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PubMed2005

Temporal genetic structure of a drone congregation area of the giant Asian honeybee (Apis dorsata).

The giant Asian honeybee (Apis dorsata), like all other members of the genus Apis, has a complex mating system in which the queens and males (drones) mate at spatially defined drone congregation areas (DCAs). Here, we studied the temporal genetic structure of a DCA of A. dorsata over an 8-day time window by the genotyping of sampled drones with microsatellite markers. Analysis of the genotypic data revealed a significant genetic differentiation between 3 sampling days and indicated that the DCA was used by at least two subpopulations at all days in varying proportions. The estimation of the number of colonies which used the DCA ranged between 20 and 40 colonies per subpopulation, depending on the estimation procedure and population. The overall effective population size was estimated as high as N (e)=140. The DCA seems to counteract known tendencies of A. dorsata for inbreeding within colony aggregations by facilitating gene flow among subpopulations and increasing the effective population size.

Animals↗
PubMed1969

Polymorphism resulting from the mating advantage of rare male genotypes.

An algebraic model is presented for selection by the mating advantage of rare genotypes. In accordance with the results of recent experiments, the selective advantage is formulated as inversely proportional to genotype frequency. The model applies to any number of alleles at an autosomal locus or at a sex-linked locus, and it provides for a different intensity of selection for each genotype in each sex. The frequency of an allele under this selection proceeds to a stable, nontrivial equilibrium when any one of the genotypes carrying the allele and any one of those carrying another allele possess some degree of the advantage which varies inversely with genotype frequency. The changes in gene frequency are not affected by the mating system, being, for instance, the same with random mating as with inbreeding. With low values for the selection parameters, genetic polymorphisms could be maintained with little selection apparent except at rather low or rather high gene frequencies. The rare genotype advantage may be a significant element among the mechanisms which maintain the extensive genetic polymorphisms of natural populations.

Animals↗
PubMed1999

Supply of genetic information--amount, format, and frequency.

The volume and complexity of genetic information is increasing because of new traits and better models. New traits may include reproduction, health, and carcass. More comprehensive models include the test day model in dairy cattle or a growth model in beef cattle. More complex models, which may include nonadditive effects such as inbreeding and dominance, also provide additional information. The amount of information per animal may increase drastically if DNA marker typing becomes routine and quantitative trait loci information is utilized. In many industries, evaluations are run more frequently. They result in faster genetic progress and improved management and marketing opportunities but also in extra costs and information overload. Adopting new technology and making some organizational changes can help realize all the added benefits of the improvements to the genetic evaluation systems at an acceptable cost. Continuous genetic evaluation, in which new records are accepted and breeding values are updated continuously, will relieve time pressures. An online mating system with access to both genetic and marketing information can result in mating recommendations customized for each user. Such a system could utilize inbreeding and dominance information that cannot efficiently be accommodated in the current sire summaries or off-line mating programs. The new systems will require a new organizational approach in which the task of scientists and technicians will not be simply running the evaluations but also providing the research, design, supervision, and maintenance required in the entire system of evaluation, decision making, and distribution.

Animals↗
PubMed2005

Male mate choice influences female promiscuity in Soay sheep.

In most animal species, males are predicted to compete for reproductive opportunities, while females are expected to choose between potential mates. However, when males' rate of reproduction is constrained, or females vary widely in 'quality', male mate choice is also predicted to occur. Such conditions exist in the promiscuous mating system of feral Soay sheep on St Kilda, Scotland, where a highly synchronized mating season, intense sperm competition and limitations on sperm production constrain males' potential reproductive rate, and females vary substantially in their ability to produce successful offspring. We show that, consistent with predictions, competitive rams focus their mating activity and siring success towards heavier females with higher inclusive fitness. To our knowledge, this is the first time that male mate choice has been identified and shown to lead to assortative patterns of parentage in a natural mammalian system, and occurs despite fierce male-male competition for mates. An additional consequence of assortative mating in this population is that lighter females experience a series of unstable consorts with less adept rams, and hence are mated by a greater number of males during their oestrus. We have thus also identified a novel male-driven mechanism that generates variation in female promiscuity, which suggests that the high levels of female promiscuity in this system are not part of an adaptive female tactic to intensify post-copulatory competition between males.

Animals↗
PubMed1993

Effect of a founder event on variation in the genetic sex-determining system of the fire ant Solenopsis invicta.

Effects of a recent founder event on genetic diversity in wild populations of the fire ant Solenopsis invicta were studied, with particular attention given to the genetic sex-determining system. Diploid males are far more common relative to haploid males in introduced populations than in native populations of fire ants, and queens that produce diploid males account for a significantly larger proportion of the mated queens in introduced than in native populations. Differences between native and introduced populations in attributes of the mating systems (i.e., queen mating frequency or level of inbreeding) can be excluded as factors contributing to these different levels of diploid male production. Thus, we conclude that diploid males have increased in frequency in introduced populations because of a loss of allelic diversity at the sex-determining locus (loci). This loss of sex alleles has generated a substantial increase in the estimated segregational genetic load associated with production of sterile diploid males in introduced populations over the load in native populations. The loss of allelic diversity in the sex-determining system in introduced S. invicta is paralleled by a loss of electrophoretically detectable rare alleles at protein-encoding loci. Such concordance between these different types of markers is predicted because each of the many sex alleles present in the native populations is expected to be rare. Estimates of expected heterozygosity (Hexp) based on 76 electrophoretic loci do not differ significantly between the native and introduced fire ant populations, illustrating the lack of sensitivity of this measure for detecting many types of bottlenecks.

Alleles↗
PubMed2000

Local Competition, Inbreeding, and the Evolution of Sex-Biased Dispersal.

Using game theory, we developed a kin-selection model to investigate the consequences of local competition and inbreeding depression on the evolution of natal dispersal. Mating systems have the potential to favor strong sex biases in dispersal because sex differences in potential reproductive success affect the balance between local resource competition and local mate competition. No bias is expected when local competition equally affects males and females, as happens in monogamous systems and also in polygynous or promiscuous ones as long as female fitness is limited by extrinsic factors (breeding resources). In contrast, a male-biased dispersal is predicted when local mate competition exceeds local resource competition, as happens under polygyny/promiscuity when female fitness is limited by intrinsic factors (maximal rate of processing resources rather than resources themselves). This bias is reinforced by among-sex interactions: female philopatry enhances breeding opportunities for related males, while male dispersal decreases the chances that related females will inbreed. These results meet empirical patterns in mammals: polygynous/promiscuous species usually display a male-biased dispersal, while both sexes disperse in monogamous species. A parallel is drawn with sex-ratio theory, which also predicts biases toward the sex that suffers less from local competition. Optimal sex ratios and optimal sex-specific dispersal show mutual dependence, which argues for the development of coevolution models.

kin selection↗
PubMed2000

Female mate choice for large males in several species of seaweed fly (Diptera: Coelopidae).

The mating system of the seaweed fly Coelopa frigida involves a vigorous premating struggle during which females attempt to dislodge mounted males by kicking and shaking from side to side. Additionally females can prevent engagement of genitalia by curling their abdomens downwards. Large males gain a mating advantage. Male size is partially determined by a chromosomal inversion polymorphism which is maintained by strong heterosis. Thus female mate choice on the basis of size will affect offspring fitness. We report the occurrence of premating struggles and mate choice for large males in five additional species of seaweed fly, namely, C. nebularum, C. vanduzeei, C. pilipes, Gluma musgravei and G. nitida. Four of these species appear to lack the inversion system, suggesting that mate choice for large males can be maintained in its absence and also evolved before its establishment. Gluma females had stronger preferences than Coelopa females and showed an additional response to mounting, namely, curling their abdomens upwards into the male. This may allow assessment of male size. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1992

Development of partner preferences in female prairie voles (Microtus ochrogaster): the role of social and sexual experience.

Prairie voles (Microtus ochrogaster) exhibit a monogamous mating system characterized by long-term pair bonds between mates. The purpose of this study was to examine the effect of cohabitation time and sexual experience on the development of pair bond formation in female prairie voles. Females that were allowed to cohabit for 24 hr or more, with or without mating, exhibited a strong social preference for a familiar partner versus a strange male. Females that cohabited and mated for 6 hr showed strong preferences for a familiar partner, while cohabitation for less than 24 hr, without mating, did not result in preferences for the familiar male. These results indicate that mating was not essential for partner preference formation; however, preferences developed more rapidly when mating occurred.

Aggression↗
PubMed2004

Incorporating mating preferences into a host-parasite model.

Mating preferences are incorporated into a host-macroparasite system. Mating preferences of the host and/or parasite can affect the outcome of the host-parasite relationship if certain genotypes of the host are more (or less) affected by the parasite induced death rate than others. Several examples illustrate the situations that can occur.

Algorithms↗
PubMed1969

Conjugation in Escherichia coli K-12 and its modification by irradiation.

The steps of normal bacterial conjugation (union, transfer, integration and segregation) are described in analytical terms. Only two parameters are utilized: nu(mt) (0), the probability of interruption of transfer of the male chromosome per unit chromosomal distance; and nu(r) (0), the probability per unit chromosomal distance of a recombinational event. Experimentally these two parameters have the same value (0.06 min(-1) or 10(-6) per nucleotide pair). Irradiation of the donor parent prior to mating increases the transfer parameter (nu(mt) = nu(mt) (0) + sigma(mt)D) and a complete description of the radiation response of recombinant production is obtained by a consideration of the single parameter sigma(mt). Irradiation of the recipient parent prior to mating increases the recombination parameter (nu(r) = nu(r) (0) + sigma(r)D) and a complete description of the radiation response of recombinant production is obtained by the addition of the parameter sigma(r). Experimentally sigma(mt) and sigma(r) are found to have the same value, approximately 0.004 krad(-1) min(-1) for X-irradiation. It is thus possible to describe mathematically the behavior of the unperturbed mating system by a single parameter nu(0); a single additional parameter sigma is adequate to describe the behavior of the system when either parental type is irradiated prior to mating. The unexpected observation that nu(mt) and nu(r) have the same value suggests that common molecular mechanisms are involved in the transfer and integration steps.

Conjugation, Genetic↗
PubMed2005

The multiple signals assessed by female satin bowerbirds: could they be used to narrow down females' choices of mates?

Female choice based on multiple male traits has been documented in many species but the functions of such multiple traits are still under debate. The satin bowerbird has a polygynous mating system in which males attract females to bowers for mating; females choose mates based on multiple aspects of males and their bowers. In this paper, we demonstrate that females use some cues to decide which males to examine closely and other cues to decide which males to mate with. Female visitation rates to bowers were significantly related to male size and the males' 'solitary' display rates, and, to a lesser extent, to the numbers of bower decorations. After controlling for female visitation rates, it was found that a male's mating success was significantly related to his size and the rate at which he 'painted' his bower with saliva and chewed up plant material.

Adult↗
PubMed2001

Heterothallism in Peronospora farinosa f.sp. chenopodii, the causal agent of downy mildew of quinoa (Chenopodium quinoa).

Heterothallism in Peronospora farinosa f.sp. chenopodii, the causal agent of downy mildew of quinoa (Chenopodium quinoa) is reported for the first time. Downy mildew is the most important disease of this crop in the Andean region. Eight single-lesion isolates from different regions in Peru and Bolivia were crossed in all possible combinations using a detached leaf assay, to determine the mating system of the downy mildew pathogen. The presence of two mating types, P1 and P2, was revealed showing that P. farinosa f.sp. chenopodii is heterothallic. It is suggested that frequent sexual reproduction is an important evolutionary force in this pathogen in South America.

Chenopodium quinoa↗
PubMed1997

Infanticide by males in a spider with suicidal maternal care, Stegodyphus lineatus (Eresidae)

Infanticide by males in species with high maternal investment may be the most extreme example of a reproductive conflict of interests between males and females. The subsocial spider Stegodyphus lineatus is semelparous, and the offspring eat their mother. Male and female maturation overlap, such that late maturing males encounter females that are already guarding the single clutch. A late male may try to remove the existing egg sac, thereby forcing the female to replace the clutch and use his sperm to fertilize at least some of the eggs. Males were responsible for 33% of all the egg losses in a population of 278 females with eggs. By losing her clutch, the female loses time equivalent to the age of the lost clutch plus the time it takes to replace it. The earlier in the season a female lost a clutch and the younger the eggs were, the longer was the interval between clutch loss and clutch replacement. Females that lost their egg sacs by infanticide replaced them after a significantly longer time than females that lost their egg sacs from other causes. The time loss of 18.5 days on average corresponds to a 23% reduction in female survival probability. In addition to reduced survival, females suffered a fecundity cost: replacement clutches were smaller than the original clutches and the reduction in egg number was greater with increasing intervals between the first and second clutch. Females defended their egg sacs aggressively against males. In field tests, the outcome of fights between males and females was determined by the relative size difference of the contestants. The mating system of S. lineatus provides an example of a male mating strategy that evolved despite being very costly for the females.

Journal Article↗
PubMed1999

Parasites promote mating success: the case of a midge and a mite.

I tested the prediction that the hydracharinid mite Unionicola ypsilophora reduces mating success in the chironomid midge Paratrichocladius rufiventris. Males of the midge form mating swarms through which females fly to emerge after a few minutes with a mate. This mating system is believed to depend upon the male capturing a mate after aerial competition between males. Thus aerobatic ability is expected to determine success and a large ectoparasite should impair aerial performance. The proportion of infested males in swarms (ca. 4%) was less than that in mated pairs (ca. 15%). Infestation thus improved the expected mating success of the male midge. This finding is counterintuitive and may be a chance effect of no adaptive value to host or parasite. Alternatively, it may be an adaptive manipulation of the host by the parasite. This study provides evidence for the latter explanation. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1998

Microsatellite evidence for monogamy and sex-biased recombination in the Western Australian seahorse Hippocampus angustus.

Four polymorphic microsatellite loci were used to assess biological parentage of 453 offspring from 15 pregnant males from a natural population of the Western Australian seahorse Hippocampus angustus. Microsatellite genotypes in the progeny arrays were consistent with a monogamous mating system in which both females and males had a single mate during a male brooding period. Multilocus genotypes implicated four females in the adult population sample as contributors of eggs to the broods of collected males, but there was no evidence for multiple mating by females. Based on genotypic data from the progeny arrays, two loci were linked tightly and the recombination rate appeared to be approximately 10-fold higher in females than in males. The utility of linked loci for parentage analyses is discussed.

Animals↗
PubMed2003

Sexual selection and the risk of extinction in birds.

The relationship between sexual selection and extinction risk has rarely been investigated. This is unfortunate because extinction plays a key role in determining the patterns of species richness seen in extant clades, which form the basis of comparative studies into the role that sexual selection may play in promoting speciation. We investigate the extent to which the perceived risk of extinction relates to four different estimates of sexual selection in 1030 species of birds. We find no evidence that the number of threatened species is distributed unevenly according to a social mating system, and neither of our two measures of pre-mating sexual selection (sexual dimorphism and dichromatism) was related to extinction risk, after controlling for phylogenetic inertia. However, threatened species apparently experience more intense post-mating sexual selection, measured as testis size, than non-threatened species. These results persisted after including body size as a covariate in the analysis, and became even stronger after controlling for clutch size (two known correlates of extinction risk). Sexual selection may therefore be a double-edged process-promoting speciation on one hand but promoting extinction on the other. Furthermore, we suggest that it is post-mating sexual selection, in particular, that is responsible for the negative effect of sexual selection on clade size. Why this might be is unclear, but the mean population fitness of species with high intensities of post-mating sexual selection may be especially low if costs associated with multiple mating are high or if the selection load imposed by post-mating selection is higher relative to that of pre-mating sexual selection.

Animals↗
PubMed2004

Post-mating clutch piracy in an amphibian.

Female multiple mating and alternative mating systems can decrease the opportunity for sexual selection. Sperm competition is often the outcome of females mating with multiple males and has been observed in many animals, and alternative reproductive systems are widespread among species with external fertilization and parental care. Multiple paternity without associated complex behaviour related to mating or parental care is also seen in simultaneously spawning amphibians and fishes that release gametes into water. Here we report 'clutch piracy' in a montane population of the common frog Rana temporaria, a reproductive behaviour previously unknown in vertebrates with external fertilization. Males of this species clasp the females and the pair deposits one spherical clutch of eggs. No parental care is provided. 'Pirate' males search for freshly laid clutches, clasp them as they would do a female and fertilize the eggs that were left unfertilized by the 'parental' male. This behaviour does not seem to be size-dependent, and some males mate with a female and perform clutch piracy in the same season. Piracy affected 84% of the clutches and in some cases increased the proportion of eggs fertilized, providing direct fitness benefits both for the pirate males and the females. Sexual selection--probably caused by a strong male-biased sex ratio--occurs in this population, as indicated by size-assortative mating; however, clutch piracy may reduce its impact. This provides a good model to explore how alternative mating strategies can affect the intensity of sexual selection.

Animals↗
PubMed2006

The population genetics of sporophytic self-incompatibility in Senecio squalidus L. (Asteraceae): the number, frequency, and dominance interactions of S alleles across its British range.

Sporophytic self-incompatibility (SSI) was studied in 11 British Senecio squalidus populations to quantify mating system variation and determine how its recent colonization of the United Kingdom has influenced its mating behavior. S allele number, frequency, and dominance interactions in populations were assessed using full diallels of controlled pollinations. A mean of 5.1 S alleles per population was observed, and no population contained more than six S alleles. Numbers of S alleles within populations of S. squalidus declined with increasing distance from the center of its introduction (Oxford). Cross-classification of S alleles allowed an estimate of approximately seven and no more than 11 S alleles for the entire British S. squalidus population. The low number of S alleles observed in British S. squalidus compared to other SI species is consistent with the population bottleneck associated with S. squalidus' introduction to the Oxford Botanic Garden and subsequent colonization of Britain. Extensive S allele dominance interactions were observed to be a feature of the S. squalidus SSI system and may represent an adaptive response to improve limited mate availability imposed by the presence of so few S alleles. Multilocus allozyme genotypes were also identified for individuals in all populations and geographic patterns of S locus and allozyme loci variation investigated. Less interpopulation structure was observed for the S locus than for allozyme diversity--a finding indicative of the effects of negative frequency-dependent selection at the S locus maintaining equal S phenotypes within populations and enhancing effective migration between populations.

Alleles↗