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Eija Lönn
University of Jyväskylä
Finland

A likely role for antagonistic selection in the maintenance of genetic variation at the arginine vasopressin receptors 1a

poster 

Author(s): Lönn, E, Koskela, E, Mappes, T, Mokkonen, M, Watts, PC

Summary:

Vasopressin modulates a range of socio-reproductive behavior in mammals, largely through its interaction with expression of the arginine vasopressin receptor 1a (avpr1a). In microtine voles, the length of the microsatellite locus situated in the avpr1a promoter region regulates expression of this gene in certain regions of the brain and this has a concomitant effect upon a variety of male-associated behaviors. We quantified the effect of variation in the length of the microsatellite in the promoter regions of avpr1a upon reproductive success in semi-natural populations of bank voles (Myodes glareolus). After artificial breeding was used to create lines with contrasting microsatellite genotypes, we released animals into 0.25 ha enclosures in the field and measured survival and reproductive success over a breeding season. Our study revealed a sex-by-density interaction for avpr1a microsatellite length, such that males with longer- and females with shorter- avpr1a microsatellite alleles enjoyed greater reproductive success in low density populations; conversely, males with shorter- and females with longer- avpr1a alleles produced more offspring in high density populations. Both sexually antagonistic selection and density dependent selection are reasonable candidate mechanisms behind the maintenance of variation in microsatellite allelic diversity in avpr1a.

Joanna Rutkowska
Jagiellonian University
Institute of Environmental Sciences
Poland

All eggs are made equal

poster 

Author(s): Rutkowska, J, Dubiec, A, Nakagawa, S

Summary:

Maternal effects mediated by egg size may have profound effects on offspring fitness. Sex-biased resource allocation in birds gains increasing interest, but it is not known to what extent the egg sexual size dimorphism (SSD) is a wide-spread phenomenon in this group. To answer that question we performed meta-analysis of 33 published and 2 unpublished studies, which included information on egg SSD of 31 avian species. Many of those studies suggested adaptive explanation for the reported egg SSD, which helped us to formulate predictions for our analyses. In some species, egg SSD was suggested to promote future size differences between the adults. If that is the case, then across species, adult SSD should be a significant predictor of egg SSD. However, in other species, egg SSD was invoked as an adaptive means by which a female balances nestling mortality differences between sexes, therefore producing bigger eggs for the smaller sex. Based on these two hypotheses, we derived a general prediction that there should be a significant relationship between the magnitude of adult SSD and the magnitude of egg SSD irrespective of the direction of those differences. Our analyses found no support for either of those hypotheses. Across species, adult SSD does not predict egg SSD. More importantly, our meta-analysis revealed no heterogeneity, with the meta-analytic mean very close to 0. That is, the observed variation in effect sizes in our dataset was almost exclusively explained by sampling error and there was no difference in avian egg sizes between the sexes whatsoever. Although adult SSD is undoubtedly a prominent feature of avian species, we conclude that, in general, there is no evidence for egg SSD across bird species.

Marija Savic Veselinovic
Faculty of Biology of the University of Belgrade
Chair Genetics and Evolution
Serbia

Can mutational load be reduced through selection on males?

poster 

Author(s): Savic Veselinovic, MN, Pavkovic-Lucic, S, Kurbalija Novicic, Z, Jelic, M, Tanaskovic, M, Andjelkovic, M

Summary:

According to theoretical predictions sexual selection will purge mutational load and increase nonsexual fitness if most mutations are deleterious to both nonsexual fitness and condition-dependent traits affecting mating success. To test this hypothesis we manipulated the genetic quality of Drosophila subobscura males by inducing mutations with ionizing radiation and observed the effect of the obtained heterozygous mutations on mating behavior. We used the progeny of both groups (manipulated and non-manipulated) to test if sexual selection is efficient to reduce induced mutational load, by measuring nonsexual fitness. Within the non-manipulated and manipulated treatments we formed two groups with different opportunity for sexual selection, with presence or absence of female choice. Females mated more frequently with non-manipulated males and non-manipulated males courted females faster. Fecundity differences were obtained only in manipulated treatment. Group with the presence of female choice exhibited higher fecundity than group in which sexual selection was experimentally eliminated. There was no overall difference in egg-to-adult viability between different sexual selection regimes in any of the group. Our findings hint to an important role of sexual selection in purging deleterious mutations.

Katja Heubel
University of Tuebingen
Animal Evolutionary Ecology
Germany

Context-dependent plasticity of sex-roles

poster 

Author(s): Heubel, K

Summary:

Most research on sexual selection thus far has been carried out while ignoring the social and population ecological context. Here I address the question how sexual selection and its natural context interact in a small annual marine fish with exclusive paternal care, the common goby (Pomatoschistus microps). Specifically, field experiments were carried out to study interactions between operational sex ratio, reproductive rates, mate competition and nest availability and its impact on reproductive decisions. The results elucidate the seasonal plasticity of sex roles in populations with changing environmental contexts and highlight the importance of nest density. Insights in temporal dynamics of the mating system interacting with the natural context and its potential population level evolutionary consequences shall be discussed.

Roland Schultheiß
University of Turku
Department of Biology
Finland

Deep RNA sequencing suggests a lack of global dosage compensation in threespine sticklebacks

poster 

Author(s): Schultheiß, R, Viitaniemi, HM, Sävilammi, T, Leder, EH

Summary:

The establishment of non-recombining regions is a critical early step in the evolution of sex chromosomes. To compensate for the resulting difference in the expression of X-linked genes the heterogametic sex will increase the expression of X-linked genes or the homogametic sex will shut down one of the X chromosomes. This process is known as dosage compensation. It has recently been suggested that incomplete or imperfect dosage compensation may have a stronger influence on sex-biased expression than previously thought. We use the threespine stickleback (Gasterosteus aculeatus) as a model system to study the role of dosage compensation in the evolution and maintenance of sex-biased gene expression. Threespine sticklebacks constitute a particular interesting system in this respect because its chromosome group 19 are nascent sex chromosomes: Whereas there is still recombination between sexes in the region spanning the first 3 million bases on the chromosome, recombination is significantly reduced in the region from 3-12 million bases. The last 6 million bases are mostly deleted from the male Y-chromosome. We collected five specimens of each sex from a benthic and a limnetic population in four Alaskan lakes, respectively, and utilized deep RNA sequencing of brain tissue to study gene and transcript isoform expression differences between the sexes. Preliminary results from expression of genes corresponding to the missing region of the X chromosome suggest no dosage compensation as the expression pattern is indicative of a copy number variation biased towards females. In other areas of the genome, there is more varied sex-biased expression.

Isobel Booksmythe
Evolutionary Biology Centre, Uppsala University
Animal Ecology
Sweden

Exploring a female sexual signal

poster 

Author(s): Booksmythe, I, Rundle, H, Arnqvist, G

Summary:

It is now well recognized that exaggerated sexual signalling traits occur in females across many taxa. However, it remains empirically true that such traits are less common in females than in males. Their relative rarity in females is attributed to more restrictive conditions under which they can evolve: theoretically, female investment into signals of mate quality should be restricted due to trade offs with investment into fecundity. The conditions necessary for the evolution and maintenance of exaggerated female traits are not fully understood and their exact signalling function is not always clear. We investigated the chemical signalling role of a conspicuous, female-limited trait in a beetle showing female courtship and male mate choice. Megabruchidius tonkineus females court males by repeatedly presenting their abdomen, which bears two large, dark, pore-enriched patches that the male probes and antennates before deciding whether to copulate. We manipulated female mating status, age, and size, measured male mating preferences and compared female chemical profiles to determine whether this exaggerated female trait functions to signal female fecundity.

Ally Harari
The Volcani Center
Department of Entomology
Israel

Female moths do it all: advertise, compete and choose

poster 

Author(s): Harari, A, Steinitz, HHS, Sadeh, AAS, Zahavi, TTZ

Summary:

The concept of a male sex pheromone as a sexual trait that is used by females to evaluate males as mates is widely accepted. By contrast, the idea of a female sex pheromone as a secondary sexual trait is fairly new and evidence is scarce. In order to serve as an honest signal, sex pheromones, as other secondary traits that advertise condition, should bear a significant cost. Female sex pheromone, as opposed to male sex pheromone, is typically released in minute amounts. Nevertheless, accumulating evidence demonstrates an imposed cost on female produced pheromone. Male moths, at the other side of the sexual selection equation, are generally sperm limited and as such are expected to gain from choosing a mate. We will discuss the option of mutual mate choice and intrasexual competition among both, males and females in the context of operational sex ratio in monandrous and polyandrous females.

Johanna Dunn
University of Nottingham
School of Biosciences
United Kingdom

Higher aggression towards closer relatives by soldier larvae in a polyembryonic wasp

poster 

Author(s): Dunn, J, Dunn, DW, Strand, MR, Hardy, ICW

Summary:

In the polyembryonic wasp Copidosoma floridanum females commonly lay one male and one female egg in a lepidopteran host. Both sexes proliferate clonally within the growing host larvae. Distinct larval castes develop from each wasp egg: the majority being ‘reproductives’ plus some ‘soldiers’ which sacrifice reproduction and attack competitors. Maturing mixed sex broods are usually female biased, as expected when intra-brood mating is common. Pre-mating dispersal followed by outbreeding is expected to increase sexual conflict over brood sex ratios and result in greater soldier attack rates. Due to sexually asymmetric relatedness, intra-brood conflicts are expected to be resolved primarily via female soldier attack. We observed soldier behaviour in vitro to test whether lower intra-brood relatedness (manipulated by whether or not the father was from the maternal population) increased inter-sexual aggression by female as well as male soldiers. As found in prior studies, females were more aggressive than males but, contrary to expectations, soldiers of both sexes showed more aggression towards more closely related embryos. We speculate that lower intra-brood relatedness indicates maternal outbreeding and may suggest a rarity of mating opportunities for reproductives maturing from the current brood, which may thus enhance the value of opposite sex brood-mates.

Kenyon Mobley
Max Planck Institute for Evolutionary Biology
Evolutionary Ecology
Germany

No evidence for size-assortative mating in the wild despite mutual mate choice in two species of sex-role-reversed pipefish

poster 

Author(s): Mobley, KB, Chakra, MABOU, Jones, AG

Summary:

Size-assortative mating is expected to be common in species with mutual preferences for body size. In this study, we investigated whether there is direct evidence for assortative mating in two species of pipefishes, Syngnathus floridae and S. typhle, that share the characteristics of male pregnancy, sex-role reversal and a polygynandrous mating system. We take advantage of microsatellite-based ‘genetic-capture’ techniques to match wild caught females with female genotypes reconstructed from broods of pregnant males and use these data to explore patterns of size-assortative mating in these species. We also developed a simulation model to explore the conditions under which preferences for body size can lead to size-assortative mating. Contrary to expectations, we were unable to find any evidence of size-assortative mating in either species. Results from simulations demonstrate that strong size-assortative mating preferences are unlikely to explain the observed patterns of mating in the studied populations. Our study suggests that individual mating preferences, as ascertained by laboratory-based mating trials, can be decoupled from realized patterns of mating in nature.

Remi Charge
CoE in Biological Interactions Research, University of Jyväskylä
Department of Biological and Environmental Science
Finland

Post-mating sexual selection and maintenance of colour polymorphism in an aposematic species

poster 

Author(s): Charge, R, Lindstedt, C, Hämäläinen, L, Övermark, E, Wedell, N, Mappes, J

Summary:

Predation is assumed to select for signal uniformity and conspicuousness in aposematic species, but colour polymorphism is surprisingly common. Sexual selection can maintain colour polymorphism, but only a few studies have examined its role in the maintenance of polymorphism in aposematic species. Previous studies in the aposematic Wood Tiger moth, Parasemia plantaginis, suggest that the conspicuous yellow male morph is better defended against predators, whereas females seem to prefer to mate with the white morph offering one potential explanation for the maintenance of colour polymorphism. Here we test the possible direct benefits that female could gain by mating with white males by examining whether white males provide females with bigger spermatophores and more sperm and whether white males recover faster after mating than yellow males. Spermatophores of either white or yellow males were collected from recently mated females. To measure male recovery rate, the amount of fertile sperm stored in males’ reproductive tract was assessed in mated males over several days post-copulation. We found that white males transferred bigger spermatophores than yellow males, but this difference was found only in older males. No difference in the pattern of sperm recovery was observed between male morphs. Contrary to our prediction, we found slightly higher number of fertile sperm stored in the reproductive tract of yellow males compared to white males, regardless of the recovery period. One explanation is that white males invest more in sperm competition by producing more non-fertile sperm that may suppress female receptivity. This would result in bigger spermatophores but with reduced number of fertile sperm. White males might also transfer other compounds such as defensive chemicals into the spermatophore that may benefit females. Altogether our results suggest that fertilization benefits do not solely explain how colour polymorphism is maintained in P. plantaginis.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028
email: mail@eseb2013.com

Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
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