Bill colour and body condition in the Moorhen Gallinula chloropus

Capsule We found yellow to be an honest signal of health status.     

Observational and Experimental Evidence for the Function of Tail Flicking in Eurasian Moorhen Gallinula chloropus

Tail movements such as wagging, flicking or pumping are reported from many bird species but their adaptive functions remain poorly understood. To investigate whether tail flicking functions as an alarm signal, either to predators or neighbouring birds, or as a signal of submission to conspecifics, I observed this behaviour in moorhen in a natural context, and conducted playback experiments using vocalizations of predators, conspecifics and heterospecifics. I found positive relationships between flicking and vigilance and nearest neighbour distance, and negative relationships between flicking and moorhen flock size and total flock size. Moorhen at the edge of a flock flicked at a higher rate. Single moorhen flicked more often compared with individuals in groups, both in single‐ and mixed‐species flocks, and there was a tendency that single moorhen flicked more often than single moorhen within a mixed‐species flock. Moorhen responded differently to conspecific and predator calls. While in both cases vigilance increased, tail flick rate was higher during predator playbacks and lower during conspecific playbacks. Furthermore, moorhen remained rather motionless when conspecific calls were played back, but not during predator calls, and, moorhen resumed to a baseline level of tail flicking more quickly after the playback of conspecific calls. Taken together, the results suggest that flicking may be considered as a honest signal of vigilance directed towards ambushing predators.     

Gene flow from multiple sources maintains high genetic diversity and stable population history of Common Moorhen Gallinula chloropus in China

In this study, we used mitochondrial control sequences and microsatellite data from 231 Common Moorhen Gallinula chloropus individuals sampled from 19 sites in China to analyse their genetic structure and evolutionary history. High genetic diversity was found for all populations, although microsatellite analysis showed that the genetic diversity in non‐migratory populations was significantly higher than in migratory populations. High gene flow occurred between neighbouring populations, although long‐distance gene flow also occurred. The Huazhong population was the single greatest genetic source for other populations. High gene flow probably led to the shallow genetic structure that we observed. Demographic expansion was found in migratory populations, non‐migratory populations and with all individuals combined. The expansion time for all populations combined was estimated to be 221 000 years ago. The Common Moorhen population grew rapidly during the interglacial before the last glacial maximum (LGM), then remained generally stable from the LGM to the present.     

Age differences in the feeding ability of Moorhens Gallinula chloropus

Numerous studies have shown that juvenile birds obtain food at a slower rate than do adults (Norton-Griffiths 1968, Recher & Recher 1969, Orians 1969, Dunn 1972, Davies& Green 1976, Groves 1978), We compared the foraging behaviour of adult and juvenile Moorhens Gallinula chloropus and tried to assess the relative importance of different components of feeding in determining the intake rate.     

Juvenile helping in the moorhen,Gallinula chloropus

In a 3-year study of the moorhen, Gallinula chloropus, some chicks from first broods stayed on their natal territory once they had reached independence, and helped to rear their younger, second brood, siblings. Juvenile dispersal was constrained by habitat saturation, and first brood young were forced to stay on their natal territory. Juveniles that hatched early in the year were forced to stay longer, and helped more than those that hatched late. The total feeding rates to broods with and without juvenile helpers were the same, but parents with helpers reduced their feeding rates relative to parents without helpers. Pairs with helpers (=pairs attempting second broods) reared more chicks per nesting, attempt than pairs rearing chicks at the same time of year without helpers (=pairs attempting first clutch renests). This was true both for all clutches, and for hatched clutches only, even when controlling for parental quality, territory size and scasonal effects.     

Beyond lifetime reproductive success: the posthumous reproductive dynamics of male Trinidadian guppies

In semelparous populations, dormant germ banks (e.g. seeds) have been proposed as important in maintaining genotypes that are adaptive at different times in fluctuating environments. Such hidden storage of genetic diversity need not be exclusive to dormant banks. Genotype diversity may be preserved in many iteroparous animals through sperm-storage mechanisms in females. This allows males to reproduce posthumously and increase the effective sizes of seemingly female-biased populations. Although long-term sperm storage has been demonstrated in many organisms, the understanding of its importance in the wild is very poor. We here show the prevalence of male posthumous reproduction in wild Trinidadian guppies, through the combination of mark–recapture and pedigree analyses of a multigenerational individual-based dataset. A significant proportion of the reproductive population consisted of dead males, who could conceive up to 10 months after death (the maximum allowed by the length of the dataset), which is more than twice the estimated generation time. Demographic analysis shows that the fecundity of dead males can play an important role in population growth and selection.     

Factors affecting the reproductive success of dominant male meerkats

Identifying traits that affect the reproductive success of individuals is fundamental for our understanding of evolutionary processes. In cooperative breeders, a dominant male typically restricts mating access to the dominant female for extended periods, resulting in pronounced variation in reproductive success among males. This may result in strong selection for traits that increase the likelihood of dominance acquisition, dominance retention and reproductive rates while dominant. However, despite considerable research on reproductive skew, few studies have explored the factors that influence these three processes among males in cooperative species. Here we use genetic, behavioural and demographic data to investigate the factors affecting reproductive success in dominant male meerkats (Suricata suricatta). Our data show that dominant males sire the majority of all offspring surviving to 1 year. A male's likelihood of becoming dominant is strongly influenced by age, but not by weight. Tenure length and reproductive rate, both important components of dominant male reproductive success, are largely affected by group size and composition, rather than individual traits. Dominant males in large groups have longer tenures, but after this effect is controlled, male tenure length also correlates negatively to the number of adult females in the group. Male reproductive rate also declines as the number of intra- and extra-group competitors increases. As the time spent in the dominant position and reproductive rate while dominant explain > 80% of the total variance in reproductive success, group composition thus has major implications for male reproductive success.     

Differential male reproductive success in Douglas fir

Summary Differential male reproductive success was studied in clones at two seed orchards of Douglas fir, Pseudotsuga menziesii (Mirb.) Franco. The performance of tester pollen parents was compared in controlled pollinations with two-parent pollen mixes. Marker pollen homozygous for a rare IDH allele was the genetic marker in each pollen mix. The resulting seeds were analyzed electrophoretically. At both seed orchards, the proportion of seeds sired by tester pollen significantly varied among the tester pollen parents. Tester pollen parents did not perform the same across all seed parents. The significant interaction effect was evidence of male-female complementarity. These results suggest a genetic basis to differential male reproductive success in Douglas fir.     

Overt and covert competition in a promiscuous mammal: the importance of weaponry and testes size to male reproductive success

Male contests for access to receptive females are thought to have selected for the larger male body size and conspicuous weaponry frequently observed in mammalian species. However, when females copulate with multiple males within an oestrus, male reproductive success is a function of both pre- and postcopulatory strategies. The relative importance of these overt and covert forms of sexual competition has rarely been assessed in wild populations. The Soay sheep mating system is characterized by male contests for mating opportunities and high female promiscuity. We find that greater horn length, body size and good condition each independently influence a male's ability to monopolize receptive females. For males with large horns at least, this behavioural success translates into greater siring success. Consistent with sperm-competition theory, we also find that larger testes are independently associated with both higher copulation rates and increased siring success. This advantage of larger testes emerges, and strengthens, as the number of oestrous females increases, as dominant males can no longer control access to them all. Our results thus provide direct quantitative evidence that male reproductive success in wild populations of mammals is dependent upon the relative magnitude of both overt contest competition and covert sperm competition.     

Seasonal variation in male alternative reproductive tactics

Genetic parentage analyses reveal considerable diversity in alternative reproductive behaviours (e.g. sneaking) in many taxa. However, little is known about whether these behaviours vary seasonally and between populations. Here, we investigate seasonal variation in male reproductive behaviours in a population of two‐spotted gobies (Gobiusculus flavescens) in Norway. Male two‐spotted gobies guard nests, attract females and care for fertilized eggs. We collected clutches and nest‐guarding males early and late in the breeding season in artificial nests and used microsatellite markers to reconstruct parentage from a subset of offspring from each nest. We hypothesized that mating, reproductive success and sneaking should be more prevalent early in the breeding season when competition for mates among males is predicted to be higher. However, parentage analyses revealed similar values of mating, reproductive success and high frequencies of successful sneaking early (30% of nests) and late (27% of nests) in the season. We also found that multiple females with eggs in the same nest were fertilized by one or more sneaker males, indicating that some males in this population engage in a satellite strategy. We contrast our results to previous work that demonstrates low levels of cuckoldry in a population in Sweden. Our results demonstrate marked stability in both the genetic mating system and male alternative reproductive tactics over the breeding season. However, sneaking rates may vary geographically within a species, likely due to local selection influencing ecological factors encountered at different locations.     

Variance in the reproductive success of dominant male mountain gorillas

Using 30 years of demographic data from 15 groups, this study estimates how harem size, female fertility, and offspring survival may contribute to variance in the siring rates of dominant male mountain gorillas throughout the Virunga Volcano Region. As predicted for polygynous species, differences in harem size were the greatest source of variance in the siring rate, whereas differences in female fertility and offspring survival were relatively minor. Harem size was positively correlated with offspring survival, even after removing all known and suspected cases of infanticide, so the correlation does not seem to reflect differences in the ability of males to protect their offspring. Harem size was not significantly correlated with female fertility, which is consistent with the hypothesis that mountain gorillas have minimal feeding competition. Harem size, offspring survival, and siring rates were not significantly correlated with the proportion of dominant tenures that occurred in multimale groups versus one-male groups; even though infanticide is less likely when those tenures end in multimale groups than one-male groups. In contrast with the relatively small contribution of offspring survival to variance in the siring rates of this study, offspring survival is a major source of variance in the male reproductive success of western gorillas, which have greater predation risks and significantly higher rates of infanticide. If differences in offspring protection are less important among male mountain gorillas than western gorillas, then the relative importance of other factors may be greater for mountain gorillas. Thus, our study illustrates how variance in male reproductive success and its components can differ between closely related species.     

Sexual selection: harem size and the variance in male reproductive success

Sexual selection is potentially stronger than natural selection when the variance in male reproductive fitness exceeds all other components of fitness variance combined. However, measuring the variance in male reproductive fitness is difficult when nonmating males are absent, inconspicuous, or otherwise difficult to find. Omitting the nonmating males inflates estimates of average male reproductive success and diminishes the variance, leading to underestimates of the potential strength of sexual selection. We show that, in theory, the proportion of the total variance in male fitness owing to sexual selection is approximately equal to H, the mean harem size, as long as H is large and females are randomly distributed across mating males (i.e., Vharem=H). In this case, mean harem size not only provides an easy way to estimate the potential strength of sexual selection but also equals the opportunity for sexual selection, I(mates). In nature, however, females may be overdispersed with VharemH. We show that H+(k-1) is a good measure of the opportunity for sexual selection, where k is the ratio Vharem/H. A review of mating system data reveals that in nature the median ratio for Vharem/H is 1.04, but as H increases, females tend to become more aggregated across mating males with V(harem) two to three times larger than H.     

Voice pitch predicts reproductive success in male hunter-gatherers

The validity of evolutionary explanations of vocal sexual dimorphism hinges upon whether or not individuals with more sexually dimorphic voices have higher reproductive success than individuals with less dimorphic voices. However, due to modern birth control methods, these data are rarely described, and mating success is often used as a second-rate proxy. Here, we test whether voice pitch predicts reproductive success, number of children born and child mortality in an evolutionarily relevant population of hunter-gatherers. While we find that voice pitch is not related to reproductive outcomes in women, we find that men with low voice pitch have higher reproductive success and more children born to them. However, voice pitch in men does not predict child mortality. These findings suggest that the association between voice pitch and reproductive success in men is mediated by differential access to fecund women. Furthermore, they show that there is currently selection pressure for low-pitch voices in men.     

Social bonds enhance reproductive success in male macaques

For animals living in mixed-sex social groups, females who form strong social bonds with other females live longer and have higher offspring survival [1-3]. These bonds are highly nepotistic, but sometimes strong bonds may also occur between unrelated females if kin are rare [2, 3] and even among postdispersal unrelated females in chimpanzees and horses [4, 5]. Because of fundamental differences between the resources that limit reproductive success in females (food and safety) and males (fertilizations), it has been predicted that bonding among males should be rare and found only for kin and among philopatric males [6] like chimpanzees [7-9]. We studied social bonds among dispersing male Assamese macaques (Macaca assamensis) to see whether males in multimale groups form differentiated social bonds and whether and how males derive fitness benefits from close bonds. We found that strong bonds were linked to coalition formation, which in turn predicted future social dominance, which influenced paternity success. The strength of males' social bonds was directly linked to the number of offspring they sired. Our results show that differentiated social relationships exert an important influence on the breeding success of both sexes that transcends contrasts in relatedness.