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Journal ArticleDOI

A phylogenetic interpretation of sexual dimorphism in body size and ornament in relation to mating system in birds

01 May 1990-Journal of Evolutionary Biology (Blackwell Science Ltd)-Vol. 3, pp 171-183
TL;DR: Comparative data on birds using an autocorrelation model suggests that an evolutionary change in mating system is associated with a change in overall size, and in degree of dimorphism in secondary sexual traits.
Abstract: Sexual dimorphism in body size and ornament is commonly assumed to be a result of sexual selection. Therefore, a pattern among species is expected where the type of mating system correlates with the degree of sexual dimorphism. This was analysed using comparative data on birds using an autocorrelation model. Mating system did correlate with sexual dimorphism in ornament (tail), but was only weakly correlated with sexual size (tarsus) dimorphism. Polygynous species were significantly larger than monogamous species. After correcting for size, there was no difference in size dimorphism between polygynous and monogamous species. The reverse was true for tail dimorphism; polygynous species exhibited a larger degree of tail dimorphism, but there was no difference in absolute size of the tail. This pattern suggests that an evolutionary change in mating system is associated with a change in overall size, and in degree of dimorphism in secondary sexual traits.
Citations
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Journal ArticleDOI
TL;DR: These trends are derived from a sample of 40 independent clades of terrestrial animals, primarily vertebrates, and indicate that SSD increases with size where males are the larger sex, but decreases with sizeWhere females are larger, a trend formalized as “Rensch's rule.”
Abstract: Sexual size dimorphism (SSD) is common in both plants and animals, and current evidence suggests that it reflects the adaptation of males and females to their different reproductive roles. When species are compared within a clade, SSD is frequently found to vary with body size. This allometry is detected as β ≠ 1, where β is the slope of a model II regression of log(male size) on log(female size). Most frequently, β exceeds 1, indicating that SSD increases with size where males are the larger sex, but decreases with size where females are larger, a trend formalized as “Rensch's rule.” Exceptions are uncommon and associated with female-biased SSD. These trends are derived from a sample of 40 independent clades of terrestrial animals, primarily vertebrates. Their extension to plants and aquatic animals awaits quantitative assessments of allometry for SSD within these groups. Many functional hypotheses have been proposed to explain the evolution of allometry for SSD, most featuring sexual selection on males ...

898 citations

Journal ArticleDOI
TL;DR: The results suggest that size dimorphism is associated with the sort of intrasexual competition described by traditional classifications of social mating system, whereas plumage–colour dimorphisms is associatedWith cryptic female choice.
Abstract: Variation in the extent of sexual dimorphism among bird species is traditionally attributed to differences in social mating system. However, there are many different forms of dimorphism among birds, and not all of them show an obvious correlation with social mating system. For example, recent work has shown that many highly polygamous species are, in fact, monomorphic, whereas many putatively monogamous species are dimorphic. In this paper we break up sexual dimorphism into subcomponents and then use comparative analyses to examine the pattern of covariation between these subcomponents and various aspects of sexual, social, and par ental behaviour. Our first finding is that size dimorphism and plumage-colour dimorphism do not show the same pattern of covariation. Differences in size dimorphism are associated with variation in social mating system and sex differences in parental care, whereas differences in plumage-colour dimorphism are associated with variation in the frequency of extra-bond paternity. These results suggest that size dimorphism is associated with the sort of intrasexual competition described by traditional classifications of social mating system, whereas plumage-colour dimorphism is associated with cryptic female choice. However, when we break up plumage-colour dimorphism according to whether it is due to melanins, carotenoids or structural colours, we find that each category of plumage-colour dimorphism shows a different pattern of covariation. The correlation between overall plumage-colour dimorphism and the rate of extra-bond paternity is due to structural colours, whereas melanin-based dimorphism is associated with sex differences in parental care. The former result is particularly interesting given that new work suggests structural colours are associated with active sexual displays and the reflection of ultraviolet light.

426 citations


Cites background or result from "A phylogenetic interpretation of se..."

  • ...…polygamy and large di¡erences between the sexes in parental care agrees with the traditional explanation of size dimorphism based on intrasexual competition, and Webster's (1992) careful analysis of the New World blackbirds (Icterinae) but is contrary to the conclusions of Bjo« rklund (1990)....

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  • ...Again, these ¢ndings are contrary to Bjo« rklund's (1990) analysis, who found that plumage dimorphism was associated with a high frequency of social polygyny....

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  • ...Our ¢nding that extensive size dimorphism is associated with social polygamy and large di¡erences between the sexes in parental care agrees with the traditional explanation of size dimorphism based on intrasexual competition, and Webster's (1992) careful analysis of the New World blackbirds (Icterinae) but is contrary to the conclusions of Bjo« rklund (1990). In a detailed phylogenetic analysis within the ¢nches (Fringillidae) and buntings (Emberizidae), Bjo« rklund found that size dimorphism was only correlated with mating system before the e¡ects of body size were removed....

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  • ...This scenario, originally favoured byWallace (1889), has recently received support from a series of comparative analyses (Bjo« rklund 1991; Irwin 1994; Martin & Badyaev 1996; Bleiweiss 1997) and is consistent with our ¢nding based on the raw data that overall plumage-colour dimorphism is correlated with sex di¡erences in parental care....

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  • ...However, in this case we suspect the answer may lie in the fact that, whereas we estimated plumage-colour dimorphism, Bjo« rklund used tail length as an index of plumage dimorphism....

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Journal ArticleDOI
TL;DR: Analysis of growth-rate variability in a wild population of savannah baboons found that relative juvenile size was a stable individual trait during the juvenile period: individuals generally remained consistently large- for-age or small-for-age throughout development.
Abstract: Growth rate is a life-history trait often linked to various fitness components, including survival, age of first reproduction, and fecundity. Here we present an analysis of growth-rate variability in a wild population of savannah baboons (Papio cynocephalus). We found that relative juvenile size was a stable individual trait during the juvenile period: individuals generally remained consistently large-for-age or small-for-age throughout development. Resource availability, which varied greatly in the study population (between completely wild-foraging and partially food-enhanced social groups), had major effects on growth. Sexual maturity was accelerated for animals in the food-enhanced foraging condition, and the extent and ontogeny of sexual dimorphism differed with resource availability. Maternal characteristics also had significant effects on growth. Under both foraging conditions, females of high dominance rank and multiparous females had relatively large-for-age juveniles. Large relative juvenile size predicted earlier age of sexual maturation for both males and females in the wild-feeding condition. This confirmed that maternal effects were pervasive and contributed to differences among individuals in fitness components.

338 citations


Cites background from "A phylogenetic interpretation of se..."

  • ...…dimorphism, its ontogeny, ecological basis and relationship to mating systems, has been the subject of several reviews (e.g. Jarman 1983 for large mammalian herbivores; Hedrick and Temeles 1989; Shine 1989; Bjorklund 1990 for birds; Leigh 1992, 1995; Leigh and Shea 1996 for captive primates)....

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  • ...Jarman 1983 for large mammalian herbivores; Hedrick and Temeles 1989; Shine 1989; Bjorklund 1990 for birds; Leigh 1992, 1995; Leigh and Shea 1996 for captive primates)....

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Journal ArticleDOI
TL;DR: Although there is much interest in the effects of sperm competition on sexual dimorphism, this work suggests that traditional explanations based on social mating systems are better predictors ofDimorphism in birds.
Abstract: Comparative analyses suggest that a variety of factors influence the evolution of sexual dimorphism in birds. We analyzed the relative importance of social mating system and sperm competition to sexual differences in plumage and body size (mass and tail and wing length) of more than 1000 species of birds from throughout the world. In these analyses we controlled for phylogeny and a variety of ecological and life-history variables. We used testis size (corrected for total body mass) as an index of sperm competition in each species, because testis size is correlated with levels of extrapair paternity and is available for a large number of species. In contrast to recent studies, we found strong and consistent effects of social mating system on most forms of dimorphism. Social mating system strongly influenced dimorphism in plumage, body mass, and wing length and had some effect on dimorphism in tail length. Sexual dimorphism was relatively greater in species with polygynous or lekking than monogamous mating systems. This was true when we used both species and phylogenetically independent contrasts for analysis. Relative testis size was also related positively to dimorphism in tail and wing length, but in most analyses it was a poorer predictor of plumage dimorphism than social mating system. There was no association between relative testis size and mass dimorphism. Geographic region and life history were also associated with the four types of dimorphism, although their influence varied between the different types of dimorphism. Although there is much interest in the effects of sperm competition on sexual dimorphism, we suggest that traditional explanations based on social mating systems are better predictors of dimorphism in birds.

336 citations


Cites background from "A phylogenetic interpretation of se..."

  • ...Similarly, Bjorklund (1990) and Winquist and Lemon (1994) found that dimorphism in tail length was related to mating system....

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  • ...This has led some to suggest that sexual selection has little influence on some types of size dimorphism (e.g., Bjorklund 1990)....

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Journal ArticleDOI
TL;DR: A weight-corrected measure of sexual dimorphism and a biologically realistic assay of mating competition, the operational sex ratio, are employed to reexamine the factors favoring the evolution of sexual sizeDimorphism in primates and produce results consistent with the sexual selection hypothesis.
Abstract: Male mating competition is generally regarded to account for sexual dimorphism in body size, but levels of sexual dimorphism do not appear to be associated with the intensity of intrasexual selection in polygynous mammals. In contrast, observations of accentuated dimorphism in certain taxa and in large species are consistent with nonadaptive explanations for the evolution of sexual size dimorphism based on phylogenetic inertia and allometry. Here we employ a weight-corrected measure of sexual dimorphism and a biologically realistic assay of mating competition, the operational sex ratio, to reexamine the factors favoring the evolution of sexual size dimorphism in primates. Independent contrasts that control for the effects of allometry and phylogeny produce results consistent with the sexual selection hypothesis; a strong relationship exists between sexual dimorphism in size and the intensity of male mating competition among polygynously mating primates. Increased sexual dimorphism in large primates may no...

277 citations

References
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Journal ArticleDOI
TL;DR: A method of correcting for the phylogeny has been proposed, which specifies a set of contrasts among species, contrasts that are statistically independent and can be used in regression or correlation studies.
Abstract: Recent years have seen a growth in numerical studies using the comparative method. The method usually involves a comparison of two phenotypes across a range of species or higher taxa, or a comparison of one phenotype with an environmental variable. Objectives of such studies vary, and include assessing whether one variable is correlated with another and assessing whether the regression of one variable on another differs significantly from some expected value. Notable recent studies using statistical methods of this type include Pilbeam and Gould's (1974) regressions of tooth area on several size measurements in mammals; Sherman's (1979) test of the relation between insect chromosome numbers and social behavior; Damuth's (1981) investigation of population density and body size in mammals; Martin's (1981) regression of brain weight in mammals on body weight; Givnish's (1982) examination of traits associated with dioecy across the families of angiosperms; and Armstrong's (1983) regressions of brain weight on body weight and basal metabolism rate in mammals. My intention is to point out a serious statistical problem with this approach, a problem that affects all of these studies. It arises from the fact that species are part of a hierarchically structured phylogeny, and thus cannot be regarded for statistical purposes as if drawn independently from the same distribution. This problem has been noticed before, and previous suggestions of ways of coping with it are briefly discussed. The nonindependence can be circumvented in principle if adequate information on the phylogeny is available. The information needed to do so and the limitations on its use will be discussed. The problem will be discussed and illustrated with reference to continuous variables, but the same statistical issues arise when one or both of the variables are discrete, in which case the statistical methods involve contingency tables rather than regressions and correlations.

8,833 citations


"A phylogenetic interpretation of se..." refers background in this paper

  • ...However, there are dangers involved in this kind of study (Harvey and Mace, 1982; Ridley, 1983; Bjiirklund, 1984; Felsenstein, 1985, 1988; Cheverud et al., 1985; Page1 and Harvey, 1988)....

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Journal ArticleDOI
TL;DR: Measures of directional and stabilizing selection on each of a set of phenotypically correlated characters are derived, retrospective, based on observed changes in the multivariate distribution of characters within a generation, not on the evolutionary response to selection.
Abstract: Natural selection acts on phenotypes, regardless of their genetic basis, and produces immediate phenotypic effects within a generation that can be measured without recourse to principles of heredity or evolution. In contrast, evolutionary response to selection, the genetic change that occurs from one generation to the next, does depend on genetic variation. Animal and plant breeders routinely distinguish phenotypic selection from evolutionary response to selection (Mayo, 1980; Falconer, 1981). Upon making this critical distinction, emphasized by Haldane (1954), precise methods can be formulated for the measurement of phenotypic natural selection. Correlations between characters seriously complicate the measurement of phenotypic selection, because selection on a particular trait produces not only a direct effect on the distribution of that trait in a population, but also produces indirect effects on the distribution of correlated characters. The problem of character correlations has been largely ignored in current methods for measuring natural selection on quantitative traits. Selection has usually been treated as if it acted only on single characters (e.g., Haldane, 1954; Van Valen, 1965a; O'Donald, 1968, 1970; reviewed by Johnson, 1976 Ch. 7). This is obviously a tremendous oversimplification, since natural selection acts on many characters simultaneously and phenotypic correlations between traits are ubiquitous. In an important but neglected paper, Pearson (1903) showed that multivariate statistics could be used to disentangle the direct and indirect effects of selection to determine which traits in a correlated ensemble are the focus of direct selection. Here we extend and generalize Pearson's major results. The purpose of this paper is to derive measures of directional and stabilizing (or disruptive) selection on each of a set of phenotypically correlated characters. The analysis is retrospective, based on observed changes in the multivariate distribution of characters within a generation, not on the evolutionary response to selection. Nevertheless, the measures we propose have a close connection with equations for evolutionary change. Many other commonly used measures of the intensity of selection (such as selective mortality, change in mean fitness, variance in fitness, or estimates of particular forms of fitness functions) have little predictive value in relation to evolutionary change in quantitative traits. To demonstrate the utility of our approach, we analyze selection on four morphological characters in a population of pentatomid bugs during a brief period of high mortality. We also summarize a multivariate selection analysis on nine morphological characters of house sparrows caught in a severe winter storm, using the classic data of Bumpus (1899). Direct observations and measurements of natural selection serve to clarify one of the major factors of evolution. Critiques of the "adaptationist program" (Lewontin, 1978; Gould and Lewontin, 1979) stress that adaptation and selection are often invoked without strong supporting evidence. We suggest quantitative measurements of selection as the best alternative to the fabrication of adaptive scenarios. Our optimism that measurement can replace rhetorical claims for adaptation and selection is founded in the growing success of field workers in their efforts to measure major components of fitness in natural populations (e.g., Thornhill, 1976; Howard, 1979; Downhower and Brown, 1980; Boag and Grant, 1981; Clutton-Brock et

4,990 citations


"A phylogenetic interpretation of se..." refers background in this paper

  • ...A problem recently highlighted by developments in quantitative genetics is that a character can change in evolution, not owing to selection for the trait itself, but as a result of selection of another trait, with which the first trait is correlated genetically (Lande, 1980, 198 1; Lande and Arnold, 1983; Arnold and Wade, 1984; Endler, 1985)....

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  • ...…in quantitative genetics is that a character can change in evolution, not owing to selection for the trait itself, but as a result of selection of another trait, with which the first trait is correlated genetically (Lande, 1980, 198 1; Lande and Arnold, 1983; Arnold and Wade, 1984; Endler, 1985)....

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Journal ArticleDOI
Amotz Zahavi1
TL;DR: It is suggested that characters which develop through mate preference confer handicaps on the selected individuals in their survival, which are of use to the selecting sex since they test the quality of the mate.

4,744 citations

Journal ArticleDOI
06 Apr 1871-Nature
TL;DR: The Descent of Man, and Selection in relation to Sex as mentioned in this paper, by Charles Darwin, &c. In two volumes. Pp. 428, 475, as mentioned in this paper.
Abstract: I. IF Mr. Darwin had closed his rich series of contributions to Science by the publication of the “Origin of Species,“he would have made an epoch in Natural History like that which Socrates made in philosophy, or Harvey in medicine. The theory identified with his name has stimulated ethnological and anatomical inquiries in every direction; it has been largely adopted and followed out by naturalists in this country and America, but most of all in the great work-room of modern science, whence a complete literature on “Darwinismus“has sprung up, and there disciples have appeared who stand in the same relation to their master as Muntzer and the Anabaptists did to Luther. Like most great advances in knowledge, the theory of Evolution found everything ripe for it. This is shown by the well-known fact that Mr. Wallace arrived at the same conclusion as to the origin of species while working in the Eastern Archipelago, and scarcely less so by the manner in which the theory has been worked out by men so distinguished as Mr. Herbert Spencer and Prof. Haeckel. But it was known when the “Origin of Species “was published, that instead of being the mere brilliant hypothesis of a man of genius, of which the proofs were to be furnished and the fruits gathered in by his successors, it was really only a summary of opinions based upon the most extensive and long-continued researches. Its author did not simply open a new province for future travellers to explore, he had already surveyed it himself, and the present volumes show him still at the head of his followers. They are written in a more popular style than those on "Animals and Plants under Domestication,“as they deal with subjects of more general interest; but all the great qualities of industry and accuracy in research, of fertility in framing hypotheses, and of impartiality in judgment, are as apparent in this as in Mr. Darwin's previous works. To one who bears in mind the too frequent tone of the controversies these works have excited, the turgid rhetoric and ignorant presumption of those "who are not of his school -or any school,“and the still more lamentable bad taste which mars the writings of Vogt and even occasionally of Haeckel, it is very admirable to see the calmness and moderation (for which philosophical would be too low an epithet) with which the author handles his subject. If prejudice can be conciliated, it will surely be by a book like this. The Descent of Man, and Selection in relation to Sex. By Charles Darwin, &c. In two volumes. Pp. 428, 475. (Murray, 1871.)

4,740 citations


"A phylogenetic interpretation of se..." refers background in this paper

  • ...Introduction Sexual dimorphism in body size in birds is commonly regarded as a result of sexual selection favouring large males through the size-advantage in combats over females (i.e. intra-sexual selection, Darwin, 1871; Selander, 1965, 1972)....

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  • ...Either species become larger when polygyny evolves, which is the traditional prediction in sexual selection theory (Darwin, 1871), or smaller when...

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  • ...Either the dimorphism increases when polygyny evolves, as predicted by sexual selection theory (Darwin, 1871; Arnold, 1983) or decreases when monogamy evolves....

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  • ...Either species become larger when polygyny evolves, which is the traditional prediction in sexual selection theory (Darwin, 1871), or smaller when Sexual dimorphism in birds 179 monogamy evolves....

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