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Final Report Summary - HYBRID-GENES (The Repeatability of Genetic Architecture)

A major challenge in evolutionary biology is to understand how genetic variation is created and maintained. Recent studies confirm the old idea introduced by Anderson in the 1940’s in his monograph “introgressive hybridisation”, namely that hybridisation can provide a bridge for the genetic exchange of adaptations (genes that increase fitness). In general, it is thought that adaptive genes have a greater chance to cross species boundaries than key “speciation genes” or genes residing inside “genomic islands of divergence”, which should both be more resistant to introgression. An exciting opportunity to tackle this question is to study novel genetic combinations in recently originated hybrid zones, because they allow to study the creation and maintenance of genetic combinations within ecological time frames. In the last five years, the rapid development of next generation sequencing (NGS) technologies and the computational advancements to analyse big data (such as large sub-sections of the genome) allows testing these ideas for the first time in unprecedented detail. In the granted Marie Curie postdoctoral fellowship, I have worked with two closely related damselfly species (Ischnura elegans and I. graellsii) which show extensive and recent population overlap in southern Europe with strong hybridisation. The main hypothesis that was tested in this proposal is that adaptive genes have a greater chance to cross species boundaries than key speciation genes. To test this hypothesis, this proposal had three main objectives that addressed key challenges in the field: i) detailed quantification of introgression levels across the genome; ii) repeatability of the genetic architecture of speciation; and iii) repeatability of the genetic architecture of adaptation via introgressive hybridisation.

We have collected population samples, and ecological and morphological data to evaluate how introgression shapes genomic regions affecting ecological factors and morphological traits. We have also tested prezygotic reproductive barriers between allopatric and parapatric populations, obtained a hybrid pedigree in the laboratory and genetic data (genotyping and RAD-sequencing) for the inference of SNPs and genotypes.

We are currently analysing introgression levels in natural populations; and 2) the genetic architecture of speciation and adaptation. We will identify genes responsible for reproductive isolation, and selective sweeps; and I will investigate if certain genomic regions (chromosomal blocks) are repeatedly inherited from the same parental species, the size of genomic linkage islands, and if these differ between populations.

This project will contribute to Europeans excellence and competitiveness from multiple perspectives. First, it will provide new insights into the evolutionary puzzle of insect speciation by understanding the processes leading to the origin of reproductive barriers. Secondly, it will provide new insights of the genomic patterns of introgression. Over the past decade, European research has played an extensive role in identifying and assessing global change as a major tools to gain insights into the genetic consequences. Only with this knowledge is it possible to approach decision makers to formulate conservation plans for European species. This highlighted benefit from my project should not be underestimated as this scenario is unfortunately highly realistic for many populations in rapidly changing and fragmented habitats, and is therefore of major concern for conserving biodiversity on the global scale.

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