Abstracts (first author)


Expression levels of genes belonging to the melanocortin system are associated with melanin-based coloration in two colour polymorphic owl species

Author(s): Roulin A, Ducrest A


The adaptive function of colour polymorphism is a long-standing debate, principally because of limited knowledge of the genetic mechanism underlying morph production. A recent genetic model suggested that the melanocortin system could account for covariations between melanin-based colour morphs, behaviour, morphology and physiology. This genetic system may therefore account for the observed morph-specific life history strategies. In two owl species we explored whether the expression levels of genes belonging to the melanocortin system (MC1R, POMC, PC1, PC2 and the antagonist ASIP) as well as 15 other melanogenic genes are associated with melanin-based coloration. We considered the tawny owl (Strix aluco) because individuals vary continuously from light to dark reddish. We measured gene expression in feather follicles collected in nestlings at the time of melanin production. Our results are consistent with a key role of the melanocortin system on the expression of colour morphs. We indeed found that the expression levels of convertases (that process melanocortin hormones) covary with melanin-based coloration, an effect that strongly depends on genetic polymorphism at the melanocortin-1-receptor (MC1R). We conclude that the melanocortin system may explain why dark and light melanic morphs adopt alternative life history strategies and differentially cope with stressful factors.

Abstracts (coauthor)


Major histocompatibility complex (MHC) genes play an essential role in the adaptive immune response and thus constitute a good model to study adaptive genetic variability. The extraordinary diversity exhibited by MHC genes is thought to be maintained by pathogen-driven selection, for which three hypotheses have been proposed: rare-allele advantage, heterozygote advantage and fluctuating selection. Despite a growing amount of empirical data, it is still difficult to distinguish the relative role of the different forms of selection in maintaining MHC variability. Moreover other mechanisms such as sexual selection through mate choice can shape the MHC diversity. The barn owl (Tyto alba) exhibits a number of characteristics that make it an ideal model to study MHC diversity. Indeed it is one of the most widespread birds worldwide and it has been shown that this species exhibits mate choice related to an ornamental trait that is associated to parasite resistance. In addition, this bird possesses a relatively simple MHC organization, and is one of only few species in which the two functional MHC class IIB genes can be amplified specifically. Using 454 technology, we sequenced exon 2 of the two MHC class IIB loci in a large number of individuals sampled throughout Europe (N=384) and Switzerland (N=960), for the latter of which information related to individual fitness is available (e.g. immunocompetence, parasite fecundity). We examined the effects of particular alleles and MHC diversity on these fitness parameters. First results indicate a positive effect of heterozygosity on parasite resistance, in agreement with expectations of the heterozygote advantage hypothesis. With the sampling across Europe we will be able to study spatial patterns of MHC diversity and evaluate if MHC genotypes are locally adapted or under balancing selection at the spatial scale. Therefore, this study provides interesting perspectives for the understanding of MHC evolutionary ecology.


Chairman: Octávio S. Paulo
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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


Computational Biology & Population Genomics Group