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In polygynous ungulates, males are often larger than females and bear more elaborate/larger weapons. Quantifying sexual dimorphism in different traits could provide insights into species-specific evolutionary pathways of sexual selection. Concerning the combination of secondary sexual traits, we found that Himalayan tahr (Hemitragus jemlahicus) is unique among the ~20 species in the tribe Caprini, as its body mass dimorphism is ~2-fold greater than the dimorphism in horn size, whereas horn shape appears to be near-monomorphic. Whilst horns show the same growth rate in both sexes, body mass increases faster in males. Considering age variation, dominant, golden-ruffed males are also heavier than brown-ruffed, lower-ranking males. Unlike most bovids, male–male competition in tahr does not seem to have influenced weapon development, suggesting a lower importance of horns in male–male competition compared to body mass, as their unritualized combat style also suggests. Our study highlights alternative evolutionary pathways occurring in the Caprinae, where intraspecific signals involve different traits, from weapons to pelage features. Accordingly, male tahr use their ruff colour as an 'honest' signal of rank. [ABSTRACT FROM AUTHOR]

Understanding what processes shape the formation of species' geographic range limits is one central objective linking ecology and evolutionary biology. One potentially key process is sexual selection; yet, theory examining how sexual selection could shape eco-evolutionary dynamics in marginal populations is still lacking. In species with separate sexes, range limits could be shaped by limitations in encountering mates at low densities. Sexual selection could therefore modulate mate limitation and resulting extinction–colonization dynamics at range margins, through evolution of mate encounter ability and/or mate competition traits, and their demographic consequences. We use a spatially explicit eco-genetic model to reveal how different forms of sexual selection can variably affect emerging range limits. Larger ranges emerged when sexual selection acted exclusively on traits increasing mate encounter probability, thus reducing female's mate limitation toward the range margins. In contrast, sexual selection via mate competition narrowed range limits due to increased trait-dependent mortality in males and elevated mate limitation for females. When mate encounter coevolved with mate competition, their combined effects on range limits depended on the mating system (polygyny vs. monogamy). Our results demonstrate that evolution of species' ranges may be importantly shaped by feedbacks between sexual selection and spatial population demography and dynamics. [ABSTRACT FROM AUTHOR]

Female spiders and praying mantises are renowned for their cannibalism of male partners before, during, or after mating. While several hypotheses have been proposed to explain species-specific examples of sexual cannibalism, much variation remains unexplained, including why the timing of cannibalism varies across taxa. Here, I outline how sexually cannibalistic behavior could evolve via sexually antagonistic selection as a type of behavioral resistance to male-imposed mating costs, and how such a generalizable interpretation provides a framework for understanding the evolution of both sexual cannibalism in females and anti-cannibalistic traits in males. I discuss how differences between mating systems that physiologically constrain males to mate only once (monogyny) or twice (bigyny) and systems where the sexes can potentially mate multiply (polygyny and polyandry) are likely to influence how sexual conflict shapes cannibalistic behavior. I review key examples from the literature that suggest how sexually cannibalistic behavior might function as a female resistance trait and provide comprehensive predictions for testing this hypothesis empirically. [ABSTRACT FROM AUTHOR]

In polygynous systems, such as that exhibited by reindeer Rangifer tarandus , mate choice can be difficult to disentangle from male intrasexual competition because male behavior may constrain female choice. Multiple mating may provide an avenue for female mate choice, though it is difficult to identify using behavioral estimators alone. Molecular techniques address this issue by affording ecologists an opportunity to reassess mating systems from a genetic perspective. We assessed the frequency and possible explanations for multiple mating in reindeer using a genetic approach to determine the success of observed copulations in a semi-domesticated herd in Kaamanen, Finland. Behavioral and genetic data were synthesized with population characteristics over a 7-year period to test the hypothesis that, if present, polyandry in reindeer is driven by sexual harassment from sub-dominant males. We observed multiple mating in 42% of females, with as many as 60% exhibiting multiple mating in certain years. We found no evidence that multiple mating resulted from sexual harassment by sub-dominant males, suggesting that it is likely a deliberate strategy among females. Conversion rate of copulations into paternities varied with male size, with smaller males more likely to experience mismatch than larger males. Female preference for larger males persisted despite the occurrence of multiple mating, possibly suggesting a mechanism for cryptic post-copulatory selection. We suggest further research to delineate the possible influence of cryptic post-copulatory selection and multiple mating to defend against infertility in exhausted males. [ABSTRACT FROM AUTHOR]

Burrowing rodents display diverse patterns of social organization, ranging from solitary to group living. Differences in social organization are often inferred from patterns of space use, particularly differences in the degree to which individual home ranges overlap. Here, we characterize patterns of space use in a poorly studied species of burrow-dwelling echimyid rodent, the Broad-headed Spiny Rat (Clyomys laticeps). Specifically, we use radiotelemetry studies of a free-living population in Parque Estadual da Serra de Caldas Novas (Goiás, Brazil) to evaluate previous, apparently contradictory reports suggesting that this species is both solitary and social. A total of 20 adult (12 females, 8 males) C. laticeps were monitored via telemetry during two consecutive cycles of annual wet and dry seasons. The resulting data indicate that although overlap of individual home ranges was common, co-occurrence of adults in time and space was rare and was limited to male–female pairs, a pattern that is most consistent with a solitary lifestyle in which individuals occupy distinct burrow systems. Neither sex nor season affected spatial overlap; this outcome is consistent with evidence suggesting that reproduction in this species occurs throughout the year. Although home ranges for males were larger than those for females, areas occupied by both males and females overlapped with multiple opposite-sex individuals, making it difficult to determine from spatial data whether the study population was polygynous or polygynandrous. While genetic data are needed to characterize fully the mating system of these animals, our analyses provide the first detailed information regarding spatial relationships in C. laticeps , thereby allowing more accurate placement of this species within a larger, comparative behavioral framework and facilitating efforts to identify factors contributing to social diversity among burrow-dwelling rodents. [ABSTRACT FROM AUTHOR]

Polyandry can profoundly affect the strength of pre-copulatory sexual selection acting on males because each additional mate acquired by a female means that, all else being equal, a male's paternity share declines. However, accruing additional mates could benefit male fitness if males with greater mating success also tend to have less promiscuous females as partners. If this is indeed the case, then males should experience strong sexual selection to acquire more mates. We tested these predictions by collecting detailed mating data on male and female Cook Strait giant weta (Deinacrida rugosa) in the wild via daily radio tracking. Our sexual network-based approach indeed revealed that the most polygynous male D. rugosa mated the least polyandrous females. This finding therefore suggests that the most successful males likely face lower intensities of sperm competition and so should be selected to accrue more mates. Further, our selection analysis revealed significant pre-copulatory sexual selection on males with those having relatively smaller body size, lighter body mass, and longer legs accruing more mates than otherwise. Thus, it appears that both pre- and post-copulatory episodes of sexual selection reinforce the same male phenotype. [ABSTRACT FROM AUTHOR]

Habitat fragmentation is considered an important threat to biodiversity, increasing species exposure to edge effects. The Brazilian Cerrado savanna is considered a biodiversity hotspot and has been converted to small, isolated fragments due to human activities. Ant communities and colony survivorship are known to be affected by edge effects in Cerrado, but to date there is no information on the genetic diversity of ant colonies at the edge of fragmented areas. Here, we investigate if colony genetic diversity and structure of Odontomachus chelifer (Latreille) ants (Hymenoptera: Formicidae) are subject to edge effects in a Cerrado reserve in southeast Brazil. Using microsatellites, we evaluated the number of breeders (queens and males) and the genetic diversity in O. chelifer colonies located in the interior versus edge of a Cerrado fragment. All O. chelifer nests had multiple queens, which presented a low mating frequency. The number of breeders and most estimates of genetic diversity did not differ between colonies at the edge versus interior of the fragment. Genetic structure was not influenced by nest location as well. However, we detected a small and positive increase in the observed heterozygosity in colonies located at fragment edges. High heterozygosity is thought to be particularly important in fast-changing environments, such as edges, providing an advantage for genetic diversity. Further investigation is needed to assess in greater detail how habitat loss affects O. chelifer biology. Our study is a first step toward elucidating edge effects on genetic diversity of ant colonies, a topic still poorly explored in tropical environments. [ABSTRACT FROM AUTHOR]

Evidence of an association between cooperative breeding systems and average coefficients of relatedness between group members in vertebrates have led to increased interest in the social and ecological factors affecting average kinship within groups. Previous studies have suggested that polygynous mating systems and high degrees of male reproductive skew increase average relatedness because they increase the proportion of offspring born in each group that are paternal siblings. Although this may be the case in semelparous organisms, in many multiparous polygynous animals, intense competition between males shortens the breeding tenure of males and leads to their frequent replacement by competitors which reduces paternal relatedness and average kinship between members of multigenerational groups. Here, we explore the interaction between male reproductive skew and the frequency of turnover in breeding males and its effects on within-group relatedness. Our theoretical model shows that increases in rates of dominance turnover in polygynous systems can offset the positive effect of male skew on relatedness between group members within seasons, showing that polygynous mating systems will not necessarily lead to significant increases in average relatedness, especially in species where there is extensive overlap between generations among group members. [ABSTRACT FROM AUTHOR]

A widely held principle in behavioral ecological research is that polygynous social systems evolve either by direct male defense of females or male defense of resources, although which of these mechanisms applies in particular species is rarely examined experimentally. We tested the relative importance of female versus resource defense in polygynous territorial male collared lizards (Crotaphytus collaris). Using a novel experimental design, we temporarily removed some of the resident females from male territories to create a female-free removal zone, whereas resident females were left intact within a non-removal zone. We then compared activity of males within each zone during three experimental phases; before we removed females, for two days when females were absent, and the day after return of females. If males defend females directly, we expected them to adjust the location of their patrol and display within removal and non-removal zones depending on the presence/absence of females, whereas we expected no such change if males defend resources. Male activity in the removal zone generally decreased when females were removed but then increased when females were replaced, whereas we observed the opposite pattern in the non-removal zone. The observed shifts in the location of patrol and display in response to the presence/absence of females, while resources remained constant, indicate that polygynous male collared lizards defend females directly. Our results suggest that male collared lizards take advantage of strong female philopatry to relatively small areas by focusing their patrol and display activities where potential mates reside. [ABSTRACT FROM AUTHOR]

Previous studies have reported that males augment their reproductive success by increasing the number of females with which they copulate, and that such copulations are not energetically demanding in terms of trivial sperm production costs. However, we now know that males do pay reproductive costs. As males mate successively, a reduction in the performance of copulatory behaviours would be expected, as well as in the number of sperm transferred. Here we compared the duration of courtship, mating and post-insemination phase, the number of genital and non-genital copulatory courtship occurrences, and the number of sperm transferred in successive matings in Holocnemus pluchei spider males. As matings increased in males, there was no effect on the duration of courtship, mating or post-insemination phase. Interestingly, genital copulatory courtship varied in successive copulations depending on male size, but there was no change in the number of sperm transferred. In addition, the occurrence of non-genital copulatory courtship decreased along successive copulations. The negative effects of successive matings on copulatory courtship indicate that these behaviours are costly for males, except for the number of sperm transferred. Our research lays the foundation for future studies on male costs as a function of mating history in spiders. [ABSTRACT FROM AUTHOR]

Kin selection plays a major role in the evolution of cooperative systems. However, many social species exhibit complex within‐group relatedness structures, where kin selection alone cannot explain the occurrence of cooperative behavior. Understanding such social structures is crucial to elucidate the evolution and maintenance of multi‐layered cooperative societies. In lamprologine cichlids, intragroup relatedness seems to correlate positively with reproductive skew, suggesting that in this clade dominants tend to provide reproductive concessions to unrelated subordinates to secure their participation in brood care. We investigate how patterns of within‐group relatedness covary with direct and indirect fitness benefits of cooperation in a highly social vertebrate, the cooperatively breeding, polygynous lamprologine cichlid Neolamprologus savoryi. Behavioral and genetic data from 43 groups containing 578 individuals show that groups are socially and genetically structured into subgroups. About 17% of group members were unrelated immigrants, and average relatedness between breeders and brood care helpers declined with helper age due to group membership dynamics. Hence the relative importance of direct and indirect fitness benefits of cooperation depends on helper age. Our findings highlight how both direct and indirect fitness benefits of cooperation and group membership can select for cooperative behavior in societies comprising complex social and relatedness structures. [ABSTRACT FROM AUTHOR]

The neotropical manakins (family Pipridae) provide a great opportunity for integrative studies of sexual selection as nearly all of the 51 species are lek-breeding, an extreme form of polygyny, and highly sexually dimorphic both in appearance and behavior. Male courtship displays are often elaborate and include auditory cues, both vocal and mechanical, as well as visual elements. In addition, the displays are often extremely rapid, highly acrobatic, and, in some species, multiple males perform coordinated displays that form the basis of long-term coalitions. Male manakins also exhibit unique neuroendocrine, physiological, and anatomical adaptations to support the performance of these complex displays and the maintenance of their intricate social systems. The Manakin Genomics Research Coordination Network (Manakin RCN, https://www.manakinsrcn.org) has brought together researchers (many in this symposium and this issue) from across disciplines to address the implications of sexual selection on evolution, ecology, behavior, and physiology in manakins. The objective of this paper is to present some of the most pertinent and integrative manakin research as well as introducing the papers presented in this issue. The results discussed at the manakin symposium, part of the 2021 Society for Integrative and Comparative Biology Conference, highlight the remarkable genomic, behavioral, and physiological adaptations as well as the evolutionary causes and consequences of strong sexual selection pressures that are evident in manakins. [ABSTRACT FROM AUTHOR]

The harvester ant genus Pogonomyrmex is endemic to arid and semiarid habitats and deserts of North and South America. The California harvester ant Pogonomyrmex californicus is the most widely distributed Pogonomyrmex species in North America. Pogonomyrmex californicus colonies are usually monogynous, i.e. a colony has one queen. However, in a few populations in California, primary polygyny evolved, i.e. several queens cooperate in colony founding after their mating flights and continue to coexist in mature colonies. Here, we present a genome assembly and annotation of P. californicus. The size of the assembly is 241 Mb, which is in agreement with the previously estimated genome size. We were able to annotate 17,889 genes in total, including 15,688 protein-coding ones with BUSCO (Benchmarking Universal Single-Copy Orthologs) completeness at a 95% level. The presented P. californicus genome assembly will pave the way for investigations of the genomic underpinnings of social polymorphism in the number of queens, regulation of aggression, and the evolution of adaptations to dry habitats. [ABSTRACT FROM AUTHOR]

Eusocial insects tend to present low genetic diversity (GD) within colonies, which can increase with the co-occurrence of multiple queens (polygyny) or with multiple mating by a single queen (polyandry). Therefore, it is important to elucidate how these strategies influence GD, which in turn mediate population ecology and how organisms respond to their environment. We studied two carpenter ant species from the Brazilian savanna, Camponotus renggeri and C. rufipes. Using microsatellites, we evaluated the number of breeders, the genetic relatedness and the contribution of polygyny and polyandry to GD within colonies. Both species exhibited facultative polygyny. In C. renggeri , low related queens formed colonies jointly and present low mating frequency. In this species, colony GD increased with the number of queens. Contrastingly, closely related queens of C. rufipes formed polygynous colonies, exhibiting high mating frequency. In C. rufipes , both queens and males contributed to colony GD. Despite the differences, the two species have similar GD at the colony scale. Under low mating frequency, our data support that polygyny has evolutionary importance for increasing GD in ant colonies, a mechanism mainly conferred to polyandry. Although the impact of GD in variable ecological and adaptive contexts remains uncertain, this study highlights how distinct reproductive strategies may generate similar patterns of GD in ants. [ABSTRACT FROM AUTHOR]

Why females pair with already mated males and the mechanisms behind variation in such polygynous events within and across populations and years remain open questions. Here, we used a 19-year data set from a pied flycatcher (Ficedula hypoleuca) population to investigate, through local networks of breeding pairs, the socio-ecological factors related to the probability of being involved in a polygynous event in both sexes. Then, we examined how the breeding contexts experienced by individuals shaped the spatial and temporal separation between broods of polygamous males. The probability of polygyny decreased with the distance between nests. Indeed, secondary females were often close neighbors of primary females, although the distance between both nests increased slightly with increasing synchrony between them. The probability of polygyny was also related to the breeding time of individuals because early breeding males were more likely to become polygynous with late-breeding females. Throughout the season, there was substantial variation in the temporal separation between primary and secondary broods, and this separation was, in turn, related to the breeding asynchrony of the polygamous males (in the primary nest) relative to the neighbors. Polygynous males that bred late relative to their neighbors had a short time window to attract a second female and, thus, the breeding interval between their primary and secondary broods was reduced. Overall, the spatial proximity between polygynous males' broods and, if the opportunity existed, their temporal staggering are compatible with a male strategy to maximize paternity and reduce the costs of caring for two broods, though the effect of female's interest, either primary or secondary, cannot be fully ruled out. We highlight that a comprehensive assessment of the breeding contexts faced by individuals is essential to understand mating decisions and reconcile the discrepancies raised by previous work on social polygyny. [ABSTRACT FROM AUTHOR]

The interaction between males and females (adults and/or larvae) of Caecognathia sp., a parasite of fishes, was studied in the laboratory to investigate the attraction of the opposite sexes and the induction of metamorphosis to adults. We reared the third-stage larvae collected by a light trap to develop them into adults. Their sex ratio was 104 males to 100 females, suggesting that females and males have similar fitness. The attraction experiments using an experimental chamber demonstrate that adult males attract female larvae that were also attracted by the dichloromethane extract of males but not the female extract. The males also induce the praniza females to develop into adults. When there are no males present, females can prolong the larval phase and moreover can spontaneously start to develop into adults after the prolonged larval phase. As in other isopods, the gnathiid female is supposed to be able to copulate immediately after metamorphosis, and the timing of metamorphosis is therefore crucial. The prolongable larval phase in the gnathiid female could be an adaptation to a polygynous, semelparous system and brief copulatory phase after the metamorphosis into adult female. [ABSTRACT FROM AUTHOR]

In 2001, Nasutitermes corniger (Motschulsky), common name conehead termite, were discovered near a marina in Dania Beach, FL, where the invasive species was probably transported from its native range in Central and South America or the Caribbean. In January 2016, an infestation was found in Pompano Beach, Florida, approximately 21 km north of the Dania Beach population. This study compares variants in seven microsatellite loci across specimens from 11 nests in Dania Beach and 8 nests in Pompano Beach. Results are consistent with all N. corniger in both locations being descendants of a single introduced colony, spreading within Broward County, FL through human transport of infested materials. No more than four alleles were found at any of the seven microsatellite loci analyzed, inferring that a single Queen and King, or multiple sibling reproductives descended from a monogamous pair, headed the colony that arrived in Florida. The potential economic and environmental impacts of this invasive termite are enormous due to its broad diet, including agricultural crops and orchards, native and ornamental plants, natural landscapes, and structures. Conspicuous tunnels and aboveground nests are the key aspects of N. corniger biology that render colonies vulnerable to discovery and control. The now proven ability of N. corniger to establish breeding populations in the United States, to cause extensive property and landscape destruction, and to spread by human transport underscores the need for continued aggressive efforts toward eradication of known infestations as well as quick operational actions the next time invasive N. corniger are discovered. [ABSTRACT FROM AUTHOR]

Abstract: The recent advances of new genomic technologies have enabled the identification and characterization of sex chromosomes in an increasing number of nonmodel species, revealing that many plants and animals undergo frequent sex chromosome turnovers. What evolutionary forces drive these turnovers remains poorly understood, but it was recently proposed that drift might play a more important role than generally assumed. We analysed the dynamics of different types of turnovers using individual‐based simulations and show that when mediated by genetic drift, turnovers are usually easier to achieve than substitutions at neutral markers, but that their dynamics and relative likelihoods vary with the type of the resident and emergent sex chromosome system (XY and/or ZW) and the dominance relationships among the sex‐determining factors. Focusing on turnovers driven by epistatically dominant mutations, we find that drift‐mediated turnovers that preserve the heterogamety pattern are 2–4× more likely than those along which the heterogametic sex changes. This ratio nevertheless decreases along with effective population size and can even reverse in case of extreme polygyny. This can be attributed to a ‘drift‐induced’ selective force, known to influence transitions between male and female heterogamety, but which according to our study does not affect turnovers that preserve the heterogametic sex. [ABSTRACT FROM AUTHOR]

Males are often expected to benefit from mating with multiple females; however, in species where females are highly cannibalistic, achieving multiple matings may be a difficult task. When males employ strategies to avoid sexual cannibalism, it is presumed that there are benefits associated with survival--e.g. increased fitness associated with more mating opportunities. In the nursery web spider (Pisaurina mira), all males attempt to avoid sexual cannibalism by wrapping female's legs in silk prior to copulation. If males are unsuccessful, however, there are fitness benefits obtained by both sexes that are associated with their consumption--heavier and longerlived offspring. Regardless, we hypothesize that P. mira males can achieve higher fitness by avoiding sexual cannibalism. Specifically, we predict that males can and will mate with multiple females and that mating with multiple partners benefits males. To test these predictions, we conducted 1) laboratory assays to determine if males will mate with multiple females and 2) field assays to determine natural sex ratios, density, and female and male movement patterns. Finally, 3) we used our field data to construct a mathematical model that predicts natural male encounter rates with potential mates. We found that male P. mira will mate with multiple females and that increased mating numbers leads to increased offspring production. Our model suggests that under natural conditions, males have the opportunity to mate with multiple females. Overall, our findings strongly suggest that P. mira males are likely to benefit from avoiding sexual cannibalism through increased mating opportunities. [ABSTRACT FROM AUTHOR]

Polygyny is a common mating system in lizards. In polygynous species, males usually display status badges and use weaponry to prevent reproductive access of competitors to mates. Such secondary sexual traits are frequently linked to signalling costs and the handicap principle is widely used to explain the potential reduction of fitness components. Here, we (1) evaluate the allometric relationship of two known secondary sexual traits with body size: head width (a weapon) and the total coloured lateral area (an ornament), (2) assess the effects of such traits on male and female survival probabilities and (3) evaluate patterns of linear and quadratic selection of both traits for the whiptail lizard Cnemidophorus cf. ocellifer. We detected evidence of sexual dimorphism in both traits, but contrary to our expectations, both sexes presented hyperallometric growth of both weapon size and badge size. We found no support for the handicap principle since no detrimental effects of secondary sexual traits were found on individual survival probability. Furthermore, no evidence of directional selection, neither stabilizing nor disruptive selection was found. The costs of faking signals in male animal contests could maintain the honesty, as previously suggested. [ABSTRACT FROM AUTHOR]

While polygyny is the dominant mating system in mammals, it is increasingly recognized that promiscuity occurs in most species. Using a long-term genetic and space-use data set, we documented the mating system for 2 sedentary and uniparous species of tree sloths, brown-throated three-toed (Bradypus variegatus) and Hoffmann’s two-toed (Choloepus hoffmanni) sloths. We predicted that the life history of these species facilitates female strategies that promote mating with multiple males across breeding seasons, and shape central features of the mating system in tree sloths. We found that many female sloths mated with different males during our study: 70% of female B. variegatus and 50% of female C. hoffmanni switched mates among years at least once during our study. Our observations of individual movements suggested that females employed 2 strategies that appeared to influence mate switching across breeding seasons: 1) selecting a male from a pool of males in their activity center and 2) mating with different males by shifting their home ranges during estrus. Collectively, our findings suggest that individual variation in female reproductive strategies contributes to shaping the mating systems for a sedentary mammal like sloths and highlights the need for long-term studies to effectively capture the mating systems of mammals with slow life histories. [ABSTRACT FROM AUTHOR]

Although much work has analysed how individual behavioural plasticity and adaptations to ecological conditions (e.g. density, sexratio, resource distribution) shape mating systems, few studies have assessed the relative importance of multiple factors in explaining why mating systems vary from one sub-population to the next even in the same ecological conditions. Differences among groups in their phenotypic composition, such as their average phenotype, within-group variation in phenotype, or the phenotype of individuals occupying key social roles might shape the mating system emerging at the group level and explain some portion of mating system variability. Here, we take advantage of the mating system flexibility of stream water striders (Aquarius remigis) to investigate how phenotypic composition affects the mating system emerging at the group level. Groups exhibited stable mating systems varying from scramble polygyny with intense sexual conflict, to systems with a clear dominant male guarding a "harem" of females. We found that male size asymmetries and the personality of the largest individuals within groups had important effects on the group's mating system. The group's average male and female personality, size, and social plasticity also explained some of the variation in mating systems. Our study is one of the first to quantify significant relationships between group phenotypic composition and mating system variability. [ABSTRACT FROM AUTHOR]

Mating systems can vary within-species but the environmental drivers and behavioral mechanisms underlying this variation are seldom investigated experimentally. We experimentally assessed how individual behavioral plasticity in response to changes in pool and group size resulted in fundamental shifts in mating systems in water striders. We observed the same animals in larger and smaller pools, mimicking variation in pool size in natural streams, and observed a rapid, reversible change in the entire mating system. In large pools, striders exhibited scramble promiscuity with intense sexual conflict. Most males were active, harassing and driving females into hiding. Matings were frequent and typically lasted for more than 100 min. In contrast, when placed in small pools, the same animals often exhibited harem polygyny where the largest male drove other males into hiding, but allowed females to be relatively active. Matings were less frequent and of much shorter duration. Harem polygyny took several days to emerge after animals were moved to small pools, while these same animals returned to scramble promiscuity within hours after being moved to larger pools. Such variability in mating systems likely has important implications for the evolution of individual mating tactics. [ABSTRACT FROM AUTHOR]

Evolutionary theory predicts that when intrasexual competition is intense, risky behaviors can evolve if they enhance reproductive success. Here we tested the idea that polygynous males exhibit predictable variation in risk-taking during intense competition for mates. We conducted an observational study of a village weaverbird (Ploceus cucullatus) breeding colony, and video recorded synchronous fleeing events, a common predator avoidance behavior. Males adjusted their flight from the colony according to the amplitude (loudness) and Wiener entropy (harshness) of conspecific alarm calls during a perceived threat. Males also varied in how often they fled the colony. Specifically, in line with predictions based on the value of a male's territory, males with more nesting females were less likely to flee, and returned sooner if they did flee, compared to males with fewer nesting females. Males with a nest under construction also returned to their nests sooner than males without constructions in progress, consistent with predictions based on nest sabotage by conspecifics. These results suggest that male weavers perform a cost-benefit analysis in real time in order to decide how to respond to a perceived threat, with self-protection trading off with the security of one's territory and mates. [ABSTRACT FROM AUTHOR]

Demographic changes in populations, such as skewed sex ratios, are of concern to conservationists, especially in small populations in which stochastic and other events can produce declines leading to extirpation. We documented a decline in one of the few remaining populations of Southwestern Willow Flycatcher (Empidonax traillii extimus) in southern California, USA, which dropped from 40 to 5 adults between 2000 and 2015. Declines were unequal between sexes (94% for males, 82% for females). Adult sex ratios were female-biased in 10 of 16 yr. The proportion of paired males that were polygynous ranged from 0% to 100%, depending on the ratio of females to males in the adult population. Some males paired with up to 5 females simultaneously. We investigated the role of nestling sex ratio in the female-biased adult sex ratio by using genetic techniques to determine sex from blood samples collected from 162 nestlings in 72 nests from 2002 to 2009. Both population-level and within-brood nestling sex ratios were female- biased, and were not influenced by nest order (first or subsequent), parental mating type (monogamous or polygynous), or year. Disproportionately more females than males were recruited into the breeding population, mirroring nestling and fledgling sex ratios. It thus appears that a skewed nestling sex ratio has contributed to a female- biased adult population, which in turn has influenced mating behavior. We propose that the capacity for polygyny, which generally occurs at low levels in Southwestern Willow Flycatchers, has allowed this population to persist through a decline that might otherwise have resulted in extinction. [ABSTRACT FROM AUTHOR]

Observations of male mate choice are increasingly common, even in species with traditional sex roles. In addition, female traits that bear the hallmarks of secondary sexual characters are increasingly reported. These concurrent empirical trends have led to the repeated inference that, even under polygyny, male mate choice is a mechanism of sexual selection on female traits. It is often either assumed or argued that in these cases females are competing for males of superior 'quality'; females might experience sexual selection under polygyny if they compete for mates that provide either direct or indirect benefits. However, the theoretical foundation of this testable hypothesis remains largely uninvestigated. We develop a population genetic model to probe the logic of this hypothesis and demonstrate that, contrary to common inferences, male mate choice, variation in male quality (in the form of a direct fecundity benefit to females), and female ornamentation can coexist in a population without any sexual selection on female ornamentation taking place at all. Furthermore, even in a 'best case scenario' where high quality males with a preference for ornamented females are able to mate disproportionately more often with them, the evolution of female traits by sexual selection may be relatively weak. We discuss the implication of these findings for ongoing empirical and theoretical research on the evolution of sexual-signaling in females. [ABSTRACT FROM AUTHOR]

The distribution of resources should influence mate availability and the costs and benefits of pursuing different mating strategies. Where resources are dispersed, males may be constrained in the extent to which they can monopolize more than 1 partner, resulting in social and genetic monogamy. There is abundant correlational evidence that resource distribution influences social and mating systems, but experiments that demonstrate a causal link between these variables are relatively rare. Here, we used a replicated experiment involving 160 animals to examine how the distribution of a key resource, crevice sites used as nesting habitat, shapes social and mating behavior of a family living lizard, Liopholis whitii. The distribution of crevice sites had significant effects on several important aspects of the social and mating system. When habitat was aggregated, adults had larger home ranges and overlapped with more individuals of the opposite sex, resulting in increased opportunity for social polygyny. Aggressive female territoriality appears to impose upper limits on opportunities for polygyny by restricting female-female home range overlap. Despite this, males in aggregated habitats still formed polygynous social groups more often than males in dispersed habitat. Aggregated habitat also increased the opportunity for sexual selection, resulting in greater variance in male reproductive success and a steeper Bateman gradient compared with males occupying dispersed habitat. These effects were independent of the increase in social polygyny. Overall, our study is consistent with the hypothesis that habitat structure is fundamentally important to the evolution of social and mating systems. [ABSTRACT FROM AUTHOR]

In polygynous mammals, mature males are usually much heavier than females. Competition for females is intense, and few males reproduce. Given the importance of the male's body size for the reproduction and social life of these species, levels of sexual dimorphism were studied in 27 species of polygynous terrestrial cetartiodactyls at the 3 most significant stages of development: birth, 6 months of age, and adulthood. Overall, there were 3 different types of changes in male-to-female (M/F) mass ratios between birth and adulthood, corresponding to the 3 categories of adult dimorphism. The change in mass ratio between birth and 6 months of age was inversely correlated to the degree of dimorphism at birth. Most adult dimorphism was acquired after weaning. On the whole, postnatal maternal care seems to have no or even an inverse effect on the evolution of dimorphism, which is apparently not consistent with the assumption of greater maternal investment in male than in female offspring among polygynous mammals. [ABSTRACT FROM AUTHOR]

In leks, females are often attracted to males bearing costly secondary sexual traits that are thought to honestly signal male genetic quality. The Good Genes Hypothesis predicts 1) consistent male attractiveness across a variety of environments, 2) directional selection on male attractiveness, and 3) a positive correlation between paternal attractiveness and offspring fitness. We tested these predictions in a natural population of the Italian tree frog, Hyla intermedia. We recorded the calling activity of all males at a small lek for 2 breeding seasons and we carried out an incomplete factorial breeding experiment to test for an association between paternal attractiveness and offspring fitness. Because we found no evidence for temperature-dependent genotype-by-environment interactions in calling properties, we provided evidence that male attractiveness was consistent across different thermic conditions (first prediction). Moreover, in 1 breeding season, we showed a statistically significant association between mating success and call rate, call duration, and spectral properties, suggesting that multivariate directional selection did act on these properties (second prediction). However, we found no conclusive evidence for either accepting or rejecting our third prediction. Indeed, although paternal call rate showed a marginally significant, negative correlation with offspring age at metamorphosis, the other call properties did not show any statistically significant association with offspring fitness. These results suggest that, in our study population, alternative mechanisms, such as male-male competition for signal detectability, might be a stronger driving force for the evolution of male costly displays than good genes. [ABSTRACT FROM AUTHOR]

The use of alternative reproductive tactics (ARTs) is widespread in animals. Males of some species may change tactics depending on age, body condition and social environment. Many bat species are polygynous where a fraction of males only have access to fertile females. For polygynous bats, knowledge of the reproductive success of males using different ARTs is scarce, and it remains unclear how age of males is related to switching decisions between social statuses. We studied a large captive population of Carollia perspicillata, where males are either harem holders, bachelors or peripheral males. Using a multistate procedure, we modelled the age-related switches in reproductive tactics and in survival probability. From the model, we calculated the reproductive success and the frequencies of males displaying different reproductive tactics. As in mammals, the switch between social statuses is often related to age, we predicted that the transition probability of bachelor and peripheral males to harem status would increase with age. We show, however, that social status transition towards a harem holding position was not related to age. Reproductive success changed with age and social status. Harem males had a significantly higher reproductive success than bachelor males except between a short period from 3.8 to 4.4 years of age where success was similar, and a significantly higher reproductive success than peripheral males between 2.6 and 4.4 years of age. Harem males showed a clear decrease in the probability of maintaining social status with age, which suggests that senescence reduces resource holding potential. [ABSTRACT FROM AUTHOR]

Although ecologists and managers have been increasingly preoccupied with the crowding consequences of overabundant herbivores, the potential role of territorial behavior as a self-regulatory agent has seldom been considered. The crowding mechanism underlies most regulation models in ungulate demography and relies on the assumption of an equal share of available supplies among individuals. In contrast, in territorial systems dominant individuals monopolize resources, predicting deviations from the expected demographic outcomes under the crowding approach. We used empirical data on a protected guanaco (Lama guanicoe) population to test competing hypotheses about crowding and territorial defense as the mechanism driving density regulation in a resource-defense polygyny ungulate. We assessed density dependence on recruitment at different spatial scales and density effects on preferred forage availability. The guanaco density inside the reserve increased rapidly and then stabilized during the last third of the study period. The absence of density effects on recruitment questions the existence of crowding mechanisms. Guanaco numbers stabilized below the environmental carrying capacity predicted by an equal share of available forage, supporting territorial defense as the mechanism shaping population density in the area. Variability in forage cover was independent from changes in population density, rejecting crowding effects on food supplies. These results are consistent with the hypothesis of a self-regulatory mechanism derived from resource defense that may prevent overgrazing. Our findings suggest that other factors in addition to food availability may determine the demographic carrying capacity under resource defense systems, stressing the importance of accounting for behavioral traits when addressing management issues. [ABSTRACT FROM AUTHOR]

Traits of interest to evolutionary biologists often have complex genetic architectures, the nature of which can confound traditional experimental study at single levels of analysis. In the fire ant Solenopsis invicta, the presence of a Mendelian 'supergene' is both necessary and sufficient to induce a shift in a fundamental property of social organization, from single-queen (monogyne) to multiple-queen (polygyne) colonies. This selfish genetic element, termed the Social b ( Sb) supergene, contains > 600 genes that collectively promote its fitness by inducing the characteristic polygyne syndrome, in part by causing polygyne workers to accept only queens bearing the Sb element (a behaviour termed 'worker Sb discrimination'). Here, we employ a newly developed behavioural assay to reveal that polygyne workers, many of which bear the Sb element, employ chemical cues on the cuticle of queens to achieve worker Sb discrimination, but we found no evidence for such pheromonally mediated worker Sb discrimination in monogyne workers, which universally lack the Sb element. This polygyne worker Sb discrimination was then verified through a 'green beard' effect previously described in this system. We thus have demonstrated that the Sb element is required both for production of relevant chemical cues of queens and for expression of the behaviours of workers that collectively result in worker Sb discrimination. This information fills a critical gap in the map between genotype and complex phenotype in S. invicta by restricting the search for candidate genes and molecules involved in producing this complex social trait to factors associated with the Sb element itself. [ABSTRACT FROM AUTHOR]

Previous research has shown how religious observances produce religious selves with religious dispositions. Still, more could be done to empirically compare how religious observances encourage men and women to develop distinctively gendered dispositions. Using ethnographic fieldwork at an American mosque and in-depth interviews with American converts to Islam, this paper focuses on how converts contend with accepting religious injunctions around clothing choices and polygyny. This paper demonstrates how the normalization of particular religious observances within specific contexts makes different demands on men and women and in so doing produces gendered religious subjects. Men at my field-site strive to develop a disposition of responsibility that is positioned in opposition to secular masculinity and claimed as being better for women. Women here develop a sacrificial disposition, positioned primarily against Muslim men, and to a lesser extent against non-Muslim women, where they frame their individual sacrifices as necessary for the maintenance of a morally distinct religious order. Individuals thus seek to become religious subjects against the image of non-Muslim Others as well as religious counterparts of the opposite sex. [ABSTRACT FROM AUTHOR]

Polygynous males can change their mating tactics across their lifetime, but information is scarce on the flexibility of this trait within a given season and the relative costs and benefits of using different tactics. Here, we monitored individually marked male reindeer Rangifer tarandus and classified their mating tactics as harem-defense, sneaking, or mixed. The costs of the male reproductive effort were assessed using both direct (i.e. percentage of body mass lost) and indirect measures (i.e. activity patterns such as feeding, standing, and walking), while mating group size and reproductive success were recorded as mating effort benefits. Our results show that reindeer males may switch between the harem-defense and sneaking tactics throughout the same breeding season, providing further support to the notion that reproductive tactics are flexible in ungulates. The costs and benefits of male mating effort vary according to the mating tactic, reaching the highest values in harem-holders and the lowest values in sneaking males. Moreover, males who switched between the sneaking tactic and the harem-defence tactic tended to achieve higher mating success than males who consistently used the least costly tactic. Indeed, all harem-holders successfully sired offspring, whereas only two out of three mixed-tactic males sired one calf, and sneaking males did not sire any calves. In conclusion, our results show that reindeer males can modulate their mating efforts during the same breeding season by switching between the most costly harem-defense tactic and the least costly sneaking tactic, suggesting individual solutions to the balance between reproductive effort and mating opportunities. [ABSTRACT FROM AUTHOR]

Marriage institutions have changed over time, evolving from polygyny to monogamy, and then to serial monogamy (as defined by divorce and remarriage).We propose a unified theory of such institutional changes, where the dynamics of income distribution are the driving force. We characterize the marriagemarket equilibrium in each of the three alternative regimes, and determine which one emerges as a political equilibrium, depending on the state of the economy. In a two-class society, a rise in the share of rich males drives the change from polygyny to monogamy. The introduction of serial monogamy follows from a further rise in the proportion of either rich females or rich males. Monogamy eases the transition to serial monogamy, since it promotes social mobility. [ABSTRACT FROM AUTHOR]

In scramble competition polygyny, male and female mobility may be under strong selection as a result of fitness effects of searching for reproductive resources such as mates, oviposition sites, or resources for egg production. We analyzed the relationship between mating frequency, mobility, and body size in males and females of the chrysomelid beetle Leptinotarsa undecimlineata. We obtained a detailed data set of movement and mating frequency of an entire population (1037 adults) over a full reproductive season using individual tagging and direct behavioral observations. Unlike previous studies, we found a negative relationship between mobility and mating success for both sexes. Size was positively correlated to mating frequency in females, but negatively in males. High male mobility may be the result, and not a cause, of low mating success in scramble mating polygynies where rejected or displaced males switch plants more often searching for mating opportunities. More mobile females may be looking for competition-free oviposition substrate and thus experiencing fewer sexual encounters. [ABSTRACT FROM AUTHOR]

Alternative mating tactics are common among species exhibiting resource defense polygyny. While large territorial males aggressively defend harems, small sneaker males generally invade these harems to mate furtively. The result is a sexual network that provides information on the sperm competition intensity (SCI) faced by males of both morphs. Here, we use metrics derived from the network approach to compare SCI between sneakers and territorials of the male-dimorphic harvestman Serracutisoma proximum. We also tested hypotheses about the influence of harem size and spatial distribution of harems on the SCI faced by territorial males. Sneakers faced, on average, higher levels of SCI than territorials, while the SCI faced by territorials was more variable than that of sneakers. Owners of large harems faced less intense sperm competition than owners of small harems, suggesting that sperm competition is more diluted among females in large harems. At the population level, sneakers concentrated their invasions on neighboring harems that were spatially aggregated. We argue that the spatial distribution of harems is an important element influencing the topology of the sexual network, and that the spatially explicit approach we used here can bring new insights to the study of sperm competition and mating systems in a wide range of organisms. [ABSTRACT FROM AUTHOR]

The reliability and consistency of the many measures proposed to quantify sexual selection have been questioned for decades. Realized selection on quantitative characters measured by the selection differential i was approximated by metrics based on variance in breeding success, using either the opportunity for sexual selection I s or indices of inequality. There is no consensus about which metric best approximates realized selection on sexual characters. Recently, the opportunity for selection on character mean OSM was proposed to quantify the maximum potential selection on characters. Using 21 years of data on bighorn sheep ( Ovis canadensis), we investigated the correlations between seven indices of inequality, I s, OSM and i on horn length of males. Bighorn sheep are ideal for this comparison because they are highly polygynous and sexually dimorphic, ram horn length is under strong sexual selection, and we have detailed knowledge of individual breeding success. Different metrics provided conflicting information, potentially leading to spurious conclusions about selection patterns. I δ, an index of breeding inequality, and, to a lesser extent, I s showed the highest correlation with i on horn length, suggesting that these indices document breeding inequality in a selection context. OSM on horn length was strongly correlated with i, I s and indices of inequality. By integrating information on both realized sexual selection and breeding inequality, OSM appeared to be the best proxy of sexual selection and may be best suited to explore its ecological bases. [ABSTRACT FROM AUTHOR]

The evolution of weaponry occurs less frequently in females than in males and is most often important for protecting ecological resources or offspring rather than winning mates. The purpose of female weapons is often confounded by the presence of similar weapons in males, so cases where only females need weapons provide important tests of our understanding of how and why weapons evolve. In some populations of the ant, Messor pergandei ( Mayr), newly mated queens initiate new nests in social groups that subsequently break down when queens engage in battles for control. The incipient social environment differs geographically, so that lethal fighting occurs in some populations but not others. Consistent with the hypothesis that queens in populations where lethal fighting occurs should show selection for weaponry (broad heads and strong mandibles), we found that heads of queens from sites where lethal fighting occurs were broader than those at sites with non-fighting queens and a site with solitary queens. Evolution of weaponry is specific to queens, because regression results from workers often did not follow this pattern. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 1011-1020. [ABSTRACT FROM AUTHOR]

How polygyny evolved in social insect societies is a long-standing question. This phenomenon, which is functionally similar to communal breeding in vertebrates, occurs when several queens come together in the same nest to lay eggs that are raised by workers. As a consequence, polygyny drastically reduces genetic relatedness among nestmates. It has been suggested that the short-term benefits procured by group living may outweigh the costs of sharing the same nesting site and thus contribute to organisms rearing unrelated individuals. However, tests of this hypothesis are still limited. To examine the evolutionary emergence of polygyny, we reviewed the literature to build a data set containing life-history traits for 149 Palearctic ant species and combined this data set with a reconstructed phylogeny. We show that monogyny is the ancestral state and that polygyny has evolved secondarily and independently throughout the phylogenetic tree. The occurrence of polygyny is significantly correlated with larger colony size, dependent colony founding and ecological dominance. Although polydomy (when a colony simultaneously uses several connected nests) tends to occur more frequently in polygynous species, this trend is not significant when phylogenetic history is accounted for. Overall, our results indicate that polygyny may have evolved in ants in spite of the reduction in nestmate relatedness because large colony size provides immediate ecological advantages, such as the more efficient use of temporal food resources. We suggest that the competitive context of ant communities may have provided the conditions necessary for the evolution of polygyny in some clades. [ABSTRACT FROM AUTHOR]

Knowledge of the demography and habitat requirements of the endangered Golden-cheeked Warbler (Setophaga chrysoparia) is needed for its recovery, including measures of productivity instead of reproductive indices. We report on breeding phenology and demography, calculate model-based estimates of nest survival and seasonal productivity and evaluate support for relationships with forest type, forest edge density, day of year, and year, and determine correspondence in these 2 measures of reproductive success. Males arrived in early March. Females laid the first egg of the first clutch in early April, made up to 5 nesting attempts, and completed nesting by mid-June. The most-supported nest survival model included day of year, proportion of juniper and juniper-oak forest within a 100-m radius of each nest, and the interactive effect of year and forest edge density. The most-supported seasonal productivity model included proportion of each forest type and the interactive effect of year and forest edge density. Seasonal productivity increased from 1.38 to 3.96 fledglings per territory and from 1.38 to 2.40 fledglings per territory across 0.00 to 0.87 and 0.00 to 1.00 proportion of juniper and proportion of juniper-oak forest, respectively. Seasonal productivity ranged from 1.86 to 3.12 fledglings per territory in 2010 and 2004, respectively (mean ± SD = 2.36 ± 0.37). Correlations between nest survival and seasonal productivity were strong when we controlled for the effect of year indicating demographic parameters other than nest survival, particularly renesting, double brooding, and polygyny, made an important contribution to actual seasonal productivity. The similarity in relationships of both measures of reproductive success with forest type and edge density and parallel findings for density with these habitat metrics reported in other studies provide strong rationale for protecting sites with high proportions of juniper and juniper-oak forest and less forest edge to further recovery efforts for the Golden-cheeked Warbler. [ABSTRACT FROM AUTHOR]

Males of polygynous mammalian species may adopt different reproductive tactics to accomplish female fertilization, with dominant males often attaining a higher reproductive success than those adopting alternative breeding tactics. We worked on the largest breeding colony of the South American fur seal to determine its mating system and quantify the breeding success of male reproductive tactics using behavioral data and paternity assignment. We sampled ~50% of reproductive males during the 2010 breeding season and 85% of pups born during the following breeding season. Paternity analyses were made with 10 microsatellite markers, and 80% (n = 36) of the candidate fathers had at least 1 offspring (mean = 2.9, range = 0–13). Paternity was determined for 47% (n = 220) of pups at 80% and 95% confidence levels. We assessed the importance of different behavioral variables (tenure, copulation, and agonistic interactions) and reproductive tactics (territorial/satellite) in South American fur seal male breeding success using generalized linear models. We used regression trees to assess the homogeneity of breeding success within each reproductive tactic. The relatively high variance in South American fur seal male breeding success and the relatively high reproductive synchrony of breeding females and their distinctive pattern of space suggest that the mating system is consistent with a lek. We found that the territorial reproductive tactic was actually composed of 3 distinct categories and that a surprisingly high proportion of territorial males had a lower breeding success than the alternative satellite male reproductive tactics. This is the first study in otariids that has assessed the breeding success of male alternative reproductive tactics.Many male mammals defend mating territories during the breeding season. Some males manage to keep their territories, whereas others, not strong enough to do so, use alternative tactics to access mates. These weaker males are not expected to be as successful in mating. However, we found this is not always true and actually sometimes their alternative tactics turned out to be the best. [ABSTRACT FROM PUBLISHER]

The evolutionary trajectories of reproductive systems, including both male and female multiple mating and hence polygyny and polyandry, are expected to depend on the additive genetic variances and covariances in and among components of male reproductive success achieved through different reproductive tactics. However, genetic covariances among key components of male reproductive success have not been estimated in wild populations. We used comprehensive paternity data from socially monogamous but genetically polygynandrous song sparrows ( Melospiza melodia) to estimate additive genetic variance and covariance in the total number of offspring a male sired per year outside his social pairings (i.e. his total extra-pair reproductive success achieved through multiple mating) and his liability to sire offspring produced by his socially paired female (i.e. his success in defending within-pair paternity). Both components of male fitness showed nonzero additive genetic variance, and the estimated genetic covariance was positive, implying that males with high additive genetic value for extra-pair reproduction also have high additive genetic propensity to sire their socially paired female's offspring. There was consequently no evidence of a genetic or phenotypic trade-off between male within-pair paternity success and extra-pair reproductive success. Such positive genetic covariance might be expected to facilitate ongoing evolution of polygyny and could also shape the ongoing evolution of polyandry through indirect selection. [ABSTRACT FROM AUTHOR]

A higher proportion of polygynous ant species in northern areas suggests that cold climates select for increased queen number per colony. However, the types of social conditions within nests that allow polygynous species to inhabit cold climates are unclear. The Japanese twig-dwelling ant, Camponotus yamaokai Terayama & Satoh, 1990, which has on average two queens per colony, also inhabit colder areas than monogynous related species. C. yamaokai alates remain in natal colonies and always overwinter with workers. A previous study demonstrated that cohabitation by workers facilitates overwintering success of C. yamaokai queens. However, how queen number influences the survival of queens cohabitating with workers and the survival of other castes was not investigated. Here, we compared overwintering survival of queens and workers among experimental groups with different social structures. Wintering experiments revealed that queen survival did not differ between monogynous (one queen) and polygynous (two queens) groups but was correlated positively with worker number. Meanwhile both queen and worker number influenced worker survival, and these factors interacted with worker type (minor or major). Worker survival increased with increasing worker number, but the effect was more pronounced for major workers than for minor workers. With respect to queen number, minor workers survived longer in polygynous groups than in monogynous groups, whereas the opposite pattern was found in major workers. In other words, major worker mortality increased with increasing queen number. These results suggest that cohabitation with workers but not other queens facilitates queen survival, and that queen number increases survival in minor workers but increases mortality in major workers. Possible explanations for this latter pattern are discussed. [ABSTRACT FROM AUTHOR]

Sexual selection is one of the earliest areas of interest in evolutionary biology. And yet, the evolutionary history of sexually dimorphic traits remains poorly characterized for most vertebrate lineages. Here, we report on evidence for the early evolution of dimorphism within a model mammal group, the pinnipeds. Pinnipeds show a range of sexual dimorphism and mating systems that span the extremes of modern mammals, from monomorphic taxa with isolated and dispersed mating to extreme size dimorphism with highly ordered polygynous harem systems. In addition, the degree of dimorphism in pinnipeds is closely tied to mating system, with strongly dimorphic taxa always exhibiting a polygynous system, and more monomorphic taxa possessing weakly polygynous systems. We perform a comparative morphological description, and provide evidence of extreme sexual dimorphism (similar to sea lions), in the Miocene-aged basal pinniped taxon Enaliarctos emlongi. Using a geometric morphometric approach and combining both modern and fossil taxa we show a close correlation between mating system and sex-related cranial dimorphism, and also reconstruct the ancestral mating system of extant pinnipeds as highly polygynous. The results suggest that sexual dimorphism and extreme polygyny in pinnipeds arose by 27 Ma, in association with changing climatic conditions. [ABSTRACT FROM AUTHOR]

The positive relationship between sexual size dimorphism (SSD) and harem size across pinnipeds is often cited as a textbook example of sexual selection. It assumes that female aggregation selected for large male size via male-male competition. Yet, it is also conceivable that SSD evolved prior to polygyny due to ecological forces. We analyzed 11 life-history traits in 35 pinniped species to determine their coevolutionary dynamics and infer their most likely evolutionary trajectories contrasting these two hypotheses. We find support for SSD having evolved prior to changes in the mating system, either as a consequence of niche partitioning during aquatic foraging or in combination with sexual selection on males to enforce copulations on females. Only subsequently did polygyny evolve, leading to further coevolution as the strength of sexual selection intensified. Evolutionary sequence analyses suggest a polar origin of pinnipeds and indicate that SSD and polygyny are intrinsically linked to a suite of ecological and life-history traits. Overall, this study calls for the inclusion of ecological variables when studying sexual selection and argues for caution when assuming causality between coevolving traits. It provides novel insights into the role of sexual selection for the coevolutionary dynamics of SSD and mating system. [ABSTRACT FROM AUTHOR]

Sandpipers and allies (Scolopacidae) show an astounding diversity in mating and parental care strategies. Comparative studies have tried to interpret this variation in terms of phylogenetic constraints and ecological shaping factors. In such analyses, mating and parental care systems are necessarily discretely classified at the species level. The few available descriptive studies on breeding strategies of the Sanderling (Calidris alba) came to variable conclusions, which, in turn, were inconsistently used in these comparative studies. We provide empirical data on mating and parental care patterns in Sanderlings studied during six summers in northeast Greenland. In 135 clutches, we determined parental care from incubation profiles using temperature loggers and confirmed that both uniparental incubation by both sexes and biparental incubation (45 and 90 clutches, respectively) occurred. We used microsatellite-based parentage analyses to describe the degree of extrapair mating. In 48 completely assayed families, we found 6 cases of polygamy (4 cases of polyandry, 2 cases of polygyny) that involved both uniparental and biparental clutches. This implies substantial variation in the patterns of mating and parental care, defying categorical assignments even at the local level. We conclude that the classification of mating strategy and parental care pattern for the Sanderling has been rather coarse, and that comparative analyses have not taken the observed intrapopulation variability into account. Because sandpipers show such variable reproductive behavior, between and within species, more detailed descriptive studies using parentage analyses are required to revisit previous statements about the intensity of sexual selection, including sexual size dimorphism, in shorebirds. In view of the great variability, methods of comparison will need elaboration too. [ABSTRACT FROM AUTHOR]

I review evidence that females deceive males in the context of sexual selection and sexual conflict in the green poison frog, Dendrobates auratus. In this species, males mate polygynously when they have the opportunity, but polygyny imposes a cost on female reproductive success. Some females attempt to guard their mates when those males are approached by other females. This behavior involves both aggression toward other females and active "pseudo-courtship" of the male. This courtship is hypothesized to be a deceptive signal that functions to prevent the male from mating with other females. Observational and comparative evidence is presented in support of the predictions of this hypothesis. This form of deception is compared to similar behaviors that occur in other species, and the possibility that other forms of deception occur in poison frogs is discussed. [ABSTRACT FROM AUTHOR]

Although learned mate preferences are suspected to have important effects during speciation, theoretical models have largely neglected the effects on speciation and population divergence of within-generational learning, that is, learning based upon prior experience with potential mates. Here, we use population genetic models to address this deficit. Focusing on the situation of secondary contact between populations that still hybridize, we consider models of learning by females and by males under polygyny. We assess the effects of learning to prefer conspecifics from previous conspecific encounters, learning to avoid heterospecifics from previous heterospecific encounters, and learning to prefer familiar types. We examine the amount of population divergence that results from learning in these models. We also assess the effect of learning on the spread of an allele that strengthens assortative mating in both models. We find that learning can have counterintuitive, but logical and understandable effects that differ with the version of the model assessed. In general, population divergence is expected to increase most consistently when females learn to strengthen their preferences for conspecifics from previous encounters with conspecifics. Our results also suggest that within-generational learning will generally inhibit the spread of alleles strengthening assortative mating. [ABSTRACT FROM AUTHOR]

Precopulatory sexual selection is the association between fitness and traits associated with mate acquisition. Although sexual selection is generally recognized to be a powerful evolutionary force, most investigations are limited to characters belonging to individuals. A broader multilevel perspective acknowledges that individual fitness can be affected by aspects of mating success that are characters of groups, such as families. Parental mating success in polygynous or polyandrous human societies may exemplify traits under group-level sexual selection. Using fitness measures that account for age-structure, I measure multilevel selection for mate number over 55 years in a human population with declining rates of polygyny. Sexual selection had three components: individual-level selection for ever-mating (whether an individual mated) and individual- and family-level selection for polyandry and polygyny. Family- and individual-level selection for polygyny was equally strong, three times stronger than family-level selection for polyandry and more than an order of magnitude stronger than individual-level selection for polyandry. However, individual-level selection for polyandry and polygyny was more effective at explaining relative fitness variance than family-level selection. Selection for ever-mating was the most important source of sexual selection for fitness; variation for ever-mating explained 23% of relative fitness variance. [ABSTRACT FROM AUTHOR]