Polygyny

The application of molecular genetic techniques has revolutionized our view of avian mating systems. Contrary to prior expectations, birds are only very rarely sexually monogamous, with 'extra-pair offspring' found in approximately 90% of species. Even among socially monogamous species, over 11% of offspring are, on average, the result of extra-pair paternity (EPP). Based on over 150 molecular genetic studies of EPP in birds, we review two topical areas: (i) ecological explanations for interspecific variation in the rate of EPP; and (ii) evidence bearing on the adaptive function of EPP. We highlight the remaining challenges of understanding the relative roles of genes and ecology in determining variation between taxa in the rate of extra paternity, and testing for differences between extra-pair offspring and those sired within-pair.

Bateman's classic paper on fly mating systems inspired quantitative study of sexual selection but also resulted in much debate and confusion. Here, I consider the meaning of Bateman's principles in the context of selection theory. Success in precopulatory sexual selection can be quantified as a "mating differential," which is the covariance between trait values and relative mating success. The mating differential is converted into a selection differential by the Bateman gradient, which is the least squares regression of relative reproductive success on relative mating success. Hence, a complete understanding of precopulatory sexual selection requires knowledge of two equally important aspects of mating patterns: the mating differential, which requires a focus on mechanisms generating covariance between trait values and mating success, and the Bateman gradient, which requires knowledge of the genetic mating system. An upper limit on the magnitude of the selection differential on any sexually selected trait is given by the product of the standard deviation in relative mating success and the Bateman gradient. This latter view of the maximum selection differential provides a clearer focus on the important aspects of precopulatory sexual selection than other methods and therefore should be an important part of future studies of sexual selection.

In this study, which is concerned with the varying degrees of sexual dimorphism of stature between human societies, adult male and female height measurements and male-female height ratiosthe measure of sexual dimorphismfrom 216 societies are statistically compared with several variables: marriage practices, protein availability, the presence of milking herds, settlement size, and climate. Our results indicate that while greater mean male height is associated with polygynous marriage, marriage practices did not exert an influence on the degree of sexual dimorphism of stature. On the other hand, the results suggest that while sexual dimorphism in height has a strong genetic component, dietary factors can influence the degree of dimorphism.

In ants of the genus Myrmica, female progeny may be the offspring of one to several different queens. In addition, both workers and queens are capable of producing haploid male offspring. Even in such complex colonies, parentage can be assigned on the basis of genotypic variation at highly polymorphic simple sequence repeat loci. Methods are described for isolating and screening dinucleotide repeat loci in ants. Three independent loci, Myrt2, Myrt3 and Myrt4, show expected heterozygosities of 0.94, 0.92 and 0.95, respectively. When used in parallel these loci should be sufficient to establish parentage in the vast majority of screened colonies. An initial screening indicates that males are produced by workers in the subalpine ant Myrmica 'near tahoensis'.

cooperative breeding Emery's rule group selection Hamilton's rule kin selection life span modular growth polygyny sib competition tragedy of the commons The hypothesis that obligate eusociality always evolved from ancestral states of strict lifetime monogamy implies that (1) facultatively eusocial lineages had to abandon multifemale breeding to achieve permanent morphologically differentiated castes, and (2) lineages of obligatorily eusocial insects had to independently re-evolve multifemale breeding when that served the inclusive fitness interests of nursing workers. Multiqueen nesting (eusocial polygyny) is known to be common across the ants, but rare in the corbiculate (eusocial) bees, the vespine wasps and the higher termites, but we show that this difference is mostly due to cases of obligate polygyny being restricted to the ants. This pattern is remarkably similar to the distribution of inquiline social parasites that use stealth rather than aggression to invade host colonies, which also repeatedly evolved in ants only. We explore the lineage-specific selection forces that have allowed or constrained de novo evolution of stable eusocial polygyny in Hamiltonian inclusive fitness terms. We argue that perennial life histories, male survival as stored sperm rather than as lifetime mates, and sib competition are possibly sufficient to explain the general prevalence of secondary polygyny across the obligatorily eusocial insects. We infer that obligate polygyny compromises eusocial 'soma' and 'germ-line' segregation in ways known to decrease developmental stability in metazoans, and we briefly evaluate the selection forces that reduce queen life span in highly, but probably not facultatively, polygynous species. We conclude that secondary polygyny in its obligate (ant) form resembles cooperative breeding with multiple 'tragedy of the commons' aspects, but in a peculiar manner because breeding females are selected to exploit the services of unmated workers rather than each other's. This breeding system has likely been maintained in ants because it allows modular extensions of colonies in directly adjacent habitat of similar quality without the re-emergence of sexual conflicts or unproductive local competition with kin.

Many sex differences are likely to be adaptive consequences of sexual selection. Sex differences in spatial ability are well described for Homo sapiens and laboratory rodents, and such cognitive traits may also be shaped by sexual selection. An evolutionary model is outlined to predict the distribution of these sex differences across species. Sex differences in spatial ability were previously believed to be universal among mammals, but the evolutionary model has correctly predicted that such differences will evolve only in species where mobility has different effects on male and female fitness. Wild microtine rodents are particularly useful for testing this model. Radiotelemetric data from field studies of ranging behavior, data from laboratory studies of maze learning, and neuroanatomical data on the hippocampus, a structure believed to be critically involved in spatial processing, all support the model. Several alternative explanations for sex differences in spatial ability are reviewed and evaluated. The proximate developmental basis of these sex differences is discussed, and a n attempt is made to integrate developmental and evolutionary perspectives. Several promising future research directions are outlined.

In this paper we review the literature on the association between polygyny and women's health in sub-Saharan Africa. We argue that polygyny is an example of ''co-operative conflict'' within households, with likely implications for the vulnerability of polygynous women to illness, and for their access to treatment. We begin with a review of polygyny and then examine vulnerability to sexually transmitted infections (STIs, including HIV) and differential reproductive outcomes. Polygyny is associated with an accelerated transmission of STIs, both because it permits a multiplication of sexual partners and because it correlates with low rates of condom use, poor communication between spouses, and age and power imbalances among other factors. Female fertility is affected by the interplay between marital rank, household status, and cultural norms in polygynous marriages. Finally, we present areas which have received only cursory attention: mental health and a premature, ''social'' menopause. Although data are scarce, polygyny seems to be associated with higher levels of anxiety and depression, particularly around stressful life events. It is our hope that the examples reviewed here will help build a framework for mixed method quality research, which in turn can inform decision makers on more appropriate, context-dependent health policies.

In the human species, the two uniparental genetic systems (mitochondrial DNA and Y chromosome) exhibit contrasting diversity patterns. It has been proposed that sex-specific behaviours, and in particular differences in migration rate between men and women, may explain these differences. The availability of high-density genomic data and the comparison of genetic patterns on autosomal and sex chromosomes at global and local scales allow a reassessment of the extent to which sex-specific behaviours shape our genome. In this article, we first review studies comparing the genetic patterns at uniparental and biparental genetic systems and assess the extent to which sex-specific migration processes explain the differences between these genetic systems. We show that differences between male and female migration rates matter, but that they are certainly not the only contributing factor. In particular, differences in effective population size between men and women are also likely to account for these differences. Then, we present and discuss three anthropological processes that may explain sex-specific differences in effective population size and thus human genomic variation: (i) variance in reproductive success arising from, for example, polygyny; (ii) descent rules; and (iii) transmission of reproductive success.

Many models of sex-biased dispersal predict that the direction of sex-bias depends upon a species' mating system. In agreement with this, almost all polygynous mammals show male-biased dispersal whereas largely monogamous birds show female-biased dispersal (FBD). The hamadryas baboon (Papio hamadryas hamadryas) is polygynous and so dispersal is predicted to be male biased, as is found in all other baboon subspecies, but there are conflicting field data showing both female and male dispersal. Using 19 autosomal genetic markers genotyped in baboons from four Saudi Arabian populations, we found strong evidence for FBD in post-dispersal adults but not, as expected, in pre-dispersal infants and young juveniles, when we compared male and female: population structure (F st ), inbreeding (F is ), relatedness (r), and the mean assignment index (mAIc). Furthermore, we found evidence for female-biased gene flow as population genetic structure (F st ), was about four times higher for the paternally inherited Y, than for either autosomal markers or for maternally inherited mtDNA. These results contradict the direction of sex-bias predicted by the mating system and show that FBD has evolved recently from an ancestral state of male-biased dispersal. We suggest that the cost-benefit balance of dispersal to males and females is tightly linked to the unique hierarchical social structure of hamadryas baboons and that dispersal and social organization have coevolved.

We map behavioral characters related to mating system onto a phylogeny of the New World blackbirds (family Icteridae) in order to test hypotheses on the evolution of polygyny in Red-winged Blackbirds (Agelaius phoeniceus). The two hypotheses we test are "long-term models" in the sense that, unlike most polygyny hypotheses, they allow the ancestral mating system to differ from the present one in characters other than female preferences for mated versus unmated males. In one model, polygyny evolves from the typical territorial monogamy system of most terrestrial passerines; in the second model, polygyny evolves from a system resembling that of monogamous Agelaius species, with marsh breeding and without male territoriality. Both hypotheses assume that female-biased parental care coevolves with polygyny. Our reconstruction suggests that the closest non-polygynous ancestor of Red-winged Blackbirds was characterized by monogamy, male territoriality, equal sharing of parental care between the sexes, and terrestrial breeding. Further, polygyny and female-biased care are suggested to have evolved on the same branch as marsh nesting. These results refute our second hypothesis in which polygyny evolves from "Agelaius monogamy," while providing provisional support for the first model in which polygyny evolves from territorial monogamy.

In social insects, the emergence of multiple queening is linked to changes in a suite of traits such as the reproductive life span of queens, mating patterns and population structure. We investigated queen turnover, colony longevity, spatial distribution patterns and genetic differentiation in a population of the socially polymorphic ant Formica fusca. Genetic differentiation between the social forms was absent, and mating patterns were similar in the two forms. The spatial distribution of single- and multi-queen colonies indicated an absence of colony reproduction by budding in both colony types. However, the rate of queen supersedure was high in multi-queen colonies and absent in single-queen ones. The social structure of colonies remained stable across years, but colony mortality did not differ between the two social forms. These results imply that differences between social types may appear and persist also in sympatry, and that these differences may occur in some traits, but not others, despite the presence of homogenizing gene flow.

Polygyny, the marriage of a man with more than one woman at the same time is a well-known practiced in human history. Islamic law accepts the institution of polygyny as a substitute provision if it fulfills the certain conditions and reasons, -and limited the maximum number of wives to four. Although polygyny is mubah (permissible) in Islamic law, it is not an absolute right that every man can use arbitrarily. Thus in Islamic law, the legitimacy of polygyny has been attributed to the presence of two basic conditions: the observance of justice among co-wives and providing maintnance. However, the observance of these conditions that is left to the mercy of men leads to the exploitation of the right for practicing to polygyny and victimization of the first spouse. Therefore, inserting some restrictions for using this right has come to the agenda from time to time in Islamic legal history. The first legal arrangements concerning the restriction of the polygyny (taaddud al-zawjāt) in the history of Islamic law were indirectly made with the Family Law Decree of 1917 which was prepared in the last periods of the Ottoman Empire. Among the late Islamic jurists, the issue of the limitation of polygyny by public authority in Islamic law continues to be discussed. The civil laws of contemporary Muslim countries contain different regulations on the issue. In this article, the restriction of polygyny by the public authority in Islamic family law will be focused on.

Summary: Polygyny, the marriage of a man with more than one woman at the same time is a well-known practiced in human history. Islamic law accepts the institution of polygyny as a substitute provision if it fulfills the certain conditions and reasons, and limited the maximum number of wives to four. Thus, relevant verses in the Qur’an (al-Nisa 4/3, 129) and the Prophet’s own practice (al-Ahzab 33/50, 51, 59 al-Tahrim 66 / 3-5) show that it is legitimate for a man to marry more than one woman (up to four) at the same time in Islamic law.

Although polygyny is legally permissible (mubah) in Islamic law it is not an absolute right that every man can arbitrarily use. Thus in Islamic law, the legitimacy of polygyny has been attributed to the presence of two basic conditions: the observance of justice among co-wives and providing maintenance.

On the other hand, there may be some exceptional circumstances permitting polygyny in Islamic law. For example, when female population is much more than male in the society and when a, woman is can not fulfill her family duties due to her cureless illness, polygyny is permitted in Islamic law.

As it can be understood from the explanations above, polygyny in Islamic law is not a general and mandatory provision that should be applied by every man who has legal capacity to marry. On the contrary, it is an exceptional provision that is justified if there are certain conditions and justifications.

According to this; polygyny is a moral and legal institution that is made up of mutual consent based on individual and social conditions and needs in Islamic law. Therefore, men do not have to marry a second woman on their current wives, as well as women have the right to say “no” to marry a married man as a second wife.

When the conditions and rationales indicated in the relevant verses and doctrine are evaluated together, it can be said that in order to be able to legitimize the polygyny in Islamic law, there must be three basic conditions:

(1) Observing justice among spouses,

(2) Having sufficient financial power to provide maintenance for spouses,

(3) Existence of individual or social need or necessity.

Therefore, in order to prevent the exploitation of polygyny, which is justified under certain conditions and justifications in Islamic law, the above-mentioned conditions must be fulfilled. Otherwise, polygyny can cause some problems, unrest and injustice for individual, family and society. Hence, in the presence of certain conditions and justifications, polygyny accepted in Islamic law as a moral and legal institution aiming the elimination of individual and social arbitration.

Although the legitimacy of polygyny in Islamic law depends on the existence of certain conditions and special circumstances, it is a known fact that they are not always observed in practice. It can be said that the right of polygyny is a subject of abuse in practice. Therefore, the limitation of polygyny  by the public authority has come to the fore in Islamic legal history. Today, control of the public authority and inserting some restrictions of polygyny  continue to be discussed among the Islamic jurists.

In the past, it is possible to say that the control of the exercising of this right has been done relatively by society (social environment). However, nowadays, since the society cannot perform the control mechanism, it is brought up by the state (public authority) on behalf of the society.

Among the contemporary Islamic jurists regarding the supervision or limitation of polygyny  by the public authority; there are two approaches: “those who accept” and “those who do not accept” such restrictions.

Islamic jurists, who accept that public authority is allowed to intervene in polygyny, grounded their views on two perspectives: The first is that the polygyny is legally permissible and the public authority has the authority to limit the permissible (mubah) in Islamic law. The second is that polygyny is restricted with the conditions in the Qur’anic verses such as “husband’s observation supervision of justice among his wives” and “having the power for ensuring the livelihood (nafaqa) of his wives” and it is more appropriate for the benefit of society and the purpose of the legislator (Shari’) to be subject to the control of the public authority whether these conditions are present or not.

Islamic jurists, who do not agree that the public authority has the right to intervene in polygyny grounded their views on two perspectives as well: First, polygyny is a legitimate right mentioned in the verses in Islamic law and there is no definite proof that this can be prohibited or restricted by the public authority. Secondly, it is contrary to the verses to prohibit or limit the right that the Qur’an makes legitimate (free).

Thus, it is possible to say that the opinion which accepts that the public authority has to limit polygyny is more accurate in terms today’s social conditions. Namely, polygyny is linked to two basic conditions: ”husband’s observance of justice among his wives and having the power to provide maintenance for his wives. Therefore, supervision of the public authority on checking the existence of these conditions is more appropriate for the purpose of the legislator (Shari legitimizing polygyny  and social benefit.

In fact, the Ottoman Family Law Decree of 1917 indirectly limited the right of the husband to marry more than one woman, giving the woman right to stipulate a condition in her marriage contract that her husband not to marry a second woman. In the 1924 Draft of Family Law Decree, which was prepared after the repeal of the Family Law Decree of 1917, but not enacted, it was proposed that the application of polygyny should be presented to the approval judge.

In today’-s Muslim countries, there are three different practices: namely “completely prohibiting polygyny”, ”releasing polygyny” and “giving the court the right to monitor the existence of necessary conditions “. In countries such as Morocco, Algeria, Iraq, Syria, Indonesia, Malaysia (and Pakistan), the validity of polygyny  depends on the permission and supervision of the judiciary. Some of these countries which have accepted judicial review have given the judicial control for the requirement of justice, some of them the conditions of justice and maintenance some of them for the conditions of justice, maintenance and a legitimate justification.

In sum, in accordance with the provisions of the relevant verses, polygyny in Islamic law is legitimately permissible (mubah). However, the public authority has the right and authority to limit the mubah in Islamic law in the case of the elimination of damage and the necessity of the public interest. On the other hand, the public authority has the right and authority to enact the law in Islamic law by preferring one of the existing ijtihads that meet the needs of the society and conforms to the conditions of the age.

According to this, when the public authority made a statutory regulation that links the use of right of polygyny  to the permission of the judge, this regulation is binding on society.Therefore, in the event of such a legal arrangement, it is possible for the public authority to allow the men who comply with the conditions and not to allow the ones who are not to comply with the conditions after conducting the necessary investigation. As a matter of fact, now Family Laws of many Muslim countries now include such legal arrangements.

It is also worth mentioning here that there may be a necessity for a man to marry more than one woman (up to four) at the same time in terms of social benefits, when the population of male and female in a society is excessively disproportionate. In such circumstances, it is also possible that the public authority encourages, or even mandates, the marriage of men who have fulfilled the conditions to more than one woman.

In polygynous ungulates, biologists commonly assume that the role of males in population dynamics is negligible since the male's physiological capacity to inseminate females normally will not be a limiting factor for calving rates. Recently, however, research indicates that the role of males may be more important than previously acknowledged because availability of males may affect conception dates and hence calving dates and synchrony. In many harvested or otherwise managed populations, a sex ratio highly skewed toward females and a young male age structure often exist. Both a skewed sex ratio and male age structure may affect conception times and may delay calving dates. We manipulated the sex ratio and male age structure in herds of reindeer (Rangifer tarandus) fenced in large-scale enclosures (14-1 5 km 2). We compared calving rates, dates, and synchrony as well as (1) birth and autumn weights of calves among a skewed sex ratio and yearling males only, (2) a skewed sex ratio and an even male age structure, and (3) an even sex ratio and even male age structure. As predicted, calving dates were earlier in the treatment with an even sex ratio and even male age structure compared to the 2 other treatments. Neither sex ratio nor male age structure impacted calving rates or birth synchrony. Timing of births is important for the survival of newborns, and this should be considered when harvesting or otherwise managing populations of polygynous ungulates.

The number of queens per colony and the number of matings per queen are the most important determinants of the genetic structure of ant colonies, and understanding their interrelationship is essential to the study of social evolution. The polygyny-vs.-polyandry hypothesis argues that polygyny and polyandry should be negatively associated because both can result in increased intracolonial genetic variability and have costs. However, evidence for this long-debated hypothesis has been lacking at the intraspecific level. Here, we investigated the colony genetic structure in the Australian bulldog ant Myrmecia brevinoda. The numbers of queens per colony varied from 1 to 6. Nestmate queens within polygynous colonies were on average related (r qq = 0.171 ± 0.019), but the overall relatedness between queens and their mates was indistinguishable from zero (r qm = 0.037 ± 0.030). Queens were inferred to mate with 1-10 males. A lack of genetic isolation by distance among nests indicated the prevalence of independent colony foundation. In accordance with the polygyny-vs.-polyandry hypothesis, the number of queens per colony was significantly negatively associated with the estimated number of matings (Spearman rank correlation R = )0.490, P = 0.028). This study thus provides the rare intraspecific evidence for the polygyny-vs.-polyandry hypothesis. We suggest that the high costs of multiple matings and the strong effect of multiple mating on intracolonial genetic diversity may be essential to the negative association between polygyny and polyandry and that any attempt to empirically test this hypothesis should place emphasis upon these two key underlying aspects.

The breeding system of social organisms affects many important aspects of social life. Some species vary greatly in the number of breeders per group, but the mechanisms and selective pressures contributing to the maintenance of this polymorphism in social structure remain poorly understood. Here, we take advantage of a genetic dataset that spans 15 years to investigate the dynamics of colony queen number within a socially polymorphic ant species. Our study population of Formica selysi has singleand multiple-queen colonies. We found that the social structure of this species is somewhat flexible: on average, each year 3.2% of the single-queen colonies became polygynous, and conversely 1.4% of the multiple-queen colonies became monogynous. The annualized queen replacement rates were 10.3% and 11.9% for single-and multiple-queen colonies, respectively. New queens were often but not always related to previous colony members. At the population level, the social polymorphism appeared stable.

Eusocial insects vary significantly in colony queen number and mating frequency, resulting in a wide range of social structures. Detailed studies of colony genetic structure are essential to elucidate how various factors affect the relatedness and the sociogenetic organization of colonies. In this study, we investigated the colony structure of the Australian jumper ant Myrmecia pilosula using polymorphic microsatellite markers. Nestmate queens within polygynous colonies, and queens and their mates, were generally unrelated. The number of queens per colony ranged from 1 to 4. Queens were estimated to mate with 1-9 inferred and 1.0-11.4 effective mates. This is the first time that the rare co-occurrence of polygyny and high polyandry has been found in the M. pilosula species group. Significant maternity and paternity skews were detected at the population level. We also found an isolation-by-distance pattern, and together with the occurrence of polygynous polydomy, this suggests the occurrence of dependent colony foundation in M. pilosula; however, independent colony foundation may co-occur since queens of this species have fully developed wings and can fly. There is no support for the predicted negative association between polygyny and polyandry in ants.

Although members of the family Hylobatidae are known to be monogamous, adult white-handed gibbons (Hylobates lar) at Khao Yai National Park, Thailand, also show multimale groups and polyandry. A need for more than one male to successfully raise offspring cannot explain the occurrence of polyandry in these territorial primates, because direct paternal care is absent in this species. We hypothesize that polyandry is primarily related to costs/benefits for males of cooperatively defending a female and/or resources; our prediction was that polyandry would become more frequent with increasing costs of female/resource defense. We measured the ecological quality of seven gibbon home ranges over a 3-yr period (2001)(2002)(2003) to investigate how resource availability affected the probability of polyandry, and found a significant negative relationship between home range quality and home range size. Larger home ranges were of lower quality. As predicted, groups living on larger, poorer home ranges also experienced longer periods of polyandry. In forest areas of comparatively low quality, acquiring and maintaining a large home range that includes enough resources for a female to reproduce steadily may surpass a single male's capacity. Our model of cooperative male polyandry was supported by preliminary data of shared territorial defense and access to the female. However, interaction proportions were strongly skewed, and female's primary male partners monopolized grooming and mating. Nevertheless, a primary male on a large territory may benefit from the presence of a secondary male with aid in territorial/female defense, whereas a secondary male may gain by avoiding high dispersal costs.

In ants the presence of multiple reproductive queens (polygyny) decreases the relatedness among workers and the brood they rear, and subsequently dilutes their inclusive fitness benefits from helping. However, adoption of colony daughters, low male dispersal in conjunction with intranidal (within nest) mating and colony reproduction by budding may preserve local genetic differences, and slow down the erosion of relatedness. Reduced dispersal and intranidal mating may, however, also lead to detrimental effects owing to competition and inbreeding. We studied mating and dispersal patterns, and colony kinship in three populations of the polygynous ant Plagiolepis pygmaea using microsatellite markers. We found that the populations were genetically differentiated, but also a considerable degree of genetic structuring within populations. The genetic viscosity within populations can be attributed to few genetically homogeneous colony networks, which presumably have arisen through colony reproduction by budding. Hence, selection may act at different levels, the individuals, the colonies and colony networks. All populations were also significantly inbred (F = 0.265) suggesting high frequencies of intranidal mating and low male dispersal. Consequently the mean regression relatedness among workers was significantly higher (r = 0.529-0.546) than would be expected under the typically reported number (5-35) of queens in nests of the species. Furthermore, new queens were mainly recruited from their natal or a neighbouring related colony. Finally, the effective number of queens coincided with that found upon excavation, suggesting low reproductive skew.

Polygyny is regarded as a beneficial strategy for males, whereas females mated with polygynous males (males simultaneously paired to more than one female) often suffer a reduction in pair male contributions. This study examined the costs and benefits associated with polygyny in the cooperatively breeding cichlid Neolamprologus pulcher. In this species, males are facultatively polygynous; some males hold only one territory with one breeding female whereas other males hold multiple territories, each with its own breeding female. Polygynous males were larger than monogamous males and body-scraped less, a behaviour often associated with ectoparasite loads. Polygynous males also had larger testes (controlling for body mass) and higher circulating 11-ketotestosterone levels than monogamous males. Paradoxically, monogamous males occupied higher-quality territories with more shelter and fewer predators. Monogamous males also provided more parental care than polygynous males but the number and survival of young did not vary according to male mating behaviour. The results of our study suggest that females trade-off between male genetic quality and resources in N. pulcher. Our results imply that males holding only one territory may provide their mates with significant assets but may not be able to outcompete neighbours for additional breeding positions because of their small body size and possible higher parasite load. The lack of differences between monogamous and polygynous groups in terms of offspring survival (a measure of reproductive success) suggests that there may be few if any fitness consequences of polygynous pairing for females.

Some argue that cross-cultural variation in sexual dimorphism is associated with marriage practices whereas others suggest it is a function of absolute size. We reject both explanations, noting that the degree of dimorphism in humans is very consistent and the observed variance is mainly a function of sample size.

Reproductive behaviors of vertebrates are often underpinned by temporal patterns of hormone secretion. We investigated interspecific patterns of circulating testosterone in male birds to test the hypothesis that testosterone plays a crucial role in sexual selection as determined by degree of polygyny and extra-pair paternity. We predicted that the evolution of increased levels of polygyny and extra-pair paternity would have resulted in the evolution of increased levels of testosterone to allow males more efficiently to compete for mates. This hypothesis was tested in comparative analyses of 116 species of birds using Generalized Least Squares Models. We assessed the importance of latitudinal distribution, because this can confound the relationship between testosterone and mating success. There were weak positive phylogenetic correlations between measures of testosterone and estimates of mating success at the social level, but this association appeared to be confounded by latitudinal distribution, a significant correlate of testosterone titers. However, we found a significantly positive relationship between peak and residual peak testosterone (which is the peak testosterone level that is controlled for the baseline level) and extra-pair paternity independent of latitude. These results suggest that selection pressures arising from social and sexual mating differently affected testosterone levels with the former being mediated by factors associated with latitudinal distribution. An analysis of residual testes size revealed a positive association between peak and residual testosterone and testes size relative to body size. In a path analysis, we show that relative testis size primarily evolved in association with intense sperm competition and thus high sperm production, and these mechanisms had a secondary impact on blood testosterone levels at a phylogenetic scale. Our results suggest that sperm competition has played an important role in the evolution of reproductive mechanisms in birds. D

We offer the first report for a cetacean of geographical variation in mating system based in morphology. Analysis of samples from 1,678 male spinner dolphins from the eastern Pacific revealed that testis + epididymis weight was greater (to 1,354 g) in the whitebelly form of the species than in the eastern form (to 843 g). Sexual dimorphism in dorsal-fin shape is greater in the eastern form. The difference in testis size was strongly linked with shape of the dorsal fin on an individual basis. Only a few eastern males (0.6%) reached testis + epididymis weight at which all epididymides contain sperm, while a much larger proportion of whitebelly spinners (15.2%) reached this level, suggesting that a smaller proportion of eastern spinner males may participate in reproductive activity. This, and the fact that increased dimorphism and decreased testis size are indicative of increased polygyny in a wide variety of other mammal species, leads to the conclusion that the mating system varies geographically in the species, with a gradient from a more polygynous mating system in the eastern form to a more open or polygynandrous mating system in the whitebelly form. Differences in ovulation rate in the two forms are consistent with this conclusion.

hypothesis of sex-biased maternal investment in polygynous species do not apply well to species where mothers produce more than one offspring per reproductive attempt. First, as litter size increases, the benefits to the mother of adjusting sex ratio decrease because (1) she could benefit more by adjusting litter size and (2) sex differences in reproductive potential are negatively related to litter size. Second, testing sex-biased investment in these species requires predictions about the simultaneous adjustment of sex ratio and litter size. The wild boar, Sus scrofa, although polygynous, produces large litters. Here we present data for 58 litters from a free-ranging wild boar population in central Spain. Maternal expenditure per individual offspring, as measured by piglet weight, was higher for male than female fetuses. In more than 81% of cases the heaviest fetus in the litter was a male regardless of the quality of the mother; this might have influenced his ranking within the 'teat order' and consequently his development and survival. Mother quality (size and weight) appeared to be related to litter size but not to the sex ratio of the litter. However, it was highly related to a variable that combined the effects of litter size and sex ratio within the litter, thus supporting Williams' (1979, Proceedings of the Royal Society of London, Series B, 205, 567-580) hypothesis that mothers should adjust both litter size and offspring sex.

In polygynous mating systems, males often increase their fecundity via aggressive defense of mates and/or resources necessary for successful mating. Here we show that both male and female reproductive behavior during the breeding season (June-August) affect female fecundity, a vital rate that is an important determinant of population growth rate and viability. By using 4 years of data on behavior and demography of California sea lions (Zalophus californianus), we found that male behavior and spatial dynamics-aggression and territory size-are significantly related to female fecundity. Higher rates of male aggression and larger territory sizes were associated with lower estimates of female fecundity within the same year. Female aggression was significantly and positively related to fecundity both within the same year as the behavior was measured and in the following year. These results indicate that while male aggression and defense of territories may increase male fecundity, such interactions may cause a reduction in the overall population growth rate by lowering female fecundity. Females may attempt to offset male-related reductions in female fecundity by increasing their own aggressionperhaps to defend pups from incidental injury or mortality. Thus in polygynous mating systems, male aggression may increase male fitness at the cost of female fitness and overall population viability.

Due to their haplo-diploid sex determination system and the resulting conflict over optimal sex allocation between queens and workers, social Hymenoptera have become important model species to study variation in sex allocation. While many studies indeed reported sex allocation to be affected by social factors such as colony kin structure or queen number, others, however, found that sex allocation was impacted by ecological factors such as food availability. In this paper, we present one of the rare studies that simultaneously investigated the effects of social and ecological factors on social insect nest reproductive parameters (sex and reproductive allocation, nest productivity) across several years. We found that the sex ratio was extremely male biased in a polygynous (multiple queens per nest) population of the ant Formica exsecta. Nest-level sex allocation followed the pattern predicted by the queen-replenishment hypothesis, which holds that gynes (new queens) should only be produced and recruited in nests with low queen number (i.e. reduced local resource competition) to ensure nest survival. Accordingly, queen number (social factor) was the main determinant on whether a nest produced gynes or males. However, ecological factors had a large impact on nest productivity and therefore on a nest's resource pool, which determines the degree of local resource competition among co-breeding queens and at what threshold in queen number nests should switch from male to gyne production. Additionally, our genetic data revealed that gynes are recruited back to their parental nests after mating. However, our genetic data are also consistent with some adult queens dispersing on foot from nests where they were produced to nests that never produced queens. As worker production is reduced in gyne-producing nests, queen migration might be offset by workers moving in the other direction, leading to a nest network characterized by reproductive division of labour. Altogether our study shows that both, social and ecological factors can influence long-term nest reproductive strategies in insect societies.

According to the polygyny threshold model, females are compensated for the cost of sharing a territory with other females by breeding in territories of higher quality than those of monogamously mated females. In the polygynous Great Reed Warbler (Acrocephalus arundinaceus), the variation in territory quality may be associated with nest site characteristics or food supply. In this study, we examined the probability of nest predation in Great Reed Warblers in relation to an indirect measure of territory quality (territory attractiveness rank as indexed by settlement order) and to several variables of nest site structure. Artificial nests with attached soft plasticine model eggs were placed in Great Reed Warbler territories of different attractiveness. Marks in the soft model eggs were compared to marks from possible predator species. Both inter-and intraspecific predators were found to prey upon eggs in artificial nests. Marsh Harriers (Circus aeruginosus) predominantly preyed upon artificial nests located in territories of low attractiveness, in low-density reed beds, and early in the season. Bitterns (Botaurus stellaris) and Water Rails (Rallus aquaticus) showed a preference for artificial nests located inside the reeds. When all types of predators of artificial nests were pooled, the probability of nest predation was lower in more attractive territories. This pattern was corroborated in an analysis of predation on real nests. In general, polygyny occurred in territories with a low rate of nest predation, whereas unmated males held territories where the risk of predation was high. The low rate of nest predation in attractive territories on average compensated secondary females for the cost associated with sharing a male (i.e., reduced male assistance when feeding nestlings). The polygyny threshold model has been around for several decades, however, only few studies have identified the factors that may compensate secondary females for the cost of sharing a mate. In the present study we were able to show that the patterns of nest predation can be an important territory quality parameter that compensate secondary females, and, hence, contribute to the occurrence of avian polygyny.

DNA fingerprinting was used to characterize patterns of paternity in two populations of Ctenomys talarum from Buenos Aires Province, Argentina. The multilocus probe PV47-2 was used to detect variation in genomic DNA extracted from 12 females, their 32 offspring, and 14 putative sires. For 11 out of 12 litters examined, a single male capable of providing all nonmaternal bands was identified. Within each study population, individual males sired more than one litter, suggesting that C. talarum is polygynous. No evidence of multiple paternity of litters was found. High band-sharing values among females suggest that further research is needed to assess the population genetic structure of this species.

A central paradigm in life-history theory is the trade-off between offspring number and quality. Several studies have investigated this trade-off in humans, but data are inconclusive, perhaps because prosperous socio-cultural factors mask the trade-off. Therefore, we studied 2461 offspring groups in an area under adverse conditions in northern Ghana with high fertility and mortality rates. In a linear mixed model controlling for differences in age and tribe of the mother and socioeconomic status, each additional child in the offspring group resulted in a 2.3% (95% CI 1.9-2.6%, P < 0.001) lower proportional survival of the offspring. Furthermore, we made use of the polygamous population structure and compared offspring of co-wives in 388 households, thus controlling for variation in resources between compounds. Here, offspring survival decreased 2.8% (95% CI 2.3-4.0%, P < 0.001) for each increase in offspring number. We interpret these data as an apparent quality-quantity trade-off in human offspring.

We report the discovery of intraspecific variation in both colony composition and patterns of paternity in two populations of the social common mole-rat Cryptomys hottentotus hottentotus . These two populations represent the mesic and arid habitat extremes of the species' broad ecological range in South Africa. Until recently colonies of the common mole-rat were thought to consist of familial groups whereby all colony members were the offspring of a monogamous reproductive pair. The remaining colony members were thought to forego reproduction until both social and ecological conditions favoured dispersal and opportunities for independent outbreeding. Results from genetic assignment tests using microsatellite markers indicate that while colony composition is dominated by familial groups, colonies within both populations included both adult and subadult foreign conspecifics. Analysis of parentage reveals that the social organization of C. h. hottentotus is not that of strict monogamy; paternity of offspring was not assigned consistently to the largest, most dominant male within the colony. Moreover, a number of significantly smaller males were found to sire offspring, suggesting a sneak-mating strategy by subordinate within-colony males. Extra-colony extra-pair paternity (ECP) was also found to characterize C. h. hottentotus colonies, occurring with similar frequencies in both habitats. Both dominant established breeding males and subordinate males were identified as siring young in nonsource colonies. Furthermore, established breeding males were found to sire extra-colony young in the same season as siring young within their source colonies. We discuss the significance of these results within the context of the divergent ecological regimes characterizing the two sites and observe that our results revisit the accuracy of using behavioural and morphological characters, which have structured the basis of our understanding of the behavioural ecology of this species, as indicators of breeding status in mark-recapture studies.

Social insects exhibit a great variability in their social organization, and this affects colony kin structure, relatedness among nest mates, and population genetic structure. In the mosaic of arboreal ants of neotropical habitats, mutually exclusive dominant ant species occupy different territories, and their nest distribution is spatially aggregated in patches influencing patterns of population genetic structure. In this study, we performed an analysis of the population and colony genetic structure of the facultative polygynous ant Ectatomma tuberculatum to investigate how the particular breeding and social system of this species can explain its ecological dominance in the mosaic. Within-nest genetic analysis revealed that relatedness between nest mate workers was significantly greater than zero (r ¼ 0.30) with an effective number of queens per nest of Ne ¼ 2.5-3, indicating that polygyny is functional in this species. Moreover, we found that queen number was highly variable, probably due to queen adoption events, leading to the prevalence of polygyny over monogyny. Finally, the strong population genetic structure and the significant isolation by distance suggested that both budding and polydomy take place in this species. The respective role of secondary polygyny, budding, and polydomy are then discussed in the context of the mosaic of arboreal ants, and we propose that this particular social organization ensures the ecological dominance of E. tuberculatum by optimizing the colonization of new available nesting sites and by increasing territory size. Figure 1 Map of the 3 localities (Itabuna, Uruc xuca, and Buerarema) and the 15 patches (1-15) studied in Bahia, Brazil. The 3 surrounded patches in Itabuna locality (patch 1-3) are those studied for within-nest genetic analysis.

Dolichoderus mariae Forel, (Hymenoptera: Formicidae) is an uncommon, monomorphic but locally abundant, reddishbrown ant of peculiar nesting habits, whose range includes most of the eastern USA. In north Florida the ant excavates soil under wiregrass clumps or other plants with fibrous roots to form a single, large, shallow, conical or ovoid chamber broadly open to the surface around the plant base. Colonies are highly polygyne and, during the warm season, inhabit multiple nests connected only by above ground trails, over which nests exchange workers. Although monomorphic, worker size may differ significantly between colonies. The colony cycle is dominated by strong seasonal polydomy. From one or two over-wintering nests, the colonies expanded to occupy up to 60 nests by late summer, then retract once more to one or two nests by mid-winter. The worker-to-queen ratio changed greatly during this cycle, with over two thousand workers per queen during fall and winter, dropping to a low of about 300 during midsummer. Most of these summer queens probably die during the fall. Colonies reoccupy roughly the same area year to year even though they contract down to one or two nests in winter. Observation of fights in the contact zone between colonies suggested that the colonies are territorial. The ants subsist by tending aphids and scale insects for honeydew and scavenging for dead insects within their territories.

Most mammalian groups are characterized by male-biased sexual size dimorphism, in which size-dependent male-male competition and reproductive skew are tightly linked. By comparison, little is known about the opportunity for sexual selection in mammalian systems without male-biased dimorphism, where the traits under sexual selection might be less obvious. We examined 10 years of parentage data in a colony of greater horseshoe bats ( Rhinolophus ferrumequinum ) to determine the magnitude of male reproductive skew and the opportunity for sexual selection in a mammal in which females are the larger sex. Annual paternity success was weakly skewed but consistent patterns led to strong longitudinal paternity skew among breeders. Just three males accounted for a third of all paternity assignments, representing at least a fifth of all colony offspring born in a decade. Paternity success was in part determined by age but was not influenced by dispersal status. Our results show that paternity skew and the opportunity for sexual selection in a species with reversed sexual size dimorphism can approach levels reported for classical examples of species with polygyny and male-biased dimorphism, even where the traits under sexual selection are not known.

Female northern harriers Circus cyaneus are polygynous, marsh-nesting raptors, whose mate choices are enigmatic. I determined the mate choice cues employed by females by correlating the order in which males were chosen with characters that 1) significantly influenced reproductive success; 2) were assessable prior to settlement; and 3) varied between breeding situations. Only nest sites and male provisioning performance met all these conditions: wet nest sites significantly (P< 0.05) increased nest survival and high provisioning rates significantly (P<0.01) enhanced brood survival. The order in which females settled was strongly correlated with provisioning performance in both years (rs-0.65, and rs-0.84), but not with nest site quality. Females thus appeared to choose males principally on provisioning performance. Despite using the same cue, however, females choosing mated males reared only 0.28 young for every nestling raised by concurrently settling monogamous females (the lowest ratio recorded for any avian species). Extrapolation of male courtship provisioning patterns from clutch sizes and laying date indicated that females received similar proportions prior to and during egg-laying, but that males later preferentially fed ~ females. Secondary females therefore chose mated males on the basis of a temporally changing and unreliable cue. The polyterritoriality, cooperative harems, skewed sex ratio, and sexy-son hypotheses were all inadequate in explaining polygyny in harriers. Female choice of mated males among harriers is best explained by the deceitful provisioning of food by males.

As patterns of family formation change, it is important to know how children's lives are affected by their parents' marital and socioeconomic circumstances. Using data from the 1993 Kenya Demographic and Health Survey, this study shows that children of never married and formerly married mothers have significantly higher probabilities of polio dropout and acute undernutrition than those of monogamously married mothers. The number of male household members of working age greatly enhances the chances of full immunization and the nutritional status of children whose mothers were previously married. For children of never married mothers, the benefits of residing with males of working age are largely a function of ethnicity. The results also show that, although children are not disadvantaged nutritionally when their fathers have more than one wife, polygyny is associated with a higher probability of polio dropout and lower probability of full immunization than monogamy. Higher socioeconomic status is associated with a greater probability of full immunization and a lower probability of malnutrition but socioeconomic factors do not explain the effects of mothers' marital status. The findings underscore the complex realities of family interaction and the importance of the broader social context in accounting for variations in child welfare across diverse marital situations.

Positive density dependence (i.e., the Allee effect; AE) often has important implications for the dynamics and conservation of populations. Here, we show that density-dependent sex ratio adjustment in response to sexual selection may be a common AE mechanism. Specifically, using an analytical model we show that an AE is expected whenever one sex is more fecund than the other and sex ratio bias toward the less fecund sex increases with density. We illustrate the robustness of this pattern, using Monte Carlo simulations, against a range of body size-fecundity relationships and sexallocation strategies. Finally, we test the model using the sex-changing polygynous reef fish Parapercis cylindrica; positive density dependence in the strength of sexual selection for male size is evidenced as the causal mechanism driving local sex ratio adjustment, hence the AE. Model application may extend to invertebrates, reptiles, birds, and mammals, in addition to over 70 reef fishes. We suggest that protected areas may often outperform harvest quotas as a conservation tool since the latter promotes population fragmentation, reduced polygyny, a balancing of the sex ratio, and hence up to a 50% decline in per capita fecundity, while the former maximizes polygyny and source-sink potential.

It has been proposed that blue-green egg colours have evolved as a post-mating signal of female quality, selected by males allocating their parental effort in response to the strength of this signal. We tested two main assumptions of the sexually selected egg coloration hypothesis: (1) whether the intensity of eggshell bluegreen chroma (BGC) reflects female quality; and (2) whether males make their decisions on the level of parental care that they provide according to the intensity of eggshell BGC. As a model species, we chose the facultatively polygynous great reed warbler (Acrocephalus arundinaceus). In this species, females simultaneously paired with the same male, compete for his nest attendance and could benefit from signalling their quality through egg coloration. However, we found no association between the variation in eggshell BGC and the measures of female quality (physical condition, mean egg volume and age). Moreover, great reed warbler males did not adjust their investment (as measured in terms of nest defence against a brood parasite) in relation to the eggshell BGC. We conclude that blue-green egg coloration in this open-nesting passerine is unlikely to have a signalling function. Rather, the large colour variation among clutches of individual females may depend on yearly fluctuations in environmental conditions.

We investigated sex allocation in a Mediterranean population of the facultatively polygynous (multiple queen per colony) ant Pheidole pallidula. This species shows a strong split sex ratio, with most colonies producing almost exclusively a single-sex brood. Our genetic (microsatellite) analyses reveal that P. pallidula has an unusual breeding system, with colonies being headed by a single or a few unrelated queens. As expected in such a breeding system, our results show no variation in relatedness asymmetry between monogynous (single queen per colony) and polygynous colonies. Nevertheless, sex allocation was tightly associated with the breeding structure, with monogynous colonies producing a male-biased brood and polygynous colonies almost only females. In addition, sex allocation was closely correlated with colony total sexual productivity. Overall, our data show that when colonies become more productive (and presumably larger) they shift from monogyny to polygyny and from male production to female production, a pattern that has never been reported in social insects.

The question of the occurrence of nepotism in insect societies is central to inclusive fitness theory. Here we investigated the existence of nepotism in the facultative polygynous ant Ectatomma tuberculatum because various characteristics of this species may have favored the evolution of nepotistic behavior toward queens. We thus studied worker-queen care toward their mother queen vs. an unrelated unfamiliar queen, to determine if workers cared preferentially for their mother. Although we tried to facilitate the expression of nepotistic behaviors, we did not detect significant nepotism confirming the general trend of an absence of nepotism in social insects. We discuss about the specific causes that can explain the absence of nepotism in E. tuberculatum regarding the particular social organization of this species and its ecological dominance in the mosaic of arboreal ants.

Saccopteryx bilineata has a polygynous mating system in which males defend females in a harem territory. Harem defense and courtship include energetically costly flight maneuvers and hovering displays. We tested if (1) harem males have a greater field metabolic rate than non-harem males or females and if (2) the field metabolic rate of harem males is correlated with the number of females in a harem territory. We measured the energy budget in 32 S. bilineata with the doubly labeled water method and compared these estimates with behavioral observations in the daytime roost. Among adult bats, field metabolic rate varied with body mass by an exponent of approximately two. We found no significant difference in field metabolic rate or mass-specific field metabolic rate between harem and non-harem males. The mass-specific field metabolic rate of harem-males increased with harem size. The latter finding supports the hypothesis that the energy costs of courtship display and territorial defense influence the energy budget of harem males. Overall, field metabolic rates of S. bilineata were lower than those of similarly sized bats of the temperate zone and only 2.3 times above the basal metabolic rate recorded for this species. We suggest that male S. bilineata did not take advantage of their metabolic capacity because a prudent allocation of energy to activities of harem maintenance is an adaptive strategy for males in this mating system.

This study examines phylogenetic relationships among six species of the Formica rufa group ants (F. polyctena, F. rufa, F. lugubris, F. paralugubris, F. aquilonia, and F. pratensis). The phylogeny based on a 2051 bp fragment of mtDNA including cyt b, tRNA Ser , and ND1 genes supports the division of the group into three major clusters: one with the species F. polyctena and F. rufa, one with F. aquilonia, F. lugubris, and F. paralugubris, and the third one with F. pratensis. The interspecific divergence estimates (mean 0.98 AE 0.15% for the main phylogenetic groups) imply that radiation took place during the Pleistocene. Comparison of the divergence estimates among the F. rufa group species with divergence estimates among other closely related species of insects suggests that speciation in the group was relatively fast, and the mitochondrial lineages of F. polyctena and F. rufa have not fully separated. The haplotype tree shows also signs of transfer of mtDNA between species through hybridisation. The distribution of polygyny (multiple queens per nest) along the branches of the tree indicates that the social type characterised by highly polygynous societies and large colonial networks, has originated at least three times. The species F. aquilonia and F. paralugubris that build such large supercolonies, cluster tightly together with very little nucleotide variation, suggesting that this type of social organisation could be a factor promoting speciation in the ants.

Relatedness increases the likelihood of cooperation within colonies of social insects. Polygyny, the coexistence of numerous reproductive females (queens) in a colony, is common in mature colonies of the termite Macrotermes michaelseni. In this species, polygyny results from pleometrosis and from several female alates that jointly found a new colony. To explain this phenomenon, it was suggested that only related females cooperate and survive during maturation of colonies. Using multilocus fingerprints as well as microsatellites, we showed that nestmate queens in mature colonies are unrelated. Furthermore, we found that all nestmate queens contributed to the production of steriles. Even in mature colonies, several matrilines of steriles coexist within a colony. Although genetic diversity within colonies may increase the likelihood of conflicts, high genetic diversity may be important for foraging, colony growth, and resistance to disease and parasites.