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PubMed1999

Effects of mating on c-fos expression in the brains of male macaques.

The c-fos polyclonal anti-c-fos antibody was used to examine the effects of mating on Fos expression in brain neurons of 11 male macaques. Behavior tests were for 30 min, five males were unmated, four were mated, and two were social controls. Mated males were killed 60 min after ejaculation. Social controls were paired with females, but mating did not occur. Fos immunoreactive (Fos-ir) neuronal nuclei were counted in nine brain regions extending from the medial preoptic to the mammillary body area of all males. In contrast to previous reports on nonprimate laboratory species, overall there was as much Fos-ir in unmated as in mated males. Moreover, there was significantly less Fos expression in four brain regions (known to contain steroid receptors), namely, ventromedial hypothalamus, arcuate nucleus, lateral mammillary area, and bed nucleus of stria terminalis, of mated than of unmated males. There were no significant differences between mated and unmated males in the 5 other brain regions studied. These findings may reflect taxonomic differences between primates and nonprimates, or result from greater neural activation in feral animals maintained in a laboratory than in domesticated, inbred laboratory species. The simplest interpretation would be that neural activity in the male primate is turned off by mating in some brain sites but not in others.

Animals↗

PubMed1999

Poisson distribution of male mating success in laboratory populations of Drosophila melanogaster.

Variation among males and females in reproductive success is a major determinant of effective population size. Most studies of male mating success in Drosophila, however, have been done under conditions very different from those in typical cultures. We determined the distribution of male mating success in five laboratory populations of D. melanogaster maintained on a 14 d, discrete generation cycle fairly representative of standard Drosophila cultures. Mating success was measured as the number of matings a male could achieve under conditions closely approximating a regular culture vial of these populations. Preliminary studies determined that most mating in these populations occurred within 14 h of the flies attaining sexual maturity. Consequently, individual virgin males were marked with white paint on their thorax, put into vials with varying numbers of unmarked virgin flies of both sexes, and monitored continuously for matings over a period of up to 14 h. At various times during the assay, virgin males and females were added to these vials in proportions simulating the pattern of eclosion in culture vials. The observed variation in the number of matings per male in the five populations was, by and large, consistent with a Poisson distribution, suggesting that male mating success in short-generation-time, discrete-generation laboratory cultures of D. melanogaster may fulfil a fundamental assumption of the Wright-Fisher model of genetic drift in finite populations.

Animals↗

PubMed2002

Mating interactions between Schistosoma mansoni and S. margrebowiei.

Previous studies of mating interactions between schistosome species from different evolutionary lineages in mice showed that mating is not random: heterospecific pairs form but, given the choice, the preference is for homospecific partners. Mating competition and change of mate were also demonstrated. Schistosoma mansoni is a medically important parasite of humans belonging to a different evolutionary group from S. margrebowiei, a parasite of bovines of veterinary importance. Experiments were designed to investigate the mating behaviour of these two species in mice. Analysis of the data showed a preponderance of intraspecific pairs over interspecific, demonstrating a specific mate preference system for both species. The existence of mating competition between these species was indicated. Males of both species were able to actively compete for paired females by pulling them away from their partners, thus effecting a change of mate. Overall, neither species appeared to be competitively dominant to the other, and the data suggest that where this is the case in sequential infections, the most successful species in terms of worm return and ability to form pairs will be the first species to infect the host.

Animals↗

PubMed2005

Characterisation of European and North American Phytophthora ramorum isolates due to their morphology and mating behaviour in vitro with heterothallic Phytophthora species.

Vegetative growth rate, and size of sporangia, chlamydospores and oospores from 94 P. ramorum isolates were measured and the isolates were paired in vitro with four different heterothallic Phytophthora species isolated from infected nursery plants in Germany. P. ramorum isolates originated from different European countries and from Canada and the USA. 66 of the 67 European isolates were determined as mating type A1; only one isolate was of mating type A2. Of the 27 North American isolates tested, seven (all from nurseries) were determined to be the A1 mating type and 17 to be the A2 mating type. Three isolates did not produce gametangia during the incubation period. Discriminant analysis of all data allowed a grouping based on the vegetative growth rate. The two groups corresponded with the mating type no matter whether the isolates originated from Europe or North America. The A1 isolates were much more homogeneous in their morphology than the A2 isolates. They grew faster, had larger chlamydospores and did not produce gametangia with P. cambivora. Within the A2 group, the single European isolate of mating type A2 (BBA 16/02) and three US isolates showed intermediate characters and were classified with the discriminant function into that of the opposite mating type. The morphological characters and the mating behaviour of the isolates will be discussed.

Crosses, Genetic↗

PubMed1989

Mate choice on fallow deer leks.

Leks, on which males defend small clustered mating territories, may have evolved because of the unusual opportunities they provide for female choice of mating partners, and several studies of lek-breeding animals have demonstrated correlations between the mating success of males and their phenotype or behaviour. However, these could arise because (1) females select mates on the basis of male phenotypic traits; (2) males interfere with each other's mating attempts; or (3) females show preferences for particular mating territories, and larger or stronger males are more likely to win access to these territories. Here we report that when fallow bucks on a traditional lek were experimentally induced to change their territories, differences in the mating success of bucks persisted, whereas differences in the position of their territories relative to the centre of the lek did not. The observation that bucks rarely interfered with their neighbours' harems and females moved freely between bucks suggests that females choose their mates on the basis of male phenotype rather than territory type or location. In this population, the immediate factor affecting the movements of females between males was the size of a buck's harem.

Animals↗

PubMed1980

Multiple matings, effective population size and sexual selection in Drosophila melanogaster.

The distribution of sexually efficient males has been analysed in two populations made up of 5 times more females than males. When observation stops as soon as the number of inseminated females equals the number of males, 25 per cent of males in both strains had not mated, 50 per cent of the matings were performed by 50 per cent of the males who mated only once and the other 50 per cent of matings were performed by 25 per cent of the males who mated 2 or 3 times. Productivity of the successive matings falls drastically after the third mating. The relative role of sexual selection and multiple matings as components of fitness are discussed, as well as their implications for the effective population size.

Animals↗

PubMed2002

Mate recognition in fungi.

The ascomycete and basidiomycete fungi have contributed much to our understanding of eukaryotic cell biology. The study of mate recognition, in particular, has provided detailed understanding of cell signalling pathways and cell-specific gene transcription. Sexual dimorphism has little relevance to mating in these organisms, indeed specialised cells for mating are found only in filamentous ascomycetes and even here, a single individual produces both male and female structures. None the less, most species have genetic barriers to prevent selfing. The genes that determine self-incompatibility divide populations into different mating types, and only individuals with different mating types can engage in sexual reproduction. Ascomycetes have just two mating types, but basidiomycetes may have several thousands. Despite apparent differences in the biology and numbers of mating types in these fungi, it is becoming increasingly apparent that many components of their mating pathways are highly conserved.

Fungi↗

PubMed2005

No detectable genetic correlation between male and female mating frequency in the stalk-eyed fly Cyrtodiopsis dalmanni.

There is much interest in explaining why female insects mate multiply. Females of the stalk-eyed fly Cyrtodiopsis dalmanni can mate several times each day in a lifetime which may span several months. There are many adaptive explanations, but one hypothesis that has received little rigorous empirical attention is that female multiple mating has evolved for non-adaptive reasons as a correlated response to selection for high male mating frequency rather than because of direct or indirect benefits accruing to females. We tested this hypothesis in stalk-eyed flies by measuring the mating frequency of females from lines that exhibited a direct response in males to artificial selection for increased ('high') and decreased ('low') male mating frequency. We found that the mating frequency of high-line females did not differ from that of low-line females. Hence, there was no support for a genetic correlation between male and female mating frequency in this species. Our study suggests that the genes which influence remating may not be the same in the sexes, and that females remate frequently in this species to gain as yet unidentified benefits.

Analysis of Variance↗

PubMed2000

Mating system parameters of Dryobalanops aromatica Gaertn. f. (Dipterocarpaceae) in three different forest types and a seed orchard.

The mating system of Dryobalanops aromatica in three different forest types and a seed orchard was quantified by allozyme analysis of progeny arrays using a mixed-mating model. The primary forest (Bukit Sai) had the highest multilocus outcrossing rate (tm=0.923 +/- 0.035), followed by logged forest (Lesong; tm=0.766 +/- 0.056) and artificial forest (FRIM; tm=0.661 +/- 0.066) with seed orchard showing the lowest (Tampin; tm=0.551 +/- 0.095). Deviations from the mixed mating model were evident from differences in pollen and ovule allele frequencies, and heterogeneity of pollen pools in all three different forest types and the seed orchard. A high rate of outcrossing in primary forest (tm=0.92) may indicate that the species is self-incompatible, but a lower value in the seed orchard (tm=0.55) might suggest further that the self-incompatibility system is weak. The outcrossing rate was greater in the primary forest (tm=0.92) than in logged forest (tm=0.77). It is argued that this might be a consequence of the lower density of flowering trees and alteration of pollinator foraging behaviour in logged forest. Higher values of correlated mating (rp) and biparental mating (tm - ts) in primary forest (0.08 and 0.39, respectively) in comparison with logged forest (0.03 and 0.11, respectively) demonstrate that logging activities might reduce the seeds produced through consanguineous mating. Compared with primary forest, it is argued that lower rates of outcrossing in artificial forest (tm=0.67) and seed orchard (tm=0. 55) might be attributed to lack of flowering synchrony and insufficient number of pollinators. The high level of correlated mating (rp=0.43) and biparental mating (tm - ts=0.12) in the seed orchard may further suggest that the seed orchard was established using related seed sources.

Crosses, Genetic↗

PubMed1999

Evolutionary transition from single to multiple mating in fungus-growing ants.

Queens of leafcutter ants exhibit the highest known levels of multiple mating (up to 10 mates per queen) among ants. Multiple mating may have been selected to increase genetic diversity among nestmate workers, which is hypothesized to be critical in social systems with large, long-lived colonies under severe pressure of pathogens. Advanced fungus-growing (leafcutter) ants have large numbers (104-106 workers) and long-lived colonies, whereas basal genera in the attine tribe have small (< 200 workers) colonies with probably substantially shorter lifespans. Basal attines are therefore expected to have lower queen mating frequencies, similar to those found in most other ants. We tested this prediction by analysing queen mating frequency and colony kin structure in three basal attine species: Myrmicocrypta ednaella, Apterostigma collare and Cyphomyrmex longiscapus. Microsatellite marker analyses revealed that queens in all three species were single mated, and that worker-to-worker relatedness in these basal attine species is very close to 0.75, the value expected under exclusively single mating. Fungus growing per se has therefore not selected for multiple queen mating. Instead, the advanced and highly productive social structure of the higher attine ants, which is fully dependent on the rearing of an ancient clonal fungus, may have necessitated high genetic diversity among nestmate workers. This is not the case in the lower attines, which rear fungi that were more recently derived from free-living fungal populations.

Animals↗

PubMed2001

Surprising similarity of sneaking rates and genetic mating patterns in two populations of sand goby experiencing disparate sexual selection regimes.

Molecular markers have proved extremely useful in resolving mating patterns within individual populations of a number of species, but little is known about how genetic mating systems might vary geographically within a species. Here we use microsatellite markers to compare patterns of sneaked fertilization and mating success in two populations of sand goby (Pomatoschistus minutus) that differ dramatically with respect to nest-site density and the documented nature and intensity of sexual selection. At the Tvärminne site in the Baltic Sea, the microsatellite genotypes of 17 nest-tending males and mean samples of more than 50 progeny per nest indicated that approximately 35% of the nests contained eggs that had been fertilized by sneaker males. Successful nest holders mated with an average of 3.0 females, and the distribution of mate numbers for these males did not differ significantly from the Poisson expectation. These genetically deduced mating-system parameters in the Tvärminne population are remarkably similar to those in sand gobies at a distant site adjoining the North Sea. Thus, pronounced differences in the ecological setting and sexual selection regimes in these two populations have not translated into evident differences in cuckoldry rates or other monitored patterns of male mating success. In this case, the ecological setting appears not to be predictive of alternative male mating strategies, a finding of relevance to sexual selection theory.

Animals↗

PubMed2003

Frequency dependence in matings with water-borne sperm.

Negative frequency-dependent mating success--the rare male effect--is a potentially powerful evolutionary force, but disagreement exists as to whether previous work, focusing on copulating species, has robustly demonstrated this phenomenon. Noncopulating sessile organisms that release male gametes into the environment but retain their eggs for fertilization may routinely receive unequal mixtures of sperm. Although promiscuity seems unavoidable it does not follow that the resulting paternity obeys 'fair raffle' expectations. This study investigates frequency dependence in the mating of one such species, the colonial ascidian Diplosoma listerianum. In competition with an alternative sperm source males fathered more progeny if previously mated to a particular female than if no mating history existed. This suggests positive frequency-dependent selection, but may simply result from a mate order effect involving sperm storage. With fewer acclimation matings, separated by longer intervals, this pattern was not found. When, in a different experimental design, virgin females were given simultaneous mixtures of gametes at widely divergent concentrations, sperm at the lower frequency consistently achieved a greater than expected share of paternity--a rare male effect. A convincing argument as to why D. listerianum should favour rare sperm has not been identified, as sperm rarity is expected to correlate very poorly with ecological or genetic male characteristics in this pattern of mating. The existence of nongenetic female preferences at the level of colony modules, analogous in effect to fixed female preferences, is proposed. If visible to selection, indirect benefits from increasing the genetic diversity of a sibship appear the only likely explanation of the rare male effect in this system as the life history presents virtually no costs to multiple mating, and a near absence of direct (resource) benefits, whereas less controversial hypotheses of female promiscuity (e.g. trade up, genetic incompatibility) do not seem appropriate.

Animals↗

PubMed2003

Opposites attract? Mate choice for parasite evasion and the evolutionary stability of sex.

If sex is naturally selected as a way to combat parasites, then sexual selection for disease resistance might increase the overall strength of selection for outcrossing. In the present study, we compared how two forms of mate choice affect the evolutionary stability of outcrossing in simultaneous hermaphrodites. In the first form, individuals preferred to mate with uninfected individuals (condition-dependent choice). In the second form, individuals preferred to mate with individuals that shared the least number of alleles in common at disease-resistance loci. The comparisons were made using individual-based computer simulations in which we varied parasite virulence, parasite transmission rate, and the rate of deleterious mutation at 500 viability loci. We found that alleles controlling both forms of mate choice spread when rare, but their effects on the evolutionary stability of sex were markedly different. Surprisingly, condition-dependent choice for uninfected mates had little effect on the evolutionary stability of sexual reproduction. In contrast, active choice for mates having different alleles at disease-resistance loci had a pronounced positive effect, especially under low rates of deleterious mutation. Based on these results, we suggest that mate choice that increases the genetic diversity of offspring can spread when rare in a randomly mating population, and, as an indirect consequence, increase the range of conditions under which sexual reproduction is evolutionarily stable.

Animals↗

PubMed2003

Subadult experience influences adult mate choice in an arthropod: exposed female wolf spiders prefer males of a familiar phenotype.

Current sexual selection theory proposes several potential mechanisms driving the evolution of female mating preferences, few of which involve social interactions. Although vertebrate examples of socially influenced mating preferences do exist, the invertebrate examples are virtually nonexistent. Here I demonstrate that the mating preferences of female wolf spiders can be acquired through exposure as subadults to unrelated, sexually active adult males. I first conducted exposure trials during which subadult females of the wolf spider Schizocosa uetzi were allowed to interact with mature males of an experimentally manipulated phenotype (either black or brown forelegs). After maturation, these previously exposed females were paired with a male of either a familiar or unfamiliar manipulated phenotype for mate-choice trials. Subadult females that were exposed to directed courtship by mature males of a particular morphological phenotype were subsequently more likely to mate with a male of a familiar phenotype as adults. Furthermore, females that were exposed as subadults were more likely, as adults, to cannibalize a courting male with an unfamiliar phenotype. Unexposed females did not distinguish between phenotypes in either mate choice or cannibalism frequency. These results suggest a previously uncharacterized mechanism influencing the origin of female mating preferences and ultimately the evolution of male traits: subadult experience. This study also stresses the potential importance of learning and memory on adult mate choice in an arthropod.

Animals↗

PubMed2005

The effect of progesterone supplementation post mating and shearing of ewes in early pregnancy on the reproductive performance of ewes and birthweight of lambs.

AIM: To determine whether short-term progesterone supplementation post mating or shearing of ewes in early pregnancy affected either the proportion of ewes that lambed or that had multiple lambs, or the birthweight of lambs. METHODS: Romney ewes (n=457) were synchronised in oestrus using controlled internal drug-releasing (CIDR) devices containing progesterone, and mated to Romney rams over a 5-day period. The mid-point of mating (Day 0) occurred 2 days after the withdrawal of CIDR devices. Ewes mated (n=397) were randomly allocated to one of four treatment groups: shearing at Day 5, shearing at Day 30, no shearing, and no shearing plus progesterone supplementation using a CIDR device inserted on Day 3 for 6 days. During the period from Day 5 to Day 27, six harnessed Suffolk rams were placed with the ewes and matings recorded. At Day 48, all ewes that did not return to the Suffolk rams were scanned for pregnancy using ultrasound. At Day 140, single- and multiple-bearing ewes were set-stocked at 15.1 and 12.2 ewes/ha, respectively, and equivalent numbers of ewes from each treatment group were placed in each paddock. Blood samples from 10 unshorn and 10 progesterone-supplemented ewes were collected on Days 3, 6 and 9, and analysed for plasma progesterone concentrations. Lambs were identified to their dam and weighed within 12 h of birth, and again at 27 and 93 days after the mid-point of lambing. The ewes were weighed at regular intervals throughout the trial. RESULTS: Plasma progesterone concentrations of supplemented ewes were higher than those of unsupplemented ewes (3.28 vs 1.75 ng/ml) on Day 6 (p=0.02) but not on Day 9 (4.58 vs 4.63 ng/ml). Treatment of ewes had no effect on either the proportion of ewes which lambed to the synchronised mating period or that had multiple lambs. Lambs born to ewes shorn at Day 30 tended (p=0.09) to be heavier at birth (by 0.28 kg) than those born to unshorn ewes but this effect was not evident when data were corrected for length of gestation. Neither shearing at Day 5 nor progesterone supplementation had any effect on the birthweight of lambs, and the treatment of ewes had no effect on the survival rate of lambs to weaning. CONCLUSIONS: Progesterone supplementation for 6 days beginning 3 days post mating did not increase either the proportion of ewes that lambed or that had multiple lambs, or the birthweight of lambs. Shearing 5 days after mating had no significant effect on the reproductive performance of ewes and need not be avoided, but is unlikely to result in an increase in lamb birthweight. Shearing ewes at Day 30 may result in an increase in the birthweight of lambs but, ideally, ewes should be further advanced in pregnancy before shearing is undertaken.

Animal Husbandry↗

PubMed2003

Delayed selfing and resource reallocations in relation to mate availability in the freshwater snail Physa acuta.

We study the influence of mate availability on the mating behavior of the self-fertile, preferentially outcrossing freshwater snail Physa acuta. Previous optimization theory indicated that mating system interacts with life-history traits to influence the age at first reproduction, providing three testable predictions. First, isolated individuals should reproduce later than individuals with available mates in the expectancy of finding a partner and avoiding the cost of inbreeding. Second, resource reallocation to future fecundity is needed for such reproductive delays to evolve. Third, the reproductive delay can be optimized with respect to life-history traits (e.g., survival, growth) and the mating system (inbreeding depression). Our results largely validate these predictions. First, reproduction is significantly delayed in isolated individuals ("selfers") as compared with individuals frequently exposed to mates ("outcrossers"). Second, delayed reproduction is associated with reallocation to future growth, survival, and fecundity, although fecundity is also affected by the mating system (selfing vs. outcrossing). Third, the reproductive delay found (approximately 2 wk) is consistent with quantitative predictions from optimization models. The delay is largely heritable, which might be partly explained by among-family differences in the amount of inbreeding depression (mating system) but not growth or survival.

Animals↗

PubMed2004

Molecular parentage analysis in experimental newt populations: the response of mating system measures to variation in the operational sex ratio.

Molecular studies of parentage have been extremely influential in the study of sexual selection in the last decade, but a consensus statistical method for the characterization of genetic mating systems has not yet emerged. Here we study the utility of alternative mating system measures by experimentally altering the intensity of sexual selection in laboratory-based breeding populations of the rough-skinned newt. Our experiment involved skewed sex ratio (high sexual selection) and even sex ratio (low sexual selection) treatments, and we assessed the mating system by assigning parentage with microsatellite markers. Our results show that mating system measures based on Bateman's principles accurately reflect the intensity of sexual selection. One key component of this way of quantifying mating systems is the Bateman gradient, which is currently underutilized in the study of genetic mating systems. We also compare inferences based on Bateman's principles with those obtained using two other mating system measures that have been advocated recently (Morisita's index and the index of resource monopolization), and our results produce no justification for the use of these alternative measures. Overall, our results show that Bateman's principles provide the best available method for the statistical characterization of mating systems in nature.

Animals↗

PubMed2004

PAK kinases Ste20 and Pak1 govern cell polarity at different stages of mating in Cryptococcus neoformans.

Sexual identity and mating are linked to virulence of the fungal pathogen Cryptococcus neoformans. Cells of the alpha mating type are more prevalent and can be more virulent than a cells, and basidiospores are thought to be the infectious propagule. Mating in C. neoformans involves cell-cell fusion and the generation of dikaryotic hyphae, processes that involve substantial changes in cell polarity. Two p21-activated kinase (PAK) kinases, Pak1 and Ste20, are required for both mating and virulence in C. neoformans. We show here that Ste20 and Pak1 play crucial roles in polarized morphogenesis at different steps during mating: Pak1 functions during cell fusion, whereas Ste20 fulfills a distinct morphogenic role and is required to maintain polarity in the heterokaryotic mating filament. In conclusion, our studies demonstrate that PAK kinases are necessary for polar growth during mating and that polarity establishment is necessary for mating and may contribute to virulence of C. neoformans.

Cell Fusion↗