Levels Of Polyandry Research Articles

Levels of Polyandry and Intracolonial Genetic Relationships in Apis dorsata (Hymenoptera: Apidae)

Pupae and adults of 4 Apis dorsata F. colonies from northern Thailand were collected in liquid nitrogen. DNA was extracted, and microsatellite genotypes at 3 loci determined for 42-194 workers per colony. From these data, the queen genotype was inferred, and the number of males with which each queen mated deduced. These A. dorsata queens mated with a mean of 26.75 ± 5.42 (SEM) drones (range, 13-39). The mean within-colony genetic relatedness was 0.29 ± 0.009. All colonies were monogynous. Possible reasons for the very high level of polyandry and the great variance are discussed. A null allele was detected for 1 microsatellite locus in 1 queen progeny.

Sperm Competition Cannot Eliminate Protandry

Many butterfly species are protandrous, that is males emerge some time before the females. Models aiming to explain protandry generally assume that females mate only once, while males are capable of multiple matings. This assumption is not generally fulfilled, however. In polyandrous species (females mating repeatedly), protandry is often reduced or absent, and males are relatively large. A possible explanation for the observed pattern is offered by the so-called sperm competition hypothesis. According to this hypothesis, male size is positively correlated with male reproductive success, because mating with large males lowers the propensity of females to remate. After remating, females fertilize eggs with sperm of the latter male. The number of eggs fertilized as the result of a mating therefore, increases with size. According to the sperm competition hypothesis, the selection pressure for large size counterbalances that for early emergence. In this paper, it is shown that the sperm competition hypothesis fails to explain the absence of protandry in polyandrous species. The analysis shows that the proposed mechanism only affects the level of polyandry.

Levels of polyandry and intracolonial genetic relationships in Apis florea

Levels of polyandry and intracolonial genetic relationships in Apis florea

Levels of polyandry and intracolonial genetic relationships in Apis florea

DNA was extracted from worker and drone pupae of each of five colonies of the dwarf honey bee Apis florea. Polymerase chain reactions (PCR) were conducted on DNA extracts using five sets of primers known to amplify microsatellite loci in A. mellifera. Based on microsatellite allele distributions, queens of the five colonies mated with at least 5–14 drones. This is up to 3 times previous maximum estimates obtained from sperm counts. The discrepancy between sperm count and microsatellite estimates of the number of matings in A. florea suggests that despite direct injection of semen into the spermatheacal duct, either A. florea drones inject only a small proportion of their semen, or queens are able to rapidly expel excess semen after mating. A model of sexual selection (first proposed by Koeniger and Koeniger) is discussed in which males attempt to gain reproductive dominance by increasing ejaculate volume and direct injection of spermatozoa into the spermatheca, while queens attempt to maintain polyandry by retaining only a small fraction of each male's ejaculate. It is shown, at least in this limited sample, that the effective number of matings is lower in A. florea than in A. mellifera.

The function of the mating sign in honey bees, Apis mellifera L.: new evidence

Five microsatellite loci were used to determine paternities in six Apis mellifera colonies headed by naturally mated queens. The last inseminating males were identified by collecting and genotyping the mating sign left in the genital tract of each queen. Significant differences in paternity frequencies were observed between males, but the proportion of worker and queen offspring sired by the last inseminating drone did not differ significantly from those of other drones. Each male kept his rank of precedence for the different cohorts, although the variance in subfamily proportions decreased over time, most notably in the colony displaying the lowest level of polyandry. These results suggest that, if sperm competition exists in the honeybee, it does not significantly increase the fitness of the last inseminating drone. The spermatozoa of the different inseminating drones are not totally mixed before they reach the spermatheca, in particular when only few males mate with the queen. The weak difference in the subfamily proportions observed between queen and worker samples confirms that nepotistic interactions are rare. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.

Can we predict the mating pattern ofDrosophila females from the sperm length distribution in males?

In order to test the validity of the prediction of the mating pattern of females from the sperm length distribution in males, three species of Drosophila were analysed. Males in the three species are equally polygynous but females differ in the level of polyandry. A 'low recurrence polyandry' is observed in the sperm dimorphic species D. affinis while a 'high recurrence polyandry' is observed in the sperm monomorphic species D. latifasciaeformis and D. littoralis. These results are consistent with the hypothesis proposed previously that sperm dimorphism in males can only be maintained by a selective alternative in females (i.e. facultative female polygamy), whereas a stricter mating system (e.g. 'obligatory' polyandry) should only result in sperm monomorphism irrespective of the absolute value of sperm length.

SEX-INVESTMENT RATIOS AND RELATEDNESS IN THE MONOGYNOUS ANT LASIUS NIGER (L.).

The genetic variation at two marker loci in three populations of the monogynous ant Lasius niger was used to analyze the importance of relatedness structure to sex-investment ratios in sexuals produced by colonies living in different resource conditions. From a resource-rich monoculture to a population in a resource-limited environment, dry weight investment in queens decreased from female-biased (0.76) to equality with male investment (Boomsma et al., 1982). The investment ratios in sexuals expected from the estimated relatedness ratios, resulting from kin-selection theory (Trivers and Hare, 1976), were in good agreement with the observed ratios in all populations. This indicated that the workers can capitalize on the asymmetry in relatedness, opposing the queen's interest, despite the contrast in environmental conditions in the different populations. This asymmetry, however, almost disappeared in the marginal population, due to a high frequency of double mating and worker production of males, resulting in a much reduced queen-worker conflict. We suggest that different levels of polyandry might be favored at different points of the resource gradient, with the sex ratio secondarily depending on these polyandry levels. As there was no population subdivision or spatial structure within the populations, group-selection and local-mate-competition models cannot account for the observed female-biased ratios, whereas they were rather accurately predicted by kin-selection theory.