Genetic Analysis of Group Composition and Breeding System in a Wild Common Marmoset (Callithrix jacchus) Population

We established pedigree relations in three wild common marmoset social groups for which observational data were available, together with genotypes of some individuals from neighboring groups. Relatedness of 40 individuals were based on 11 microsatellite loci amplified from nDNA obtained noninvasively from plucked hair. The wild marmosets were only half as variable as a captive population characterized previously: 2–6 alleles/locus; H_O = 0.41 and H_E = 0.35. Parentage exclusion probabilities were 61.8% for an offspring and one alleged parent and 90.7% for an offspring with one confirmed and one alleged parent. Each group (n = 5–14 individuals) had two breeding females and 2 adult males. Within each group the infants and reproductively inactive adults were closely related to at least the breeding females; the latter were related to each other as closely as mother/infant pairs or sisters. Relatedness of adult males was lower, indicating recent intergroup dispersal. Genetic data confirm Callithrix jacchus live in relatively stable extended family groups of closely related individuals. Matings occurred preferentially among the least related adults and most infants were fathered by the dominant male. The genetic data are consistent with polygynmonandry as are the field observations. Callithrix have variable mating systems, ranging from monogamy to polyandry to polygyny within social groups plus extragroup copulations; our data provide no evidence for polyandry and are inconclusive with respect to extragroup paternity. Nevertheless, noninvasive multilocus genotyping methods will resolve these questions when longer-term studies of entire populations are undertaken.     

Mating frequency and genetic relatedness of workers in the hornet Vespa analis (Hymenoptera: Vespidae)

Mating frequency of Vespa analis queens and the genetic relatedness of their workers was analyzed by DNA microsatellite genotyping. Of 20 colonies studied, 18 had a queen inseminated by a single male and two had queens each inseminated by two males. The estimated effective number of matings was 1.05 ± 0.037 (mean ± SE), with 75–85% of the offspring of the two multiply mated queens sired by a single male. The pedigree relatedness between nestmate workers averaged over the 20 colonies was estimated to be 0.74 ± 0.008, almost identical to the predicted value of 0.75 for colonies headed by a singly mated queen. Multiple matrilines; that is, the presence of workers not related to the current queens, were detected in six colonies, suggesting that queen replacement occurred via usurpation of the founding queens in these six colonies. These results demonstrate that the kin structure of V. analis is similar to that reported in other vespid species.     

Are indirect genetic benefits associated with polyandry? Testing predictions in a natural population of lemon sharks

Multiple mating has clear fitness benefits for males, but uncertain benefits and costs for females. We tested for indirect genetic benefits of polyandry in a natural population, by using data from a long-term genetic and demographic study of lemon sharks ( Negaprion brevirostris ) at Bimini, Bahamas. To do so, we followed the fates of individuals from six cohorts (450 age-0 and 254 age-1 fish) in relation to their individual level of genetic variation, and whether they were from polyandrous or monoandrous litters. We find that offspring from polyandrous litters did not have a greater genetic diversity or greater survival than did the offspring of monoandrous litters. We also find no evidence of positive associations between individual offspring genetic diversity metrics and our surrogate measure of fitness (i.e. survival). In fact, age-1 individuals with fewer heterozygous microsatellite loci and more genetically similar parents were more likely to survive to age-2. Thus, polyandry in female lemon sharks does not appear to be adaptive from the perspective of indirect genetic benefits to offspring. It may instead be the result of convenience polyandry, whereby females mate multiply to avoid harassment by males. Our inability to find indirect genetic benefits of polyandry despite detailed pedigree and survival information suggests the need for similar assessments in other natural populations.     

Costs and Benefits of Mating in the Grasshopper Chorthippus parallelus (Caelifera: Acrididae)

Fitness consequences of different levels of mating benefits, viz., (1) virgin, (2) seldom mated, (3) free mating chances with the same male throughout the female's life span, and (4) free mating chances with three males always offered, were investigated in female meadow grasshoppers Chorthippus parallelus. No differences among the treatments were apparent in egg number per pod, total egg number per female, and hatching success of larvae. Seldom-mated females had offspring with the heaviest average larval dry weight. We did not find costs of mating in terms of reduced female longevity and residual dry weight between the treatments.     

Reproductive conflicts in polyandrous and polygynous ant Formica sanguinea

The occurrence of multiple reproductives within an ant colony changes the balance between indirect fitness benefits and reproductive competition. We test whether the number of matings by an ant queen (polyandry) correlates negatively with the number of reproductive queens in the colony (polygyny), whether the patrilines and matrilines differ in their contribution to the sexual and worker progeny and whether there is an overall reproductive skew. For these aims, we genotyped both worker and sexual offspring from colonies of the ant Formica sanguinea in three populations. Most colonies were monogynous, but eight (11%) were polygynous with closely related queens. Most queens in the monogynous colonies (86%) had mated with multiple males. The effective paternity was lower than the actual number of mates, and the paternity skew was significant. Furthermore, in some monogynous colonies, the patrilines were differently represented in the worker pupae and sexual pupae produced at the same time. Likewise, the matrilines in polygynous colonies were differently present in worker pupae and male offspring. The effective number of matings by a queen was significantly lower in polygynous colonies (mean m_e = 1.68) than in monogynous colonies (means 2.06–2.61). The results give support to the hypotheses that polyandry and polygyny are alternative breeding strategies and that reproductive competition can lead to different representation of patrilines and matrilines among the sexual and worker broods.     

Genotyping faeces reveals facultative kin association on capercaillie’s leks

The role that kin selection might play in the evolution of lekking in birds remains controversial. Recent molecular data suggest that males displaying on leks are related. Here we investigated the genetic structure and pattern of relatedness on leks of a declining population of capercaillie (Tetrao urogallus) using microsatellite genetic markers. Since the species is highly sensitive to disturbance, we adopted a non-invasive method by using faecal samples collected in the field. Based on a dataset of 50 males distributed in 6 sub-populations, we found significant genetic structuring among sub-populations, and a significant pattern of isolation by distance among leks. Estimates of relatedness showed that males displaying on the same lek were related, even when controlling for the effects of genetical differentiation among sub-populations. In addition, the frequency distribution of relatedness values indicated that leks contain a mixture of close kin and unrelated individuals (34 and 66%, respectively). This pattern is consistent with the hypothesis that leks often contain kin associations, which might be due to very restricted dispersal of some of the males or to joint dispersal of kin. The results are discussed with respect to their implication for the conservation of endangered populations.     

Alien eggs in duck nests: brood parasitism or a help from Grandma?

Intraspecific brood parasitism (IBP) is a remarkable phenomenon by which parasitic females can increase their reproductive output by laying eggs in conspecific females' nests in addition to incubating eggs in their own nest. Kin selection could explain the tolerance, or even the selective advantage, of IBP, but different models of IBP based on game theory yield contradicting predictions. Our analyses of seven polymorphic autosomal microsatellites in two eider duck colonies indicate that relatedness between host and parasitizing females is significantly higher than the background relatedness within the colony. This result is unlikely to be a by-product of relatives nesting in close vicinity, as nest distance and genetic identity are not correlated. For eider females that had been ring-marked during the decades prior to our study, our analyses indicate that (i) the average age of parasitized females is higher than the age of nonparasitized females, (ii) the percentage of nests with alien eggs increases with the age of nesting females, (iii) the level of IBP increases with the host females' age, and (iv) the number of own eggs in the nest of parasitized females significantly decreases with age. IBP may allow those older females unable to produce as many eggs as they can incubate to gain indirect fitness without impairing their direct fitness: genetically related females specialize in their energy allocation, with young females producing more eggs than they can incubate and entrusting these to their older relatives. Intraspecific brood parasitism in ducks may constitute cooperation among generations of closely related females.     

Brood mixing and reduced polyandry in a maternally mouthbrooding cichlid with elevated among-breeder relatedness

Uniparental maternal brood care often coincides with multiple paternity and single maternity of broods, possibly reflecting benefits of polyandry and costs of uniparental care. Genetic data from the maternally mouthbrooding cichlid fish Simochromis pleurospilus revealed the opposite pattern--low polyandry and allomaternal care. More than 70% of the investigated females had mated with a single male, and 14% of the females had unrelated fry in their broods. Broods with foreign fry were in the late stage of brood care, in which females guard free-swimming fry and recall the broods into their mouths for protection. With one exception, fostering females were related to their adopted fry at the level of first cousins (R(QG) > 0.12), but relatedness between fosters and adopted fry was not significantly higher than between fosters and fry tended by other females. Relatedness among breeders extended to the level of first-order relatives. Mean relatedness among contemporaneously breeding dams (R(QG) = 0.08) was significantly higher than among dams breeding in different seasons (R(QG) = -0.04), which suggests a temporal or spatial concentration of mouthbrooding relatives. Indeed, females sometimes brood in small groups. This behaviour may reduce brood predation but will increase the risk of brood mixing, which is possibly mitigated by low costs of brood care and indirect benefits accrued by relatedness among the breeders in the group. Remarkably, the apparent inbreeding potential did not give rise to bet-hedging polyandry or active avoidance of relatives, as half of the mated individuals were related at R(QG) > 0.13 and polyandry did not coincide with high within-pair relatedness.     

花绒寄甲的交配能力及多次交配对生殖产量的影响

花绒寄甲Dastarcus helophoroides Fairmaire为天牛类蛀干害虫的优势天敌昆虫,为明确该成虫的交配能力和多次交配行为在该虫种群繁衍中的作用,本研究评估了该虫在室内恒定条件下的性成熟期、交配次数、交配持续期和交配间隔期,以及通过设置交配1次、5次、10次和自由交配等4个处理,探讨了多次交配行为对成虫生殖产量的影响。结果表明,花绒寄甲的性成熟期平均为29.35 ± 0.34 d,交配发生时间主要集中在18:00 pm-2:00 am。在观察期内该虫的平均交配次数为4.49 ± 0.24次,其平均交配持续期为9.27 ± 0.12 min,平均交配间隔期为8.60 ± 0.26 d,且随交配次数的增加呈明显缩短趋势。此外,该虫的产卵量随交配次数的增加从交配1次的227.45 ± 15.32粒/雌增加至自由交配的1 426.03 ± 113.71粒/雌,孵化率从交配1次的68.93% ± 1.47%增加至自由交配的94.98% ± 0.90%,这些结果证实了花绒寄甲属典型的夜行性、收入型生殖的、多次交配的昆虫种类,交配能力较弱,但多次交配明显提高了该虫的生殖产量,从而支持精子补充假说。     

How many SNPs are enough?

Since the days of allozyme analysis, we have been enamored with the idea that if we just had enough polymorphic mendelian loci, we could gauge the inbreeding level of individuals by measuring heterozygosity and simultaneously measure the degree of genetic relatedness between pairs of individuals. Given Mendel’s Laws, we have always known that we would need numerous independently segregating loci to achieve any reasonable degree of accuracy. Santure et al. (2010, this issue) use a 771 marker SNP panel to assess heterozygosity levels and to assess pairwise relatedness, and compare both with theoretical expectations obtained from a carefully recorded pedigree of a zebra finch breeding colony, as a function of increasing numbers of SNP markers. They also compare the SNP results with those from a 20‐locus microsatellite panel, showing that adding SNPs to a fairly large microsatellite panel improves accuracy, but given an existing panel of 125 SNPs, little is to be gained by adding microsatellites. They show that the accuracy available for estimating individual levels of inbreeding is somewhat limited. They also show that the average pairwise relatedness measures bracket pedigree relationship very nicely, but the variances for individual pairs remain substantial, even with a very large panel.     

Multiple paternity in wild-caught Drosophila mojavensis

Female remating frequency and sperm allocation patterns can strongly influence levels of sperm competition and reproductive success in natural populations. In the laboratory, Drosophila mojavensis males transfer very few sperm per copulation and females remate often, suggesting multiple paternity should be common in nature. Here, we examine female sperm loads, incidence of multiple paternity, and sperm utilization by genotyping progeny from 20 wild-caught females at four highly polymorphic microsatellite loci. Based on indirect paternity analyses of 814 flies, we found evidence for high levels of multiple paternity coupled with relatively low reproductive output, consistent with the high levels of female remating predicted in this sperm-limited species. Overall, we found little evidence for last -- male sperm precedence though some temporal variation in sperm utilization was observed, consistent with laboratory findings.     

Polyandry in the wild: temporal changes in female mating frequency and sperm competition intensity in natural populations of the tettigoniid Requena verticalis

Empirical tests of sexual selection theory generally utilize model systems under laboratory settings, and extend conclusions to evolutionary processes occurring in nature. The biological significance of laboratory findings will depend largely on the mating rates of females and patterns of paternity in natural populations, information on which is generally lacking. Here we use microsatellite markers to provide rare estimates of female mating rates and patterns of parentage in a species of tettigoniid, Requena verticalis, which has been used extensively to test theory on the evolution of male parental investment and its influence on the direction of sexual selection. We found that although the number of males having a genetic representation in the female's sperm stores was higher for females collected late in the breeding season than those collected early in the season, overall the female mating rate was lower than that expected from laboratory observations. Analysis of parentage of offspring produced by females at the end of the breeding season revealed that all males represented in the sperm stores fathered offspring, although paternity was biased away from that expected from random sperm utilization. The data show that the complete first male sperm precedence documented in laboratory studies of this species does not persist in natural populations. Our data provide a solid underpinning for conclusions drawn from laboratory studies of this species.