Single mating type-specific genes and their 3′ UTRs control mating and fertility in Cochliobolus heterostrophus

To determine the number of proteins required for mating type (MAT) locus-regulated control of mating in Cochliobolus heterostrophus, MAT fragments of various sizes were expressed in MAT deletion strains. As little as 1.5 kb of MAT sequence, encoding a single unique protein in each mating type (MAT-1 and MAT-2), conferred mating ability, although an additional 160 bp of 3^′ UTR was needed for production of ascospores. No other mating type-specific genes involved in mating identity or fertility were found. Thus, although homologs of the C. heterostrophus MAT-1 and MAT-2 genes exist in the filamentous ascomycetes Neurospora crassa and Podospora anserina, C. heterostrophus does not appear to have mating type-specific homologs of two additional genes required by both N. crassa and P.␣anserina for successful sexual reproduction. Three genes were identified in the common DNA flanking the MAT locus: a gene encoding a GTPase-activating protein and an ORF of unknown function lie 5^′ while a β-glucosidase encoding gene lies found 3^′. None of these genes appears to be involving in the mating process. Received: 21 November 1997 / Accepted: 28 April 1998     

Isolation and amino acid sequence of a mating pheromone produced by mating type α cells of Saccharomyces exiguus

A peptide, termed α^se pheromone, was isolated as a mating pheromone from culture filtrate of mating type a cells of Saccharomyces exiguus. The peptide showed both agglutinability-inducing activity to a cells of S. cerevisiae and shmoo-inducing action to a cells of S. cerevisiae, S. kluyveri and S. exiguus. The amino acid sequence of α^se pheromone was determined as H-Trp-His-Trp-Leu-Arg-Leu-Ser-Tyr-Gly-Gln-Pro-Ile-Tyr-OH by mass spectrometry, sequence analysis and enzymatic digestion.     

Aggregation and mating success of Capnodis tenebrionis （Coleoptera： Buprestidae）

An understanding of the relative importance of extrinsic and intrinsic factors in determining the potential distribution and mating success of individuals is critical for the successful monitoring and management of pest species. Using a combination of field observations and a caged field experiment, we explored the roles of environmental and individual variation on the formation of mating aggregations and mating success in the buprestid beetle Capnodis tenebrionis （Linnaeus, 1767）, a pest species of stone fruit trees. Our field observations revealed that the formation of aggregations is influenced by a range of environmental factors including temperature, photoperiod, and population density. However, aggregations were not at random and were more likely to occur on the section of the plant with highest incidence of solar radiation and thus higher temperatures. Data from our experiment with caged beetles in the field further indicate that the reproductive behavior of this species varies with temperature. The probability of a successful mating occurring was also positively related to both male and female size. Females of C. tenebrionis mate several times over a 4-h period, but generally not with the same male. Information obtained from these studies is useful to define the most appropriate time for pest control, especially adopting strategies that interfere with reproduction.     

Why be a honeyless honey mesquite? Reproduction and mating system of nectarful and nectarless individuals

Populations of Prosopis glandulosa var. torreyana in the Chihuahuan desert have a fixed dimorphic system of nectar production in which half the individuals produce nectar (are nectarful) and the other half are nectarless. We analyzed the impact of nectar production on different estimates of fitness, comparing nectarful against nectarless individuals in size, mating system, seed traits, and fruit set in a 1-ha scrubland. Of the reproductive individuals (358), 46% were nectarful and 54% were nectarless. Neither tree size nor flowering phenology differed between nectar morphs. Fixation indices (F) for both progeny (F = −0.2) and adults (F = −0.45) were negative, and high heterozygosities were found in adults and progeny (H = 0.45). No differences were found between nectar morphs for F, H, and single (t_s = 1.1) and multilocus (t_m = 1.03) outcrossing rates. Controlled pollinations showed differences between selfing and control treatments with no differences between nectar morphs. Nectarless individuals produced significantly more pollen grains than did nectar producers, but all other measured floral traits showed no differences. Nectarful trees were visited by pollinators 21 times more often and had a significantly higher overall fruit set than did nectarless trees. No differences between nectar morphs in seed mass or in percentage seed germination were found, but heavier seeds tended to have higher heterozygosities. Both morphs had similar success as females, but nectarless trees had ∼7% higher male function. We discuss three possible scenarios for the evolution of the fixed dimorphism in nectar production, two involving unstable phases (substitution of one morph by the other, and evolution towards dioecy) and one stable scenario (maintenance of the dimorphic system).     

Diapause affects cuticular hydrocarbon composition and mating behavior of both sexes in Drosophila montana

Envipnmental cues,mainly photoperiod and temperature,are known to control female adult reproductive diapause in several insect species.Diapause enhances female survival during adverse conditions and postpones progeny production to the favorable season.Male diapause(a reversible inability to inseminate receptive females)has been studied much less than female diapause.However,if the males maximized their chances to fertilize females while minimizing their energy expenditure,they would be expected to be in diapause at the same time as females.We investigated Drosophila montana male mating bchavior under short-day conditions that induce diapause in females and found the males to be reproductively inactive.We also found that males reared under long-day conditions(reproducing individuals)court reproducing postdiapause fermales,but not diapausing ones.The diapausing fies of both sexes had more long-chain and less short-chain hydrocarbons on their cuticle than the reproducing ones,which presumably increase their survival under stressful conditions,but at the same time decrease their attractiveness.Our study shows that the mating behavior of females and males is well coordinated during and afier overwintering and it also gives support to the dual role of insect cuticular hydrocarbons in adaptation and mate choice.     

Does part reproductive history predict competitive interactions and male mating success in pupfish?

Two experiments were performed to determine the effect of past territoriality and mating success on subsequent dominance and ability to attract females. First, in 14 staged, pair-wise encounters, the development of nuptial coloration and agonistic behaviour was examined in two types of males: previously territorial (PT) and previously non-territorial (PNT) males. Previously territorial males developed a more intense nuptial coloration and won all contests. Second, to test the males' ability to attract females, other factors were controlled that could have affected female mate choice, such as male size, quality of breeding substrate and male-male interactions. In 40 trials, PT males were more active, developed a more intense nuptial coloration, courted females more vigorously, spawned sooner and had a higher mating success than PNT males. Thus, in pupfish, Cyprinodon pecosensis, previous reproductive history is a good indicator of both dominance and mating success. Only males in good physical condition achieve high mating success, and both intra- and inter-sexual selection are important in maintaining the close correlation between expression of nuptial coloration, a second sexual trait, and other male attributes, such as physical condition and vigour, that allow a male to secure and defend a territory against rivals and to attract and spawn with females.     

Broad geographic covariation between floral traits and the mating system in Camissoniopsis cheiranthifolia (Onagraceae): multiple stable mixed mating systems across the species' range?

Background and Aims

Plants vary widely in the extent to which seeds are produced via self-fertilization vs. outcrossing, and evolutionary change in the mating system is thought to be accompanied by genetic differentiation in a syndrome of floral traits. We quantified the pattern of variation and covariation in floral traits and the proportion of seeds outcrossed (t) to better understand the evolutionary processes involved in mating system differentiation among and within populations of the short-lived Pacific coastal dune endemic Camissoniopsis cheiranthifolia across its geographic range in western North America.

Methods

We quantified corolla width and herkogamy, two traits expected to influence the mating system, for 48 populations sampled in the field and for a sub-sample of 29 populations grown from seed in a glasshouse. We also measured several other floral traits for 9–19 populations, estimated t for 16 populations using seven allozyme polymorphisms, and measured the strength of self-incompatibility for nine populations.

Key Results

Floral morphology and self-incompatibility varied widely but non-randomly, such that populations could be assigned to three phenotypically and geographically divergent groups. Populations spanned the full range of outcrossing (t = 0·001–0·992), which covaried with corolla width, herkogamy and floral life span. Outcrossing also correlated with floral morphology within two populations that exhibited exceptional floral variation.

Conclusions

Populations of C. cheiranthifolia seem to have differentiated into three modal mating systems: (1) predominant outcrossing associated with self-incompatibility and large flowers; (2) moderate selfing associated with large but self-compatible flowers; and (3) higher but not complete selfing associated with small, autogamous, self-compatible flowers. The transition to complete selfing has not occurred even though the species appears to possess the required genetic capacity. We hypothesize that outcrossing populations in this species have evolved to different stable states of mixed mating.     

When does female multiple mating evolve to adjust inbreeding? Effects of inbreeding depression,direct costs,mating constraints,and polyandry as a threshold trait

Polyandry is often hypothesized to evolve to allow females to adjust the degree to which they inbreed. Multiple factors might affect such evolution, including inbreeding depression, direct costs, constraints on male availability, and the nature of polyandry as a threshold trait. Complex models are required to evaluate when evolution of polyandry to adjust inbreeding is predicted to arise. We used a genetically explicit individual‐based model to track the joint evolution of inbreeding strategy and polyandry defined as a polygenic threshold trait. Evolution of polyandry to avoid inbreeding only occurred given strong inbreeding depression, low direct costs, and severe restrictions on initial versus additional male availability. Evolution of polyandry to prefer inbreeding only occurred given zero inbreeding depression and direct costs, and given similarly severe restrictions on male availability. However, due to its threshold nature, phenotypic polyandry was frequently expressed even when strongly selected against and hence maladaptive. Further, the degree to which females adjusted inbreeding through polyandry was typically very small, and often reflected constraints on male availability rather than adaptive reproductive strategy. Evolution of polyandry solely to adjust inbreeding might consequently be highly restricted in nature, and such evolution cannot necessarily be directly inferred from observed magnitudes of inbreeding adjustment.     

Do differences in plant and flower age change mating patterns and alter offspring fitness in Raphanus sativus (Brassicaceae)?

When more pollen is present on stigmas than needed to fertilize all ovules, selection among pollen grains may occur due to effects of both pollen donors and maternal plants. We asked whether increasing plant age and flower age, two changes in maternal condition, altered the pattern of seed paternity after mixed pollination. We also asked whether changes in seed paternity affected offspring success in an experimental garden. While flower age did not affect seed paternity, there was a dramatic shift in pollen donor performance as plants aged. These differences were seen in the offspring as well, where the offspring of one pollen donor, which sired more seeds on young plants, flowered earlier in the season, and the offspring of another pollen donor, which sired more seeds on old plants, flowered later in the season. Thus, change in maternal condition resulted in altered seed paternity, perhaps because the environment for pollen tube growth was different. The pattern of seed paternity and offspring performance suggests that pollen donors may show temporal specialization.     

Male mating success and risk of predation in a wolf spider: a balance between sexual and natural selection?

1. Traits that benefit males through sexual selection are simultaneously expected to impair males by provoking costs through natural selection. If we consider the two male fitness components, mating success and viability, then we may expect that the increase in male mating success resulting from a larger trait size will be counterbalanced by an increase in viability costs.
2. We studied the benefits and costs of male mate searching and sexual signalling activity in the wolf spider Hygrolycosa rubrofasciata . In the field, males search females actively and court them by drumming dry leaves with their abdomen. Females have been shown to prefer males with high drumming rate. Male moving and especially drumming is energetically highly demanding and drumming results in significant mortality costs.
3. Our objective in this study was to determine whether male mate-searching activity or drumming activity affect male mating success and the risk of males being predated.
4. It was evident that both higher mate-searching activity and higher drumming activity benefited males by increasing their mating success. Higher mate-searching activity clearly impaired males by causing direct increase in predation risk. There was also a slight tendency that more actively drumming males had higher risk of predation and from all of the predated males 13.3% were caught directly after they had drummed. Furthermore, male drumming activity decreased drastically in the presence of the predator.
5. We conclude that in H. rubrofasciata both increased mate-searching activity and drumming activity benefit males through sexual selection, but at the same time natural selection provokes direct balancing costs on the same traits.     

Production of second generation triploid and tetraploid rainbow trout by mating tetraploid males and diploid females — Potential of tetraploid fish

Summary First generation tetraploids were produced by hydrostatic pressure treatment before the first cleavage and raised until the adult stage. Their survival and growth were severely depressed when compared to the diploid control: after two years, no ovulated females were found although males produced sperm at 1 and 2 years of age and were mated individually with diploid females. The progenies were consistently normal with high survival rates. They were found to be almost all triploids by karyology, which failed to detect a significant rate of aneuploidies. However, the fertilizing ability of tetraploid males was always low (0 to 97% of the control; average 40%). Several arguments presented here support the hypothesis that diploid spermatozoas, which are wider than haploid ones, would be frequently blocked during their penetration through the micropyle canal. Second generation tetraploids were produced after such matings by heat shocks, causing the retention of the second polar body. Their survival and growth were much more satisfactory than in the first generation, although still lower than in diploid and triploid controls issuing from diploid parents. Performances of second generation triploids were comparable to those of diploids, and slightly better than those of conventional triploids issuing from diploid parents. 94.5% of the second generation tetraploids were male.     

Does catch and release affect the mating system and individual reproductive success of wild Atlantic salmon (Salmo salar L.)?

In this study, we documented the breeding system of a wild population of Atlantic salmon (Salmo salar L.) by genetically sampling every returning adult and assessed the determinants of individual fitness. We then quantified the impacts of catch and release (C&R) on mating and reproductive success. Both sexes showed high variance in individual reproductive success, and the estimated standardized variance was higher for males (2.86) than for females (0.73). We found a weak positive relationship between body size and fitness and observed that fitness was positively correlated with the number of mates, especially in males. Mature male parr sired 44% of the analysed offspring. The impact of C&R on the number of offspring was size dependent, as the reproductive success of larger fish was more impaired than smaller ones. Also, there was an interactive negative effect of water temperature and air exposure time on reproductive success of C&R salmon. This study improves our understanding of the complex reproductive biology of the Atlantic salmon and is the first to investigate the impact of C&R on reproductive success. Our study expands the management toolbox of appropriate C&R practices that promote conservation of salmon populations and limit negative impacts on mating and reproductive success.     

Why do males emerge before females? protandry as a mating strategy in male and female butterflies

Summary The reproductive strategy of butterfly males can be defined as being to maximize the number of females mated. We have earlier shown that, if the eclosion period of females is regarded as given, males should emerge before females to achieve maximal reproductive success. However, females may also be considered to have a reproductive strategy with respect to the issue when to emerge. In this paper we assume that females are selected to minimize the time spent unmated (to minimize prereproductive death), and analyze when females should optimally emerge in relation to males to achieve this end. We show that there is no conflict between the sexes with respect to the timing of eclosion when the length of the eclosion period is approximately equal for males and females. Thus, protandry should be considered a reproductive strategy of both males and females.     

Carbon dioxide output and mating in adult cabbage looper moths exposed to discrete light régimes

Carbon dioxide discharge and the number of spermatophores transferred were recorded from populations of adult cabbage loopers, Trichoplusia ni, maintained under various wavelengths and intensities of light. Nocturnal CO₂ output was enhanced by retaining 1 per cent of the diurnal intensity of near-u.v. and blue lights during the scotophase. However, addition of < 10 per cent of the diurnal intensities of u.v., blue, and white lights suppressed CO₂ production. Exposure to gold light resulted in the lowest 24 hr CO₂ accumulations, and red was intermediate. Similarly, maximum levels of mating occurred when cabbage loopers were exposed to nocturnal intensities of 1 per cent of the diurnal u.v., blue, or white lights, even though higher intensities were inhibitory. Considering all nocturnal intensities ranging from 0 to 100 per cent of diurnal levels, u.v. and red yielded the highest mating frequencies, blue and gold were intermediate, and white was lowest. Thus, relatively unique action spectra resulted from each régime.     

Mendel’s law reveals fatal flaws in Bateman’s 1948 study of mating and fitness

Bateman’s experimental study of Drosophila melanogaster produced conclusions that are now part of the bedrock premises of modern sexual selection. Today it is the most cited experimental study in sexual selection, and famous as the first experimental demonstration of sex differences in the relationship between number of mates and relative reproductive success. We repeated the experimental methodology of the original to evaluate its reliability. The results indicate that Bateman’s methodology of visible mutations to assign parentage and reproductive success to subject adults is significantly biased. When combined in offspring, the mutations decrease offspring survival, so that counts of mate number and reproductive success are mismeasured. Bateman’s method overestimates the number of subjects with no mates and underestimates the number with one or more mates for both sexes. Here we discuss why Bateman’s paper is important and present additional analyses of data from our monogamy trials. Monogamy trials can inform inferences about the force of sexual selection in populations because in monogamy trials male–male competition and female choice are absent. Monogamy trials also would have provided Bateman with an a priori test of the fit of his data to Mendel’s laws, an unstated, but vital assumption of his methodology for assigning parentage from which he inferred the number of mates per individual subject and their reproductive success. Even under enforced monogamous mating, offspring frequencies of double mutant, single mutant and no mutant offspring were significantly different from Mendelian expectations proving that Bateman’s method was inappropriate for answering the questions he posed. Double mutant offspring (those with a mutation from each parent) suffered significant inviability as did single mutant offspring whenever they inherited their mother’s marker but the wild-type allele at their father’s marker locus. These inviability effects produced two important inaccuracies in Bateman’s results and conclusions. (1) Some matings that actually occurred were invisible and (2) reproductive success of some mothers was under-estimated. Both observations show that Bateman’s conclusions about sex differences in number of mates and reproductive success were unwarranted, based on biased observations. We speculate about why Bateman’s classic study remained without replication for so long, and we discuss why repetition almost 60 years after the original is still timely, necessary and critical to the scientific enterprise. We highlight overlooked alternative hypotheses to urge that modern tests of Bateman’s conclusions go beyond confirmatory studies to test alternative hypotheses to explain the relationship between mate number and reproductive success.     

Sexual size dimorphism and positive assortative mating in red-backed shrike Lanius collurio: an adaptive value?

During field studies in 1997–1999 in South Bohemia (Czech Republic), we found significant differences in size between the sexes in a local breeding population of red-backed shrike Lanius collurio. Males were significantly larger than females for wing length and tarsus length, but had smaller body mass than females. However, there was considerable overlap in the ranges of these parameters between the sexes. Interestingly, pairs were formed at random with respect to wing length and tarsus length, but assortative mating was significant for body mass/body condition. Among tested variables, only male wing length correlated significantly with nestling body mass at day 7. However, clutch size and the number of fledglings strongly depended on differences in tarsus length between mates, but not on body size of mates. Individual improvements in foraging skills and/or courtship feeding rates are proposed as possible explanations for these findings.