Mid-Term Report Summary - EVOLMAPPING (An integrated assessment of recent evolutionary change through genome wide mapping of regulatory changes and signatures of selection in natural sculpin (Cottus) hybrids)
The unprecedented access to genome wide data highlights the potential of current evolutionary studies. The EVOLMAPPING project analyses the evolution of a fish species through hybrid speciation. We study natural populations of freshwater fish referred to as sculpins (Cottus). In these we have identified species that have recently (<200 years) hybridized as a result of secondary contact through man-made canals between river systems. This gave rise to a new lineage with new adaptations that have allowed it to invade habitats that were not used by the parental species before. We are thus also dealing with evolutionary change that is associated with man-made ecological perturbations, the analysis of which is particularly timely. It is now possible to perform a near exhaustive search to identify genes and to study gene expression as a measure of evolutionary change in Cottus. A combination of genetic mapping experiments and screens for genotypic selection can reveal loci and functions as targets of selection in the adaptive evolution of invasive Cottus. This proposal specifically aims at identifying genomic traits such as copy number changes of coding sequences or changes in the gene regulatory architecture that have evolved as a direct consequence of hybridization and to explore their implication in adaptive evolution.
During the project we have sequenced genomes of individual fish representing the ancestral species Cottus rhenanus and Cottus perifretum. Moreover, we have sequenced DNA of fish representing the hybrid species “invasive Cottus”. Team members are involved in the assembly of the Cottus genome using the PacBio sequencing technology, which has increased the quality of the genome assembly to a point where long stretches of the Cottus genome are available. We can use this resource to analyze how the hybrid genome was assembled from genetic material that originates from the two parental species and to fully explore the genetic content of stretches of DNA. We analyze patterns of gene expression to reveal how hybrids differ from the parent species in the laboratory and under natural conditions. Moreover, we study evolutionarily important phenotypes like sex and patterns of scale development. Finally, we have crossed different species of Cottus in the laboratory to analyze the inheritance of traits and to link phenotypes with the underlying genes. Take together the data permits to identify new traits that help hybrid Cottus to adapt to those environments in nature where their parents cannot live.
The results will contribute to our understanding of the genetics of adaptation. We will link traits that have undergone evolutionary change with the underlying regions of the genome. It is particularly interesting that we can study how evolutionary change is linked with the process of natural hybridization. Natural hybridization is a widely encountered phenomenon, but the evolutionary consequences are rarely studied in depth at the genetic level and at a genome wide scale. Hence EVOLMAPPING will contribute to understand how hybridization contributes to evolution, a process that is increasingly found to occur in all kingdoms of the living world.
During the project we have sequenced genomes of individual fish representing the ancestral species Cottus rhenanus and Cottus perifretum. Moreover, we have sequenced DNA of fish representing the hybrid species “invasive Cottus”. Team members are involved in the assembly of the Cottus genome using the PacBio sequencing technology, which has increased the quality of the genome assembly to a point where long stretches of the Cottus genome are available. We can use this resource to analyze how the hybrid genome was assembled from genetic material that originates from the two parental species and to fully explore the genetic content of stretches of DNA. We analyze patterns of gene expression to reveal how hybrids differ from the parent species in the laboratory and under natural conditions. Moreover, we study evolutionarily important phenotypes like sex and patterns of scale development. Finally, we have crossed different species of Cottus in the laboratory to analyze the inheritance of traits and to link phenotypes with the underlying genes. Take together the data permits to identify new traits that help hybrid Cottus to adapt to those environments in nature where their parents cannot live.
The results will contribute to our understanding of the genetics of adaptation. We will link traits that have undergone evolutionary change with the underlying regions of the genome. It is particularly interesting that we can study how evolutionary change is linked with the process of natural hybridization. Natural hybridization is a widely encountered phenomenon, but the evolutionary consequences are rarely studied in depth at the genetic level and at a genome wide scale. Hence EVOLMAPPING will contribute to understand how hybridization contributes to evolution, a process that is increasingly found to occur in all kingdoms of the living world.