Meiotic drive and evolution of female choice.
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As a special version of the good-genes hypothesis, it was recently proposed that females could benefit from choosing drive-resistant males in a meiotic drive system. Here, we examine with a three-locus, six-allele population genetic model whether female choice for drive resistance can evolve. An allele leading to female preference for drive-resistant males was introduced at low frequency into a population polymorphic for meiotic drive and drive resistance. Our simulations show that female choice of drive-resistant males is disadvantageous when resistance is Y-linked. This disadvantage occurs because, at equilibrium, drive-resistant males have lower reproductive success than drive-susceptible males. Thus, female choice of drive-susceptible males can evolve when resistance is Y-linked. When resistance is autosomal, selection on female choice for drive resistance is less strong and depends on the frequency of choice: female preference of resistant males is favoured when choice is rare and disadvantageous when choice is frequent, leading to a stable equilibrium at a low frequency of the choice allele. Independent of the location of drive resistance alleles, males with the non-driving allele always have above average reproductive success. Female choice is therefore beneficial when choosy females prefer males with the non-driving allele. (+info)
Paternal kin discrimination in wild baboons.
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Mammals commonly avoid mating with maternal kin, probably as a result of selection for inbreeding avoidance. Mating with paternal kin should be selected against for the same reason. However, identifying paternal kin may be more difficult than identifying maternal kin in species where the mother mates with more than one male. Selection should nonetheless favour a mechanism of paternal kin recognition that allows the same level of discrimination among paternal as among maternal kin, but the hypothesis that paternal kin avoid each other as mates is largely untested in large mammals such as primates. Here I report that among wild baboons, Papio cynocephalus, paternal siblings exhibited lower levels of affiliative and sexual behaviour during sexual consortships than non-kin, although paternal siblings were not significantly less likely to consort than non-kin. I also examined age proximity as a possible social cue of paternal relatedness, because age cohorts are likely to be paternal sibships. Pairs born within two years of each other were less likely to engage in sexual consortships than pairs born at greater intervals, and were less affiliative and sexual when they did consort. Age proximity may thus be an important social cue for paternal relatedness, and phenotype matching based on shared paternal traits may play a role as well. (+info)
Song recognition in female bushcrickets Phaneroptera nana.
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Unlike most acoustic systems evolved for pair formation, in which only males signal, in many species of phaneropterine bushcrickets both sexes sing, producing a duet. We used the duetting species Phaneroptera nana as a model to explore the cues in the male's song that elicit the female's phonoresponse. Different synthetic male songs (chirps containing 2-6 pulses) were presented to Ph. nana females, and their acoustic responses were recorded. The threshold of the female response is lowest at 16 kHz (best frequency), coinciding with the dominant frequency of the male song. The specific amplitude pattern of consecutive pulses in the song of the male is not a critical factor in his signal. That is, songs with both a normal and a reversed order of pulses equally elicit a female response. By systematically deleting pulses from the synthetic male chirp, we found that at least two pulses are needed to elicit a female reply. Under no-choice conditions, increasing the number of pulses did not result in a higher probability of response and did not change the latency of the response; i.e. two pulses are necessary and sufficient to elicit a female response. The range of pulse duration that elicits a female response is 0.2-25 ms, and the inter-pulse silent interval ranges from 5 to 30 ms. (+info)
High variation in multiple paternity of domestic cats (Felis catus L.) in relation to environmental conditions.
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Paternity was analysed in two domestic cat (Felis catus) populations differing in habitat structure (rural versus urban) and density (234 cats km-2 versus 2,091 cats km-2). A total of 312 offspring, 76 mothers and 65 putative fathers were typed at nine microsatellite loci in the two populations. Our data showed a high rate of multiple paternity in the urban population (70-83% of litters with more than one father), whereas it was much lower in the rural population (0-22% of litters with more than one), as most males were able to monopolize the entire litter. However, males reproduced as soon as they reached sexual maturity (i.e. ten months of age) in the urban population, whereas most males delayed reproduction to age three years in the rural population. (+info)
Factors influencing spawning and pairing in the scale worm Harmothoe imbricata (Annelida: Polychaeta).
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Endocrine and environmental factors control reproduction of the polynoid scale worm Harmothoe imbricata. We confirmed that the rate of vitellogenesis was greater in winter specimens transferred from ambient regimes of photoperiod and temperature to a light:dark (LD) photoperiod of 16:8 at 10 degrees C and showed that the number of females spawning was significantly greater than for those transferred to LD8:16 at 10 degrees C. The endocrine mediation of this response was investigated using prostomium implantations. Significantly more LD8:16 females implanted with prostomia from LD16:8 conditioned females spawned than LD8:16 females implanted with LD8:16 prostomia. Females without prostomia failed to spawn. LD16:8 exposure may increase levels of a possible "spawning hormone" in the prostomium. Spawning proceeded in these LD16:8 females and allowed spawning to occur in LD8:16 females implanted with LD16:8 prostomia. In LD8:16 prostomia, titers of the spawning hormone reached the threshold in significantly fewer individuals, so that significantly fewer females implanted with LD8:16 prostomia spawned. Using Y-maze choice chambers, pair formation was shown to be under pheromonal control, with males being attracted to mature females but not to females carrying fertilized oocytes or to LD8:16 conditioned females. Production of this attraction pheromone can, therefore, be manipulated through photoperiodic control, suggesting a link between oogenesis, spawning, and pheromone production. (+info)
Strategic allocation of ejaculates by male Adelie penguins.
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Sperm competition theory suggests that males should strategically allocate sperm to those females that will bring them the best possible genetic returns. Although males of a number of species of insects and fishes have been shown to allocate sperm strategically, we provide, to our knowledge, the first evidence that an avian species is also capable of allocating ejaculates. Male Adelie penguins (Pygoscelis adeliae) are more likely to transfer sperm during extra-pair copulations (EPCs) than during pair copulations. We investigated the question of how males allocate ejaculates within the constraints of limited sperm availability and found (i) that males that engaged in EPC attempts ejaculated less often when copulating with their social partner than males that made no EPC attempts, and (ii) that there was no difference between males that were involved in failed EPC attempts and those that were involved in successful EPCs in the proportion of copulations that resulted in sperm transfer. These results indicate that males achieve strategic allocation of sperm within the constraints of limited sperm availability by withholding ejaculates from their social partners. (+info)
Sexual selection and speciation in field crickets.
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Recent theoretical work has shown that sexual selection may cause speciation under a much wider range of conditions than previously supposed. There are, however, no empirical studies capable of simultaneously evaluating several key predictions that contrast this with other speciation models. We present data on male pulse rates and female phonotactic responses to pulse rates for the field cricket Gryllus texensis; pulse rate is the key feature distinguishing G. texensis from its cryptic sister species G. rubens. We show (i) genetic variation in male song and in female preference for song, (ii) a genetic correlation between the male trait and the female preference, and (iii) no character displacement in male song, female song recognition, female species-level song discrimination, or female song preference. Combined with previous work demonstrating a lack of hybrid inviability, these results suggest that divergent sexual selection may have caused speciation between these taxa. (+info)
Geographical variation in reproductive character displacement in mate choice by male sailfin mollies.
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Female Amazon mollies, Poecilia formosa, are a unisexual species that reproduce by gynogenesis. They must coexist and mate with males of other species (usually the mollies Poecilia latipinna or Poecilia mexicana) to induce embryogenesis, but inheritance is strictly maternal. We examined the mating preference of the male sailfin molly, P. latipinna, for female sailfin mollies versus Amazon mollies, P. formosa. We compared the mating preferences of sympatric and allopatric populations collected throughout the Gulf Coast of North America. Male P. latipinna from six populations sympatric with Amazon mollies showed a significantly greater strength of preference for conspecific sailfin females than males from five populations that were allopatric with Amazon mollies. These results provide strong evidence for reproductive character displacement of male mate choice in sympatry. Furthermore, the large geographical range of populations that we tested revealed variation among populations within sympatry and allopatry, indicating that it is important to evaluate a large number of populations when examining reproductive character displacement. (+info)