Wing shape,wing size,and sexual dimorphism in eye‐span in stalk‐eyed flies (Diopsidae)

The eyes of stalk‐eyed flies (Diopsidae) are positioned at the end of rigid peduncles (‘stalks’) protruding laterally from the head. Eye‐stalk length varies within the family and, in some species, varies between males and females. Larger eye‐stalks in males result from sexual selection for longer stalks, a trait that increases male reproductive success. In the present study, we examined whether an increase in eye‐stalk length results in an adjustment of wing size and shape to deal with the burden of bearing an exaggerated ‘ornament’. We compared wing morphology among ten species of stalk‐eyed flies that differ in eye‐span and the degree of sexual dimorphism. Mass‐specific wing length differed between males and females in seven out of the ten species. Nondimensional wing shape parameters differed between the species (P < 0.001), but mostly did not differ between males and females of the same species. Dimorphism in eye‐span closely correlated with dimorphism in wing length (r = 0.89, P < 0.001) and the correlation remained significant (r = 0.81, P = 0.006) after correcting for phylogenetic relationships. Once corrected for phylogenetic relatedness, the mass‐specific wing length of males (but not females) was weakly correlated with mass‐specific eye‐span (r = 0.66, P = 0.042). We propose that the observed proportional increase in wing length associated with increased eye‐span can facilitate aerial manoeuverability, which would otherwise be handicapped by the elevated moment of inertia imposed by the wider head. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 860–871.     

Sexual dimorphism in wing beat frequency in relation to eye span in stalk‐eyed flies (Diopsidae)

Although male ornaments may provide benefits to individuals bearing them, such structures may also entail fitness costs. Selection should favour aspects of the phenotype that act to reduce such costs, yet such compensatory traits are often ignored in studies of sexual selection. If a male ornament increases predation risk via reduced locomotor performance, then there may be selection for changes in morphological traits to compensate for behavioural or biomechanical changes in how individuals use their morphology (or both). We took a comparative approach aiming to test whether changes in wing beat frequency are evolutionarily correlated with increases in male ornamentation across stalk‐eyed fly species. Previous studies have shown that increased male eye span is evolutionarily correlated with increased wing size; thus, we tested whether there is additional compensation via increases in size‐adjusted wing beat frequency. The results obtained revealed that relative wing beat frequency is negatively related to relative eye span in males, and sexual dimorphism in wing beat frequency is negatively related to dimorphism in eye span. These findings, in addition to our finding that eye span dimorphism is positively related to aspect ratio dimorphism, suggest that male stalk‐eyed flies compensate primarily by increasing wing size and shape, which may then have resulted in the subsequent evolutionary reduction in wing beat frequency. Thus, exaggerated ornaments can result in evolutionary modifications in wing morphology, which in turn lead to adjustments in flapping kinematics, illustrating the tight envelope of trade‐offs when compensating for exaggerated ornaments. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 670–679.     

Environmental conditions influence red grouse ornamentation at a population level

Theory suggests that condition‐dependent sexual displays should be more weakly expressed under adverse conditions than under more favourable ones. Here, we tested this hypothesis in wild red grouse Lagopus lagopus scoticus using a data set of nearly 1500 individuals from nine populations over 8 years, covering varying environmental conditions. We analysed whether male and female ornament expression (i.e. comb size) in a given site and year varied with various indices of environmental conditions: population density, Trichostrongylus tenuis nematode infection at the population level, and climate conditions [measured as winter North Atlantic oscillation (NAO) index]. We found that average comb size in males, but not in females, negatively correlated with population density, parasite infection levels, and winter NAO index. Furthermore, the coefficient of variation (CV) of comb size was higher in females than in males. CVs in both males and females were not clearly associated with the studied environmental variables. Our results support the idea that the expression of condition‐dependent sexual traits should be lower under more stressful environmental conditions, but only in males. We discuss the potential reasons behind the effect of environmental conditions on secondary sexual traits, and why these effects differ between sexes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Sexual conflict in wing size and shape in Drosophila melanogaster

Intralocus sexual conflict occurs when opposing selection pressures operate on loci expressed in both sexes, constraining the evolution of sexual dimorphism and displacing one or both sexes from their optimum. We eliminated intralocus conflict in Drosophila melanogaster by limiting transmission of all major chromosomes to males, thereby allowing them to win the intersexual tug‐of‐war. Here, we show that this male‐limited (ML) evolution treatment led to the evolution (in both sexes) of masculinized wing morphology, body size, growth rate, wing loading, and allometry. In addition to more male‐like size and shape, ML evolution resulted in an increase in developmental stability for males. However, females expressing ML chromosomes were less developmentally stable, suggesting that being ontogenetically more male‐like was disruptive to development. We suggest that sexual selection over size and shape of the imago may therefore explain the persistence of substantial genetic variation in these characters and the ontogenetic processes underlying them.     

Bite-force performance and head shape in a sexually dimorphic crevice-dwelling lizard, the common chuckwalla [Sauromalus ater (= obesus)]

The Common Chuckwalla [ Sauromalus ater (=  obesus )] is a large, sexually dimorphic lizard with a flattened head that takes refuge from predators in rock crevices. Males use their relatively large heads to bite competing males during territorial fights and to restrain females during copulation. Flattened heads with an antipredator function (i.e. seeking refuge in crevices) and enlarged heads with intrasexual competition and reproductive functions suggest possible antagonism between selective pressures on head morphology in males. To examine this hypothesis, we performed a morphometric analysis and measured the bite-force performance of 49 adult chuckwallas. Males had disproportionately wider heads than females, but did not have deeper heads. Males bit with nearly four times the force of females, consistent with the notion of sexual selection for high bite force in males. Although constrained by crevice-wedging behaviour, head depth was a good predictor of bite force in both sexes. In males, however, osteological head width also was a good predictor of bite force. These results are consistent with the hypothesis that head shape in males is under antagonistic selective pressures, which may partly explain the pattern of head shape dimorphism. The disproportionately wide head of males may reflect anatomical modifications to enhance bite force in response to sexual selection in spite of presumed constraints on head shape for crevice-wedging behaviour  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 215–222.     

Sexual bimaturation and sexual size dimorphism in animals with asymptotic growth after maturity

Many animal taxa exhibit a positive correlation between sexual size dimorphism and sex differences in age at maturity, such that members of the larger sex mature at older ages than members of the smaller sex. Previous workers have suggested that sexual bimaturation is a product of sex differences in growth trajectories, but to date no one has tested this hypothesis. The current study uses growth-based models to study relationships between sexual size dimorphism and sexual bimaturation in species with asymptotic growth after maturity. These models show that sex differences in asymptotic size would produce sexual bimaturation even if both sexes approach their respective asymptotic sizes at the same age, mature at the same proportion of asymptotic size and have otherwise equivalent growth and maturation patterns. Furthermore, our analyses show that there are three ways to reduce sexual bimaturation in sexually size-dimorphic species: (1) higher characteristic growth rates for members of the larger sex, (2) larger size at birth, hatching or metamorphosis for members of the larger sex or (3) smaller ratio of size at maturity to asymptotic size (relative size at maturity) for members of the larger sex. Of these three options, sex differences in relative size at maturity are most common in size-dimorphic species and, in both male-larger and female-larger species, members of the larger sex frequently mature at a smaller proportion of their asymptotic size than do members of the smaller sex. Information about the growth and maturation patterns of a taxon can be used to determine relationships between sexual size dimorphism and sexual bimaturation for the members of that taxon. This process is illustrated for Anolis lizards, a genus in which both sexes exhibit the same strong correlation (r 0.97) between size at maturity and asymptotic size, and in which the relative size at maturity is inversely related to asymptotic size for both sexes. As a result, sexually size-dimorphic species of anoles exhibit the expected pattern of a smaller relative size at maturity for members of the larger sex. However, for species in this genus, sex differences in the relative size at maturity are not strong enough to produce the same age at maturity for both sexes in sexually size-dimorphic species. Members of the larger sex (usually males) are still expected to mature at older ages than members of the smaller sex in Anolis lizards.     

Sexual selection as a promoter of population divergence in male phenotypic characters: a study on mainland and islet lizard populations

Sexual selection is often viewed as a promoter of population divergence, although some forms of sexual selection could rather hamper divergence. In the present study, we investigated whether sexual selection promotes divergence in sexually‐selected traits. We studied population variation in sexual selection in relation to colour morph and body size in islet and mainland populations of the Skyros wall lizard (Podarcis gaigeae). Females were most likely to mate with orange‐throated males with small body sizes, and male body size and coloration were therefore subject to correlational sexual selection. By contrast, male mating probabilities were not affected by any female phenotypic character. We also found variation in a female resistance trait (escape propensity), with females being more prone to escape when exposed to males from other habitats. Sexual selection could potentially affect the frequencies of throat colour morphs in this species by favouring orange‐throated males of small body size, although there was no evidence of sexual selection for local mates or rare phenotypes. The results obtained in the present study thus do not support a role for sexual selection as a promoter of population divergence in this species. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 374–389.     

Head shape allometry and proximate causes of head sexual dimorphism in Podarcis lizards: joining linear and geometric morphometrics

Podarcis bocagei and Podarcis carbonelli are two lacertid species endemic to the western Iberian Peninsula, and both show head size and shape sexual dimorphism. We studied immature and adult head sexual dimorphism and analysed ontogenetic trajectories of head traits with body and head size, aiming to shed light on the proximate mechanisms involved. Immatures were much less dimorphic than adults, but geometric morphometric techniques revealed that head shape sexual differences are already present at this stage. Males and females differed in allometry of all head characters with body size, with males showing a disproportionate increase of head size and dimensions. On the other hand, head dimensions and head shape changed with increasing head size following similar trends in both sexes, possibly indicating developmental restrictions. Consequently, adult sexual dimorphism for head characters in these species is the result of both shape differences in the immature stage and hypermetric growth of the head in relation to body size in males.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 111–124.     

Subtle,pervasive genetic correlation between the sexes in the evolution of dimorphic hummingbird tail ornaments*

Male hummingbirds have repeatedly evolved sexually dimorphic tails that they use as ornaments during courtship. We examine how male ornament evolution is reflected in female morphology. Lande's two-step model of the evolution of dimorphism predicts that γ (the genetic correlation between the sexes) causes trait elaboration to first evolve quickly in both sexes, then dimorphism evolves more slowly. On the hummingbird phylogeny, tail length does not fit this two-step model; although hummingbirds repeatedly evolved ornamental, elongated tails, dimorphism evolves on the same phylogenetic branch as elongation, implying that γ quickly evolves to be low over phylogenetic timescales. Male “bee” hummingbirds have evolved diverse rectrix shapes that they use to produce sound. Female morphologies exhibit subtle, pervasive correlations with male morphology. No female-adaptive hypotheses explain these correlations, since females do not also make sounds with their tail. Subtle shape similarity has arisen through the genetic correlation with males, and is subject to intralocus sexual conflict. Intralocus sexual conflict may produce increased phenotypic variation of female ornaments. Other evolutionary constraints on tail morphology include a developmental correlation between neighboring tail-feathers, biasing tail elaboration to occur most often at the ends of the feather tract (rectrix 5 or 1) and not the middle.     

Effects of ornamentation and phylogeny on the evolution of wing shape in stalk‐eyed flies (Diopsidae)

Exaggerated male ornaments are predicted to be costly to their bearers, but these negative effects may be offset by the correlated evolution of compensatory traits. However, when locomotor systems, such as wings in flying species, evolve to decrease such costs, it remains unclear whether functional changes across related species are achieved via the same morphological route or via alternate changes that have similar function. We conducted a comparative analysis of wing shape in relation to eye‐stalk elongation across 24 species of stalk‐eyed flies, using geometric morphometrics to determine how species with increased eye span, a sexually selected trait, have modified wing morphology as a compensatory mechanism. Using traditional and phylogenetically informed multivariate analyses of shape in combination with phenotypic trajectory analysis, we found a strong phylogenetic signal in wing shape. However, dimorphic species possessed shifted wing veins with the result of lengthening and narrowing wings compared to monomorphic species. Dimorphic species also had changes that seem unrelated to wing size, but instead may govern wing flexion. Nevertheless, the lack of a uniform, compensatory pattern suggests that stalk‐eyed flies used alternative modifications in wing structure to increase wing area and aspect ratio, thus taking divergent morphological routes to compensate for exaggerated eye stalks.     

Sexual differences in head form and diet in a population of Mexican lance‐headed rattlesnakes,Crotalus polystictus

Sexual dimorphism of phenotypic traits associated with resource use is common in animals, and may result from niche divergence between sexes. Snakes have become widely used in studies of the ecological basis of sexual dimorphism because they are gape‐limited predators and their head morphology is likely to be a direct indicator of the size and shape of prey consumed. We examined sexual dimorphism of body size and head morphology, as well as sexual differences in diet, in a population of Mexican lance‐headed rattlesnakes, Crotalus polystictus, from the State of México, Mexico. The maximum snout–vent length of males was greater than that of females by 21%. Males had relatively larger heads, and differed from females in head shape after removing the effects of head size. In addition, male rattlesnakes showed positive allometry in head shape: head width was amplified, whereas snout length was truncated with increased head size. By contrast, our data did not provide clear evidence of allometry in head shape of females. Adults of both males and females ate predominately mice and voles; however, males also consumed a greater proportion of larger mammalian species, and fewer small prey species. The differences in diet correspond with dimorphism in head morphology, and provide evidence of intersexual niche divergence in the study population. However, because the sexes overlapped greatly in diet, we hypothesize that diet and head dimorphisms in C. polystictus are likely related to different selection pressures in each sex arising from pre‐existing body size differences rather than from character displacement for reducing intersexual competition. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 633–640.     

Pelvic growth: ontogeny of size and shape sexual dimorphism in rat pelves

The mammalian pelvis is sexually dimorphic with respect to both size and shape. Yet little is known about the differences in postnatal growth and bone remodeling that generate adult sexual dimorphism in pelvic bones. We used Sprague-Dawley laboratory rats (Rattus norvegicus), a species that exhibits gross pelvic size and shape dimorphism, as a model to quantify pelvic morphology throughout ontogeny. We employed landmark-based geometric morphometrics methodology on digitized landmarks from radiographs to test for sexual dimorphism in size and shape, and to examine differences in the rates, magnitudes, and directional patterns of shape change during growth. On the basis of statistical significance testing, the sexes became different with respect to pelvic shape by 36 days of age, earlier than the onset of size dimorphism (45 days), although visible shape differences were observed as early as at 22 days. Males achieved larger pelvic sizes by growing faster throughout ontogeny. However, the rates of shape change in the pelvis were greater in females for nearly all time intervals scrutinized. We found that trajectories of shape change were parallel in the two sexes until age of 45 days, suggesting that both sexes underwent similar bone remodeling until puberty. After 45 days, but before reproductive maturity, shape change trajectories diverged because of specific changes in the female pelvic shape, possibly due to the influence of estrogens. Pattern of male pelvic bone remodeling remained the same throughout ontogeny, suggesting that androgen effects on male pelvic morphology were constant and did not contribute to specific shape changes at puberty. These results could be used to direct additional research on the mechanisms that generate skeletal dimorphisms at different levels of biological organization.     

Sexual selection,phenotypic variation,and allometry in genitalic and non‐genitalic traits in the sexually size‐dimorphic stick insect Micrarchus hystriculeus

The mobility hypothesis could explain the evolution of female‐biased size dimorphism if males with a smaller body size and longer legs have an advantage in scramble competition for mates. This hypothesis is tested by performing a selection analysis in the wild on Micrarchus hystriculeus (Westwood) (Phasmatodea), a sexually size dimorphic stick insect endemic to New Zealand. This analysis examined the form and strength of sexual selection on body size, leg lengths (front, mid and hind), and clasper size (a genitalic trait), and also quantified the degree of phenotypic variation and the allometric scaling pattern of these traits. By contrast to the mobility hypothesis, three lines of evidence were found to support significant stabilizing sexual selection on male hind leg length: a significant nonlinear selection gradient, negative static allometry, and a low degree of phenotypic variation. Hind leg length might be under stabilizing selection in males if having average‐sized legs facilitates female mounting or improves a male's ability to achieve the appropriate copulation position. As predicted, a negative allometric scaling pattern and low phenotypic variation of clasper size is suggestive of stabilizing selection and supports the ‘one‐size‐fits‐all’ hypothesis. Opposite to males, the mid and hind leg lengths of females showed positive static allometry. Relatively longer mid and hind leg lengths in larger females might benefit individuals via the better support of their larger abdomens. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 471–484.     

Allometry of a sexual trait in relation to diet experience and alternative mating tactics in two rubyspot damselflies (Calopterygidae: Hetaerina)

Several arguments have been put forward to explain how sexual selection drives the evolution of sexual trait allometry, especially hyperallometry. The ‘positive allometry theory’ suggests that hyperallometry is a rule in all‐secondary sexual traits, whereas the ‘display hypothesis’ suggests that only males in good condition will exhibit hyperallometric sexual display traits. In the present study, we investigated: (1) the condition‐dependence nature (by using two diet treatments that varied in the amount of food provided to the larvae) of a sexually selected trait (wing pigmentation; WP) in recently‐emerged adults of the American rubyspot damselfly, Hetaerina americana, and (2) the scaling relationship between WP and body size (wing and body length) in the rubyspot damselflies H. americana and Hetaerina vulnerata, according to alternative reproductive tactics (ARTs; territorial and nonterritorial males). First, we found support that indicated that diet positively affected WP length, although there was no significant WP allometric pattern in relation to diet regimes. Second, WP was hyperallometric in both Hetaerina species. WP size was similar between ARTs and, in H. americana (but not H. vulnerata), nonterritorial males showed steeper slopes than territorial males when wing length was used. The results obtained support the notion that sexual traits are hyperallometric, although there is no clear pattern in relation to ARTs. © 2013 The Linnean Society of London     

Limits to environmental masking of genetic quality in sexual signals

There is considerable debate over the value of male sexual ornaments as signals of genetic quality. Studies alternately report that environmental variation enhances or diminishes the genetic signal, or leads to crossover where genotypes perform well in one environment but poorly in another. A unified understanding is lacking. We conduct a novel experimental test examining the dual effects of distinct categories of genetic (inbred vs. crossed parental lines) and environmental quality (low, through high to extreme larval food stress) on a condition‐dependent male ornament. We find that differences in genetic quality signalled by the ornament (male eyespan in Diasemopsis meigenii stalk‐eyed flies) become visible and are amplified under high stress but are overwhelmed in extreme‐stress environments. Variance among independent genetic lines increases with environmental stress in both genetic quality classes, but at a slower rate in high quality outcrossed flies. Individual genetic lines generally maintain their ranks across environments, except among high quality lines under low environmental stress, where low genetic variance among lines precludes differentiation between ranks. Our results provide a conceptual advance, demonstrating a unified pattern for how genetic and environmental quality interact. They show when environmental conditions lead to the amplification of differences in signals of genetic quality and thereby enhance the potential indirect genetic benefits gained by female mate choice.     

EVOLUTION OF STATIC ALLOMETRIES: ADAPTIVE CHANGE IN ALLOMETRIC SLOPES OF EYE SPAN IN STALK‐EYED FLIES

Julian Huxley showed that within‐species (static) allometric (power‐law) relations can arise from proportional growth regulation with the exponent in the power law equaling the factor of proportionality. Allometric exponents may therefore be hard to change and act as constraints on the independent evolution of traits. In apparent contradiction to this, many empirical studies have concluded that static allometries are evolvable. Many of these studies have been based, however, on a broad definition of allometry that includes any monotonic shape change with size, and do not falsify the hypothesis of constrained narrow‐sense allometry. Here, we present the first phylogenetic comparative study of narrow‐sense allometric exponents based on a reanalysis of data on eye span and body size in stalk‐eyed flies (Diopsidae). Consistent with a role in sexual selection, we found strong evidence that male slopes were tracking “optima” based on sexual dimorphism and relative male trait size. This tracking was slow, however, with estimated times of 2–3 million years for adaptation to exceed ancestral influence on the trait. Our results are therefore consistent with adaptive evolution on million‐year time scales, but cannot rule out that static allometry may act as a constraint on eye‐span adaptation at shorter time scales.     

The complexity of mating decisions in stalk‐eyed flies

All too often, studies of sexual selection focus exclusively on the responses in one sex, on single traits, typically those that are exaggerated and strongly sexually dimorphic. They ignore a range of less obvious traits and behavior, in both sexes, involved in the interactions leading to mate choice. To remedy this imbalance, we analyze a textbook example of sexual selection in the stalk‐eyed fly (Diasemopsis meigenii). We studied several traits in a novel, insightful, and efficient experimental design, examining 2,400 male–female pairs in a “round‐robin” array, where each female was tested against multiple males and vice versa. In D. meigenii, females exhibit strong mate preference for males with highly exaggerated eyespan, and so we deliberately constrained variation in male eyespan to reveal the importance of other traits. Males performing more precopulatory behavior were more likely to attempt to mate with females and be accepted by them. However, behavior was not a necessary part of courtship, as it was absent from over almost half the interactions. Males with larger reproductive organs (testes and accessory glands) did not make more mating attempts, but there was a strong tendency for females to accept mating attempts from such males. How females detect differences in male reproductive organ size remains unclear. In addition, females with larger eyespan, an indicator of size and fecundity, attracted more mating attempts from males, but this trait did not alter female acceptance. Genetic variation among males had a strong influence on male mating attempts and female acceptance, both via the traits we studied and other unmeasured attributes. These findings demonstrate the importance of assaying multiple traits in males and females, rather than focusing solely on prominent and exaggerated sexually dimorphic traits. The approach allows a more complete understanding of the complex mating decisions made by both males and females.     

Sexual dimorphism in traits related to locomotion: ontogenetic patterns of variation in Podarcis wall lizards

Sexual dimorphism in body size and shape in animals is normally linked to sexual selection mechanisms that modify the morphological properties of each sex. However, sexual dimorphism of ecologically relevant traits may be amplified by natural selection and result in the ecological segregation of both sexes. In the present study, we investigated patterns of sexual dimorphism of morphological traits relevant for locomotion in two lacertid lizards, Podarcis bocagei and Podarcis carbonelli, aiming to identify ontogenetic sources of variation. We analysed trunk and limb variation in relation to total body size, as well as the covariation of different traits, aiming to shed light on the proximate causation of adult sexual dimorphism. We find that, although immatures are generally monomorphic, adult females have a longer trunk, and adult males have longer fore and hind limbs. Both sexes differ substantially with respect to their growth trajectories and relationships between traits, whereas, in some cases, there are signs of morphological constraints delimiting the observed patterns. Because of the direct connection between limb size/shape and locomotor performance, which is relevant both for habitat use and escape from predators, the observed patterns of sexual dimorphism are expected to translate into ecological differences between both sexes. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 530–543.     

Patterns of sexual size dimorphism in Chelonia

Macroevolutionary patterns of sexual size dimorphism (SSD) indicate how sexual selection, natural selection, and genetic and developmental constraints mold sex differences in body size. One putative pattern, known as Rensch's rule, posits that, among species with female‐larger SSD, the relative degree of SSD declines with species' body size, whereas, among male‐larger SSD species, relative SSD increases with size. Using a dataset of 196 chelonian species from all fourteen families, we investigated the correlation in body size evolution between male and female Chelonia and the validity of Rensch's rule for the taxon and within its major clades. We conclude that male–female correlations in body size evolution are high, although these correlations differ among chelonian families. Overall, SSD scales isometrically with body size; Rensch's rule is valid for only one family, Testudinidae (tortoises). Because macroevolutionary patterns of SSD can vary markedly among clades, even in a taxon as morphologically conservative as Testudines, one must guard against inappropriately pooling clades in comparative studies of SSD. The results of the present study also indicate that regression models that assume the x‐variable (e.g. male body size) is measured without statistical error, although frequently reported, will result in erroneous conclusions about phylogenetic trends in sexual size dimorphism. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 108 , 396–413.     

Dynamic phenotypic correlates of social status and mating effort in male and female red junglefowl,Gallus gallus

Despite widespread evidence that mating and intrasexual competition are costly, relatively little is known about how these costs dynamically change male and female phenotypes. Here, we test multiple hypotheses addressing this question in replicate flocks of red junglefowl (Gallus gallus). First, we test the interrelationships between social status, comb size (a fleshy ornament) and body mass at the onset of a mating trial. While comb size covaried positively with body mass across individuals of both sexes, comb size was positively related to social status in females but not in males. Second, we test for changes within individuals in body mass and comb size throughout the mating trial. Both body mass and comb size declined at the end of a trial in both sexes, suggesting that mating effort and exposure to the opposite sex are generally costly. Males lost more body mass if they (a) were socially subordinate, (b) were chased by other males or (c) mated frequently, indicating that subordinate status and mating are independently costly. Conversely, females lost more body mass if they were exposed to a higher frequency of coerced matings, suggesting costs associated with male sexual harassment and female resistance, although costs of mating per se could not be completely ruled out. Neither competitive nor mating interactions predicted comb size change in either sex. Collectively, these results support the notion that sex‐specific costs associated with social status and mating effort result in differential, sex‐specific dynamics of phenotypic change.