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PubMed2001

Sexual conflict and cooperation in butterfly reproduction: a comparative study of polyandry and female fitness.

Most butterfly species can be characterized as capital breeders, meaning that reproductive output is strongly coupled to the amount of resources they have procured during the larval stage. Accordingly, female fecundity is generally correlated with female mass, both within and across species. However, the females of some species can be partly characterized as income breeders, in the sense that their reproductive output is dependent not only on larval-derived capital but also on resources acquired during the adult stage. These adult resources can be derived from female feeding or from male-transferred nuptial gifts. Recent studies on the within-species effects of multiple matings on female fitness show that females generally gain directly from multiple matings in terms of increased lifetime offspring production. Here, we test whether the positive effects of multiple mating on female fitness also hold at a comparative level, by conducting a laboratory study of female reproductive output in eight pierid species that differ in life-time female mating frequency. Female reproductive output, measured as cumulative egg mass divided by female mass, increased significantly with polyandry (r = 0.942, p < 0.001), demonstrating that the positive effect of mating rate on female reproductive fitness also holds between species. The positive effect of male nutrient contribution is substantial, and the per capita reproductive output is more than twice as high in the most polyandrous species as in the most monandrous ones. Hence, the positive net effect of the ejaculates is highly substantial, although males and females can have sexual interests that run counter to each other, setting the stage for sexually antagonistic coevolution, so that the various component parts of the male ejaculate-sperm, nutrients, anti-aphrodisiacs, and gonadotrophic hormones-may each correspond to a separate conflict-cooperation balance between the sexes. Two scenarios for the evolution of nuptial gifts in butterflies are discussed, one arguing that variation in larval food is the underlying factor and the other arguing that sexually antagonistic coevolution is the driving force. The two views are complementary rather than mutually exclusive, although the former hypothesis predicts that variation in female mating rate depends on variation in larval food availability, whereas the latter suggests that variation in female mating rate between species results from species-specific idiosyncrasies.

Animals↗

PubMed2003

Ultrastructure meets reproductive success: performance of a sphecid wasp is correlated with the fine structure of the flight-muscle mitochondria.

Organisms show a remarkable inter-individual variation in reproductive success. The proximate causes of this variation are not well understood. We hypothesized that the ultrastructure of costly or complex tissues or organelles might affect reproductive performance. We tested this hypothesis in females of a sphecid wasp, the European beewolf, Philanthus triangulum (Hymenoptera, Sphecidae), that show considerable variation in reproductive success. The most critical component of reproduction in beewolf females is flying with paralysed honeybees, which more than double their weight. Because of the high energetic requirements for flight, we predicted that the ultrastructure of the flight-muscle mitochondria might influence female success. We determined the density of mitochondria and the density of the inner mitochondrial membranes (DIMM) of the flight muscles as well as age, body size and fat content. Only DIMM had a significant influence on female reproductive success, which might be mediated by an elevated adenosine triphosphate (ATP) supply. The variation in DIMM might result from differences in larval provisions or from an accumulation of mutations in the mitochondrial genome. Our results support the hypothesis that the organization of complex structures contributes to inter-individual variation in reproductive success.

Adenosine Triphosphate↗

PubMed2004

Optimal reproductive-skew models fail to predict aggression in wasps.

Optimal-skew models (OSMs) predict that cooperative breeding occurs as a result of dominants conceding reproductive benefits to subordinates, and that division of reproduction within groups reflects each cooperator's willingness and ability to contest aggressively for dominance. Polistine paper wasps are a leading model system for testing OSMs, and data on reproduction and aggression appear to support OSMs. These studies, however, measure aggression as a single rate rather than by the activity patterns of individuals. This leads to a potential error: if individuals are more likely to receive aggression when active than when inactive, differences in aggression across samples can reflect changes in activity rather than hostility. This study replicates a field manipulation cited as strongly supporting OSMs. We show that fundamentally different conclusions arise when controlling for individual activity states. Our analyses strongly suggest that behaviours classified as 'aggression' in paper wasps are unlikely to function in establishing, maintaining or responding to changes in reproductive skew. This illustrates that OSM tests using aggression or other non-reproductive behaviour as a metric for reproductive partitioning must demonstrate those links rather than assume them.

Aggression↗

PubMed2006

Senescent birds redouble reproductive effort when ill: confirmation of the terminal investment hypothesis.

This study reports an experimental confirmation of the terminal investment hypothesis, a longstanding theoretical idea that animals should increase their reproductive effort as they age and their prospects for survival and reproduction decline. Previous correlational and experimental attempts to test this hypothesis have yielded contradictory results. In the blue-footed booby, Sula nebouxii, a long-lived bird, after initial increase, male reproductive success declines progressively with age. Before laying, males of two age classes were challenged with lipopolysaccharide to elicit an immune response, which induced symptoms of declining survival prospects. Reproductive success of immune-challenged mature males fell, while that of immune-challenged old males showed a 98% increase. These results demonstrate that senescent males with poor reproductive prospects increase their effort when those prospects are threatened, whereas younger males with good reproductive prospects do not.

Age Factors↗

PubMed2006

Reproductive strategy, sexual development and attraction to facial characteristics.

Sexual reproduction strategies vary both between and within species in the level of investment in offspring. Life-history theories suggest that the rate of sexual maturation is critically linked to reproductive strategy, with high investment being associated with few offspring and delayed maturation. For humans, age of puberty and age of first sex are two developmental milestones that have been associated with reproductive strategies. Stress during early development can retard or accelerate sexual maturation and reproduction. Early age of menarche is associated with absence of younger siblings, absence of a father figure during early life and increased weight. Father absence during early life is also associated with early marriage, pregnancy and divorce. Choice of partner characteristics is critical to successful implementation of sexual strategies. It has been suggested that sexually dimorphic traits (including those evident in the face) signal high-quality immune function and reproductive status. Masculinity in males has also been associated with low investment in mate and offspring. Thus, women's reproductive strategy should be matched to the probability of male investment, hence to male masculinity. Our review leads us to predict associations between the rate of sexual maturation and adult preferences for facial characteristics (enhanced sexual dimorphism and attractiveness). We find for men, engaging in sex at an early age is related to an increased preference for feminized female faces. Similarly, for women, the earlier the age of first sex the greater the preference for masculinity in opposite-sex faces. When we controlled sexual dimorphism in male faces, the speed of sexual development in women was not associated with differences in preference for male facial attractiveness. These developmental influences on partner choice were not mediated by self-rated attractiveness or parental relationships. We conclude that individuals assort in preferences based on the rapidity of their sexual development. Fast developing individuals prefer opposite-sex partners with an increased level of sexually dimorphic facial characteristics.

Adolescent↗

PubMed2002

Hormonal manipulation of offspring number: maternal effort and reproductive costs.

We used exogenous gonadotropin hormones to physiologically enlarge litter size in the bank vole (Clethrionomys glareolus). This method allowed the study design to include possible production costs of reproduction and a trade-off between offspring number and body size at birth. Furthermore, progeny rearing and survival and postpartum survival of the females took place in outdoor enclosures to capture salient naturalistic effects that might be present during the fall and early winter. The aim of the study was to assess the effects of the manipulation on the growth and survival of the offspring and on the reproductive effort, survival, and future fecundity of the mothers. Mean offspring body size was smaller in enlarged litters compared to control litters at weaning, but the differences disappeared by the winter. Differences in litter sizes disappeared before weaning age due to higher mortality in enlarged litters. In addition to the effects of the litter size, offspring performance was probably also influenced by the ability of the mother to support the litter. Experimental females had higher reproductive effort at birth, and they also tended to have higher mortality during nursing. Combined effects of high reproductive effort at birth and high investment in nursing the litter entailed costs for the experimental females in terms of decreased probability of producing a second litter and a decreased body mass gain. Thus, enlarged litter size had both survival and fecundity costs for the mothers. Our results suggest that the evolution of litter size and reproductive effort is determined by reproductive costs for the mothers as well as by a trade-off between offspring number and quality.

Animals↗

PubMed2003

Reproductive character displacement and the genetics of gamete recognition in tropical sea urchins.

Reproductive character displacement occurs when sympatric and allopatric populations of a species differ in traits crucial to reproduction, and it is commonly thought of as a signal of selection acting to limit hybridization. Most documented cases of reproductive character displacement involve characters that are poorly understood at the genetic level, and rejecting alternative hypotheses for biogeographic shifts in reproductive traits is often very difficult. In sea urchins, the gamete recognition protein bindin evolves under positive selection when species are broadly sympatric, suggesting character displacement may be operating in this system. We sampled sympatric and allopatric populations of two species in the sea urchin genus Echinometra for variation in bindin and for the mitochondrial cytochrome oxidase I to examine patterns of population differentiation and molecular evolution at a reproductive gene. We found a major shift in bindin alleles between central Pacific (allopatric) and western Pacific (sympatric) populations of E. oblonga. Allopatric populations of E. oblonga are polyphyletic with E. sp. C at bindin, whereas sympatric populations of the two species are reciprocally monophyletic. There is a strong signal of positive selection (P(N)/P(S) = 4.5) in the variable region of the first exon of bindin, which is associated with alleles found in sympatric populations of E. oblonga. These results indicate that there is a strong pattern of reproductive character displacement between E. oblonga and E. sp. C and that the divergence is driven by selection. There is much higher population structure in sympatric populations at the bindin locus than at the neutral mitochondrial locus, but this difference is not seen in allopatric populations. These data suggest a pattern of speciation driven by selection for local gamete coevolution as a result of interactions between sympatric species. Although this pattern is highly suggestive of speciation by reinforcement, further research into hybrid fitness and egg-sperm interactions is required to address this potential mechanism for character displacement.

Amino Acid Sequence↗

PubMed2003

Reproductive isolation and phylogenetic divergence in Neurospora: comparing methods of species recognition in a model eukaryote.

We critically examined methods for recognizing species in the model filamentous fungal genus Neurospora by comparing traditional biological species recognition (BSR) with more comprehensive applications of both BSR and phylogenetic species recognition (PSR). Comprehensive BSR was applied to a set of 73 individuals by performing extensive crossing experiments and delineating biological species based on patterns of reproductive success. Within what were originally considered two species, N. crassa and N. intermedia, we recognized four reproductively isolated biological species. In a concurrent study (Dettman et al. 2003), we used genealogical concordance of four independent nuclear loci to recognize phylogenetic species in Neurospora. Overall, the groups of individuals identified as species were similar whether recognized by reproductive success or by phylogenetic criteria, and increased genetic distance between parents was associated with decreased reproductive success of crosses, suggesting that PSR using genealogical concordance can be used to reliably recognize species in organisms that are not candidates for BSR. In one case, two phylogenetic species were recognized as a single biological species, indicating that significant phylogenetic divergence preceded the development of reproductive isolation. However, multiple biological species were never recognized as a single phylogenetic species. Each of the putative N. crassa x N. intermedia hybrids included in this study was confidently assigned to a single species, using both PSR and BSR. As such, no evidence for a history of hybridization in nature among Neurospora species was observed. By performing reciprocal mating tests, we found that mating type, parental role, and species identity of parental individuals could all influence the reproductive success of matings. We also observed sympatry-associated sexual dysfunction in interspecific crosses, which was consistent with the existence of reinforcement mechanisms.

Cluster Analysis↗

PubMed2004

Patterns of reproductive isolation in three angiosperm genera.

Analyses among animal species have found that reproductive isolation increases monotonically with genetic distance, evolves more quickly for prezygotic than postzygotic traits, and is stronger among sympatric than allopatric species pairs. The latter pattern is consistent with expectations under the reinforcement hypothesis. To determine whether similar trends are found among plant species, patterns of reproductive isolation (postpollination prezygotic, postzygotic, and "total" isolation) in three plant genera (Glycine, Silene, Streptanthus) were examined using data from previously published artificial hybridization experiments. In Silene, all measures of reproductive isolation were positively correlated with genetic distance. In contrast, in Glycine and Streptanthus, correlations between reproductive isolation and genetic distance were weak or nonsignificant, possibly due to the influence of biologically unusual taxa, variable evolutionary forces acting in different lineages, or insufficient time to accumulate reproductive isolation. There was no evidence that postpollination prezygotic reproductive isolation evolved faster than postzygotic isolation in Glycine or Silene. We also detected no evidence for faster accumulation of postmating prezygotic isolation between sympatric than allopatric species pairs; thus we found no evidence for the operation of speciation via reinforcement. In Silene, which included six polyploid species, results suggest that changes in ploidy disrupt a simple monotonic relationship between isolation and genetic distance.

Evolution, Molecular↗

PubMed2004

The interaction between reproductive lifespan and protandry in seasonal breeders.

The timing and duration of reproductive activities are highly variable both at the individual and population level. Understanding how this variation evolved by natural selection is fundamental to understanding many important aspects of an organism's life history, ecology and behaviour. Here, we combine game theoretic principles governing reproductive timing and the evolutionary theory of senescence to study the interaction between protandry (the earlier arrival or emergence of males to breeding areas than females) and senescence in seasonal breeders. Our general model applies to males who are seeking to mate as frequently as possible over a relatively short period, and so is relevant to many organisms including annual insects and semelparous vertebrates. The model predicts that protandry and maximum reproductive lifespans should increase in environments characterized by high survival and by a low competitive cost of maintaining the somatic machinery necessary for survival. In relatively short seasons under these same conditions, seasonal declines in the reproductive lifespans of males of equivalent quality will be evolutionarily stable. However, over a broad range of potential values for daily survival and maintenance cost, reproductive lifespan is expected to be relatively short and constant throughout a large fraction of the season. We applied the model to sockeye (or kokanee) salmon Oncorhynchus nerka and show that pronounced seasonal declines in reproductive lifespan, a distinctive feature of semelparous Oncorhynchus spp., is likely part of a male mating strategy to maximize mating opportunities.

Aging↗

PubMed2006

Effects of forest fragmentation on phenological patterns and reproductive success of the tropical dry forest tree Ceiba aesculifolia.

Spatial isolation caused by forest fragmentation and temporal isolation caused by asynchronous flowering of plants have been proposed as important factors that affect the reproduction ofplant populations. In a 4-year study, we determined the effects of forest fragmentation and spatial isolation on flowering phenology and reproductive success of the tropical tree Ceiba aesculifolia ([Kunth] Britton & Rose). We conducted our study in the dry forest of Mexico and compared populations in two habitat conditions based on density and environmental conditions: (1) disturbed habitat (four populations of < or =3 reproductive individuals/ha surrounded by agriculturalfields or pastures) and (2) undisturbed habitat (three populations of groups of >6 reproductive individuals/ha surrounded by undisturbed mature forest). We compared the following variables within these populations over 4 years: flowering overlap, proportion of individuals with flowers and fruit, total flower production, total fruit production, fruit set, seed production, and seed abortion. Little overlap in flowering occurred among the populations in the two habitat conditions. The flowering period of trees in the disturbed habitat initiated between 15 to 20 days before the flowering period of trees in the undisturbed habitat during 3 years. Flowering of trees in the undisturbed habitat peaked at the end of the flowering period of the trees in the disturbed habitat. The proportion of trees that flowered was greater in the undisturbed habitat. Nevertheless, total flower production was greater in the disturbed habitat and these differences were maintained across 3 years. The proportion of individuals that produced fruit did not differ across habitat conditions but did differ across years. Total fruit production was greater in the disturbed habitat, but fruit set and seed production were the same across years and between habitat conditions. Seed abortion varied over years between habitats. We concluded that forest fragmentation does not negatively affect the reproductive success of C. aesculifolia It appears that the highly mobile bat pollinators maintain reproductive connectivity between trees in both habitats.

Animals↗

PubMedDate not supplied

The complement system in human reproduction.

Regulation of the complement system in reproduction is unique inasmuch as reproductive tissues represent the only condition where allogeneic interactions occur naturally. Both allogeneic extraembryonic membranes and semen that contact and interact with maternal cells and tissues must avert complement-mediated damage to ensure reproductive success. Several regulators of complement activation exist. Membrane cofactor protein (MCP) and decay accelerating factor (DAF) inactivate C3 and C5 convertases on cell surfaces. In addition, CD59 inhibits the membrane attack complex (MAC) of the complement cascade. Strong expression of these membrane glycoproteins by trophoblast and amniotic epithelium has been observed. MCP, DAF, and CD59 likely safeguard extraembryonic tissues from complement damage originating from maternal and fetal blood or amniotic fluid. Different reproductive tract fluids vary in complement levels. With the exception of ovarian follicular fluid, these levels are generally much less than those in blood. Endometrial and cervical content of C3 appear to be regulated by hormones. These observations suggest that the effects of complement activation may vary in reproductive tissues. MCP is absent from the surfaces of oocytes. Sperm express MCP and DAF in discrete areas that would not be associated with the known complement-regulatory functions of these proteins. Seminal plasma contains MCP and the MAC inhibitor SP-40,40 but not DAF.SP-40,40 may exemplify how complement-regulatory proteins perform alternative functions as it interacts with molecules other than complement components. We have reviewed aspects of the complement system that relate to allogeneic interactions in reproduction and that suggest fruitful areas for further research.

Antigens, CD↗

PubMed1997

Genetic factors in reproduction and their evolutionary significance.

PROBLEM: The reproductive process is a major driving force in human evolution. An evolutionary perspective was brought to bear on some aspects of reproduction and its aberrations, and, conversely, some of the insights of modern reproductive genetics were used to investigate problems in evolution. METHOD: The data used were obtained from the literature in evolution, anthropology, archeology, linguistics, and genetics. RESULTS: The evolutionary line leading to modern humans diverged from that leading to the chimpanzees approximately 5-7 million years ago (Mya). Archaic Homo sapiens emerged ca. 0.3 Mya, and modern Homo sapiens and the development of language ca. 0.1 Mya; thus, modern humans occupy approximately 2% of the evolutionary history of the hominid line. During all of this time, the ancestors of modern humans were migratory hunter-gatherers. It was only during the Neolithic transition ca. 0.01 Mya (approximately 0.2% of hominid evolutionary history) that agriculture was developed, and with it a settled lifestyle that allowed a more stable existence and the development of a different reproductive pattern. Various estimates indicate that the human population increased from 0.05 million at the time of the emergence of modern Homo sapiens to 6,000 million at the present time (120,000-fold increase). CONCLUSIONS: These evolutionary considerations were used to explore three areas: (1) the extinction of the Neanderthals, who coexisted for ca. 65,000 years with modern humans; (2) the relatively low and stable rate of human conceptions (20-35% of ova fertilized naturally or fertilized in vitro); and (3) the long postnatal period required for the full maturation of the immune response. From these considerations, a broad view of the human reproductive process was obtained that may provide some insight into the rationale for the development of effective reproductive technologies.

Animals↗

PubMed2004

Reproductive functions of corticotropin-releasing hormone. Research and potential clinical utility of antalarmins (CRH receptor type 1 antagonists).

BACKGROUND: The hypothalamic-pituitary-adrenal (HPA) axis exerts a complex, mostly inhibitory, effect on the female reproductive system. In addition, the principal regulator of this axis, the hypothalamic neuropeptide corticotropin-releasing hormone (CRH) and its receptors have been identified in most female reproductive tissues, including the ovary, uterus, and placenta. Furthermore, CRH is secreted in peripheral inflammatory sites where it exerts strong inflammatory actions. Antalarmins (CRH receptor type 1 antagonists) have been used to elucidate the roles of CRH in stress, inflammation and reproduction. METHOD OF STUDY: We review existing data on the effects of CRH in the female reproductive system. RESULTS: Ovarian CRH participates in female sex steroid production, follicular maturation, ovulation and luteolysis. Uterine CRH participates in decidualization, implantation, and early maternal tolerance. Placental CRH participates in the physiology of pregnancy and the onset of parturition. Circulating placental CRH is secreted mostly during the latter half of pregnancy and is responsible for the concurrently increasing physiologic hypercortisolism of this period. After labor and delivery, this hypercortisolism is ensued by a transient suppression of hypothalamic CRH secretion, which may explain the postpartum blues and depression and the increased autoimmune manifestations depression of period, the postpartum period. CONCLUSIONS: These data show that CRH is present in female reproductive tissues, and is regulating key reproductive functions with an inflammatory component, such as ovulation, luteolysis, implantation, and parturition.

Animals↗

PubMed1994

Aspects of reproduction in female Bos indicus cattle: a review.

Differences occur between female Bos indicus and Bos taurus cattle in various aspects of reproductive physiology and behaviour. These may be associated with different natural and human selection pressures, compounded by strong genotype-environment interactions. B indicus cattle are better adapted for tropical environments (despite overall poor cattle reproductive rates in these regions) which tend to be more stressful for B taurus genotypes. Conversely, B taurus cattle generally show superior reproductive and productive traits under more favoured, temperate conditions. Despite genotype-environment effects, B indicus females are generally considered to take longer to achieve puberty and to have longer gestation lengths, exhibit prolonged postpartum anoestrus, show greater seasonality of reproductive traits (tending to be long-day breeders), display a shorter, less overt oestrus as well as less tendency to allow riding behaviour by subordinate females. Some groups appear to have increased losses both during pregnancy and in the neonatal period. On the positive side, B indicus females respond well to managerial and nutritional interventions, tend to have greater reproductive longevity and they generally exhibit strong maternal traits. Culling of infertile females and selection for greater male scrotal circumference and sex-drive, in conjunction with the use of target weights, body condition scoring and weaning stratagems can improve reproductive rates in B indicus females.

Animals↗

PubMed2005

A survey comparing TCM diagnosis, health status and medical diagnosis in women undergoing assisted reproduction.

INTRODUCTION: For many women, undergoing assisted reproductive technology can be a difficult experience, and can result in changes in physical and emotional health and wellbeing. Recent research has suggested that acupuncture may be helpful for women undergoing assisted reproductive technology. To date, there is no information describing the traditional Chinese medicine (TCM) syndromes seen in women undergoing assisted reproductive technology, or relationships between TCM and Western medicine diagnoses. OBJECTIVE: To examine the health status of women undergoing assisted reproductive technology from both Western and Chinese medicine perspectives. METHODS: One hundred and eighty women were included in the study. All underwent a TCM diagnosis, 177 (98.3%) completed the quality of life questionnaire SF36. Information about Western medicine diagnosis was collected from case notes and was available for 176 (97.7%) women. RESULTS: Women in the trial reported poorer health on several domains of the SF36 compared with the South Australian population. The most common TCM diagnosis was 'Kidney Yang deficiency', diagnosed for 53.9% of patients. A TCM diagnosis of Qi or 'Blood stagnation' was associated with poorer quality of life on the mental health, emotional role function and social function domains of the SF36. No associations were found between TCM diagnosis and physical or general health components of the SF36. CONCLUSIONS: Associations between TCM and reproductive health diagnoses were demonstrated. Emotional health and wellbeing is an important aspect of patient care that needs to be addressed in clinical practice and research studies, as the findings suggest that this aspect of their health is often poorer during assisted reproductive technology.

Adult↗

PubMed2005

A survey of sexual and reproductive health in men with cystic fibrosis: new challenges for adolescent and adult services.

BACKGROUND: Improved survival dramatically alters the consequences of adult co-morbidities in men with cystic fibrosis (CF) such as male infertility. Few studies have systematically addressed the impact of sexual and reproductive health issues in these men or considered the implications for healthcare delivery. METHOD: A descriptive cohort study was undertaken using a sexual and reproductive health survey of men from a large adult CF centre, including men with lung transplantation. RESULTS: The mean (SD) age of the 94 men (response rate 75%) was 30.5 (7.6) years. 94% knew that men with CF had reduced fertility. Men first heard about infertility later than desired (p<0.001) and only 53% heard from their preferred source. Men who were told about infertility when older were more likely to be upset than those told earlier (p<0.01). 53% of men had undergone semen analysis: 68% of men who had not been tested wanted semen analysis. 73% believed semen analysis should occur before 18, but the youngest age of testing was 24 years. In adolescence, one in three men had assumed they did not need to use condoms and one in 10 had confused infertility with impotence. 66% of men wanted more information on reproductive options and 84% wanted children. Seventeen men were parents by natural conception (n = 1), micro-epididymal sperm aspiration (n = 6), donor sperm (n = 9), and through step children (n = 1). CONCLUSIONS: Men with CF desire more sexual and reproductive health information. Earlier discussion of sexual and reproductive health is indicated in paediatric settings, and semen analysis should be routinely offered. In adult services greater discussion of reproductive health options is indicated.

Adolescent↗

PubMed2001

Tests of reproductive-skew models in social insects.

Reproductive-skew theory can be broadly divided into transactional models, in which reproduction is shared among group members in return for some fitness benefit, and tug-of-war models, in which reproductive sharing arises solely from an inability of each group member to fully control the others. For small-colony social insects in which complete reproductive control by a single individual is plausible, transactional-concession models account, better than any other existing model, for observed relationships between each of the dependent variables of skew, changes in reproductive partitioning over time, group size, and within-group aggression, and each of the predictor variables of genetic relatedness, ecological constraints on solitary breeding, and benefits of group living. An extension of transactional-concession models via the "workers-as-a-collective-dominant" model potentially offers new insights into some of the most striking reproductive patterns in large-colony eusocial Hymenopteran species, from the loss of worker capacity to produce female offspring to patterns of skew and aggression in polygynous societies.

Animals↗