Abstracts (first author)

Talk 

Inversions, supergenes and the genomic evolution of loci of large effect

Author(s): Joron M

Summary:

Supergenes are defined as clusters of genetic elements maintaining fitness-related traits maintained in high linkage disequilibrium in response to selection for specific combinations of those traits. Recent studies have uncovered that supergenes may be maintained by structural variation presumed to help avoid recombination and the deleterious effects of maladaptive trait combinations. Chromosomal inversions are well-known for their suppressing effect on recombination, and can lock together multiple beneficial gene variants controlling specific trait combinations. There are historical examples, as well as numerous new cases of structural variation associated with the maintenance of well-differentiated morphotypes, ecotypes, or species in sympatry in diverse taxa. Chromosomal rearrangements are therefore important mechanisms of genomic architecture evolution, which merge the control of multiple beneficial traits under a simple inheritance. Thus they provide a way of building up loci of large phenotypic effect, often found to be associated with adaptive variation and radiations. But exactly how multiple beneficial traits become recruited within inversions at the population level is still unclear. In this talk, I will discuss the origins of rearrangement-associated adaptations from plant and animal taxa. I will highlight the role of the ecology of each individual trait and their different combinations, the role of the selection regimes underlying the fitness benefits of tight linkage, and the role of introgression. A continuum of genomic architectures underlies adaptive variation from stable polymorphisms within populations to ecotypes and to ecological speciation. Inversions and supergenes are therefore excellent genomic microcosms to improve our understanding of the process of adaptation and the ecology and tempo of the build-up of linkage disequilibrium between multiple traits.



Abstracts (coauthor)

Summary:

Dominance is a widespread mechanism by which the phenotype of heterozygotes is determined. In polymorphic loci, dominance thus plays an important role in the dynamic of the phenotypic polymorphism because of the high number of heterozygotes. This talk focuses on dominance in a striking case of colour polymorphism caused by Müllerian mimicry. In the unpalatable butterfly species Heliconius numata, several wing colour patterns are co-existing and these patterns exhibit high resemblance with other unpalatable species. Colour patterns thus seem to act as a warning signal of toxicity for predators. In H. numata, this protective mimicry is adapted to the spatial variation in communities of unpalatable butterflies, leading to a stable polymorphism of wing colour patterns due to selection/migration equilibrium. These complex wing colour patterns are mainly controlled by a single locus, the supergene P, which contains about 18 co-segregating genes. Dominance relationships among the haplotypes at the supergene P are predicted to be under high selective constraint due to an increased predation risk for non-mimetic intermediate heterozygotes. Using an original morphological approach based on automatic detection of pattern variation, we quantify the coefficient of dominance between haplotypes at the supergene P. The study of controlled crosses between sympatric and allopatric morphs suggests a complete dominance among haplotypes occurring within populations whereas mosaic of dominance is mainly observed in allopatric haplotypes. This highlights the important role of dominance in the polymorphism of distinct wing colour patterns involved in mimicry relationships and allow us to open research on the possible mechanisms of dominance at the supergene P.

Summary:

Mimicry as a defensive strategy is one of the most compelling example of adaptation. Mimicry communities often involve numerous species, and both mutualistic (Müllerian) and deceptive (Batesian) mimics coexist. In deceptive mimicry, palatable prey mimic unprofitable species (e.g. chemically defended prey which predators avoid) with a negative impact on avoidance learning by predators. In mutualistic mimicry, appearances of defended prey converge on a similar warning signal, thereby reinforcing it and decreasing the per-capita cost of training predators. Theoretical and experimental studies on mimicry phenotypes abound, but studies empirically testing their predictions in real mimicry communities remain scarce. Indeed, the quantitative distribution of phenotypes within and among mimicry complexes is largely unknown, and how phenotypic variations are influenced by the type of mimicry, selection intensity, and/or phylogeny remains unaddressed. We first developed a novel framework that enables for the automatic and precise quantification and comparison of colour pattern. We then used this tool on over 2000 specimens, consisting of 130 butterfly species, collected from distinct Neotropical butterfly communities in the Peruvian Amazon. We quantified the distribution of phenotypes and their structure into a number of separate mimicry optima, using a morphological space encompassing the variation and frequencies of all coexisting colours patterns. We analysed this structure to extract the ecological and phylogenetic patterns underlying the coexistence of multiple mimicry groups within a given locality. We then demonstrated the influence of deceptive vs. mutualistic mimics on phenotypic variability around a mimicry optimum in order to address the effective impact of deception on mimicry.

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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