CE02 - Terre vivante

Diversification and adaptation along environmental gradients: identification of genes and traits involved in species differentiation in alpine butterflies – DIVALPS

Alpine butterfly diversitication

Diversification and adaptation along environmental gradients: Identification of genes and traits involved in species differentiation in alpine butterflies

Genomic landscape of speciation

Our aim is to identify the mechanisms underlying the repeated evolution of reproductive barriers among entities adapted to different altitudinal niches, but that are still interconnected by gene-flow. This will be achieved by identifying genomic regions that are more or less permeable to introgression and by testing the role of associated traits in reproductive isolation and local adaptation.

Assembly and annotation of 5 reference genomes (2 parental species, 2 species from an ancient hybridization event, 1 recent hybrid); search for structural variants; population analysis: search for genomic islands of differentiation, identification of genes and biological traits involved. Analysis of phenotypic (pheromones, cuticular compounds, morphometry, thermotolerance), genomic and environmental clines in areas of contact between species, and genotype x phenotype x environment association analyses.

Five genomes assembled at the chromosomal level and annotated; publication in preparation
Development of the Structure Variant genotyping software with long reads, SVJedi-graph, released in open-source via github and Bioconda: github.com/SandraLouise/SVJedi-graph; publication in progress
The demographic analysis of the 4 species confirms that 1/ the two parental species diverged about 2 million years ago and have asynchronous demographic histories related to Quaternary climate fluctuations, 2/ the two hybrid species originated from a hybridization event about 12000 years ago, and have different recent introgression histories with the parental species whose adaptive role remains to be demonstrated. Differences in chemical compounds and thermotolerance of eggs have been found between species.

Cline analysis in contact zones will confirm the role of islands of genomic differentiation in altitude adaptation in this species complex, and the association study will link genetic variation, phenotypic variation and environmental variation.

SVJedi-graph: Open-source package for structural variants genotyping via github et Bioconda : github.com/SandraLouise/SVJedi-graph.

Repeated adaptation in related lineages to similar environmental conditions could result from natural selection acting independently in each lineage, or from adaptive introgression between lineages during periods of range overlap. Here we focus on a complex of butterfly species distributed along the altitudinal gradient, and with different histories of altitudinal adaptation, to understand how populations adapt to higher elevation. We will analyse genomes of butterflies in contact zones to identify introgressions and rearrangements between taxa, i.e. regions more or less permeable to gene flow, and associate them with adaptive phenotypic variation. By using hybrid taxa originating from ancient hybridization, we will untangle the effects of genome-wide differentiation due to allopatry and demography from those of selection on genes involved in local adaptation and reproductive isolation. We will reveal to what extent these genes were exchanged between lineages. To understand how the key traits conferring altitudinal adaptation are shared by introgression among alpine lineages or act as barriers to gene flow, we will use admixed populations in contact zones, taking advantage of a natural recombination experiment allowing the segregation of the phenotypic traits characterising each taxon through many generations of recombination. This will allow linking traits and candidate genes with adaptation to changes in climatic and biotic conditions with altitude. This system offers an excellent opportunity to decipher the processes involved in adaptation to new conditions along the altitudinal gradient, and identify the key traits and candidate genes involved. This project will mobilise forces from thres distinct labs with expertise in bioinformatics, population genomics, ecology, and experimental approaches.trogressions with adaptation to changes in climatic and biotic conditions with altitude.

Project coordination

Laurence DESPRES (LABORATOIRE D'ECOLOGIE ALPINE)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

Inria Rennes Bretagne - Atlantique Centre de Recherche Inria Rennes - Bretagne Atlantique
CEFE Centre d'Ecologie Fonctionnelle et Evolutive
LECA LABORATOIRE D'ECOLOGIE ALPINE

Help of the ANR 588,497 euros
Beginning and duration of the scientific project: December 2020 - 48 Months

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