Conservatism and novelty in the genetic architecture of adaptation in Heliconius butterflies

10 pagesInternational audienceUnderstanding the genetic architecture of adaptive traits has been at the centre of modern evolutionary biology since Fisher; however, evaluating how the genetic architecture of ecologically important traits influences their diversification has been hampered by the scarcity of empirical data. Now, high-throughput genomics facilitates the detailed exploration of variation in the genome-to-phenotype map among closely related taxa. Here, we investigate the evolution of wing pattern diversity in Heliconius, a clade of neotropical butterflies that have undergone an adaptive radiation for wing-pattern mimicry and are influenced by distinct selection regimes. Using crosses between natural wing-pattern variants, we used genome-wide restriction site-associated DNA (RAD) genotyping, traditional linkage mapping and multivariate image analysis to study the evolution of the architecture of adaptive variation in two closely related species: Heliconius hecale and H. ismenius. We implemented a new morphometric procedure for the analysis of whole-wing pattern variation, which allows visualising spatial heatmaps of genotype-to-phenotype association for each quantitative trait locus separately. We used the H. melpomene reference genome to fine-map variation for each major wing-patterning region uncovered, evaluated the role of candidate genes and compared genetic architectures across the genus. Our results show that, although the loci responding to mimicry selection are highly conserved between species, their effect size and phenotypic action vary throughout the clade. Multilocus architecture is ancestral and maintained across species under directional selection, whereas the single-locus (supergene) inheritance controlling polymorphism in H. numata appears to have evolved only once. Nevertheless, the conservatism in the wing-patterning toolkit found throughout the genus does not appear to constrain phenotypic evolution towards local adaptive optima

Carbon nanotubes: Synthesis, structure, functionalization, and characterization

Carbon nanotubes have generated great expectations in the scientific arena, mainly due to their spectacular properties, which include a high aspect ratio, high strain resistance, and high strength, along with high conductivities. Nowadays, carbon nanotubes are produced by a variety of methods, each of them with advantages and disadvantages. Once produced, carbon nanotubes can be chemically modified, using a wide range of chemical reactions. Functionalization makes these long wires much easier to manipulate and dispersible in several solvents. In addition, the properties of carbon nanotubes can be combined with those of organic appendages. Finally, carbon nanotubes need to be carefully characterized, either as pristine or modified materials