Opposite Latitudinal Clines for First Mating and Second Mating (Remating) in Males of Drosophila melanogaster

Although female remating has been studied extensively in insects, few studies have been carried out for male remating (second mating). In this study, we analyzed Drosophila melanogaster males for their remating potential, using iso‐female line culture initiated with wild flies collected from eight Indian geographic localities. We examined the association of latitude and percent melanization with first and second male mating (including mating‐related traits). Our results indicated that second male mating has a negative latitudinal cline opposite to that of first mating. Body melanization is negatively correlated with second mating by male and positively with first mating (measured in terms of percent mated pairs). Mating latency during first (ML1) and second (ML2) male mating has a negative latitudinal cline, but slope values differ significantly as ML2 is great at higher latitudes as compared to ML1. The difference between ML1 and ML2 is non‐significant at lower latitudes. However, copulation period of second mating (CP2) has a negative latitudinal cline, whereas copulation period of first mating (CP1) has positive latitudinal cline. Next, the latency and copulation period differ significantly between first and second male mating treatments in within‐population analyses as well as in melanic strains. Furthermore, male remating ability (number of maximum successful remating attempts continuously by a male in 12 h) also follows negative latitudinal cline. The lower latitudinal lighter males have more remating ability as compared to darker males from higher latitudes.     

When do host–parasite interactions drive the evolution of non‐random mating?

Interactions with parasites may promote the evolution of disassortative mating in host populations as a mechanism through which genetically diverse offspring can be produced. This possibility has been confirmed through simulation studies and suggested for some empirical systems in which disassortative mating by disease resistance genotype has been documented. The generality of this phenomenon is unclear, however, because existing theory has considered only a subset of possible genetic and mating scenarios. Here we present results from analytical models that consider a broader range of genetic and mating scenarios and allow the evolution of non-random mating in the parasite as well. Our results confirm results of previous simulation studies, demonstrating that coevolutionary interactions with parasites can indeed lead to the evolution of host disassortative mating. However, our results also show that the conditions under which this occurs are significantly more fickle than previously thought, requiring specific forms of infection genetics and modes of non-random mating that do not generate substantial sexual selection. In cases where such conditions are not met, hosts may evolve random or assortative mating. Our analyses also reveal that coevolutionary interactions with hosts cause the evolution of non-random mating in parasites as well. In some cases, particularly those where mating occurs within groups, we find that assortative mating evolves sufficiently to catalyze sympatric speciation in the interacting species.     

Sex ratio and gamete size across eastern North America in Dictyostelium discoideum,a social amoeba with three sexes

Theory indicates that numbers of mating types should tend towards infinity or remain at two. The social amoeba, Dictyostelium discoideum, however, has three mating types. It is therefore a mystery how this species has broken the threshold of two mating types, but has not increased towards a much higher number. Frequency‐dependent selection on rare types in combination with isogamy, a form of reproduction involving gametes similar in size, could explain the evolution of multiple mating types in this system. Other factors, such as drift, may be preventing the evolution of more than three. We first looked for evidence of isogamy by measuring gamete size associated with each type. We found no evidence of size dissimilarities between gametes. We then looked for evidence of balancing selection, by examining mating type distributions in natural populations and comparing genetic differentiation at the mating type locus to that at more neutral loci. We found that mating type frequency varied among the three populations we examined, with only one of the three showing an even sex ratio, which does not support balancing selection. However, we found more population structure at neutral loci than the mating type locus, suggesting that the three mating types are indeed maintained at intermediate frequencies by balancing selection. Overall, the data are consistent with balancing selection acting on D. discoideum mating types, but with a sufficiently weak rare sex advantage to allow for drift, a potential explanation for why these amoebae have only three mating types.     

Male mating biology

Before sterile mass-reared mosquitoes are released in an attempt to control local populations, many facets of male mating biology need to be elucidated. Large knowledge gaps exist in how both sexes meet in space and time, the correlation of male size and mating success and in which arenas matings are successful. Previous failures in mosquito sterile insect technique (SIT) projects have been linked to poor knowledge of local mating behaviours or the selection of deleterious phenotypes during colonisation and long-term mass rearing. Careful selection of mating characteristics must be combined with intensive field trials to ensure phenotypic characters are not antagonistic to longevity, dispersal, or mating behaviours in released males. Success has been achieved, even when colonised vectors were less competitive, due in part to extensive field trials to ensure mating compatibility and effective dispersal. The study of male mating biology in other dipterans has improved the success of operational SIT programmes. Contributing factors include inter-sexual selection, pheromone based attraction, the ability to detect alterations in local mating behaviours, and the effects of long-term colonisation on mating competitiveness. Although great strides have been made in other SIT programmes, this knowledge may not be germane to anophelines, and this has led to a recent increase in research in this area.     

The effects of male harassment on mating duration in the seed bug,Togo hemipterus

Harassment on mating pairs by solitary males is usually considered an attempt by the male to (1) take over the female, (2) guard the female against further insemination (when the solitary male has previously copulated with this female), or (3) influence mating duration. Paired males of a seed bug repel harassment on mating pairs by solitary males by firmly grasping females using their legs and/or genital claspers; in this way, mating duration is prolonged. Male fertilization success increases as mating duration increases. Males of the seed bug, Togo hemipterus (Scott) (Heteroptera: Lygaeidae), use seminal substances to inhibit female remating. These substances induce protracted female refractory periods and are transferred to the females in a time‐dependent manner. Consequently, mating duration has important effects on fitness in this species. We observed harassment on T. hemipterus mating pairs by solitary males, and examined conflicts between paired and solitary males over mating duration. None of the solitary males were able to take over a mating female, and this may be due to the unique male genital structure in this species. All conflicts over mating duration resulted in wins by the paired males over the solitary males. Paired males prolonged mating durations, whereas severe harassment on mating pairs by solitary males shortened durations. We show that even though there is no immediate reward for the solitary male (i.e., it is unable to take over the mating female), this harassment behavior may be adaptive.     

Sexual conflict and the evolutionary ecology of mating patterns: water striders as a model system

Two core ideas in the study of mating systems and sexual selection are (1) the existence of a conflict between the sexes over mating decisions, and (2) that variation in ecological conditions drives the evolution of adaptive mating strategies and the diversification of mating systems. A recent burst of experimental studies of mating behavior and sexual selection in water striders has focused on the interaction of these ideas and led to new insights into the evolutionary ecology of mating systems and sexual selection.     

Mating pattern variability among western toad (Bufo boreas) populations

Summary Breeding ecology and mating patterns of the western toad, Bufo boreas, were examined in three large explosively breeding populations in the Oregon Cascade Mountains. Two mating patterns occurred variably within and among the three populations. First, a large male mating advantage was observed in two of the three populations when data from all the days of data collection were combined. When each day of breeding was analyzed separately, there was a large male mating advantage on 3 of 5 days at one population, and mating was random on all days at the two other populations. The second mating pattern, positive assortative mating by size, was observed at two of the three populations. This pattern was found on separate days of breeding as well as when data from all days were combined at one population, and on only one day of breeding at the second population.In a survey of anuran amphibian mating patterns, intraspecific variation was found in 13 of 15 species, including the present study of the western toad. Intrapopulation variation in mating patterns among breeding years has been observed in 5 of 8 anurans, whereas within-site, within-year mating pattern variation has only been reported for the western toad. These results strongly suggest that anuran mating patterns are frequently neither species-specific nor population-specific attributes. Variable mating patterns were most commonly observed in explosively-breeding anurans. Explosive breeders may be susceptible to variable mating patterns because they may be more sensitive to fluctuations in environmental conditions, demographic parameters, and the intensities of intrasexual competition and mate choice.     

细纹豆芫菁交配与繁殖力的关系

将采自野外的细纹豆芫菁EpicautamannerhimiMkl的雌雄成虫各50头在室内进行人工随机配对,共发生75次交配,平均交配1.5次。雄虫1生可交配0～4次,雌虫0～2次。交配持续时间为(188±55)min,交配持续时间与交配次数之间、交配持续时间与繁殖力之间均无相关性。交配次数与两性的繁殖力呈负相关。交配后有36头雌虫43次产卵,其中有35次产卵发生在本次交配后,有8次产卵发生在连续2次交配后。作者认为雌虫在性感受性上的差异,与不育雄虫参与雌虫的前次交配有关。雄虫能否产生足够数量的交配因子来抑制雌虫的性感受性,是决定雌虫在产卵前交配次数的重要因素。     

The role of mating preferences in shaping interspecific divergence in mating signals in vertebrates

Vertebrates represent one of the best-studied groups in terms of the role that mating preferences have played in the evolution of exaggerated secondary sexual characters and mating behaviours within species. Vertebrate species however, also exhibit enormous interspecific diversity in features of mating signals that has potentially led to reproductive isolation and speciation in many groups. The role that sexual selection has played in interspecific divergence in mating signals has been less fully explored. This review summarizes our current knowledge of how mating preferences within species have shaped interspecific divergence in mate recognition signals among the major vertebrate groups. Certain signal modalities appear to characterize mating signal diversification among different vertebrate taxa. Acoustic signals play an important role in mating decisions in anuran amphibians and birds. Here, different properties of the signal may convey information regarding individual, neighbor and species recognition. Mating preferences for particular features of the acoustic signal have led to interspecific divergence in calls and songs. Divergence in morphological traits such as colouration or ornamentation appears to be important in interspecific diversity in certain groups of fishes and birds. Pheromonal signals serve as the primary basis for species-specific mating cues in many salamander species, most mammals and even some fishes. The evolution of interspecific divergence in elaborate courtship displays may have played an important role in speciation of lizards, and particular groups of fishes, salamanders, birds and mammals. While much research has focused on the importance of mating preferences in shaping the evolution of these types of mating signals within species, the link between intraspecific preferences and interspecific divergence and speciation remains to be more fully tested. Future studies should focus on identifying how variation in mating preferences within a species shapes interspecific diversity in features of mating signals in order to better understand how sexual selection may have led to speciation in vertebrates.     

Disentangling signaling gradients generated by equivalent sources

Yeast cells approach a mating partner by polarizing along a gradient of mating pheromones that are secreted by cells of the opposite mating type. The Bar1 protease is secreted by a-cells and, paradoxically, degrades the α-factor pheromones which are produced by cells of the opposite mating type and trigger mating in a-cells. This degradation may assist in the recovery from pheromone signaling but has also been shown to play a positive role in mating. Previous studies suggested that widely diffusing protease can bias the pheromone gradient towards the closest secreting cell. Here, we show that restricting the Bar1 protease to the secreting cell itself, preventing its wide diffusion, facilitates discrimination between equivalent mating partners. This may be mostly relevant during spore germination, where most mating events occur in nature.     

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.     

On Nonrandom Mating Systems for Attaining Hardy-Weinberg Equilibrium

LI (1988) showed that random mating is a sufficient, not a necessary condition for the Hardy-Weinberg principle. A nonrandom mating population that behaves like a random mating population is thus called a ‘pseudo-random mating population’ by him. The pseudo-random mating system studied by him has been focused on those populations in which the parental generation is in Hardy-Weinberg proportions. In other words, the mating type frequency deviations from random mating for each parental genotype add up to zero. In this article these restrictions are relaxed and new pseudo-random mating systems that immediately yield Hardy-Weinberg offspring are also obtained. This is possible because reciprocal crosses have identical segregation probabilities for an autosomal locus, and the manipulation of the combined frequency of reciprocal crosses does not change the gene frequency of the population. A comparison of these new patterns with that of Li is given in the Discussion.     

Synthesis of the mating factor of Saccharomyces cerevisiae and its truncated peptides : the structure-activity relationship.

The mating factor of Saccharomyces cerevisiae, Trp-His-Trp-Leu-Gln-Leu-Lys-Pro-Gly-Gln-Pro-Met-Tyr, has been synthesized to confirm the structure of the natural mating factor. The tridecapeptide has the same biological activity as the natural mating factor. From the studies on the biological activity of its truncated peptide synthesized the minimum sequence of the peptide require for the mating factor was deduced to be as His-Trp-Leu-Gln-Leu-Lys-Pro-Gly-Gln.     

昆虫交配因子及其分子基础

概述了目前昆虫交配因子的研究概况,包括昆虫交配因子的来源、类别、对雌虫行为和性信息素滴度的影响;在雌虫体内的传递路径及作用机理,以及交配因子的分子生物学研究。     

The evolution of intratetrad mating rates

Intratetrad mating, the fusion of gametes formed in a single meiosis, has unusual consequences for genetic diversity, especially in genome regions linked to mating type loci. Here we investigate the fate of modifier alleles that alter the rate of intratetrad mating, under models of heterozygote advantage and of genetic load resulting from recurrent mutation. In both cases, intratetrad mating is favored if the recombination rate between the selected locus and mating type is less than the frequency of lethal recessive alleles at that locus in the population. Positive feedback often accelerates the invasion of modifiers to the intratetrad mating rate. Recombination rate and intratetrad mating rate exert indirect selection on one another, resulting in a cascading decline in outcrossing, even in the absence of any cost of sex. However, under recurrent mutation, alleles for obligate intratetrad mating invade only very slowly, perhaps explaining why outcrossing can persist at low frequencies in a largely intratetrad mating population.     

Emasculation to plug up females: the significance of pedipalp damage in Nephila fenestrata

Female multiple mating selects for male adaptations that maximizefertilization success in a context of sperm competition. Whilemale mating strategies usually reflect a trade-off between presentand future reproduction, this trade-off is largely removed insystems where the maximum number of matings for males is verysmall. Selection may then favor extreme mechanisms of paternityprotection that amount to a maximal investment in a single mating.Males in several arthropod taxa break off parts of their copulatoryorgans during mating, and it has frequently been suggested thatmutilated males can thus secure their paternity. Nevertheless,such a mechanism has rarely been confirmed directly. Here westudy the golden orb spider Nephila fenestrata, which has amating system with potentially cannibalistic, polyandrous females,and males that are often functionally sterile after mating withone female only. We show that males in this species can indeedprotect their paternity by obstructing the female's genitalopenings with fragments of their copulatory organs.     

CSR ecological strategies and plant mating systems: outcrossing increases with competitiveness but stress‐tolerance is related to mixed mating

A number of plant traits influence the success of fertilization and reproduction in plants. Collectively these traits represent ecological syndromes that are of evolutionary significance. However, while an association between mating system and colonizing ability has been proposed, the existence of a broader relationship between mating system and a species’ position in ecological succession has not been extensively investigated. Grime's CSR theory stresses that an ecological succession can involve changes from colonizing to either competitive or stress‐tolerant strategies. How distinct dimensions of competitiveness and stress tolerance covary with mating systems has still not been considered. We designed a comparative approach to evaluate the link between mating system, life form and CSR strategies for 1996 herbaceous and woody species. We found that CSR strategies are significantly related to mating systems. Ruderal species – colonizers in early succession – were mostly selfers while more competitive species were more often outcrossers. On the other hand, greater physiological stress tolerance was associated with mixed mating systems. Outcrossing is classically expected to be advantageous for most life history strategies other than colonizers, but we suggest that reproductive assurance can counterbalance this effect in stressful environments where populations are sparse and pollinators are rare. Therefore, our results emphasize that competition and abiotic stresses are not equivalent selective pressures on the evolution of mating systems. Finally, we found plant life span to convey additional information on mating system variation, supporting its role for mating system evolution. These findings encourage further investigation of the evolutionary role of ecological strategies as syndromes of traits and suggest that the emergence of large databases of plant traits will help address the major evolutionary hypotheses on such syndromes.     

The structure and measurement of human mating strategies: toward a multidimensional model of sociosexuality

Recent theoretical perspectives concerning the structure of variation in human mating have focused less on conceptualizations of alternate mating strategies and more on the evolution of a conditional strategy. Empirical evidence suggests that this conditional strategy may involve the simultaneous pursuit of long-term and short-term mating tactics. Despite these developments, empirical measurement has proceeded using the Sociosexual Orientation Inventory (SOI), which measures restricted and unrestricted mating orientations along a single bipolar continuum. To fully capture the pluralistic nature of human mating, we suggest that a multidimensional empirical measure is required. To test our hypothesis, we subjected an expanded version of the SOI, which included items measuring psychological orientation toward short-term mating and long-term mating, to principal components analysis. A three-factor structure representing short-term mating orientation, long-term mating orientation, and previous sexual behavior emerged. In subsequent analyses, we demonstrate that our newly developed long-term and short-term dimensions (a) are largely independent and (b) correlate differentially with other theoretically relevant variables.