Mating behavior in mutant strains of Drosophila melanogaster at different population densities

The effects of mutations and genetic background on the mating activity of males and receptivity of females Drosophila melanogaster have been studied at different population densities. Population density, as well as its combinations with other factors, significantly affects mating behavior of D. melanogaster. There are two distinct trends in the effect of this factor on mating behavior: the maximum larval overpopulation may cause either a significant suppression of the behaviors studied or an increase in their expressivity. The mating behaviors of w ^a and cn mutants against a certain genetic background changed similarly in response to varying population density.     

Genetic effects on mating success and partner choice in a social mammal

Mating behavior has profound consequences for two phenomena--individual reproductive success and the maintenance of species boundaries--that contribute to evolutionary processes. Studies of mating behavior in relation to individual reproductive success are common in many species, but studies of mating behavior in relation to genetic variation and species boundaries are less commonly conducted in socially complex species. Here we leveraged extensive observations of a wild yellow baboon (Papio cynocephalus) population that has experienced recent gene flow from a close sister taxon, the anubis baboon (Papio anubis), to examine how admixture-related genetic background affects mating behavior. We identified novel effects of genetic background on mating patterns, including an advantage accruing to anubis-like males and assortative mating among both yellow-like and anubis-like pairs. These genetic effects acted alongside social dominance rank, inbreeding avoidance, and age to produce highly nonrandom mating patterns. Our results suggest that this population may be undergoing admixture-related evolutionary change, driven in part by nonrandom mating. However, the strength of the genetic effect is mediated by behavioral plasticity and social interactions, emphasizing the strong influence of social context on mating behavior in socially complex species.     

Quantitative genetics of natural variation of behavior in Drosophila melanogaster: the possible role of the social environment on creating persistent patterns of group activity

Using a set of nine effectively isogenic lines collected from nature in 1998, we observed unperturbed behaviors of mixed-sex groups of Drosophila melanogaster. We repeatedly scanned replicated groups of genetically identical individuals, five females and five males, and recorded the behavior of each individual (i.e., walking, feeding, grooming, flying, courting, mating, fighting, or resting). From these behaviors, we made a composite variable of activity for our quantitative genetic analysis. Genotypes differed in activity, explaining 14.41% of the variation in activity; 8.60% of the variation was explained by a significant genotype x sex interaction, which signifies genetic variation for sexual dimorphism in behavior. Phenotypic plasticity explained 11.13% of the variation in activity. Different genotypes and sexes within genotypes had different rank orders of the component behaviors that contribute to activity. We found no effect of common rearing environment. Instead, differences between replicate groups within genotype accounted for 19.47% variation in activity, and activity was significantly repeatable across scans. This emergent group behavior is likely caused by differences between groups of interacting individuals, even though individuals were genetically identical across groups. Thus, emergent group behavior explained almost as much variation in activity as the combined sources of genetic variation (23.01%), and this is an additional level on which selection could operate: individuals and groups. We discuss how differences among groups could change patterns of additive genetic variation available for evolution. Furthermore, because the behavior of an individual is influenced by conspecifics, genotype interactions between individuals could contribute to indirect selection. Finally, if we consider activity as a syndrome governing all component behaviors with strong genetic correlations among behaviors within an individual, then these component behaviors cannot evolve independently. These results suggest that reductionist approaches of molecular behavior genetics may be incomplete and/or misleading when considering similar phenotypes at the population level or when trying to understand how behaviors evolve.     

Genetics of Drosophila simulans male mating discrimination in crosses with D. melanogaster

The genetic bases of sexual isolation between Drosophila melanogaster and D. simulans have been mainly studied in females, and there is little information about the role of the males in interspecific mating discrimination. Using D. simulans synthetic lines with compound chromosomes from a population of the Seychelles Islands (high frequency of interspecific mating) and a multimarker strain (low frequency), we show that D. simulans males play an important role in discriminating D. melanogaster females. The genetics of male discrimination fits well with the inheritance mode of a single locus, dominant for sexual isolation, located in chromosome II near the net mutation (2L-0.0). The heterospecific mating success of the male was not related to his sexual vigor. The specific load of male cuticular hydrocarbons was counted as a possible source of discrimination used by the D. melanogaster female.     

Differences in the effect of ethanol on fertility and viability components among laboratory strains of Drosophila melanogaster

We studied the effect of ethanol on several fitness components in six Drosophila melanogaster strains. Mating success, fecundity, egg-to-larva, egg-to-pupa and egg-to-adult survival and the number of emerging adults were estimated in a single series of experiments. The strains either had different combinations of genetic background and Adh genotypes with identical OdhF genotype or different Adh-Odh two-locus genotypes with similar genetic background. Ethanol had the greatest effect on mating success and fecundity, while its influence was lower on survival. When the experimental conditions were contrasted to the natural environment of the flies the most significant results were the ones related to fecundity and larval survival. Ethanol had the highest selective effect on fecundity. The genetic factors contributed substantially to the variation in the fertility and viability components. The Adh locus hardly influenced mating success while it had a sizable effect on fecundity and on all survival components. The influence of Adh on fecundity greatly depended on the other genetic factors. Genetic background had the largest influence on the different survival components. The influence of the Odh locus was mostly observed through the Adh-Odh interaction.     

A maximum likelihood-based method for mining major genes affecting a quantitative character

In this article, we present a maximum likelihood-based analytical approach for detecting a major gene of large effect on a quantitative trait in a progeny population derived from a mating design. Our analysis is based on a mixed genetic model specifying both major gene and background polygenic inheritance. The likelihood of the data is formulated by combining the information about population behaviors of the major gene during hybridization and its phenotypic distribution densities. The EM algorithm is implemented to obtain maximum likelihood estimates for population and quantitative genetic parameters of the major locus. This approach is applied to detect an overdominant gene governing stem volume growth in a factorial mating design of aspen trees. It is suggested that further molecular genetic research toward mapping single genes affecting aspen growth and production based on the same experimental data has a high probability of success.     

Mating-induced recombination in fruit flies

In traditional deterministic models the conditions for the evolution of sex and sexual behavior are limited because their benefits are context dependent. In novel and adverse environments both multiple mating and recombination can help generate gene combinations that allow for rapid adaptation. Mating frequency often increases in conditions in which recombination might be beneficial; therefore, increased sexual behavior might evolve to act as a cue that stimulates recombination. We conducted two experiments in the fruit fly, Drosophila melanogaster, using linked phenotypic markers to determine how recent bouts of additional mating affect female recombination rate. The first experiment examined the effect of additional mating, mating history, and age on female recombination rate. The second experiment assessed the effect of recent mating events on recombination rate. Together, the experiments suggest that each additional bout of mating temporarily increases female recombination rate. These findings imply that the conditions favoring the evolution of sexual reproduction and multiple mating behaviors are broader than currently appreciated.     

南美斑潜蝇成虫的生物学特性与行为

通过室内饲养观察及野外调查,研究了昆明地区南美斑潜蝇（Ｌｉｒｉｏｍｙｚａ ｈｕｉｄｏｂｒｅｎｓｉｓ）成虫的生物学特性,包括羽化、日活动规律、寿命、求偶与交配、取食和产卵。通过观察成虫的行为,发现雄虫在求偶过程中用腿节摩擦腹部摩擦器以吸引雌虫交配。在较高的种群密度下,雄虫之间在交配过程中表现出强较的攻击性。雌虫在搜索寄主时利用跗节、产卵器和喙上的感受器对寄主植物进行探查和评估。本研究的结果为斑潜蝇的     

A simple assay to study social behavior in Drosophila: measurement of social space within a group

We have established a new simple behavioral paradigm in Drosophila melanogaster to determine how genes and the environment influence the behavior of flies within a social group. Specifically, we measure social space as the distance between two flies. The majority of Canton-s flies, regardless of their gender, are within two body lengths from each other. Their social experience affects this behavior, with social isolation reducing and mating enhancing social space respectively, in both males and females. Unlike several other social behaviors in the fly, including the formation of social groups themselves (a well-described behavior), social space does not require the perception of the previously identified aggregation pheromone cis-vaccenyl acetate. Conversely, performance of the assay in darkness or mutations in the eye pigmentation gene white increased social space. Our results establish a new assay for the genetic dissection of a fundamental mode of social interaction.     

Inheritance features of mating behavior components in Drosophila melanogaster and their significance for fitness

Components of mating behavior of Drosophila melanogaster mutant and wild-type strains were studied with respect to fitness. The magnitude of the effect of genotype on the male mating activity, female sexual receptivity, fertility and viability was determined. Strong positive correlation was found between the male mating activity and fitness components. It was shown that mating of strains contrasting in sexual behavior features can be accompanied by both heterosis and maternal effect. Inheritance coefficients were determined for sexual behavior components.     

Ecological, social, and genetic contingency of extrapair behavior in a socially monogamous bird

Extrapair mating strategies are common among socially monogamous birds, but vary widely across ecological and social contexts in which breeding occurs. This variation is thought to reflect a compromise between the direct costs of mates' extrapair behavior and indirect benefits of extrapair fertilizations (EPF) to offspring fitness. However, in most free-living populations, the complete spatial and temporal distribution of mating attempts, genetic characteristics of available mates, and their relative contribution to EPF strategies are difficult to assess. Here we examined prevalence of EPF in relation to breeding density, synchrony, and genetic variability of available mates in a wild population of house finches Carpodacus mexicanus where all breeding attempts are known and all offspring are genotyped. We found that 15% of 59 nests contained extra-pair offspring and 9% of 212 offspring were sired by extra-pair males. We show experimentally that paired males and females avoided EPF displays in the presence of their social partners, revealing direct selection against EPF behavior. However, at the population level, the occurrence of EPF did not vary with nests dispersion, initiation date, synchrony, or with distance between the nests of extrapair partners. Instead, the occurrence of EPF closely covaried with genetic relatedness of a pool of available mates and offspring of genetically dissimilar mating tended to be resistant to a novel pathogen. These results corroborate findings that, in this population, strong fitness benefits of EPF are specific to each individual, thus highlighting the ecological, social, and genetic contingency of costs and benefits of an individual's extrapair behaviors.     

Similar mating and sperm displacement patterns in two highly divergent D. simulans populations from Africa and Europe

The frequency of remating in Drosophila melanogaster is affected by both genetic and ecological factors. We studied the remating behaviour in one European (Italy) and one African (Uganda) Drosophila simulans population using six highly polymorphic microsatellite markers. Despite that the populations were genetically distinct (F(ST) = 0.18) and originated from very dissimilar ecological settings with different population densities, we inferred a very similar mating pattern. The remating parameter alpha was similar in both populations (a = 1.3-1.4). No more than two distinct paternal genotypes per family were detected in each population.     

Mating speed and the interplay between female and male courtship responses inDrosophila melanogaster (Diptera: Drosophilidae)

The objective of this study was to compare measures of general activity and sexual behavior for various genotypes within a strain of Drosophila melanogaster, which had known differences in mating speed. Three inbred lines of D. melanogaster differed significantly in mating speed when tested in female-choice and in single-pair experiments. Analyses of locomotor activity and sexual activity of females and males revealed no significant differences between the inbred lines. An analysis of the interplay between female and male courtship behaviors enabled the examination of signal-response differences between the inbred lines. The inbred lines with intermediate and slow mean mating speed showed a decreased number of significant transitions between female and male behavioral responses. This decrease was more severe in the slow mating line. Further, the intermediate- and slow-mating females and males displayed courtship responses toward signals of the opposite sex that were different from those of the fastmating line. Models of the relationship between behavioral activity and mating speed in Drosophila are discussed and a different explanation for variation in mating speed among the three inbred lines is considered.     

An analysis of genetic differentiation among assortatively mating Drosophila melanogaster in Zimbabwe

African Drosophila melanogaster populations, and those from Zimbabwe in particular, have attracted much interest recently. African flies differ genetically from 'cosmopolitan' populations and were found to exhibit discriminative mating behaviour against individuals from 'cosmopolitan' populations. It has therefore been proposed that Zimbabwean and some other African populations are in an 'incipient stage of speciation'. However, whether the mating behaviour is an effective barrier against gene flow from other populations, and whether intra-population genetic differentiation has already evolved in sympatry is not known. Here, we took a population-based approach to test whether the well-characterized mating type differences have resulted in a genome-wide differentiation at the population level. Using 122 polymorphic microsatellite loci mapping to the third chromosome, we demonstrate a significant genetic differentiation between Zimbabwean flies differing in their mating behaviour. We also provide evidence to suggest that this difference is unlikely to be attributable to population structure within Zimbabwe. However, the analysis of individual microsatellite loci did not indicate more loci differentiating these two groups than expected by chance. Our data suggest that the 'Z'-'M' mating behaviour is strong enough to result in a small but significant genetic differentiation. Thus, future studies based on a larger population sample of flies characterized for their mating behaviour and using more markers are expected to provide more information on the genetic basis of the mating traits in the Zimbabwe flies.     

Coordination of opposing sex-specific and core muscle groups regulates male tail posture during Caenorhabditis elegans male mating behavior

Background  

To survive and reproduce, animals must be able to modify their motor behavior in response to changes in the environment. We studied a complex behavior of Caenorhabditis elegans, male mating behavior, which provided a model for understanding motor behaviors at the genetic, molecular as well as circuit level. C. elegans male mating behavior consists of a series of six sub-steps: response to contact, backing, turning, vulva location, spicule insertion, and sperm transfer. The male tail contains most of the sensory structures required for mating, in addition to the copulatory structures, and thus to carry out the steps of mating behavior, the male must keep his tail in contact with the hermaphrodite. However, because the hermaphrodite does not play an active role in mating and continues moving, the male must modify his tail posture to maintain contact. We provide a better understanding of the molecular and neuro-muscular pathways that regulate male tail posture during mating.     

The influence of internal fluctuations and external noise on the gene frequency in a haploid population

We consider a Markov chain modeling competition between two alleles in a haploid population of constant size and undergoing mutation, selection and Fisher-Wright mating. The Markov chain is rescaled to a diffusion process. We study the interaction of external noise (due to a random selection coefficient) and internal fluctuations (due to mating); the interaction is found to be additive. The stationary probability density displays a critical point. We draw an analogy between the behavior of the probability density at the critical point and the theory of phase transitions; critical exponents are introduced and calculated. We also analyze the effect of external noise on the genetic diversity of the population and on mean first passage times of the gene frequency.     

The impact of extra-pair mating behavior on hybridization and genetic introgression

Hybridization and genetic introgression can be associated with secondary contact between closely related species. Previous models have examined the ecological and demographic conditions leading to hybridization and introgression, but few have examined the role of behavior. Alternative mating behaviors are common throughout the animal kingdom but have rarely been recognized as a potential mechanism for hybridization. We developed an individual-based genetic model to examine the hypothesis that extra-pair copulations (EPCs) can lead to hybridization and genetic introgression even when assortative mating preferences are intact. Our model showed that female choice, whether pre- or post-copulation, reinforced species boundaries and that hybrids were relatively uncommon when no EPCs occurred. However, when EPCs were introduced into the model, the proportion of hybrids in the population depended on the strength of female mate or sperm choice, the strength of male pursuit of EPCs, and habitat-induced effects on the species composition of the neighborhood. As predicted, male pursuit of EPCs caused extensive introgression, but female preference for conspecific paternity reinforced species differences. Inclusion of mitochondrial markers of species identity revealed significant effects of interspecific and intersexual behavior during EPCs on the direction of introgression. These results suggest that an alternative mating tactic may have major effects on the level of genetic homogenization and can cause local extinction of a species.     

Mating success of wild type and sepia mutants Drosophila melanogaster in different choice.

Mating behaviour of red-eyed (wt) and brown-eyed (sepia) Drosophila melanogaster was studied under light conditions. Mating success was directly observed in mating vials and techniques usually applied in the studies of sexual selection ("female choice" and "multiple choice"). The comparison of sexual activity of mutant and wild types clearly indicates that they are not equally successful in matings. Sepia eye colour mutation decreases sexual activity of Drosophila melanogaster males, influences the preference ability of females and decreases the number of progeny from homogamic mating of the se x se type, as well as from heterogamic copulations in which sepia females take part. Non-random mating of wild type males and sepia females (in "multiple-choice" situation), with genetically and phenotypically different individuals, could be another mechanism for conservation of genetic polymorphism in natural populations.     

Cautions on direct gene flow estimation in plant populations

Through simulations we have investigated the statistical properties of two of the main approaches for directly estimating pollen gene flow (m) in plant populations: genotypic exclusion and mating models. When the assumptions about accurately known background pollen pool allelic frequencies are met, both methods provide unbiased results with comparable variances across a range of true m values. However, when presumed allelic frequencies differ from actual ones, which is more likely in research practice, both estimators are biased. We demonstrate that the extent and direction of bias largely depend on the difference (measured as genetic distance) between the presumed and actual pollen pools, and on the degree of genetic differentiation between the local population and the actual background pollen sources. However, one feature of the mating model is its ability to estimate pollen gene flow simultaneously with background pollen pool allelic frequencies. We have found that this approach gives nearly unbiased pollen gene flow estimates, and is practical because it eliminates the necessity of providing independent estimates of background pollen pool allelic frequencies. Violations of the mating model assumptions of random mating within local population affect the precision of the estimates only to a limited degree.     

Natural genetic variation in social niche construction: social effects of aggression drive disruptive sexual selection in Drosophila melanogaster

Social niche construction (SNC) occurs when animals actively shape their social environments. Currently the fitness consequences of SNC are poorly understood, and no study has examined whether variation in SNC has a genetic basis. Here we report the first instance of genetic variation in SNC by showing that Drosophila male aggression shapes the social environment. We allowed flies of different genotypes to interact in complex arenas; we measured the number and sex of individuals in the groups that formed and counted instances of mating. Arenas containing more aggressive male genotypes formed groups with fewer males, demonstrating that aggressive male genotypes experienced different social environments than nonaggressive genotypes. Further, genotypes with highest mating success were those whose SNC behavior generated the social environment in which they were most adept at mating: genotypes who mate most often after winning aggressive encounters benefit from aggressive SNC, while genotypes who mate most often after losing achieve high mating rates by forgoing aggression. The presence of these alternative strategies-which were robust across eight population densities-revealed that selection on aggression and context-dependent mating was disruptive, consistent with the hypothesis that SNC can maintain genetic variation in multiple behaviors.