Male Lifetime Reproductive Success Research Articles

Reproductive success of jack and full-size males in a wild coho salmon population.

Despite the wealth of research on Pacific salmon Oncorhynchus spp. life histories there is limited understanding of the lifetime reproductive success of males that spend less time at sea and mature at a smaller size (jacks) than full-size males. Over half of returning male spawners can be jacks in some populations, so it is crucial to understand their contribution to population productivity. We quantified adult-to-adult reproductive success (RS) of jacks and their relative reproductive success (RRS) compared to full-size males in a wild population of coho salmon in the Auke Creek watershed, Juneau, Alaska. We used genetic data from nearly all individuals (approx. 8000) returning to spawn over a decade (2009-2019) to conduct parentage analysis and calculate individual RS. The average adult-to-adult RS of jacks (mean = 0.7 and s.e. = 0.1) was less than that of full-size males (mean = 1.1 and s.e. = 0.1). Jack RRS was consistently below 1.0 but ranged widely (0.23 to 0.96). Despite their lower average success, jacks contributed substantially to the population by siring 23% of the total returning adult offspring (1033 of 4456) produced between 2009 and 2015. Our results imply that jacks can affect evolutionary and population dynamics, and are relevant to the conservation and management of Pacific salmon.

Variance in lifetime reproductive success of male polar bears

Abstract Despite the important role that population density plays in ecological and evolutionary processes, studies of solitary species that occur at low densities remain scarce. In the context of mating systems, density is expected to influence the ability of males to find and monopolize mates, in turn, influencing variance in lifetime mating/reproductive success and the opportunity for selection. Herein, we investigate variance in male lifetime mating success (LMS), lifetime reproductive success (LRS), and the mating system of a sexually dimorphic carnivore that occurs at low densities, the polar bear (Ursus maritimus). Across 17 cohorts, born from 1975 to 1991, male LMS ranged from 0 to10 mates and LRS from 0 to 14 cubs; 40% of known-age males were not known to have reproduced. The opportunity for sexual selection (Is = 1.66, range = 0.60–4.99) and selection (I = 1.76, range: 0.65–4.89) were low compared to species with similar levels of sexual size dimorphism. Skew in male LRS was also low but significant for most cohorts indicating nonrandom reproductive success. Age-specific reproductive success was biased toward males from 11 to 17 years of age, with variation in fecundity (54%) but not longevity (10%) playing an important role in male reproduction. Our results support a growing body of evidence that suggests that male-biased size dimorphism and polygynous mating systems need not be associated with high variance in male mating and/or reproductive success.

Objective and subjective components of resource value in lethal fights between male entomopathogenic nematodes

Males sometimes engage in fights over contested resources such as access to mates; in this case, fighting behaviour may be adjusted based on the value they place on the females. Resource value (RV) can have two components. First, males can assess the quality of females, which constitutes an objective assessment of RV. Second, internal state such as previous mating experience can also influence motivation to fight thus constituting a subjective assessment of RV. If mating opportunities are scarce and available females have a major impact on the lifetime reproductive success of males, then fighting can be fatal; in this situation it is uncertain whether males would adjust fighting behaviour based on RV. We found that both female quality, that is, virginity (objective component of RV) and male mating status (subjective component of RV) influenced fighting intensity between males of the entomopathogenic nematode Steinernema longicaudum which engage in lethal fights. Male nematodes were more likely to engage in fighting and fought longer and more frequently in the presence of virgin (high-quality) females than in the presence of mated (lower-quality) females. Male mating status was also found to influence fighting behaviour: mated males were the winners in staged fights between mated and virgin males. Mated males may have superior fighting ability (greater resource-holding potential), but RV asymmetries between mated and virgin males cannot be excluded. Males were more likely to win when they were resident, but we did not find a significant interaction effect between male mating and residency status.

Is there indirect selection on female extra-pair reproduction through cross-sex genetic correlations with male reproductive fitness?

One key hypothesis explaining the evolution and persistence of polyandry, and resulting female extra‐pair reproduction in socially monogamous systems, is that female propensity for extra‐pair reproduction is positively genetically correlated with male reproductive fitness and consequently experiences positive cross‐sex indirect selection. However, key genetic correlations have rarely been estimated, especially in free‐living populations experiencing natural (co)variation in reproductive strategies and fitness. We used long‐term life‐history and pedigree data from song sparrows (Melospiza melodia) to estimate the cross‐sex genetic correlation between female propensity for extra‐pair reproduction and adult male lifetime reproductive success, and thereby test a key hypothesis regarding mating system evolution. There was substantial additive genetic variance in both traits, providing substantial potential for indirect selection on female reproductive strategy. However, the cross‐sex genetic correlation was estimated to be close to zero. Such small correlations might arise because male reproductive success achieved through extra‐pair paternity was strongly positively genetically correlated with success achieved through within‐pair paternity, implying that the same successful males commonly sire offspring produced by polyandrous and monogamous females. Cross‐sex indirect selection may consequently have limited capacity to drive evolution of female extra‐pair reproduction, or hence underlying polyandry, in systems where multiple routes to paternity success exist.

Strong sexual selection in males against a mutation load that reduces offspring production in seed beetles.

Theory predicts that sexual reproduction can increase population viability relative to asexual reproduction by allowing sexual selection in males to remove deleterious mutations from the population without large demographic costs. This requires that selection acts more strongly in males than females and that mutations affecting male reproductive success have pleiotropic effects on population productivity, but empirical support for these assumptions is mixed. We used the seed beetle Callosobruchus maculatus to implement a three-generation breeding design where we induced mutations via ionizing radiation (IR) in the F0 generation and measured mutational effects (relative to nonirradiated controls) on an estimate of population productivity in the F1 and effects on sex-specific competitive lifetime reproductive success (LRS) in the F2 . Regardless of whether mutations were induced via F0 males or females, they had strong negative effects on male LRS, but a nonsignificant influence on female LRS, suggesting that selection is more efficient in removing deleterious alleles in males. Moreover, mutations had seemingly shared effects on population productivity and competitive LRS in both sexes. Thus, our results lend support to the hypothesis that strong sexual selection on males can act to remove the mutation load on population viability, thereby offering a benefit to sexual reproduction.

Sexual selection on skeletal shape in Carnivora.

Lifetime reproductive success of males is often dependent upon the ability to physically compete for mates. However, species variation in social structure leads to differences in the relative importance of intraspecific aggression. Here, we present a large comparative dataset on sexual dimorphism in skeletal shape in Carnivora to test the hypotheses that carnivorans exhibit sexual dimorphism in skeletal anatomy that is reflective of greater specialization for physical aggression in males relative to females and that this dimorphism is associated with the intensity of sexual selection. We tested these hypotheses using a set of functional indices predicted to improve aggressive performance. Our results indicate that skeletal shape dimorphism is widespread within our sample. Functional traits thought to enhance aggressive performance are more pronounced in males. Phylogenetic model selection suggests that the evolution of this dimorphism is driven by sexual selection, with the best-fitting model indicating greater dimorphism in polygynous versus nonpolygynous species. Skeletal shape dimorphism is correlated with body size dimorphism, a common indicator of the intensity of male-male competition, but not with mean body size. These results represent the first evidence of sexual dimorphism in the primary locomotor system of a large sample of mammals.

Female access and diet affect insemination success, senescence, and the cost of reproduction in male Mexican fruit flies Anastrepha ludens.

Hypotheses exploring the influence of dietary conditions on the life history trade-off between survival and reproductive success are extensively tested in female insects, but are rarely explored in males. Here, the impact of dietary quality and female access on age-specific reproduction and survival of male Mexican fruit flies, Anastrepha ludens Loew (Diptera: Tephritidae), are examined. There is a clear cost of female access for males with access to dietary protein, measurable as a decrease in life expectancy, which is further influenced by the age when females are introduced. A protein deficient diet reduces the lifespan benefit of virginity and masks the detrimental effect of female access on male life expectancy. Dietary protein is not necessary for reproductive success, but access to protein at eclosion improves the lifetime reproductive success of males compared to when it is delayed. Overall, reproductive success diminishes as the male flies age, regardless of the dietary conditions, providing evidence for reproductive senescence in males. Delaying the males' access to a protein source fails to influence the negative effect of age on reproductive ability. Because age specific reproductive rates decline with age, regardless of diet, male fitness does not benefit from lifespan extension. Therefore, males can be expected to allocate available resources towards reproductive effort in favour of extended lifespan, regardless of mate and protein availability.

Variance in male lifetime reproductive success and estimation of the degree of polygyny in a primate.

The degree of polygyny is predicted to influence the strength of direct male-male competition, leading to a high variance in male lifetime reproductive success and to reproduction limited to the prime period of adulthood. Here, we explore the variance in male lifetime reproductive success and reproductive time in an anthropoid primate forming multimale-multifemale groups. Males of this species form dominance hierarchies, which are expected to skew reproduction toward few high-ranking males. At the same time, however, females mate with multiple males (polygynandry), which should limit the degree of polygyny. Using 20 years of genetic and demographic data, we calculated lifetime reproductive success for the free-ranging rhesus macaque (Macaca mulatta) population of Cayo Santiago for subjects that died naturally or reached senescence. Our results show that 1) male lifetime reproductive success was significantly skewed (range: 0-47 offspring; males reproducing below average: 62.8%; nonbreeders: 17.4%), 2) variance in male lifetime reproductive success was 5 times larger than in females, and 3) male lifetime reproductive success was more influenced by variation in fecundity (60%) than longevity (25%), suggesting that some direct male-male competition takes place. However, the opportunity for selection (i.e., standardized variance in male lifetime reproductive success) is low compared with that in other large mammal species characterized by a high degree of polygyny. Moreover, male reproductive life extended much beyond the prime period, showing that physical strength was not required to acquire mates. We conclude that rhesus macaques exhibit a moderate degree of polygyny and, therefore, low levels of direct male-male competition for fertile females, despite the fact that males form linear dominance hierarchies.

Canalization of body size matters for lifetime reproductive success of male predatory mites (Acari: Phytoseiidae).

The adaptive canalization hypothesis predicts that highly fitness-relevant traits are canalized via past selection, resulting in low phenotypic plasticity and high robustness to environmental stress. Accordingly, we hypothesized that the level of phenotypic plasticity of male body size of the predatory mites Phytoseiulus persimilis (low plasticity) and Neoseiulus californicus (high plasticity) reflects the effects of body size variation on fitness, especially male lifetime reproductive success (LRS). We first generated small and standard-sized males of P. persimilis and N. californicus by rearing them to adulthood under limited and ample prey supply, respectively. Then, adult small and standard-sized males were provided with surplus virgin females throughout life to assess their mating and reproductive traits. Small male body size did not affect male longevity or the number of fertilized females but reduced male LRS of P. persimilis but not N. californicus. Proximately, the lower LRS of small than standard-sized P. persimilis males correlated with shorter mating durations, probably decreasing the amount of transferred sperm. Ultimately, we suggest that male body size is more strongly canalized in P. persimilis than N. californicus because deviation from standard body size has larger detrimental fitness effects in P. persimilis than N. californicus. © 2014 The Authors. Biological Journal of the Linnean Society published by John Wiley & Sons Ltd on behalf of The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 889–899.

No preference for novel mating partners in the polyandrous nuptial-feeding spider Pisaura mirabilis (Araneae: Pisauridae)

Polyandrous females may gain genetic benefits for their offspring through postmating sexual selection. To facilitate postcopulatory choice for males of superior genetic quality females are expected to bias precopulatory mate choice towards novel males (i.e. genetically novel sources). Preference for novel partners is also expected to maximize male lifetime reproductive success by allowing males to increase the number of mates. We investigated male and female preference for novel or former mating partners in the spider Pisaura mirabilis by offering females novel males (polyandry) or the same male (monogamy). Precopulatory (mate acceptance) and prefertilization (latency to copulation, mating interruption and copulation duration) behaviours were compared between the two treatments. Males provide females with a nuptial prey gift during courtship. Because of the direct benefit associated with nuptial feeding, females should accept males indiscriminately and exert preference only at the prefertilization level. We found that monogamous females remated more readily than polyandrous females, suggesting less resistance to remating with the same male than with novel mates. No differences in female prefertilization responses were found. Lack of preference for novel mates may suggest that direct selection exerted by the nuptial gift rather than indirect selection for genetic benefits is a more likely driver of female remating propensity. Females were nevertheless resistant to remating, suggesting a trade-off between direct benefits and costs of remating. We found no effect of mate novelty on male mating behaviour, indicating either lack of discriminatory ability or that risk of sperm competition creates paternity benefits from remating with the same female.

Canine tooth size and fitness in male mandrills ( Mandrillus sphinx)

Sexual selection theory explains the evolution of exaggerated male morphologies and weaponry, but the fitness consequences of developmental and age-related changes in these features remain poorly understood. This long-term study of mandrill monkeys ( Mandrillus sphinx) demonstrates how age-related changes in canine tooth weaponry and adult canine size correlate closely with male lifetime reproductive success. Combining long-term demographic and morphometric data reveals that male fitness covaries simply and directly with canine ontogeny, adult maximum size, and wear. However, fitness is largely independent of other somatometrics. Male mandrills sire offspring almost exclusively when their canines exceed approximately 30 mm, or two-thirds of average adult value (45 mm). Moreover, sires have larger canines than nonsires. The tooth diminishes through wear as animals age, corresponding with, and perhaps influencing, reproductive senescence. These factors combine to constrain male reproductive opportunities to a brief timespan, defined by the period of maximum canine length. Sexually-selected weaponry, especially when it is nonrenewable like the primate canine tooth, is intimately tied to the male life course. Our analyses of this extremely dimorphic species indicate that sexual selection is closely intertwined with growth, development, and aging, pointing to new directions for sexual selection theory. Moreover, the primate canine tooth has potential as a simple mammalian system for testing genetically-based models of aging. Finally, the tooth may record details of life histories in fossil primates, especially when sexual selection has played a role in the evolution of dimorphism.

Mating system, sexual dimorphism, and the opportunity for sexual selection in a territorial ungulate

In mammals, species with high sexual size dimorphism tend to have highly polygynous mating systems associated with high variance in male lifetime reproductive success (LRS), leading to a high opportunity for sexual selection. However, little information is available for species with weak sexual size dimorphism. In a long-term study population, we used parentage analysis based on 21 microsatellite markers to describe, for the first time, variance in male lifetime breeding success (LBS) of roe deer, a territorial ungulate where males weigh less than 10% more than females. LBS ranged from 0 to 14 (mean = 4.54, variance = 15.5), and its distribution was highly skewed, with only a few males obtaining high LBS and many males failing to breed or siring only one fawn. As predicted for polygynous species with low sexual size dimorphism, the standardized variance in male LBS was low (I m = 0.75) and was only slightly higher than the standardized variance in female LRS (I f = 0.53), suggesting a low opportunity for sexual selection. The I m value reported here for roe deer is much lower than values reported for highly dimorphic ungulates such as red deer (I m > 3). We suggest that, along a continuum of opportunity for sexual selection, roe deer occupy a position closer to monogamous and monomorphic territorial ungulates than to highly polygynous, sexually dimorphic ungulates with dominance rank-based mating systems such as harems or roving mating systems.

Delayed Breeding Affects Lifetime Reproductive Success Differently in Male and Female Green Woodhoopoes

In cooperatively breeding species, many individuals only start breeding long after reaching physiological maturity [1], and this delay is expected to reduce lifetime reproductive success (LRS) [1-3]. Although many studies have investigated how nonbreeding helpers might mitigate the assumed cost of delayed breeding (reviewed in [3]), few have directly quantified the cost itself [4, 5] (but see [6, 7]). Moreover, although life-history tradeoffs frequently influence the sexes in profoundly different ways [8, 9], it has been generally assumed that males and females are similarly affected by a delayed start to breeding [7]. Here, we use 24 years of data to investigate the sex-specific cost of delayed breeding in the cooperatively breeding green woodhoopoe (Phoeniculus purpureus) and show that age at first breeding is related to LRS differently in males and females. As is traditionally expected, males that started to breed earlier in life had greater LRS than those that started later. However, females showed the opposite pattern: Those individuals that started to breed later in life actually had greater LRS than those that started earlier. In both sexes, the association between age at first breeding and LRS was driven by differences in breeding-career length, rather than per-season productivity. We hypothesize that the high mortality rate of young female breeders, and thus their short breeding careers, is related to a reduced ability to deal with the high physiological costs of reproduction in this species. These results demonstrate the importance of considering sex-specific reproductive costs when estimating the payoffs of life-history decisions and bring into question the long-held assumption that delayed breeding is necessarily costly.

Fitness and extra‐group reproduction in male Verreaux's sifaka: An analysis of reproductive success from 1989–1999

Adult males in social groups often compete with other male group members for access to adult females. In some primate species, males also seek mating opportunities in neighboring social groups. Such extra-group fertilizations (EGFs) provide an additional source of variation in male fitness. This additional component of fitness provided by EGFs must be incorporated into analyses that investigate sources of variation in male lifetime reproductive success. In this study, a model is analyzed in which male fitness over a 10-year sample period is decomposed into additive and multiplicative variance and covariance components. The data come from an ongoing study of a wild population of Verreaux's sifaka (Propithecus verreauxi verreauxi) located at Beza Mahafaly Special Reserve, Southwest Madagascar. Paternity and demographic data for 134 males are used to decompose male fitness into the following three multiplicative components: reproductive lifespan during sample period, fertility, and offspring survival. These multiplicative components are estimated for males reproducing within their resident groups plus (i.e., the additive portion) for males reproducing in neighboring social groups. The analysis shows that variation in fertility makes the largest contribution to variation in total fitness, followed by variation in amount of time spent in sample period (which is a proxy of total reproductive lifespan) and variation in offspring survival. EGFs contribute an important source of variation to male fitness, and numerous factors enhance the opportunities for EGFs in male sifaka. These include female choice, a high degree of home range overlap, and a limited mating season.

Individual differences and reproductive success in yellow-bellied marmots

Mirror-image stimulation (MIS) was used to determine the individual behavioral phenotypes of 90 adult, 132 yearling, and 135 young yellow-bellied marmots (Marmota flaviventris). Linear typal analysis (LTA) was used to group individuals based on similarities in their MIS scores. Principal component analysis (PCA) was used to evaluate the patterns of variation in behaviors and discriminant function analysis (DFA) was used to determine if there were consistent differences in marmot behavior. LTA produced two interpretable groups that were significantly and negatively correlated. Marmots in each group formed a shy-bold continuum. Bold animals were those that approached the mirror early and made nose contact with the image whereas shy animals approached the mirror late in the run, spent time in the back half of the arena, and frequently chirped at the image. Behaviors shifted with age; young were predominantly bold and adults were predominantly shy. This shift appears to be developmental and not genetically determined. Reliability and predictability analyses indicated that there is a 75% probability that a MIS run correctly identifies an individual's behavioral phenotype. The probability increases to 90% for those individuals with high loading scores. Play, agonistic, and amicable behaviors of female yearlings recorded in the field were significantly correlated with their MIS behavioral phenotypes whereas only play of male yearlings was so correlated. Correlations among eight life-history traits of adult females were independent of behavioral phenotypes. Shy females were more likely to be associated with female non-kin, produced more daughters, and were more likely to be immigrants. Among female yearlings, shy phenotypes were likely to become recruits and bold phenotypes were more likely to disperse. Bold adult females recruited yearlings regardless of their behavioral phenotype whereas shy adult females recruited primarily shy yearlings and the majority of bold yearlings dispersed. Among adult males, shy phenotypes were more likely to be territorial-colonial and to produce more young. Lifetime reproductive success (LRS) of females was strongly related to the number of years of residency, which was strongly correlated with the frequency of reproduction and the production and recruitment of offspring. The demographic patterns were independent of behavioral phenotype. Behavioral phenotype impacts demographic trends mainly by increasing the recruitment of daughters by bold females. LRS of males depends on the length of residency. Shy males have a higher LRS because they are territorial-colonial for a longer time and produce more young. Bold individuals appear to be those that are sub- ordinate and attempt to affiliate with other marmots whereas shy individuals appear to be dominant and less likely to be affiliative. By being more aggressive, the shy marmot is more likely to achieve residency as a yearling or adult whereas the more affiliative adult is more likely to recruit offspring, but affiliative yearlings are less likely to become recruits, especially when the adults are the dominant, “shy” individuals.

Effects of body size on male mating tactics and paternity in black bears,Ursus americanus

The reproductive behaviour of large, solitary mammals is difficult to study. Owing to their secretive nature and wide-ranging habits, aspects of male mating behaviour are poorly documented in solitary than in social species. We used radiotelemetry and microsatellite DNA analysis to investigate the influence of body size on male mating tactics and short-term reproductive success in the black bear, Ursus americanus, a solitary carnivore. We investigated male ranging behaviour and documented male encounters with breeding females to determine whether males employed conditional mating tactics according to their body sizes. We found that male home-range sizes were not positively associated with body size, but encounter rates with breeding females were. Although all males searched widely for females, mating access appeared to be largely determined by fighting ability. Large males encountered more breeding females and had more frequent encounters during the females' estimated receptive periods than did small- and medium-sized males. Paternity was highly skewed toward the three dominant males who fathered 91% of the cubs sampled during the 3-year study. Paternity was correlated with the frequency of male encounters during female receptive periods. Male encounters, however, overestimated the success of medium-sized males and underestimated the overall variance in male reproductive success. Multiple paternity occurred in two of seven litters, indicating that sperm competition is important in black bear mating behaviour. Implications for male lifetime reproductive success are discussed.

Sex ratio in relation to timing of breeding, and laying sequence in a dimorphic seabird

When the cost of rearing sons and daughters differs and the subsequent survival and reproductive success of one sex is more dependent than the other, on the amount of parental investment, adult females tend to produce more chicks of the more dependent sex if the females are in good condition themselves. One method of varying the total investment in each sex is through modifying the sex ratio of offspring produced. This study shows that in broods of European Shags Phalacrocorax aristotelis, the sex ratio varied with laying date. Presumably in this species, the lifetime reproductive success of males is more dependent on the level of parental investment. Early breeders are in better condition, the brood sex ratio of early broods was male biased (0.63), while that of late broods was female biased (0.36). The overall difference in sex ratio found between early and late nests could be attributed to manipulation of sex in the first laid egg. In early broods, 77% of the first hatched chicks were male but only 30% of the first hatched chicks in late broods were male. The sex combination of the first two chicks in a brood significantly affected growth as measured by asymptotic mass.

INBREEDING AND ITS FITNESS EFFECTS IN AN INSULAR POPULATION OF SONG SPARROWS (MELOSPIZA MELODIA).

Inbreeding depression is thought to be a major factor affecting the evolution of mating systems and dispersal. While there is ample evidence for inbreeding depression in captivity, it has rarely been documented in natural populations. In this study, I examine data from a long-term demographic study of an insular population of song sparrows (Melospiza melodia) and present evidence for inbreeding depression. Forty-four percent of all matings on Mandarte Island, British Columbia, were among known relatives. Offspring of a full-sib mating (f = 0.25) experienced a reduction in annual survival rate of 17.5% on average. Over their lifetime, females with f = 0.25 produced 48% fewer young that reached independence from parental care. In contrast, male lifetime reproductive success was not affected by inbreeding. Reduced female lifetime reproductive success was mostly due to reduced hatching rates of the eggs of inbred females. Relatedness among the parents did not affect their reproductive success. Using data on survival from egg stage to breeding age, I estimated the average song sparrow egg on Mandarte Island to carry a minimum of 5.38 lethal equivalents (the number of deleterious genes whose cumulative effect is equivalent to one lethal); 2.88 of these lethal equivalents were expressed from egg stage to independence of parental care. This estimate is higher than most estimates reported for laboratory populations and lower than those reported for zoo populations. Hence, the costs of inbreeding in this population were substantial and slightly above those expected from laboratory studies. Variability in estimates of lethal equivalents among years showed that costs of inbreeding were not constant across years.

Philopatry or dispersal: competition for territory vacancies in the splendid fairy-wren, Malurus splendens

Abstract. This study examines intra-sexual competition for territory vacancies and natal dispersal in the cooperatively breeding splendid fairy-wren resident near Perth, Western Australia. Observational data from a 17-year study were used to test several current hypotheses of natal dispersal. Demographic and environmental factors influenced dispersal within the cooperative social system and promiscuous mating system. Survival of breeding adults was high, and in most years the few available vacancies were in established groups; new groups were formed infrequently. Surplus males were always available for any vacancy that occurred; in some years, there were more vacancies than spare females. Birds of both sexes inherited the senior positions in their natal territory (61% of known males and 39% of females). Natal dispersal was female biased, but many birds of both sexes delayed dispersal and helped for 1 or more years in their natal territory before acquiring a senior position there or elsewhere. Few birds of either sex dispersed more than one territory away front their natal territory; more than 75% of males and females bred in their natal territory or an adjacent one. Vacancies for both males and females were filled by birds from outside the group only if no replacement was available from within; replacement was rapid during the breeding season with no overt competition, even though, in most cases, several non-breeding candidates were available in adjacent territories. Vacancies filled from outside the group were not always taken by the oldest available bird. Once past their first year, male helpers were more likely to stay in their natal territory, often eventually inheriting it; males rarely left groups in which they were the sole male helper. No synchronized pulse of post-fledging dispersal occurred, but some juveniles did disperse and wander. Most dispersal occurred in response to an obvious opportunity. No evidence of inbreeding avoidance was found and dispersal was unrelated to the lifetime reproductive success of males or females.

Male Reproductive Investment and Venereal Diseases in Plants: The Case of the Sticky Catchfly, Lychnis viscaria

The fungus Ustilago violacea is dispersed between certain caryophyllaceous plants, including Lychnis viscaria, by pollinating insects. Infection leads to sterility the following season when the infected plant produces fungal spores instead of pollen. Attraction of pollinators is thus associated not only with the cost of producing flowers but also with a risk of becoming infected by the fungus. In this paper I analyse male lifetime reproductive success as a function of incidence of infection in a population, cost of flower production and attractiveness to pollinators (measured as size of the inflorescence)