Learning decreases heterospecific courtship and mating in fruit flies

Recent theory and data suggest that adaptive use of learning in the context of sexual behaviour could contribute to assortative mating. Experiments examining this issue indicated that male Drosophila persimilis that experienced courtship and rejection by heterospecific females exhibited significantly lower levels of heterospecific courtship and mating compared with those of inexperienced males. These results indicate that experience in the context of sexual behaviour in fruit flies could reduce gene flow between diverging populations, which may contribute to incipient speciation.     

Inhibition of female mating receptivity by male-derived extracts in two Callosobruchus species: Consequences for interspecific mating

We investigated the effects of injecting male-derived extracts on congeneric female receptivity in two species of Callosobruchus beetle, C. chinensis and C. maculatus. We also examined the influence of interspecific mating on female remating behaviour in these two species. Male-derived extracts reduced congeneric female receptivity in both species. As quick-acting components, extracts of C. chinensis male seminal vesicles reduced the receptivity of C. maculatus females, whereas extracts of C. maculatus male testes reduced the receptivity of C. chinensis females. As slow-acting components, extracts of male accessory glands of other species reduced the receptivity of both C. maculatus and chinensis females. After interspecific mating, the sperm of C. maculatus males were transferred to the reproductive organs of C. chinensis females, thereby reducing their receptivity. In contrast, no C. chinensis sperm were transferred to the reproductive organs of C. maculatus females; accordingly, the latter's receptivity was not reduced. Furthermore, the survival rate of C. chinensis females decreased markedly after interspecific mating. These results raise the possibility that under circumstances where populations of these two species share the same habitat, reproductive interference would occur only in the interactions between C. maculatus males and C. chinensis females.     

Disruptive ecological selection on a mating cue

Adaptation to divergent ecological niches can result in speciation. Traits subject to disruptive selection that also contribute to non-random mating will facilitate speciation with gene flow. Such ‘magic’ or ‘multiple-effect’ traits may be widespread and important for generating biodiversity, but strong empirical evidence is still lacking. Although there is evidence that putative ecological traits are indeed involved in assortative mating, evidence that these same traits are under divergent selection is considerably weaker. Heliconius butterfly wing patterns are subject to positive frequency-dependent selection by predators, owing to aposematism and Müllerian mimicry, and divergent colour patterns are used by closely related species to recognize potential mates. The amenability of colour patterns to experimental manipulation, independent of other traits, presents an excellent opportunity to test their role during speciation. We conducted field experiments with artificial butterflies, designed to match natural butterflies with respect to avian vision. These were complemented with enclosure trials with live birds and real butterflies. Our experiments showed that hybrid colour-pattern phenotypes are attacked more frequently than parental forms. For the first time, we demonstrate disruptive ecological selection on a trait that also acts as a mating cue.     

Social common mole-rats enhance outbreeding via extra-pair mating

Females in many species engage in matings with males that are not their social mates. These matings are predicted to increase offspring heterozygosity and fitness, and thereby prevent the deleterious effects of inbreeding. We tested this hypothesis in a cooperative breeding mammal, the common mole-rat Cryptomys hottentotus hottentotus. Laboratory-based studies suggested a system of strict social monogamy, while recent molecular studies indicate extensive extra-pair paternity despite colonies being founded by an outbred pair. Our data show that extra-pair and within-colony breeding males differed significantly in relatedness to breeding females, suggesting that females may gain genetic benefits from breeding with non-resident males. Extra-colony male mating success was not based on heterozygosity criteria at microsatellite loci; however, litters sired by extra-colony males exhibited increased heterozygosity. While we do not have the data that refute a relationship between individual levels of inbreeding (Hs) and fitness, we propose that a combination of both male and female factors most likely explain the adaptive significance of extra-pair mating whereby common mole-rats maximize offspring fitness by detecting genetic compatibility with extra-pair mates at other key loci, but it is not known which sex controls these matings.     

Cytonuclear models of epistatic mating with backcrossing and selection

We develop hybrid zone models that explore the combined effects of mating system and either backcrossing or viability selection on the disequilibria between nuclear and cytoplasmic genes. In the epistatic mating plus backcrossing model, we find patterns of permanent cytonuclear disequilibria like those found when epistatic mating is the only factor, as well as a novel combination of significant cytonuclear disequilibria sign patterns. The second group of models evaluates the potential of epistatic mating and postzygotic viability selection to maintain cytonuclear disequilibria. Simulations are used to evaluate nine patterns of selection, each of which represent differing forms of selection against hybrids, and show that while all disequilibria usually decay to zero, under certain circumstances a number of different patterns of significant cytonuclear disequilibria are possible at equilibrium. The results from these models are compared to the observed cytonuclear disequilibria previously found in a hybrid population of Hyla treefrogs.     

Satyrization without evidence of successful insemination from interspecific mating between invasive mosquitoes

Previous research has documented low frequencies of interspecific mating in nature between the invasive vectors Aedes aegypti and Aedes albopictus. It is also known that heterospecific male accessory gland substances transferred during mating sterilize A. aegypti but not A. albopictus females, leading to satyrization, a form of reproductive interference. This paper demonstrates that satyrization of A. aegypti by A. albopictus may occur without evidence of successful insemination. Our results show that A. aegypti females, previously exposed to A. albopictus males, are rendered refractory to subsequent conspecific mating even though their spermathecae contain no heterospecific sperm. Additional experiments demonstrating transfer of labelled semen from A. albopictus males to A. aegypti females and low production of viable eggs of females housed with conspecific males, following exposure to A. albopictus males, confirm higher incidences of satyrization than expected, based on heterospecific insemination rates. We conclude that frequencies of satyrization based on detection of interspecific sperm in spermathecae may underestimate the impact of this form of reproductive interference.     

Dual reproductive cost of aging in male Medflies: dramatic decrease in mating competitiveness and gradual reduction in mating performance

Although age-based effects on the reproductive success of males have been reported in several animal taxa the cost of aging on male mating success in lekking species has not been fully explored. We used the Mediterranean fruit fly, a lekking species, to investigate possible cost of aging on male reproductive success. We performed no choice and choice mating tests to test the hypothesis that aging does not affect the mating performance (mating success in conditions lacking competition) or the mating competitiveness (mating success against younger rivals) of males. The mating probability of older males decreased significantly when competing with younger males. Aging gradually reduced the mating performance of males but older males were still accepted as mating partners in conditions lacking competition. Therefore, older males are capable of performing the complete repertoire of sexual performance but fail to be chosen by females in the presence of young rivals. Older males achieved shorter copulations than younger ones, and female readiness to mate was negatively affected by male age. Older and younger males transferred similar amount of spermatozoids to female spermathecae. Females stored spermatozoids asymmetrically in the two spermathecae regardless the age of their mating partner. Aging positively affected the amount of spermatozoids in testes of both mated and nonmated males. No significant differences were observed on the amount of spermatozoids between mated and nonmated males.     

Field crickets change mating preferences using remembered social information

Plasticity in female mate choice can fundamentally alter selection on male ornaments, but surprisingly few studies have examined the role of social learning in shaping female mating decisions in invertebrates. We used the field cricket Teleogryllus oceanicus to show that females retain information about the attractiveness of available males based on previous social experience, compare that information with incoming signals and then dramatically reverse their preferences to produce final, predictable, mating decisions. Male ornament evolution in the wild may depend much more on the social environment and behavioural flexibility through learning than was previously thought for non-social invertebrates. The predictive power of these results points to a pressing need for theoretical models of sexual selection that incorporate effects of social experience.     

The impact of plant and flower age on mating patterns

Background

Over a season, plant condition, amount of ongoing reproduction and biotic and abiotic environmental factors vary. As flowers age, flower condition and amount of pollen donated and received also vary. These internal and external changes are significant for fitness if they result in changes in reproduction and mating.

Scope

Literature from several fields was reviewed to provide a picture of the changes that occur in plants and flowers that can affect mating over a season. As flowers age, both the entire flower and individual floral whorls show changes in appearance and function. Over a season, changes in mating often appear as alteration in seed production vs. pollen donation. In several species, older, unpollinated flowers are more likely to self. If flowers are receiving pollen, staying open longer may increase the number of mates. In wild radish, for which there is considerable information on seed paternity, older flowers produce fewer seeds and appear to discriminate less among pollen donors. Pollen donor performance can also be linked to maternal plant age. Different pollinators and mates are available across the season. Also in wild radish, maternal plants appear to exert the most control over paternity when they are of intermediate age.

Conclusions

Although much is known about the characters of plants and flowers that can change over a season, there is less information on the effects of age on mating. Several studies document changes in self-pollination over time, but very few, other than those on wild radish, consider more subtle aspects of differential success of pollen donors over time.     

Sex allocation predicts mating rate in a simultaneous hermaphrodite

Sexual selection theory for separate-sexed animals predicts that the sexes differ in the benefit they can obtain from multiple mating. Conventional sex roles assume that the relationship between the number of mates and the fitness of an individual is steeper in males compared with females. Under these conditions, males are expected to be more eager to mate, whereas females are expected to be choosier. Here we hypothesize that the sex allocation, i.e. the reproductive investment devoted to the male versus female function, can be an important predictor of the mating strategy in simultaneous hermaphrodites. We argue that within-species variation in sex allocation can cause differences in the proportional fitness gain derived through each sex function. Individuals should therefore adjust their mating strategy in a way that is more beneficial to the sex function that is relatively more pronounced. To test this, we experimentally manipulated the sex allocation in a simultaneously hermaphroditic flatworm and investigated whether this affects the mating behaviour. The results demonstrate that individuals with a more male-biased sex allocation (i.e. relatively large testes and small ovaries) are more eager to mate compared with individuals with a more female-biased sex allocation (i.e. relatively small testes and large ovaries). We argue that this pattern is comparable to conventional gender roles in separate-sexed organisms.