Urophora cardui Genome sequencing and assembly. Urophora cardui

The study investigates parapatric diversification in Urophora cardui. Parapatry assumes primary, ecological adaptation along environmental gradients. The process results in genetic clines at loci experiencing selection where the width of a cline is determined by a balance between selection and gene flow. In the face of homogenising gene flow, parapatric diversification leading to speciation is controversial. The tephritid fly Urophora cardui is characterised by genetic diversification and the “rare allele phenomenon” in a contiguous, one-dimensional landscape on the Jutland peninsula. Rare alleles are often found in hybrid zones between reproductively impaired species. The present study combines field data, laboratory experiments and molecular evolution in an integrative approach to study the evolution and adaptive significance of clines. The study addresses where population-groups are found in the continuum between population and species, and it analyses the relative importance of primary and secondary selection in the parapatric diversification process. The study contributes to our understanding of speciation-with-gene-flow processes.