridization and genetic introgression can be associated with secondary contact between closely related species. Previous models have examined the ecological and demographic conditions leading to hybridization and introgression, but few have examined the role of behavior. Alternative mating behaviors are common throughout the animal kingdom but have rarely been recognized as a potential mechanism for hybridization. We developed an individual-based genetic model to examine the hypothesis that extra-pair copulations (EPCs) can lead to hybridization and genetic introgression even when assortative mating preferences are intact. Our model showed that female choice, whether pre- or post-copulation, reinforced species boundaries and that hybrids were relatively uncommon when no EPCs occurred. However, when EPCs were introduced into the model, the proportion of hybrids in the population depended on the strength of female mate or sperm choice, the strength of male pursuit of EPCs, and habitat-induced effects on the species composition of the neighborhood. As predicted, male pursuit of EPCs caused extensive introgression, but female preference for conspecific paternity reinforced species differences. Inclusion of mitochondrial markers of species identity revealed significant effects of interspecific and intersexual behavior during EPCs on the direction of introgression. These results suggest that an alternative mating tactic may have major effects on the level of genetic homogenization and can cause local extinction of a species.

Conditional male dimorphism and alternative reproductive tactics in a Neotropical arachnid (Opiliones)

In arthropods, most cases of morphological dimorphism within males are the result of a conditional evolutionarily stable strategy (ESS) with status-dependent tactics. In conditionally male-dimorphic species, the status’ distributions of male morphs often overlap, and the environmentally cued threshold model (ET) states that the degree of overlap depends on the genetic variation in the distribution of the switchpoints that determine which morph is expressed in each value of status. Here we describe male dimorphism and alternative mating behaviors in the harvestman Serracutisoma proximum. Majors express elongated second legs and use them in territorial fights; minors possess short second legs and do not fight, but rather sneak into majors’ territories and copulate with egg-guarding females. The static allometry of second legs reveals that major phenotype expression depends on body size (status), and that the switchpoint underlying the dimorphism presents a large amount of genetic variation in the population, which probably results from weak selective pressure on this trait. With a mark-recapture study, we show that major phenotype expression does not result in survival costs, which is consistent with our hypothesis that there is weak selection on the switchpoint. Finally, we demonstrate that switchpoint is independent of status distribution. In conclusion, our data support the ET model prediction that the genetic correlation between status and switchpoint is low, allowing the status distribution to evolve or to fluctuate seasonally, without any effect on the position of the mean switchpoint.

Variation in mating preference within a wild population influences the mating success of alternative mating strategies

The evolutionary importance of variation in female preferences has been ignored until recently, in part because evidence that variation in specific female preferences results in variation in mate choice in the wild has been lacking. In the laboratory, females of the swordtail fish Xiphophorus multilineatus prefer large males that court (courters) to small males that sneak (sneakers). However, variation in this preference is related to female size, with the strength of preference for courter males increasing with female size. In this study we found that both a female's size and her strength of preference for courter males were significantly related to whether or not she mated with a courter male. These results provide strong evidence for variation in female mate preference influencing the mating success of males in the wild. When combined with previous results demonstrating a correlation between female size distribution and frequency of the two types of males across populations, our results suggest that variation in female preference helps to promote variation in male alternative mating behaviours, and ultimately heritable variation in male traits.

Is commercial harvesting of spawning aggregations sustainable?—The reproductive status of the squid Loligo bleekeri

As marine species that are harvested during spawning aggregation tend to be overfished, sufficient “reproductive escapement” is required to manage such overexploited populations. Because the reproductive value of short-lived organisms changes towards the end of their life span, information is required not only on the total amount harvested but also on the characteristics of the individuals caught. As spawning aggregations of the squid Loligo bleekeri are targeted by the commercial fishing industry, we analysed biological data of harvested squid to identify indicators of reproductive status. Females of this species had several sperm resources associated with alternative mating behaviours: in seminal receptacle near the mouth, around the seminal receptacle, and inside the opening of the oviduct, associated with alternative mating behaviours. However, only the mass of sperm on the oviduct was significantly related to oviduct weight (including ovulated eggs): oviduct weight was less when sperm mass was attached to the oviduct than when it was not, indicating that the female had paired with a consort male and had spawned before she was caught. Using this indicator to confirm a recent spawning event, we determined that only 22.9% of females spawned before they were harvested. Our results show that the commercial fishing industry mainly harvests squid that have not spawned and have high reproductive values. Further information on the movement and reproductive behaviour of squid is required to develop a management strategy for the coastal fishing industry that ensure sufficient reproductive escapement.

Influence of alternative mating tactics on predation risk in the damselfly Calopteryx virgo

Alternative mating tactics are a widespread feature in insects. A typical form of alternative mating behaviour is being a sneaker in the vicinity of a territorial male. Such nonterritorial males have lower mating success, but they may benefit from lower energetic costs and decreased predation risk. In this study, we examined whether nonterritorial male damselflies Calopteryx virgo (L., 1758) are subject to lower predation risk than territorial males. To distinguish predation from other sources of mortality, we used models. The experiment consisted of dried male damselflies settled into the typical perching positions of territorial and nonterritorial males. Also the spatiotemporal patterns of predation risk were studied. The survival of nonterritorial male models was consistently higher than that of territorial male models, which can be attributed to different predation risk. Survival of the models was lower in the presence of avian predators and in large populations. Survival rates were affected by habitat type but did not change during the season. We conclude that nonterritorial male damselflies are less vulnerable to predation and that there may be a trade-off which could potentially make the fitness of sneakers equal to that of territorial males.

BREEDING RESOURCE DISTRIBUTION AFFECTS SELECTION GRADIENTS ON MALE PHENOTYPIC TRAITS: EXPERIMENTAL STUDY ON LIFETIME REPRODUCTIVE SUCCESS IN THE BITTERLING FISH (RHODEUS AMARUS)

The spatial distribution of breeding resources can have pronounced demographic and evolutionary consequences. We used 20 experimental groups of the bitterling (Rhodeus amarus), an annual fish with a promiscuous, resource-based mating system, and extended breeding season to investigate how the spatial distribution (clumped or regular) of bitterling oviposition sites (live freshwater mussels) affected offspring production, variation in reproductive success, and directional selection on phenotypic traits over their entire reproductive lifetime. We did not detect any effect of resource distribution on offspring production or variation in reproductive success among individual fish, although variation between replicates was higher with a clumped distribution. This finding is discussed with regard to the incidence of alternative mating behaviors (sneaking) within the limitations imposed by our experimental design. Breeding resource distribution had a significant effect on selection on male phenotypic traits. Stronger directional selection on traits associated with intrasexual competition for fertilizations, gonad mass (an indicator of sperm competition), and the extent of red, carotenoid-based pigment in the iris (an index of dominance status), was detected with a clumped resource distribution. With a regular resource distribution, a stronger positive selection on male body size was detected. We discuss the implications of our results for natural populations.

Behavioural profiles: individual consistency in male mating behaviour under varying sex ratios

Variation in sex ratio can affect mating behaviour, with more intense competition predicted at biased sex ratios. In species with alternative mating behaviours, sex ratio variation can induce switches between behaviour types and this, together with the consistency with which behaviours are expressed, may also affect the intensity of sexual selection. All these factors can be combined to elucidate individual mating behaviour profiles. The establishment of individual behavioural profiles for male mating behaviour in one species, the guppy, Poecilia reticulata, is the focus of this study; specifically, we ask whether individual male mating behaviour profiles show that males have consistent reproductive behaviour across contexts where the advantages of using alternative mating tactics differ. The frequency of both sneak mating and display behaviours varied between sex ratios. Male display and sneak frequency were highly repeatable and males maintained consistent rankings of behaviour under equal, male- and female-biased sex ratios. We conclude, therefore, that male guppies have individual mating behaviour profiles. The use of behavioural profiles fills a gap in the existing literature by allowing behaviours that are functionally related but not correlated, such as alternative mating behaviours, to be treated as an integrated unit.