SEXUAL SELECTION CAN INCREASE THE EFFECT OF RANDOM GENETIC DRIFT—A QUANTITATIVE GENETIC MODEL OF POLYMORPHISM IN OOPHAGA PUMILIO,THE STRAWBERRY POISON‐DART FROG

The variation in color pattern between populations of the poison‐dart frog Oophaga pumilio across the Bocas del Toro archipelago in Panama is suggested to be due to sexual selection, as two other nonsexually selecting Dendrobatid species found in the same habitat and range do not exhibit this variation. We theoretically test this assertion using a quantitative genetic sexual selection model incorporating aposematic coloration and random drift. We find that sexual selection could cause the observed variation via a novel process we call “coupled drift.” Within our model, for certain parameter values, sexual selection forces frog color to closely follow the evolution of female preference. Any between‐population variation in preference due to genetic drift is passed on to color. If female preference in O. pumilio is strongly affected by drift, whereas color in the nonsexually selecting Dendrobatid species is not, coupled drift will cause increased between‐population phenotypic variation. However, with different parameter values, coupled drift will result in between‐population variation in color being suppressed compared to its neutral value, or in little or no effect. We suggest that coupled drift is a novel theoretical process that could have a role linking sexual selection with speciation both in O. pumilio, and perhaps more generally.     

Melanin‐based sexual dichromatism in the Western Palearctic avifauna implies darker males and lighter females

Melanins are the most common pigments providing coloration in the plumage and bare skin of birds and other vertebrates. Numerous species are dichromatic in the adult or definitive plumage, but the direction of this type of sexual dichromatism (i.e. whether one sex tends to be darker than the other) has not been thoroughly investigated. Using color plates, we analysed the presence of melanin‐based color patches in 666 species belonging to 69 families regularly breeding in the Western Palearctic. Sexual dichromatism based on melanins in at least one integumentary part involved 205 (30.7%) species. The body parts contributing more frequently to dichromatism were the dorsal areas, head and breast, whereas the less dichromatic body parts were the belly and the exposed integumentary parts (i.e. bill and legs). Regarding the phylogenetic spread of dichromatisms, 37 (53.6%) families contained at least one species with melanin‐based sexual dimorphism in the definitive adult plumage. As for the direction of the color difference, males are darker than females in a majority of species, meaning that males tend to produce more eumelanin and females tend to synthesize more pheomelanin. This survey has revealed the high prevalence of melanins in the emergence of sexual dichromatism in birds, at least in the Western Palearctic. Whether the described pattern is due to sexual selection promoting more conspicuous males or to natural selection for more cryptic females remains to be determined. Given that pheomelanin synthesis concurrently consumes the antioxidant glutathione but may also reduces toxic cysteine, sex‐biased physiological factors should also be given consideration in the evolution of bird plumages.     

Light matters: testing the “Light Environment Hypothesis” under intra‐ and interspecific contexts

The “Light Environment Hypothesis” (LEH) proposes that evolution of interspecific variation in plumage color is driven by variation in light environments across habitats. If ambient light has the potential to drive interspecific variation, a similar influence should be expected for intraspecific recognition, as color signals are an adaptive response to the change in ambient light levels in different habitats. Using spectrometry, avian‐appropriate models of vision, and phylogenetic comparative methods, I quantified dichromatism and tested the LEH in both intra‐ and interspecific contexts in 33 Amazonian species from the infraorder Furnariides living in environments with different light levels. Although these birds are sexually monochromatic to humans, 81.8% of the species had at least one dichromatic patch in their plumage, mostly from dorsal areas, which provides evidence for a role for dichromatism in sex recognition. Furthermore, birds from habitats with high levels of ambient light had higher dichromatism levels, as well as brighter, more saturated, and more diverse plumages, suggesting that visual communication is less constrained in these habitats. Overall, my results provide support for the LEH and suggest that ambient light plays a major role in the evolution of color signals in this group of birds in both intra‐ and interspecific contexts. Additionally, plumage variation across light environments for these drab birds highlights the importance of considering ambient light and avian‐appropriate models of vision when studying the evolution of color signals in birds.     

The role of sexual and natural selection in shaping patterns of sexual dichromatism in the largest family of songbirds (Aves: Thraupidae)

Males and females can be under different evolutionary pressures if sexual and natural selection is differentially operating in each sex. As a result, many species have evolved sexual dichromatism, or differences in coloration between sexes. Although sexual dichromatism is often used as an index of the magnitude of sexual selection, sexual dichromatism is a composite trait. Here, we examine the evolution of sexual dichromatism in one of the largest and most ecologically diverse families of birds, the tanagers, using the avian visual perspective and a species‐level phylogeny. Our results demonstrate that the evolutionary decreases of sexual dichromatism are more often associated with larger and more frequent changes in male plumage coloration, and evolutionary increases are not more often associated with larger changes in either sex. Furthermore, we show that the crown and ventral plumage regions are correlated with sexual dichromatism in males, and that only male plumage complexity is positively correlated with sexual dichromatism. Finally, we demonstrate that light environment is important in shaping both plumage brilliance and complexity. By conducting a multilevel analysis of plumage evolution in males and females, we show that sexual dichromatism evolves via a mosaic of sexual and natural selection in both sexes.     

Different modes of evolution in males and females generate dichromatism in fairy‐wrens (Maluridae)

Sexual dichromatism in birds is often attributed to selection for elaboration in males. However, evolutionary changes in either sex can result in plumage differences between them, and such changes can result in either gains or losses of dimorphism. We reconstructed the evolution of plumage colors in both males and females of species in Maluridae, a family comprising the fairy‐wrens (Malurus, Clytomias, Sipodotus), emu‐wrens (Stipiturus), and grasswrens (Amytornis). Our results show that, across species, males and females differ in their patterns of color evolution. Male plumage has diverged at relatively steady rates, whereas female coloration has changed dramatically in some lineages and little in others. Accordingly, in comparisons against evolutionary models, plumage changes in males best fit a Brownian motion (BM) model, whereas plumage changes in females fit an Ornstein Uhlenbeck (OU) multioptimum model, with different adaptive peaks corresponding to distributions in either Australia or New Guinea. Levels of dichromatism were significantly associated with latitude, with greater dichromatism in more southerly taxa. Our results suggest that current patterns of plumage diversity in fairy‐wrens are a product of evolutionary changes in both sexes, driven in part by environmental differences across the distribution of the family.     

Direct benefits of choosing a high‐fitness mate can offset the indirect costs associated with intralocus sexual conflict

Intralocus sexual conflict generates a cost to mate choice: high‐fitness partners transmit genetic variation that confers lower fitness to offspring of the opposite sex. Our earlier work in the fruit fly, Drosophila melanogaster, revealed that these indirect genetic costs were sufficient to reverse potential “good genes” benefits of sexual selection. However, mate choice can also confer direct fitness benefits by inducing larger numbers of progeny. Here, we consider whether direct benefits through enhanced fertility could offset the costs associated with intralocus sexual conflict in D. melanogaster. Using hemiclonal analysis, we found that females mated to high‐fitness males produced 11% more offspring compared to those mated to low‐fitness males, and high‐fitness females produced 34% more offspring than low‐fitness females. These direct benefits more than offset the reduction in offspring fitness caused by intralocus sexual conflict, creating a net fitness benefit for each sex to pairing with a high‐fitness partner. Our findings highlight the need to consider both direct and indirect effects when investigating the fitness impacts of mate choice. Direct fitness benefits may shelter sexually antagonistic alleles from selection, suggesting a novel mechanism for the maintenance of fitness variation.     

A test of ecological and sexual selection hypotheses for geographical variation in coloration and morphology of golden-crowned kinglets (Regulus satrapa)

Aim To date, studies on geographical variation have extensively investigated Bergmann’s rule, yet Gloger’s rule remains infrequently tested, and climatic predictors of variation in carotenoid coloration have not yet been studied. In addition, hypotheses based on sexual selection, which predict that sexual dimorphism should vary with population density and climatic conditions, have received little attention. Our goals were to characterize geographical variation in the coloration and morphology of golden‐crowned kinglets, Regulus satrapa (Passeriformes, Regulidae), and to investigate possible ecological and sexual selection correlates of this variation. Location The entire species range of golden‐crowned kinglets, comprising North and Central America. Methods We collected data from 511 museum specimens, dating from 1847 to 2006, encompassing all five subspecies of golden‐crowned kinglets. We used reflectance spectrometry to quantify crown and mantle coloration, and measured wing‐chord and tarsus length to approximate body size. We obtained geographical and climatic data from online databases, and population density estimates from the literature. Results There were significant subspecific and gender differences in crown coloration and morphology: male kinglets were generally larger and more colourful. Our data revealed mixed support for Bergmann’s rule: tarsus length decreased with increasing latitude, while patterns of variation in wing‐chord and tarsus length showed conflicting results with temperature. Mantle coloration exhibited an opposite trend to that predicted by Gloger’s rule: upper parts became lighter with increasing relative humidity. Crown coloration was negatively correlated with actual evapotranspiration, suggesting that levels of primary productivity are not directly linked to carotenoid abundance. Sexual dimorphism and dichromatism generally increased with greater population density, lower latitudes and elevations, and warmer temperatures, supporting a previously observed pattern of variation in sexual dimorphism. Main conclusions Geographical variation in golden‐crowned kinglets yielded mixed support for Bergmann’s rule and contradicted Gloger’s rule, suggesting that other mechanisms may be operating. Allen’s rule is likely to be a stronger factor influencing tarsus length. Differences in the degree of sexual dimorphism and dichromatism in varying climatic conditions suggest that the intensity of sexual selection differs between habitats. Further studies on geographical variation in sexual dimorphism in various taxa may reveal a previously unrecognized ecogeographical rule.     

MOLECULAR PHYLOGENETICS AND EVOLUTION OF SEXUAL DICHROMATISM AMONG POPULATIONS OF THE YARROW'S SPINY LIZARD (SCELOPORUS JARROVII)

Understanding evolution of geographic variation in sexually dimorphic traits is critical for understanding the role that sexual selection may play in speciation. We performed a phylogenetic analysis of geographic variation in sexual dichromatism in the Yarrow's spiny lizard (Sceloporus jarrovii), a taxon that exhibits remarkable diversity in male coloration among populations (e.g., black, red, green, yellow, blue, brown). An mtDNA phylogeny based on approximately 880 bp from the 12S ribosomal RNA gene and 890 bp from the ND4 gene was reconstructed for 30 populations of S. jarrovii and eight other species of the torquatus species group using maximum-likelihood and parsimony methods. The phylogeny suggests that S. jarrovii consists of at least five evolutionary species, none of which are sister taxa. Although intraspecific diversity in male coloration is less than indicated by previous taxonomy, two species formerly referred to as S. jarrovii exhibit impressive geographic variation in sexual dichromatism. In one of these species, the phylogeny shows the independent evolution of a distinctive blue color morph in different parts of the species range. This pattern suggests that sexual selection may lead to striking phenotypic divergence among conspecific populations and striking convergence. Results also demonstrate the importance of a phylogenetic perspective in studies of evolutionary processes within nominal species and the problematic nature of “polytypic” species recognized under the biological species concept.     

RECONSTRUCTING THE EVOLUTION OF SEXUAL DICHROMATISM: CURRENT COLOR DIVERSITY DOES NOT REFLECT PAST RATES OF MALE AND FEMALE CHANGE

Males of sexually dimorphic species often appear more divergent among taxa than do females, so it is often assumed that evolutionary changes have occurred primarily in males. Yet, sexual dimorphisms can result from historical changes in either or both of the sexes, and few previous studies have investigated such patterns using phylogenetic methods. Here, we describe the evolution of male and female plumage colors in the grackles and allies (Icteridae), a songbird clade with a broad range in levels of sexual dichromatism. Using a model of avian perceptual color space, we calculated color distances within and among taxa on a molecular phylogeny. Our results show that female plumage colors have changed more dramatically than male colors in the evolutionary past, yet male colors are significantly more divergent among species today. Historical increases in dichromatism have involved changes in both sexes, whereas decreases in dichromatism have nearly always involved females evolving rapidly to look like males. Dichromatism is also associated with mating system in this group, with monogamous taxa tending to exhibit relatively low levels of sexual dichromatism. Our findings suggest that, despite appearances, female plumage evolution plays a more prominent role in sexual dichromatism than is generally assumed.     

Sexual dimorphism and dichromatism in Steere's Liocichla (Liocichla steerii)

ABSTRACT.   Although sexual differences in birds can be extreme, differences between males and females in body size and plumage color are more subtle in many species. We used a genetic-based approach to determine the sex of male and female Steere's Liocichla ( Liocichla steerii ) and examine the degree of size dimorphism and plumage dichromatism in this apparently monomorphic species. We found that males were significantly larger than females. In addition, Steere's Liocichla have a prominent yellow plumage patch on the lores that was significantly larger in males than females for both live birds and museum specimens. We also used reflectance spectrometry to quantify the color of the yellow-green breast feathers of Steere's Liocichla and found no significant differences between males and females in brightness, intensity, saturation, or hue. However, females tended to have brighter breast plumage, particularly at long wavelengths. Collectively, these color variables were useful in discriminating birds according to sex when used in a discriminant function analysis. Our study suggests that sexual selection may be more widespread than once assumed, even among birds considered monomorphic, and emphasizes the need for additional data from tropical and subtropical species.     

Size dimorphism and avian‐perceived sexual dichromatism in a New Zealand endemic bird,the whitehead Mohoua albicilla

Sex differences in behavior, morphology, and physiology are common in animals. In many bird species, differences in the feather colors of the sexes are apparent when judged by human observers and using physical measures of plumage reflectance, cryptic (to human) plumage dichromatism has also been detected in several additional avian lineages. However, it remains to be confirmed in almost all species whether sexual dichromatism is perceivable by individuals of the studied species. This latter step is essential because it allows the evaluation of alternative hypotheses regarding the signaling and communication functions of plumage variation. We applied perceptual modeling of the avian visual system for the first time to an endemic New Zealand bird to provide evidence of subtle but consistent sexual dichromatism in the whitehead, Mohoua albicilla. Molecular sexing techniques were also used in this species to confirm the extent of the sexual size dimorphism in plumage and body mass. Despite the small sample sizes, we now validate previous reports based on human perception that in male whiteheads head and chest feathers are physically brighter than in females. We further suggest that the extent of sexual plumage dichromatism is pronounced and can be perceived by these birds. In contrast, although sexual dimorphism was also detectable in the mass among the DNA‐sexed individuals, it was found to be less extensive than previously thought. Sexual size dimorphism and intraspecifically perceivable plumage dichromatism represent reliable traits that differ between female and male whiteheads. These traits, in turn, may contribute to honest communication displays within the complex social recognition systems of communally breeding whitehead and other group‐breeding taxa. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

Sexually selected dichromatism in the hihi Notiomystis cincta: multiple colours for multiple receivers

Why do some bird species show dramatic sexual dichromatism in their plumage? Sexual selection is the most common answer to this question. However, other competing explanations mean it is unwise to assume that all sexual dichromatism has evolved by this mechanism. Even if sexual selection is involved, further work is necessary to determine whether dichromatism results from competition amongst rival males, or by female choice for attractive traits, or both. Here, we test whether sexually dichromatic hihi (Notiomystis cincta) plumage is currently under sexual selection, with detailed behavioural and genetic analyses of a free‐living island population. Bateman gradients measured for males and females reveal the potential for sexual selection, whilst selection gradients, relating reproductive success to specific colourful traits, show that there is stabilizing selection on white ear tuft length in males. By correlating colourful male plumage with different components of reproductive success, we show that properties of yellow plumage are most likely a product of male–male competition, whilst properties of the black and white plumage are an outcome of both male–male competition and female choice. Male plumage therefore potentially signals to multiple receivers (rival males and potential mates), and this may explain the multicoloured appearance of one of the most strikingly dichromatic species in New Zealand.     

Multiple origins of sexual dichromatism and aposematism within large carpenter bees

The evolution of reversed sexual dichromatism and aposematic coloration has long been of interest to both theoreticians and empiricists. Yet despite the potential connections between these phenomena, they have seldom been jointly studied. Large carpenter bees (genus Xylocopa) are a promising group for such comparative investigations as they are a diverse clade in which both aposematism and reversed sexual dichromatism can occur either together or separately. We investigated the evolutionary history of dichromatism and aposematism and a potential correlation of these traits with diversification rates within Xylocopa, using a newly generated phylogeny for 179 Xylocopa species based on ultraconserved elements (UCEs). A monochromatic, inconspicuous ancestor is indicated for the genus, with subsequent convergent evolution of sexual dichromatism and aposematism in multiple lineages. Aposematism is found to covary with reversed sexual dichromatism in many species; however, reversed dichromatism also evolved in non‐aposematic species. Bayesian Analysis of Macroevolutionary Models (BAMM) did not show increased diversification in any specific clade in Xylocopa, whereas support from Hidden State Speciation and Extinction (HiSSE) models remained inconclusive regarding an association of increased diversification rates with dichromatism or aposematism. We discuss the evolution of color patterns and diversification in Xylocopa by considering potential drivers of dichromatism and aposematism.     

Evolution of color variation in dragon lizards: quantitative tests of the role of crypsis and local adaptation

Abstract Many animal species display striking color differences with respect to geographic location, sex, and body region. Traditional adaptive explanations for such complex patterns invoke an interaction between selection for conspicuous signals and natural selection for crypsis. Although there is now a substantial body of evidence supporting the role of sexual selection for signaling functions, quantitative studies of crypsis remain comparatively rare. Here, we combine objective measures of coloration with information on predator visual sensitivities to study the role of crypsis in the evolution of color variation in an Australian lizard species complex (Ctenophorus decresii). We apply a model that allows us to quantify crypsis in terms of the visual contrast of the lizards against their natural backgrounds, as perceived by potential avian predators. We then use these quantitative estimates of crypsis to answer the following questions. Are there significant differences in crypsis conspicuousness among populations? Are there significant differences in crypsis conspicuousness between the sexes? Are body regions “exposed” to visual predators more cryptic than “hidden” body regions? Is there evidence for local adaptation with respect to crypsis against different substrates? In general, our results confirmed that there are real differences in crypsis conspicuousness both between populations and between sexes; that exposed body regions were significantly more cryptic than hidden ones, particularly in females; and that females, but not males, are more cryptic against their own local background than against the background of other populations. Body regions that varied most in contrast between the sexes and between populations were also most conspicuous and are emphasized by males during social and sexual signaling. However, results varied with respect to the aspect of coloration studied. Results based on chromatic contrast (“hue’ of color) provided better support for the crypsis hypothesis than did results based on achromatic contrast (“brightness’ of color). Taken together, these results support the view that crypsis plays a substantial role in the evolution of color variation and that color patterns represent a balance between the need for conspicuousness for signaling and the need for crypsis to avoid predation.     

Sex‐specific selection on plant architecture through “budget” and “direct” effects in experimental populations of the wind‐pollinated herb,Mercurialis annua

Sexual selection may contribute to the evolution of plant sexual dimorphism by favoring architectural traits in males that improve pollen dispersal to mates. In both sexes, larger individuals may be favored by allowing the allocation of more resources to gamete production (a “budget” effect of size). In wind‐pollinated plants, large size may also benefit males by allowing the liberation of pollen from a greater height, fostering its dispersal (a “direct” effect of size). To assess these effects and their implications for trait selection, we measured selection on plant morphology in both males and females of the wind‐pollinated dioecious herb Mercurialis annua in two separate experimental common gardens at contrasting density. In both gardens, selection strongly favored males that disperse their pollen further. Selection for pollen production was observed in the high‐density garden only, and was weak. In addition, male morphologies associated with increased mean pollen dispersal differed between the two gardens, as elongated branches were favored in the high‐density garden, whereas shorter plants with longer inflorescence stalks were favored in the low‐density garden. Larger females were selected in both gardens. Our results point to the importance of both a direct effect of selection on male traits that affect pollen dispersal, and, to a lesser extent, a budget effect of selection on pollen production.     

Broad‐scale variation in sexual dichromatism in songbirds is not explained by sex differences in exposure to predators during incubation

The evolution of sexual dichromatism provoked one of the greatest disagreements between Charles Darwin and Alfred Russel Wallace. According to Darwin the main driving force is sexual selection, whereby choosy females prefer showy males, leading to the evolution of conspicuous male plumage. On the other hand, Wallace suggested that dichromatism may arise because nest predation favors more cryptic females. To test the role of natural selection in the evolution of dichromatism we combined quantitative data on differences in parental share in nest attentiveness (representing the strength of natural selection on males vs females) with spectrophotometric measurements of dichromatism in 412 species of songbirds from 69 families. We expected to find stronger dichromatism in open‐nesting species with more divergent parental roles and in body parts exposed during incubation. Dichromatism was not related to the differences in parental share during incubation, but it was most pronounced in lekking species, migrants, and small species. Our results thus suggest that Wallace's hypothesis is not able to explain broad‐scale variation in the dichromatism of songbirds, but point to a role for sexual selection, mutual mate choice, and migration strategy in shaping the extraordinary variation in dichromatism exhibited by songbirds.     

Males in seemingly female‐like plumage do not mimic females: UV reflectance reveals temporal cryptic dimorphism in a manakin species exhibiting delayed plumage maturation

Manakins (Pipridae) are neotropical birds that usually exhibit delayed plumage maturation (DPM). Thus, while plumage of most adult male manakins is brightly conspicuous, subadult males and females are basically dull‐olive green. Although sexual dichromatism in some bird species may be evident only through UV reflectance, this phenomenon, known as hidden sexual dichromatism, has not been previously studied in manakins to compare subadult males and females. Within this framework, we carried out spectrophotometric analyses in searching for hidden sexual dichromatism in the white‐bearded manakin Manacus manacus, through comparison of UV spectra in females and subadult males in green plumage. Our results revealed UV reflectance in both sexes in green plumage. Moreover, we found UV spectral differences in homologous color patches between sexes, particularly at belly. Since the observed differences may allow intraspecific sex recognition of individuals in green plumage, our results do not support the female‐mimicry hypothesis to explain delayed plumage maturation in the white‐bearded manakin. Although our findings dismiss the female mimicry hypothesis, we cannot state whether these results support the non‐mutually exclusive cryptic and status signaling hypotheses. We propose then, that dull coloration of subadult males may serve both as a cryptic trait and to limit the energetic costs of acquiring the adult plumage before sexual maturity. Meanwhile, differential UV color traits between sexes in green plumage may allow adult males to avoid unnecessary energy expenditures in courtship displays in the presence of males near leks, and to selectively focus their the courtship displays on females. In accordance with the status signaling hypothesis, subadult males can be recognized both as males and subordinates and consequently may practice courtship displays without suffering aggressions by adult males. Our results highlight the importance to include a wider range of spectrophotometric information analyses for testing hypotheses regarding delayed plumage maturation.     

Ecological constraint and the evolution of sexual dichromatism in darters

It is not known how environmental pressures and sexual selection interact to influence the evolution of extravagant male traits. Sexual and natural selection are often viewed as antagonistic forces shaping the evolution of visual signals, where conspicuousness is favored by sexual selection and crypsis is favored by natural selection. Although typically investigated independently, the interaction between natural and sexual selection remains poorly understood. Here, we investigate whether sexual dichromatism evolves stochastically, independent from, or in concert with habitat use in darters, a species‐rich lineage of North American freshwater fish. We find the evolution of sexual dichromatism is coupled to habitat use in darter species. Comparative analyses reveal that mid‐water darter lineages exhibit a narrow distribution of dichromatism trait space surrounding a low optimum, suggesting a constraint imposed on the evolution of dichromatism, potentially through predator‐mediated selection. Alternatively, the transition to benthic habitats coincides with greater variability in the levels of dichromatism that surround a higher optimum, likely due to relaxation of the predator‐mediated selection and heterogeneous microhabitat dependent selection regimes. These results suggest a complex interaction of sexual selection with potentially two mechanisms of natural selection, predation and sensory drive, that influence the evolution of diverse male nuptial coloration in darters.     

Background matching,disruptive coloration,and differential use of microhabitats in two neotropical grasshoppers with sexual dichromatism

Cryptic coloration is an adaptative defensive mechanism against predators. Color patterns can become cryptic through background coloration‐matching and disruptive coloration. Disruptive coloration may evolve in visually heterogeneous microhabitats, whereas background matching could be favored in chromatically homogeneous microhabitats. In this work, we used digital photography to explore the potential use of disruptive coloration and background matching in males and females of two grasshopper species of the Sphenarium genus in different habitats. We found chromatic differences in the two grasshopper species that may be explained by local adaptation. We also found that the females and males of both species are dichromatic and seem to follow different color cryptic strategies, males are more disruptive than females, whereas females have a high background matching with less disruptive elements. The selective pressures of the predators in different microhabitats and the differences in mobility between sexes may explain the color pattern divergence between females and males. Nevertheless, more field experiments are needed in order to understand the relative importance of disruptive and background matching coloration in the evolution of sexual dichromatism in these grasshoppers.     

Fisherian and “good genes” benefits of mate choice: how (not) to distinguish between them

“Good genes” models of mate choice are commonly tested by examining whether attractive males sire offspring with improved survival. If offspring do not survive better (or indeed survive less well), but instead inherit the attractiveness of their father, results are typically interpreted to support the Fisherian process, which allows the evolution of preferences for arbitrary traits. Here, I show that the above view is mistaken. Because of life‐history trade‐offs, an attractive male may perform less well in other components of fitness. A female obtains a “good genes” benefit whenever males show heritable variation in quality, even if high‐quality males invest so much in sexual advertisement that attractiveness has no positive correlation with any other life‐history trait than male mating success itself. Therefore, a negative correlation between attractiveness and viability does not falsify good genes, if mating with a high‐quality male results on average in superior offspring performance (mating success of sons included). The heritable “good genes” benefit can be sustained even if sexually antagonistic genes cause female offspring sired by high‐quality males to survive and reproduce less well. Neglecting the component of male mating success from measurements of fitness returns from sons and daughters will bias the advantage of mating with a high‐quality male downwards. This result may partly account for the rather weak “good genes” effects found in a recent meta‐analysis.