SEARCH · PubMed Health

Results for “mating systems”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources

PubMed2005

Termitomyces sp. associated with the termite Macrotermes natalensis has a heterothallic mating system and multinucleate cells.

Fungi of the genus Termitomyces live in an obligate symbiosis with termites of the subfamily Macrotermitinae. Many species of Termitomyces frequently form fruit bodies, which develop from the fungus comb within the nest. In this study, we determined the mating system of a species of Termitomyces associated with the South African termite Macrotermes natalensis. Termite nests were excavated and a Termitomyces sp. was isolated into pure culture from the asexual fruit bodies (nodules) growing in the fungus gardens. For one strain, single basidiospore cultures were obtained from basidiomes growing from the fungus comb after incubation without termites. Using nuclear staining, we show that both comb cultures and single spore cultures have multinucleate cells and that the majority of spores has a single nucleus. However, DNA sequencing of the ITS region in the nuclear RNA gene revealed that the comb mycelium had two different ITS types that segregated in the single spore cultures, which consequently had only a single ITS type. These results unambiguously prove that the strain of Termitomyces studied here has a heterothallic mating system, with the fungus garden of the termite mound being in the heterokaryotic phase. This is the first time the mating system of a Termitomnyces species has been studied.

Animals↗

PubMed2006

Lonely hearts or sex in the city? Density-dependent effects in mating systems.

Two very basic ideas in sexual selection are heavily influenced by numbers of potential mates: the evolution of anisogamy, leading to sex role differentiation, and the frequency dependence of reproductive success that tends to equalize primary sex ratios. However, being explicit about the numbers of potential mates is not typical to most evolutionary theory of sexual selection. Here, we argue that this may prevent us from finding the appropriate ecological equilibria that determine the evolutionary endpoints of selection. We review both theoretical and empirical advances on how population density may influence aspects of mating systems such as intrasexual competition, female choice or resistance, and parental care. Density can have strong effects on selective pressures, whether or not there is phenotypic plasticity in individual strategies with respect to density. Mating skew may either increase or decrease with density, which may be aided or counteracted by changes in female behaviour. Switchpoints between alternative mating strategies can be density dependent, and mate encounter rates may influence mate choice (including mutual mate choice), multiple mating, female resistance to male mating attempts, mate searching, mate guarding, parental care, and the probability of divorce. Considering density-dependent selection may be essential for understanding how populations can persist at all despite sexual conflict, but simple models seem to fail to predict the diversity of observed responses in nature. This highlights the importance of considering the interaction between mating systems and population dynamics, and we strongly encourage further work in this area.

Animals↗

PubMed2001

Mating system and genetic variance in a polygynous mustelid, the European polecat.

The population genetic implications of mating system were investigated in European polecat Mustela putorius populations from western France, combining radiotracking survey and allozyme variation analysis. Mating period occurred from February to June and polecats showed a strategy of successive polygyny, a male consorting with 1.44 females during a brief period (2.9 days). Relatedness was largely sex biased, females (21%) being almost twice more related than males (13%) suggesting a natal philopatry. Nonetheless, breeding dispersal pattern appeared relatively complex. Males were the sex dispersing but the main strategy for male polecats consisted of short-term mating excursions in adjacent females ranges whereas long-distance dispersal only constituted an alternative breeding strategy. Despite their allozymic polymorphism level reaching 24% at p<0.05 for 38 scored loci, populations showed a high heterozygote deficiency as revealed by the F(IS) index averaging F(IS) = 0.383. Thus the mating system of such solitary mustelids may be poorly efficient to prevent inbreeding within populations.

Alleles↗

PubMed2000

Clutch size evolution under sexual conflict enhances the stability of mating systems.

Models of optimal clutch size often implicitly assume a situation with uniparental care. However, the evolutionary conflict between males and females over the division of parental care will have a major influence on the evolution of clutch size. Since clutch size is a female trait, a male has little possibility of directly influencing it. However, the optimal clutch size from a female's perspective will depend on the amount of paternal care her mate is expected to provide. The sexual conflict over parental care will in its turn be affected by clutch size, since a larger clutch makes male care more valuable. Hence, there will be joint evolution of mating system and clutch size. In this paper, we demonstrate that this joint evolution will tend to stabilize the mating system. In a situation with conventional sex roles, this joint evolution might result in either increased clutch size and biparental care or reduced clutch size and uniparental female care. Under some circumstances the initial conditions might determine which will be the outcome. These results demonstrate that it may be difficult to deduce whether biparental care evolved because of few opportunities for breeding males increasing their fitness by attracting additional mates or because of the importance of male care for offspring fitness by studying prevailing mating systems using, for example, male removals or manipulation of males' opportunities for finding additional mates. In general terms, we demonstrate that models of life-history evolution have to consider the social context in which they evolve.

Animals↗

PubMed2003

Population structure, mating system, and sex-determining allele diversity of the parasitoid wasp Habrobracon hebetor.

Besides haplo-diploid sex determination, where females develop from fertilized diploid eggs and males from unfertilized haploid eggs, some Hymenoptera have a secondary system called complementary sex determination (CSD). This depends on genotypes of a 'sex locus' with numerous sex-determining alleles. Diploid heterozygotes develop as females, but diploid homozygotes become sterile or nonviable diploid males. Thus, when females share sex-determining alleles with their mates and produce low fitness diploid males, CSD creates a genetic load. The parasitoid wasp Habrobracon hebetor has CSD and displays mating behaviours that lessen CSD load, including mating at aggregations of males and inbreeding avoidance by females. To examine the influence of population structure and the mating system on CSD load, we conducted genetic analyses of an H. hebetor population in Wisconsin. Given the frequency of diploid males, we estimated that the population harboured 10-16 sex-determining alleles. Overall, marker allele frequencies did not differ between subpopulations, but frequencies changed dramatically between years. This reduced estimates of effective size of subpopulations to only N3 approximately 20-50, which probably reflected annual fluctuations of abundance of H. hebetor. We also determined that the mating system is effectively monogamous. Models relating sex-determining allele diversity and the mating system to female productivity showed that inbreeding avoidance always decreased CSD loads, but multiple mating only reduced loads in populations with fewer than five sex-determining alleles. Populations with N3 less than 100 should have fewer sex-determining alleles than we found, but high diversity could be maintained by a combination of frequency-dependent selection and gene flow between populations.

Alleles↗

PubMed2005

Reproductive success of broiler breeders in natural mating systems: the effect of male-male competition, sperm quality, and morphological characteristics.

In natural mating systems in which broiler breeder males compete for females, reproductive behavior plays an important role in male fertility, along with sperm competition and morphological and physiological characteristics. We investigated the effect of male-male competition compared with a noncompetitive situation on fertility, sperm quality, and morphological traits. Six groups of 3 males and 12 females were housed in mixed-sex pens. Their frequency of mating was recorded, and progeny of each male was determined through DNA fingerprinting. Males with the highest and the lowest mating frequencies were later placed into groups of 1 male and 4 females, their behavior was recorded, and their fertility was calculated. We collected data on semen quality (semen volume, sperm concentration, and mobility) and morphometrical characters. Finally, females were artificially inseminated with sperm from highest frequency, lowest frequency, or a mix, paternity and fertility were estimated. Our results indicate that heavier males had higher frequency of matings without cloacal contact, and males with smaller combs had more mating attempts. We also detected that males with high sperm concentration had lower fertility. However, we found an overall lack of association between mating behavior, morphometrical traits, sperm quality, and fertility. This, together with the discrepancy of results in fertility when compared with artificial insemination conditions, suggest a multifactorial nature of the fertility of broiler breeder males in natural mating systems. In addition we observed a high male fertility when housed individually, suggesting that male fertility is a relative parameter that depends upon the reproductive quality of the other male competitors within the group.

Animals↗

PubMed2001

Analysis of character correlations among wood decay mechanisms, mating systems, and substrate ranges in homobasidiomycetes.

Homobasidiomycetes include the majority of wood-decaying fungi. Two basic forms of wood decay are known in homobasidiomycetes: white rot, in which lignin and cellulose are degraded, and brown rot, in which lignin is not appreciably degraded. An apparent correlation has been noted between production of a brown rot, decay of conifer substrates, and possession of a bipolar mating system (which has a single mating-type locus, in contrast to tetrapolar systems, which have two mating-type loci). The goals of this study were to infer the historical pattern of transformations in decay mode, mating type, and substrate range characters, and to determine if a causal relationship exists among them. Using nuclear and mitochondrial rDNA sequences, we performed a phylogenetic analysis of 130 species of homobasidiomycetes and performed ancestral state reconstructions by using parsimony on a range of trees, with various loss:gain cost ratios. We evaluated pairwise character correlations by using the concentrated changes test (CCT) of Maddison and the maximum likelihood (ML) method of Pagel. White rot, tetrapolar mating systems, and the ability to decay conifers and hardwoods appear to be plesiomorphic in homobasidiomycetes, whereas brown rot, bipolar mating systems, and exclusive decay of conifers appear to have evolved repeatedly. The only significant correlation among characters was that between brown rot (as the independent character) and exclusive decay of conifer substrates (P < 0.03). This correlation was supported by the CCT on a range of plausible trees, although not with every reconstruction of ancestral states, and by the ML test. Our findings suggest that the evolution of brown rot has promoted repeated shifts to specialization for confier substrates.

Basidiomycota↗

PubMed2003

Comparative analysis of male androgen responsiveness to social environment in birds: the effects of mating system and paternal incubation.

Male androgen responses to social challenges have been predicted to vary with mating system, male-male aggressiveness, and the degree of paternal investment in birds ("challenge hypothesis," Am. Nat. 136 (1990), 829). This study focused on the interspecific predictions of the challenge hypothesis. Comparative methods were used to control for effects of the phylogenetic relatedness among the sampled species. Male androgen data of 84 bird species were collected from literature records on seasonal androgen patterns. From these, the androgen responsiveness (AR) was calculated as described in the original challenge hypothesis (i.e., maximum physiological level/breeding baseline). Scatterplots of AR versus mating strategy, male-male aggressiveness, and the degree of paternal care confirmed the expected interspecific patterns. When phylogenetic analyses were performed among all of the sampled species, the effects of paternal investment disappeared while the AR remained covarying to a high degree with mating system and male-male aggressiveness. Although these mechanisms may be different at the intraspecific level, this suggests that interspecific differences of AR in male birds may have evolved in response to changes of mating strategies, rather than in response to altered paternal duties. However, control for phylogeny among the subsample of 32 passerine species revealed that if any paternal investment contributed to the observed variance in AR, then the change from "no male incubation" to "male shares incubation duties" represented the most effective, whereas the male's contribution to feeding offspring did not explain the observed variation of AR.

Aggression↗

PubMed2001

Mating system evolution in sperm-heteromorphic Drosophila.

In Drosophila species of the obscura group, males exhibit sperm-heteromorphism, simultaneously producing both long sperm, capable of fertilization, and short sperm that are not. The production of multiple sperm types calls into question whether mating system correlates, such as sperm length and number trade-offs and female remating behavior, are the same as previously described in sperm-monomorphic systems. We examine three obscura group species, D. pseudoobscura, D. persimilis, and D. affinis that differ significantly in the lengths of their long fertilizing sperm, to test predictions about the relationship between sperm length and four mating system characters: male age at sexual maturity; sperm number; female remating; and male reproductive output. In D. affinis, where males produce the longest fertilizing sperm, their sexual maturity is delayed and they produce fewer long sperm compared to the other two species, as predicted if long sperm are costly to produce. Female D. affinis, although they receive fewer sperm than females of the other two species, do not remate more frequently or produce fewer progeny from a single mating. Different responses between sperm-heteromorphic and sperm-monomorphic systems underscore the complex nature of the coevolution between male and female mating system characters.

Journal Article↗

PubMed2006

Mating system in a low-density natural population of the dioecious wind-pollinated Patagonian cypress.

The mating system of a species is an essential factor that determines the genotypic frequencies of its populations in each generation. Thus, knowledge in this regard is important in the application of practical measures in conservation and forest tree breeding. Austrocedrus chilensis (D.DON) PIC. SER. ET BIZZARRI: is a member of the Cupressaceae native to the Andean-Patagonian Forest of Argentina and Chile with regional economic importance. It is a dioecious tree with pollen and seeds distributed by wind. Isozyme markers were utilized to study the mating system of this species through the survey of individual effective pollen clouds in a natural low-density population. If random mating occurs, effective pollen clouds that pollinate single seed trees are expected to be genetically homogeneous. The classical HardyWeinberg test of panmixia was also performed. Although it failed to reject random mating, the analysis of the pollen clouds showed that this mating pattern does not occur. Evidence of locally distributed heterogeneous pollen clouds is presented. The two methods are critically compared.

Alleles↗

PubMed2002

Family-level covariation between parasite resistance and mating system in a hermaphroditic freshwater snail.

Genetic compatibility, nonspecific defenses, and environmental effects determine parasite resistance. Host mating system (selfing vs. outcrossing) should be important for parasite resistance because it determines the segregation of alleles at the resistance loci and because inbreeding depression may hamper immune defenses. Individuals of a mixed mating hermaphroditic freshwater snail, Lymnaea ovata, are commonly infected by a digenetic trematode parasite, Echinoparyphium recurvatum. We examined covariation between quantitative resistance to novel parasites and mating system by exposing snail families from four populations that differed by their inbreeding coefficients. We found that resistance was unrelated to inbreeding coefficient of the population, suggesting that the more inbred populations did not carry higher susceptibility load than the less inbred populations. Most of the variation in resistance was expressed among the families within the populations. In the population with the lowest inbreeding coefficient, resistance increased with outcrossing rate of the family, as predicted if selfing had led to inbreeding depression. In the other three populations with higher inbreeding coefficients, resistance was unrelated to outcrossing rate. The results suggest that in populations with higher inbreeding some of the genetic load has been purged, uncoupling the predicted relationship between outcrossing rate and resistance. Snail families also displayed crossing reaction norms for resistance when tested in two environments that presented low and high immune challenge, suggesting that genotype-by-environment interactions are important for parasite resistance.

Animals↗

PubMed2001

Effects of population size and metapopulation dynamics on a mating-system polymorphism.

The evolutionary dynamics of neutral alleles under the Wright-Fisher model are well understood. Similarly, the effect of population turnover on neutral genetic diversity in a metapopulation has attracted recent attention in theoretical studies. Here we present the results of computer simulations of a simple model that considers the effects of finite population size and metapopulation dynamics on a mating-system polymorphism involving selfing and outcrossing morphs. The details of the model are based on empirical data from dimorphic populations of the annual plant Eichhornia paniculata, but the results are also of relevance to species with density-dependent selfing rates in general. In our model, the prior selfing rate is determined by two alleles segregating at a single diploid locus. After prior selfing occurs, some remaining ovules are selfed through competing self-fertilisation in finite populations as a result of random mating among gametes. Fitness differences between the mating-system morphs were determined by inbreeding depression and pollen discounting in a context-dependent manner. Simulation results showed evidence of frequency dependence in the action of pollen discounting and inbreeding depression in finite populations. In particular, as a result of selfing in outcrossers through random mating among gametes, selfers experienced a "fixation bias" through drift, even when the mating-system locus was selectively neutral. In a metapopulation, high colony turnover generally favoured the fixation of the outcrossing morph, because inbreeding depression reduced opportunities for colony establishment by selfers through seed dispersal. Our results thus demonstrate that population size and metapopulation processes can lead to evolutionary dynamics involving pollen and seed dispersal that are not predicted for large populations with stable demography.

Alleles↗

PubMed2003

Genetic mating system and the significance of harem associations in the bat Saccopteryx bilineata.

We analysed the polygynous mating system of the bat Saccopteryx bilineata using behaviour observations and genetic data on 11 microsatellite DNA loci. Basic social units in S. bilineata are harem groups that consist of single males and up to eight females. Colonies comprise several harem groups, and the composition of colonies and harems is often stable over several reproductive seasons. The combination of parentage exclusion and likelihood-based parentage assignment in this study produced detailed parentage information for a large colony of S. bilineata. Reproduction occurred mostly within the colony (17% extra-colony paternity), but social associations in harems within the colony did not represent reproductive units (70% extra-harem paternity). The latter finding was consistent over three reproductive seasons. Spatial association of the roosting sites of males and females could not explain parentage patterns in the colony. Even though intra-harem paternity was less frequent than expected, it contributed significantly to reproduction of harem males. On average, the number of offspring sired by a male with females in his harem territory increased significantly with harem size, which corresponds to the higher energetic investment that is related to the maintenance of large harems. However, extra-harem paternity was not correlated with a male's harem size or intra-harem reproductive success. This suggests that individual preferences of females rather than male traits associated with the ability to defend large harems are most likely to cause the detected differences between social association and genetic mating system.

Animal Population Groups↗

PubMed2000

Profitabilities of some mating systems for dairy herds in New Zealand.

The aim of this study was to evaluate the profitability of dairy herds under three mating systems involving the Holstein-Friesian, Jersey, and Ayrshire breeds. Mating systems were straight breeding and rotational cross-breeding using two or three breeds. A deterministic model was developed to simulate the nutritional, biological, and economic performance of dairy herds under New Zealand conditions. Expected performances per cow were obtained using estimates of breed group and heterosis effects, age effects, and age distribution in the herd. Requirements for dry matter in feed were estimated per cow for maintenance, lactation, pregnancy, and growth of the replacements. Stocking rate was calculated by assuming 12,000 kg of dry matter utilized annually per hectare. Productivity per hectare was calculated as performance per cow multiplied by stocking rate. Profitability was the difference between income (sale of milk and salvage value of animals) and costs (related to the number of cows in the herd and the land area farmed). Under current market values for milk and meat, all of the rotational crossbred herds showed superior profitability to the straightbred herds (Holstein-Friesian x Jersey, NZ$505/ha; Holstein-Friesian x Jersey x Ayrshire NZ$493/ha; Jersey x Ayrshire, NZ$466/ha; Holstein-Friesian x Ayrshire, NZ$430/ha; Jersey, NZ$430/ha; Holstein-Friesian, NZ$398/ha; and Ayrshire, NZ$338/ha). Changes in the value for fat relative to protein affected profitability more significantly in herds using the Jersey breed, and changes in the value for meat affected profitabiity more significantly in herds using the Holstein-Friesian and Ayrshire breeds. Results suggested that, under New Zealand conditions, the use of rotational crossbreeding systems could increase profitability of dairy herds under the conceivable market conditions.

Animals↗

PubMed1989

The mechanism of DNA transfer in the mating system of an archaebacterium.

The genetic transfer system in the extremely halophilic archaebacterium Halobacterium volcanii is the only archaebacterial mating system known. The mechanism of genetic transfer of this archaebacterium was studied by using the immobile plasmids pHV2 and pHV11 as cytoplasmic markers. It was found that the cytoplasms of the parental types do not mix during the mating process, that each parental type can serve both as a donor and as a recipient, and that cytoplasmic bridges, with dimensions of up to 2 micrometers long and 0.1 micrometer in diameter, were formed between the parental types. These bridges appear to be used for the transfer of DNA from one cell to another. If so, this archaebacterial mating system is different from both eubacterial conjugation and eukaryotic sexual cell fusion.

Cell Fusion↗

PubMed2001

High resolution microsatellite based analysis of the mating system allows the detection of significant biparental inbreeding in Caryocar brasiliense, an endangered tropical tree species.

In this work we investigate the mating system of four populations of the endangered tropical tree species Caryocar brasiliense, using genetic data from 10 microsatellite loci. Eight to 10 open-pollinated progeny arrays of 16 individuals, together with their mother tree, were sampled per population. Mating system parameters were estimated under the mixed mating model, implemented by the software MLTR. The single-locus outcrossing rate (ts) varied among loci and populations, but multilocus outcrossing rates (tm) were equal to one for all four populations. Nevertheless, biparental inbreeding (tm - ts) was different from zero for all populations, indicating that outcrossing events may occur between relatives. Our results also indicate that the high polymorphism of microsatellite markers provide an extraordinary resolution to discriminate precisely selfing events from outcrossing events between close relatives. Our results indicate that, although highly outcrossed, C. brasiliense shows high levels of biparental inbreeding, most likely due to the limited flight range of pollinators and restriction in seed dispersal. Furthermore, these results suggest that Cerrado fragmentation could limit gene flow by isolating seed dispersers and territorial small sized bat pollinators inside fragments, increasing the rate of mating between close relatives. The conservation of nonisolated populations in large preserved areas may be necessary to foster outcrossing events between unrelated individuals and thus maintain species viability.

Crosses, Genetic↗

PubMed1975

The mating system and microevolution.

Studies of natural and experimental plant populations have revealed that genotypic frequency distributions are highly structured in predominantly selfing species. This high degree of genetic organization is manifested in intense correlations in allelic state over loci and also in striking micro-geographical heterogeneity. Both aspects of this structure are facilitated by self-fertilization. Development of non-random associations of alleles within populations is facilitated because inbreeding reduces heterozygosity and thus also the randomizing effect of recombination. Spatial differentiation is facilitated because self-fertilization retards gene flow from population to population. The effect of organizing the entire populational genotype into a sort of giant supergene is to increase the frequency in the population of genotypes which confers high fitness and hence to increase adaptation to the local environment. However the recombinational potential remains substantial. As a result considerable free genetic variability remains in the population and it is available for long-term response to natural selection. Thus the organization of genetic variability within populations provides for high immediate fitness and also for flexibility to meet longer term evolutionary needs. At the same time selfing is a barrier to migration and it promotes the development and maintenance of different multilocus organizations in adjacent populations occupying unlike habitats. In total, therfore, a pattern of genetic differentiation develops in space which is an almost exact overlay of the environmental heterogeneity. The plant genetic and plant breeding literature contains extensive evidence that the mating system in plants can be modified simply and drastically by selection and that different populations within the same species often practice very different amounts of inbreeding. Considering the ease with which the mating system can be altered, and the benefits of adjusting genetic variability through regulation of the mating system, it is not surprising that a high proportion of flowering plants self-fertilize to some extent and that at least one-third of species have adopted predominant selfing as a strategy in ecogenetic adaptation.

Adaptation, Biological↗

PubMed2005

Paternal genetic effects on offspring fitness are context dependent within the extrapair mating system of a socially monogamous passerine.

Avian extrapair mating systems provide an interesting model to assess the role of genetic benefits in the evolution of female multiple mating behavior, as potentially confounding nongenetic benefits of extrapair mate choice are seen to be of minor importance. Genetic benefit models of extrapair mating behavior predict that females engage in extrapair copulations with males of higher genetic quality compared to their social mates, thereby improving offspring reproductive value. The most straightforward test of such good genes models of extrapair mating implies pairwise comparisons of maternal half-siblings raised in the same environment, which permits direct assessment of paternal genetic effects on offspring traits. But genetic benefits of mate choice may be difficult to detect. Furthermore, the extent of genetic benefits (in terms of increased offspring viability or fecundity) may depend on the environmental context such that the proposed differences between extrapair offspring (EPO) and within-pair offspring (WPO) only appear under comparatively poor environmental conditions. We tested the hypothesis that genetic benefits of female extrapair mate choice are context dependent by analyzing offspring fitness-related traits in the coal tit (Parus ater) in relation to seasonal variation in environmental conditions. Paternal genetic effects on offspring fitness were context dependent, as shown by a significant interaction effect of differential paternal genetic contribution and offspring hatching date. EPO showed a higher local recruitment probability than their maternal half-siblings if born comparatively late in the season (i.e., when overall performance had significantly declined), while WPO performed better early in the season. The same general pattern of context dependence was evident when using the number of grandchildren born to a cuckolding female via her female WPO or EPO progeny as the respective fitness measure. However, we were unable to demonstrate that cuckolding females obtained a general genetic fitness benefit from extrapair fertilizations in terms of offspring viability or fecundity. Thus, another type of benefit could be responsible for maintaining female extrapair mating preferences in the study population. Our results suggest that more than a single selective pressure may have shaped the evolution of female extrapair mating behavior in socially monogamous passerines.

Animals↗