Level Of Polygyny Research Articles

Mountain ungulate mating systems: patterns and processes

ABSTRACTMountain ungulates of the subfamily Caprinae, including wild sheep, goats and goat‐antelopes, show remarkable interspecific diversity in habitat preferences, social organisation and morphological features. We review how this diversity relates to their mating behaviour.After introducing the ecology of mating systems and the evolution of the Caprinae, we investigate the pairwise, sequential relationships between habitat preferences, social behaviour, level of polygyny, and morphological features, and discuss the ecological processes underlying the patterns of mate monopolisation and acquisition.From forest‐dwelling, solitary, monogamous and monomorphic goat‐antelopes, to highly dimorphic, polygynous and social wild sheep and goats inhabiting open landscapes, mountain ungulates reveal a close relationship between habitat openness and sexual dimorphism, through the level of sociality and that of mate monopolisation.Although over the last few decades some information has been collected on the biology of Caprinae, our understanding of determinants of their mating systems is still hampered by limited data to estimate opportunities for sexual selection, as well as uncertainties over the occurrence and maintenance of alternative reproductive tactics, and lack of information on female mate choice.The study of mating systems and that of the factors influencing them play a key role from an evolutionary and conservation standpoint. This is relevant to the Caprinae, whose main habitat is expected to be strongly affected by the ongoing climatic change, with potential effects on the phenology of their mating systems, and whose economic value is relevant for consumptive and nonconsumptive uses. A better understanding of the diversity and ecology of mating systems will require a wealth of additional field observations on male and female behaviour, as well as genetic assessments of reproductive success.

Role of sexual and natural selection in the evolution of sexual size dimorphism in primates

AbstractIn mammals, the dominant theory proposes that sexual size dimorphism evolved by sexual selection in a polygynous reproductive scenario. Natural selection is an alternative hypothesis where dimorphism represents an adaptation to ecological pressures. I tested evolutionary models based on sexual and natural selection processes using phylogenetic confirmatory path analyses. I employed data for 225 primate species in terms of their diel activity, body mass, sexual size dimorphism, level of sociality, and level of polygyny. The model that received the most support from path analyses was a mixed model in which dimorphism evolved after an increase in body size that resulted from a response to an ecological pressure, i.e., a change from nocturnal to diurnal habits, with a lesser role of polygyny. Phylogenetic path analysis suggests that natural selection has played an important role in the evolution of sexual size dimorphism in primates.

A global analysis of aerial displays in passerines revealed an effect of habitat, mating system and migratory traits.

Aerial displaying is a flamboyant part of the sexual behaviour of several volant animal groups, including birds. Nevertheless, little attention has been focused on identifying correlates of large-scale diversity in this trait. In this study, we scored the presence and absence of aerial displays in males of 1732 species of passerine birds (Passeriformes) and employed Bayesian phylogenetically informed mixed models to test for associations between aerial displays and a set of life-history and environmental predictors. Our multi-variate models revealed that species with males that perform aerial displays inhabited open rather than closed (forested) habitats. These species also exhibited higher levels of polygyny, had more elongated wings, migrated over longer distances and bred at higher latitudes. When we included species where the sexual function of displays has not been explicitly described but is likely to occur, we found that aerial displaying was also associated with smaller body size and increased male plumage coloration. Our results suggest that both sexual selection and natural selection have been important sources of selection on aerial displays in passerines.

Acclimation of elk mating system following restoration to the Missouri Ozarks, U.S.A.

Biologists increasingly use translocation to restore animals to areas where they have been extirpated. However, we know little about how translocation decisions influence translocation‐mediated social dynamics. Breeding in polygynous ungulate mating systems is typically dominated by prime age males, but founding males within translocated ungulate populations often are comprised of only young individuals. We investigated the influence of releasing exclusively young‐aged males on mating system and male reproductive success during an elk (Cervus canadensis) restoration program in Missouri. From 2011 to 2013, we translocated and released 106 elk from Kentucky to Missouri, U.S.A. We collected tissue samples for DNA from all translocated elk and subsequently captured adults and calves in Missouri during 2014–2018 for paternity analysis. Initial levels of polygyny were low but increased and acclimated over the initial years following translocation, commensurate with advancing sire age structure and increasing population density. Sire age was positively associated with individual male reproductive success initially, but the effect of age decreased as polygyny acclimated and sire age structure became older and more variable. Polygyny levels in the reintroduced population were restored to expected values within 4 years of the last translocation event, demonstrating the acclimation of mating structure despite a translocation tactic favoring young‐aged males. Importantly, initial dampened polygyny may facilitate retention of genetic variation by maximizing the genetic contribution of more founding individuals; however, benefits to genetic variation retention should be considered against potential demographic consequences to calves sired by young males.

Where are the beachmasters? Unexpectedly weak polygyny among southern elephant seals on a South Shetland Island

AbstractIntraspecific variation in animal mating systems can have important implications for ecological, evolutionary and demographic processes in wild populations. For example, patterns of mating can impact social structure, dispersal, effective population size and inbreeding. However, few species have been studied in sufficient detail to elucidate mating system plasticity and its dependence on ecological and demographic factors. Southern elephant seals (Mirounga leonina) have long been regarded as a textbook example of a polygynous mating system, with dominant ‘beachmaster’ males controlling harems of up to several hundred females. However, behavioural and genetic studies have uncovered appreciable geographic variation in the strength of polygyny among elephant seal populations. We, therefore, used molecular parentage analysis to investigate patterns of parentage in a small satellite colony of elephant seals at the South Shetland Islands. We hypothesised that dominant males would be able to successfully monopolise the relatively small numbers of females present in the colony, leading to relatively high levels of polygyny. A total of 424 individuals (comprising 33 adult males, 101 adult females and 290 pups) sampled over 8 years were genotyped at 20 microsatellites and reproductive success was analysed by genetically assigning parents. Paternity could only be assigned to 31 pups (10.7%), despite our panel of genetic markers being highly informative and the genotyping error rate being very low. The strength of inferred polygyny was weak in comparison to previous genetic studies of the same species, with the most successful male fathering only seven pups over the entire course of our study. Our results show that, even in a species long regarded as a model for extreme polygyny, male reproductive skew can vary substantially among populations.

Capital-Income Breeding in Male Ungulates: Causes and Consequences of Strategy Differences Among Species

The capital and income breeding concept links energy resources used during reproduction to the timing of their acquisition. During reproduction, capital breeders rely on resources gained previously and accumulated for reproductive investment. By contrast, income breeders use mainly resources collected during the period of reproductive activity. Most commonly, this concept is applied to females; relatively few studies have considered males. Moreover, there has been little attention to the link between the capital-income divide and other aspects of mating strategy. We studied adult males of three wild ungulates with different levels of polygyny. A large dataset (4,264 red deer, 53,619 roe deer, and 13,537 Alpine chamois, respectively) was obtained during 2007–2017 in the whole territory of Slovenia and in the Trento province, Italy. During the rut, body mass loss of males in highly polygynous species was more than twice that of weakly polygynous species: on average, red deer stags lost 19.5%; chamois bucks 16.0%; and roe deer bucks 7.5% of their body mass. This indicates potential for a hitherto unrecognised link between the degree of intrasexual competition and the degree of capital mating. The variability in body mass at the end of the rut was clearly reduced in both highly polygynous species (from 15.1 to 9.4% in red deer, and from 12.5 to 10.5% in chamois), but did not change in roe deer. Finally, roe deer bucks had recovered body mass to that of the pre-rut period by just 2 months after the rut, while red deer stags did not manage to compensate the loss of weight until the end of the year. We suggest that, at least in ungulates, there is a link between the degree of polygyny and that of capital breeding. Males of capital and income breeders underwent body mass changes resulting from different reproductive investment during the rut. Capital breeders lost considerably more weight, and invested a variable amount of energy among individuals or among years, possibly to cope with different environmental or body conditions. In so doing, they ended the rut with poorer but more even condition among individuals.

Theoretical and practical consequences of imbalance in the coefficient of male and female population in modern Russia: impact of the factor of ratio of genders in the region upon individual level of financial wellbeing

This article presents a brief overview of the modern concept of gender selection and theory of parental investments, according to which the ration of genders in society manifests as a key forecaster of the level of polygyny on the marital market. The theory predicts that in shifting of the models of marital behavior from monogamous and polygamous, the level of matrimonial investment can decrease. The authors suggest that such targeted decrease of resources in the regions with low coefficient of genders can exert negative impact on the economic parameters of household in these regions. This research provides quantitative assessment of subjective satisfaction with financial position of the members of households in populated areas (N=10385) with various levels of coefficient of genders. The statistical analysis was conducted using the IBM SPSS software with application of the following methods: Pearson's χ2 criterion, Goodman and Kruskal's gamma (γ) criterion, and dispersion analysis. The acquired results confirm the presence of positive interconnection between the level of coefficient of genders in the region and financial wellbeing households. It was determined that in the regions of the Russian Federation with equal ration of male and female population, as well as in regions with predominant male population, the subjective assessment of own financial wellbeing was higher among both, men and women. The factor of sustained imbalance in the ratio of genders represents one of the relevant questions of Russian demography, but this phenomenon is rarely taken into consideration in quantitative research within social sciences.

Prevalence of polygyny in a critically endangered marine turtle population

Genetic analyses of nuclear DNA (e.g., microsatellites) are a primary tool for investigating mating systems in reptiles, particularly marine turtles. Whereas studies over the past two decades have demonstrated that polyandry (i.e., females mating with multiple males) is common in marine turtles, polygyny (i.e., males mating with multiple females) has rarely been reported. In this study we investigated the mating structure of Critically Endangered hawksbill turtles (Eretmochelys imbricata) at Bahía de Jiquilisco in El Salvador, one of the largest rookeries in the eastern Pacific Ocean. We collected genetic samples from 34 nesting females and hatchlings from 41 clutches during the 2015 nesting season, including one nest from each of 27 females and two nests from seven additional females. Using six highly polymorphic microsatellite loci, we reconstructed the paternal genotypes for 22 known male turtles and discovered that seven (31.8%) sired nests from multiple females, which represents the highest polygyny level reported to date for marine turtles and suggests that this is a common mating structure for this population. We also detected multiple paternity in four (11.8%) clutches from the 34 females analyzed, confirming polyandrous mating strategies are also employed. The high level of polygyny we documented suggests there may be a limited number of sexually mature males at Bahía de Jiquilisco; a scenario supported by multiple lines of empirical evidence. Our findings highlight key management uncertainties, including whether polygynous mating strategies can compensate for potential ongoing feminization and the low number of adult males found for this and possibly other marine turtle populations.

Song structure and variability in the Black-headed Bunting (Emberiza melanocephala)

Fighting and flirting are the main evolutionary forces behind the development of bird song and both contribute to different song characteristics. By comparison of vocalisations throughout bird taxa, we can help to reconstruct the evolutionary history of the song. In this study, we provide the first detailed analysis of song structure and song type variability in the Black-headed Bunting (Emberiza melanocephala). We quantify the fine structural characteristics of the song and describe the song and syllable repertoire size. Further, we describe intraindividual song variability over time and interindividual song variability over space, and we explore whether this species uses syntactic rules to create songs. Our analyses reveal that the Black-headed Bunting has a short yet rather complex song and that the syllable pool is extensive. Its song is constructed of three parts that differ in both complexity and rhythm, suggesting the use of syntactic rules in constructing a song. The male song is typically built of 9–13 syllables, with 7–12 that are non-repetitive. Each male sings only one stereotyped song, which remains identical throughout the male’s lifespan, providing evidence for age-limited song learning. Songs are individually distinct, suggesting the importance of song in individual recognition of males. Two spatial levels of song variation in the Black-headed Bunting are shown. On a microgeographical level, relatively small song neighbourhoods are formed with a handful of birds singing the same song type. On a macrogeographical level, dialects can be distinguished by the end part of a song. The most striking feature of the male Black-headed Bunting song is the immense variability of song types. Typically, only a small number of males shared the same song type, and males with unique song types occurred frequently as well. The high song complexity and single-song repertoire found in the Black-headed Bunting could reflect a high level of polygyny and a low level of parental care, therefore pointing to strong intersexual selection on the male song.

Humans as a model species for sexual selection research.

Ever since Darwin, questions about humans have driven sexual selection research. While studies of other organisms are often justified as useful for improving understanding of humans, humans themselves can be useful models. Although humans present some drawbacks as model organisms (complicated societies, slow reproduction and strong ethical constraints on experimental options), humans nonetheless offer many advantages (being abundant, accessible and having detailed historical records for some populations). As an additional challenge, humans exhibit a rather puzzling combination of traits. Some traits (pair-bonding, biparental care and modest sexual dimorphism in body size) suggest selection for monogamous mating, while other traits (including sexual dimorphism in body composition and appearance) suggest selection for polygyny. Such puzzles have motivated research on other species, resulting in a rich set of comparative data that provides insights into humans and other species. Recent studies of visual trait dimorphism suggest that human appearance reflects adaptation for multi-level societies, rather than high levels of polygyny. In addition to biological traits, human cultural traits have undergone rapid evolution. Changes in subsistence strategies profoundly affect opportunities for sexual selection. The enormous variability of human behaviour and ecology provides abundant opportunities to test key hypotheses, and poses challenging puzzles for future research.

Trends in Age at Marriage and the Onset of Fertility Transition in sub‐Saharan Africa

In this chapter the author adopts a comparative approach to examining longterm trends in female age at marriage and fertility in sub-Saharan Africa with a focus on continental countries having at least 1 million inhabitants. The author’s database on nuptiality includes over 360 censuses and national surveys conducted in these 39 countries since the 1960s. The author analyzes the association between changes in age at first union and the onset of fertility transition examining whether there is a typical pattern of association followed by most countries in the region.

Stochastic modelling of shifts in allele frequencies reveals a strongly polygynous mating system in the re-introduced Asiatic wild ass.

Small populations are prone to loss of genetic variation and hence to a reduction in their evolutionary potential. Therefore, studying the mating system of small populations and its potential effects on genetic drift and genetic diversity is of high importance for their viability assessments. The traditional method for studying genetic mating systems is paternity analysis. Yet, as small populations are often rare and elusive, the genetic data required for paternity analysis are frequently unavailable. The endangered Asiatic wild ass (Equus hemionus), like all equids, displays a behaviourally polygynous mating system; however, the level of polygyny has never been measured genetically in wild equids. Combining noninvasive genetic data with stochastic modelling of shifts in allele frequencies, we developed an alternative approach to paternity analysis for studying the genetic mating system of the re-introduced Asiatic wild ass in the Negev Desert, Israel. We compared the shifts in allele frequencies (as a measure of genetic drift) that have occurred in the wild ass population since re-introduction onset to simulated scenarios under different proportions of mating males. We revealed a strongly polygynous mating system in which less than 25% of all males participate in the mating process each generation. This strongly polygynous mating system and its potential effect on the re-introduced population's genetic diversity could have significant consequences for the long-term persistence of the population in the Negev. The stochastic modelling approach and the use of allele-frequency shifts can be further applied to systems that are affected by genetic drift and for which genetic data are limited.

Variation in male reproductive longevity across traditional societies.

Most accounts of human life history propose that women have short reproductive spans relative to their adult lifespans, while men not only remain fertile but carry on reproducing until late life. Here we argue that studies have overlooked evidence for variation in male reproductive ageing across human populations. We apply a Bayesian approach to census data from Agta hunter-gatherers and Gambian farmers to show that long post-reproductive lifespans characterise not only women but also males in some traditional human populations. We calculate three indices of reproductive ageing in men (oldest age at reproduction, male late-life reproduction, and post-reproductive representation) and identify a continuum of male reproductive longevity across eight traditional societies ranging from !Kung, Hadza and Agta hunter-gatherers exhibiting low levels of polygyny, early age at last reproduction and long post-reproductive lifespans, to male Gambian agriculturalists and Turkana pastoralists showing higher levels of polygyny, late-life reproduction and shorter post-reproductive lifespans. We conclude that the uniquely human detachment between rates of somatic senescence and reproductive decline, and the existence of post-reproductive lifespans, are features of both male and female life histories, and therefore not exclusive consequences of menopause.

The Role of Polygyny in the Intra-Household Efficiency of Agricultural Production in West Africa

Polygyny is an institution with deep roots in West Africa. Many papers have attempted to explain the rationality and persistence of this phenomenon through time. Less effort has been devoted to studying the effect of polygyny on household economic behavior. This question is policy relevant given the pressure underway to eliminate polygyny. This paper provides new empirical evidence on whether polygyny leads to an improvement or a worsening of intra-household efficiency for three countries with high levels of polygyny: Benin, Burkina Faso and Senegal. The evidence we obtain is mixed. In Benin, polygyny does not seem to have an impact on intra-household efficiency, while it appears, in the longer run, to improve it in Burkina Faso, but to decrease it in Senegal.

Male reproductive success increases with alliance size in Indo‐Pacific bottlenose dolphins (Tursiops aduncus)

1. Determining the extent of variation in male mating strategies and reproductive success is necessary to understand the fitness benefits of social and cooperative behaviour. 2. This study assesses the reproductive success of male Indo-Pacific bottlenose dolphins in a small embayment population where different behavioural strategies of males have previously been identified. Parentage for 44 sampled calves was examined using 23 microsatellite loci and one mitochondrial DNA marker. Our candidate parent pool of 70 males and 64 females contained individuals sampled from both the embayment and adjacent coastal populations. 3. A moderate level of polygyny was detected in our sample. We assigned paternity of 23 calves to 12 males at the strict 95% confidence level and an additional nine calves to two males at the 80% confidence level. The majority (92%) of successful males were identified as residents to the embayment, and 46% of offspring were located within the same social group or community as their father. 4. Our results suggest that the size of alliances was the best predictor of reproductive success for males in this population, while the strength of association among allied males, alliance stability and male ranging patterns had little influence. In line with predictions for male alliances formed between unrelated individuals, we found that reproductive skew within alliances was not large. 5. Together, our genetic and behavioural analyses demonstrate that alliance formation between male dolphins is a successful strategy to enhance reproductive output.

Why Is Polygyny More Prevalent in Western Africa? An African Slave Trade Perspective

Polygyny rates are higher in western Africa than in eastern Africa. The African slave trades help explain this difference. More male slaves were exported in the transatlantic slave trades from western Africa, while more female slaves were exported in the Indian Ocean slave trades from eastern Africa. The slave trades led to prolonged periods of abnormal sex ratios, which affected the rates of polygyny across Africa. In order to assess these claims, we present evidence from a variety of sources. We find that the transatlantic slave trades have a positive correlation with historical levels of polygyny across African ethnic groups. We also construct an ethnic group level data set linking current rates of polygyny with historical trade flow data from the transatlantic and Indian Ocean slave trades. We find that the transatlantic slave trades cause polygyny at the ethnic group level, while the Indian Ocean slave trades do not. We provide cross-country evidence corroborating our findings.

Why is Polygyny More Prevalent in Western Africa? An African Slave Trade Perspective

Polygyny rates are higher in Western Africa than in Eastern Africa. The African slave trades explain this diff erence. More male slaves were exported in the trans-Atlantic slave trades from Western Africa, while more female slaves were exported in the Indian Ocean and Red Sea slave trades from Eastern Africa. The slave trades led to prolonged periods of abnormal sex ratios, which impacted the rates of polygyny across Africa. In order to assess these claims, we present evidence from a variety of sources. We find the trans-Atlantic slave trades have a positive correlation with historical levels of polygyny across African ethnic groups. We also construct an ethnic group level data set linking current rates of polygyny with historical trade flow data from the trans-Atlantic and Indian Ocean slave trades. We find the trans-Atlantic slave trades cause polygyny at the ethnic group level, while the Indian Ocean slave trades do not. We provide cross-country evidence corroborating our findings.

The mating system of the Mediterranean monk seal in the Western Sahara

AbstractThe mating system of the Mediterranean monk seal was studied combining the use of diverse technologies. Sexual dimorphism in size was limited. Sexual activity was only observed to occur in the water. The different segments of the population segregated spatially: females, pups, and juveniles aggregated inside two main caves, whose entrances were controlled by a small number (2–3) of territorial males that defended aquatic territories situated at the very mouth of the caves. Other territorial males defended aquatic territories located further away (5–30 km). The tenure of aquatic territories was nonseasonal and spanned several years. Relatedness among pups belonging to the same cohort was low or null, indicating a low level of polygyny, which is not surprising for an aquatically mating phocid with a protracted reproductive season. However, in addition, genetic relatedness showed a remarkable temporal periodicity. These results in combination point to the existence of a complex social structure in this species.

Evolutionary History of Hunter-Gatherer Marriage Practices

BackgroundThe universality of marriage in human societies around the world suggests a deep evolutionary history of institutionalized pair-bonding that stems back at least to early modern humans. However, marriage practices vary considerably from culture to culture, ranging from strict prescriptions and arranged marriages in some societies to mostly unregulated courtship in others, presence to absence of brideservice and brideprice, and polyandrous to polygynous unions. The ancestral state of early human marriage is not well known given the lack of conclusive archaeological evidence.MethodologyComparative phylogenetic analyses using data from contemporary hunter-gatherers around the world may allow for the reconstruction of ancestral human cultural traits. We attempt to reconstruct ancestral marriage practices using hunter-gatherer phylogenies based on mitochondrial DNA sequences.ResultsArranged marriages are inferred to go back at least to first modern human migrations out of Africa. Reconstructions are equivocal on whether or not earlier human marriages were arranged because several African hunter-gatherers have courtship marriages. Phylogenetic reconstructions suggest that marriages in early ancestral human societies probably had low levels of polygyny (low reproductive skew) and reciprocal exchanges between the families of marital partners (i.e., brideservice or brideprice).DiscussionPhylogenetic results suggest a deep history of regulated exchange of mates and resources among lineages that enhanced the complexity of human meta-group social structure with coalitions and alliances spanning across multiple residential communities.

Polygyny, census and effective population size in the threatened frog, Rana latastei

AbstractEffective population size (Ne) is a key determinant of genetic diversity of populations. In amphibians, the ratio effective population size/census size (Ne/N) is often very low, raising concerns for the long‐term persistence of genetic diversity in isolated populations. It has been proposed that the phenomenon of ‘genetic compensation’ increases the ratio Ne/N in small populations, but the underlying mechanisms are poorly understood. Polygyny can decrease Ne/N because of the negative relationship between polygyny and Ne. We used genetic information (microsatellites) to evaluate the relationship between census size, polygyny and Ne in populations of the threatened Italian agile frog Rana latastei. We reconstructed parentage in tadpoles from nine populations with eight to 32 breeding females, using a likelihood‐based method; we analysed simulated datasets with known properties to confirm the reliability of this approach in reconstructing polygyny. Furthermore, we estimated Ne using approximate Bayesian computation. The level of polygyny differed strongly among populations (average number of mates per breeding male: 2–6.4). Polygyny was greater in populations with larger census sizes. Moreover, variance in male mating success was larger in large populations. Effective population size increased with population size, but was negatively related to polygyny; as polygyny increased in large populations, this was associated with reduced Ne/N. In polygynous species, increasing levels of polygyny in large populations may explain the low Ne/N values, with important implications for the conservation of genetic diversity and for long‐term population persistence.