Incidence Of Polygyny Research Articles

Alternative matings and the opportunity costs of paternal care in house sparrows

Among avian species with biparental care, male alternative reproductive opportunities can occur in the form of either extrapair fertilizations or additional social mates. We manipulated testosterone (T) levels in male house sparrows to assess whether participation in parental care detracts from male success in securing alternative matings; we also compared the annual reproductive success of males that engaged in normal levels of care with the success of males that displayed increased mating effort at the expense of parental care. Our results showed that the incidence of polygyny among high-T/low-parenting males was elevated relative to control males, but that success in obtaining extrapair mates was independent of hormonal treatment. Thus, male parental care seems to carry an opportunity cost in terms of reduced acquisition of additional social mates. Despite this cost, between-treatment comparisons of the estimated number of fledglings sired annually suggest that, in this species, the value of male contributions to care is sufficiently high to favor the reductions in T that facilitate normal male parenting.

Field Studies of the Parasitic AntSolenopsis daguerrei(Hymenoptera: Formicidae) on Fire Ants in Argentina

The workerless parasitic ant Solenopsis daguerrei (Santschi) has been considered a potential candidate for biological control of imported fire ants in the United States since the 1970s. We estimated the detrimental effects of S. daguerrei in fire ant colonies from Argentina by comparing the composition of parasitized and nonparasitized field colonies of the black imported fire ant S. richteri Forel. We recorded mound density and volume, incidence of polygyny, number of queens per colony, queen weight, and presence and abundance of brood and sexuals. Also, we studied aspects of the parasite’s biology such as parasitization rates, presence of sexuals, abundance and weight of queens, and sex ratio. S. daguerrei occurred in 1.2–23.7% of the colonies at 21 collecting sites. The mound density at parasitized sites was significantly lower than in parasite-free sites (161 versus 239 mounds per hectare). Parasitized colonies had significantly fewer host queens than nonparasitized ones (2.9 versus 5.5 queens per colony). The percentage of colonies with worker brood was significantly lower (in fall) in parasitized than in nonparasitized colonies. Also, worker brood was significantly less abundant (in fall and spring) in parasitized colonies. A short delay in the production of sexual brood by the host was observed in parasitized colonies. These detrimental effects look promising but should be evaluated in the long-term and confirmed in other areas. A better understanding of the host and parasite is required to introduce S. daguerrei into the United States to control imported fire ants.

Geographic distribution of human skin colour: A selective compromise between natural selection and sexual selection?

Modern humans have been shaped by the cumulative action of natural selection, non-adaptive random change, and sexual selection. The last of these is not universal and has prevailed in one of two circumstances: (1) A surplus of females due to high male mortality, combined with ecological constraints on female participation in food procurement which discourage males from taking second wives; (2) A surplus of single males due to generalized polygyny with relatively low male mortality. These circumstances are most likely to occur in (1) Arctic tundra environments, specifically the vast expanse of tundra covering most of Europe up to 10,000 B.P., and in (2) regions dominated by generalized polygyny, notably sub-Saharan Africa. Sexual selection often acts on existing sex differences, including perhaps sexual dimorphism in human skin colour. Whereas women are universally fairer in complexion, men are browner and ruddier; parallel to this, most human societies see lighter skin as more feminine and darker skin as more masculine. Hence, sexual selection should favour lighter pigmented women when a surplus of single females must compete for a mate. Since skin colour is only mildly sex-linked, both sexes would lighten in pigmentation within the population in question. Similarly, when a surplus of single males must compete for a mate, both sexes would darken. Geographic variation in human skin colour may thus represent a selective compromise between two counterbalancing forces: natural selection, as determined by latitudinal variation in sunlight; and sexual selection, as determined by variations in the following: male mortality rates, incidence of polygyny, and ecological constraints on female participation in food procurement.

Ecological Similarity of Shrub‐Desert Avifaunas of Australia and North America

The hypothesis that species and communities occupying vegetationally similar environments on different continents should be similar in ecology has become widely accepted, although quantitative support for this hypothesis is meagre. As an indirect assessment of the likelihood of ecological and evolutionary convergence, I quantified features of community structure and of breeding biology, behavior, and life history of birds species occupying several sites in semi—arid shrub deserts in the Great Basin of North America and the interior of Australia. Study sites on both continents were statistically indistinguishable in most quantitative measures of vegetation structure. Breeding—bird assemblages contained the same number of species per unit area, but densities of individuals in Australia averaged half those in North America. A cluster analysis based on a multivariate similarity matrix derived from 14 ecological and life—history characteristics of the species revealed little close matching of Australian species with a North American counterpart, although two such pairings suggest possible ecological convergence. The frequencies of most ecological/life—history traits among species breeding on local plots differed substantially between continents. The Australian species were characterized by longer breeding periods with more breeding attempts, greater social aggregation during breeding and feeding activities, greater use of domed nests, and sedentariness or nomadism rather than seasonal migration. The avifaunas did not differ in mean clutch sizes, the incidence of polygyny, nesting height, territory size, or general dietary patterns. Despite the close matching of vegetation structure on the two continents, differences between the species and communities are more striking than the similarities. These differences may be related to climatic differences between the areas. Although long—term mean precipitation in the Australian and North American shrub—desert regions does not differ, the monthly and yearly variance in Australia is substantially greater. Droughts may be prolonged and widespread, and this factor, together with soil—nutrient limitations, may result in generally lower and more erratic primary and secondary production in the Australian deserts. Close convergence may be lacking because, despite the similarities in habitat structure, the climates and resource levels of Australian and North American shrub deserts differ in fundamental ways, and the avifaunas are of differing phylogenetic derivation. These comparisons emphasize that (1) bird communities are frequently open, so understanding the composition and dynamics of local assemblages requires a broad—scale perspective, and (2) generalizations or explanations developed for one region of the world may not apply in other regions, even if the habitats are similar.

Female Site Fidelity and Polygyny in the Blackpoll Warbler (Dendroica Striata)

Abstract From 1980 to 1982, 8-30% of male Blackpoll Warblers (Dendroica striata) studied on Kent Island, New Brunswick, were bigamous each year (x̄ = 16.8%). I tested whether differences in the quality of the breeding situation can give rise to polygynous matings. Five territory parameters and two male parameters were used as measures of quality. Male arrival times were correlated with male mating status and the reproductive success of monogamous females. Territories of bigamous males had more large conifers than did those of monogamous males. Territory parameters did not appear to influence female choices. Strong site attachment by females may lead them to mate bigamously when few males are available early in the season near the females' former nest sites. The reproductive success of secondary females was not different from that of monogamous females. Any costs of mating bigamously may be offset by increased reproductive success associated with early nest initiation and competitive advantages conferred by site dominance. Site attachment and return patterns can account for the incidence of polygyny in this population, but probably could not give rise to high levels of polygyny or large harems. More information is needed to evaluate the influence of site fidelity on mating decisions of females in other polygynous passerine species.

Population Change in Kericho District, Kenya: An Example of Fertility Increase in Africa

The author analyzes changes in the size of the Kipsigis population in the Kericho district of western Kenya since 1905 and accompanying changes in fertility rates. Data are from administrative reports for the colonial period; the censuses of 1948 1962 and 1969; and more recent published sources concerning fertility. Age at marriage length of breast-feeding infant mortality form of marriage the economic value and cost of children income and education are among the variables considered as possible determinants of fertility. The author concludes that although mortality decline may account for part of the change in the rate of natural increase fertility changes have been instrumental as well. The initial rise in fertility can be explained through the reduction in the age at circumcision and age at marriage and the decline in the incidence of polygyny. By the 1960s the evidence pointed to a slowdown in the rate of fertility increase with a possible fertility decline. The major identifiable reason for the decline was an increase in the educational level of the female population. (EXCERPT)

Alternative Predictors of Polygyny

This paper describes how the "sex-ratio" explanation of polygyny compares with some alternative, supposedly causal explanations. The results suggest that more than occasional incidence of polygyny is best predicted by two statistically independent factors—high male mortality in warfare (which would produce an actual excess of marriageable women) and delayed age of marriage for men (which would produce an artificial excess of marriageable women). The presence of one or the other of these two factors predicts an appreciable frequency of polygyny more strongly than either one factor does by itself.

Polygyny, Descent, And Local Fission: A Comparative Hypothesis

By enabling us to predict with reasonable accuracy the presence or absence of polygyny, Goody’s latest statement on the topic (1976) represents a major step ahead although his model, like every other current one, fails to explain variations in the incidence and intensity of polygyny in polygynous societies. The Abutia Ewe, for instance, have a relatively low incidence of plural marriage (16%) and I am interested in accounting for this low incidence. After having tried to elicit what type of matrimonial strategy Abutia polygyny represents, I conclude that this approach in terms of strategy cannot serve to generate any useful hypotheses to account for variations in the incidence of polygyny across societies. Turning then to a ‘macro-structural’ approach grounded in a new model of descent elaborated elsewhere (Verdon 1980b), I contrast the Abutia to the Anlo Ewe and to the Tallensi to elucidate some of the organizational factors which seem to affect the expression of polygyny.

Polygyny: Women's Views in a Transitional Society, Nigeria 1975

Womens attitudes toward polygyny are examined in the context of a transitional urban society in western Nigeria - a society in which almost 1/2 of all wives live in polygynous unions. The data on the incidence of polygyny are drawn from a sample of 6606 women of all marital statuses; the data on attitudes is based on in-depth interviews with 250 wives. The most important finding is possibly the lack of any clear division between monogamously and polygynously married women. In a society in which polygyny is so widely accepted nearly all monogamous marriages are perceived as potentially polygynous and sole wives need to always consider the prospect of additional wives. 60% of the wives indicated straightforwardly that they would be pleased if their husbands took another wife; they would be pleased to share the housework husband care and child-minding and to have someone to gossip and play with. 23% openly expressed anger at the idea of sharing material and sexual resources with another wife while the remainder expressed some ambivalence. The more traditionally oriented uneducated wives were more inclined to be pleased with the idea of sharing their husband (67%) in contrast to those with some formal Western-style education (54%). Wives opinions on personal autonomy fertility womens issues and general development are also examined.

Urbanization, plural marriage, and family size in two African cities1

In this article we examine the degree to which two facets of traditional familial arrangements, plural marriage and familism (as measured by number of children), continue to be closely interrelated in the African urban context. We demonstrate that urbanization is, in effect, associated with changes in the number of choices available to male urban residents with regard to their familial life‐style, but not necessarily with changes in the nature of such choices. We show that male exposure to urban forces (as measured by educational and occupational attainments or by migratory experiences) is not necessarily accompanied by a decline in the incidence of polygyny or in the number of children attached to a household. Nor does it necessarily lead to a decline in the association between these variables. Further, we also examine whether the interaction between types of marriage and number of children varies with the characteristics of the immediate surroundings in which these individuals live, notably with their relative isolation from ethnic peers, or with the housing facilities that they use. Finally, we show that the responses of men and women to the problems of urbanization are not alike and that the functions performed by monogamous and polygynous wives are increasingly divergent. We conclude that the effect of urbanization on traditional life‐style is not necessarily unidirectional.

Traditional and Modern Life Styles in Africa

The present paper is concerned with an examination of the effects of urbanization on patterns of familial organization in Douala, the major city of the Cameroun. In contrast to the theories of social change that treat urbanization of means and urbanization of ends as coterminous, the paper attempts to distinguish these two dimensions from one another and to show that their effect of traditional familial institutions are distinctive. Thus the two authors show that declines in the incidence of polygyny or of extended familism are not necessarily linear and that the significance of these declines might be in some cases attributed to the restraints confronting newly urbanized populations, while it clearly results from a modernization of individual aspirations in other instances. In addition, the authors show that urbanization is associated with changes in the functions traditionally assigned to plural marriage or to extended familism as well as in the interaction between these two facets of familial arrangements.