title: Tracking changes in chromosomal arrangements and their genetic content during adaptation.
abstract: There is considerable evidence for an adaptive role of inversions, but how their genetic content evolves and affects the subsequent evolution of chromosomal polymorphism remains controversial. Here, we track how life-history traits, chromosomal arrangements and 22 microsatellites, within and outside inversions, change in three replicated populations of Drosophila subobscura for 30 generations of laboratory evolution since founding from the wild. The dynamics of fitness-related traits indicated adaptation to the new environment concomitant with directional evolution of chromosomal polymorphism. Evidence of selective changes in frequency of inversions was obtained for seven of 23 chromosomal arrangements, corroborating a role for inversions in adaptation. The evolution of linkage disequilibrium between some microsatellites and chromosomes suggested that adaptive changes in arrangements involved changes in their genetic content. Several microsatellite alleles increased in frequency more than expected by drift in targeted inversions in all replicate populations. In particular, there were signs of selection in the O3+4 arrangement favouring a combination of alleles in two loci linked to the inversion and changing along with it, although the lack of linkage disequilibrium between these loci precludes epistatic selection. Seven other alleles increased in frequency within inversions more than expected by drift, but were not in linkage disequilibrium with them. Possibly these alleles were hitchhiking along with alleles under selection that were not specific to those inversions. Overall, the selection detected on the genetic content of inversions, despite limited coverage of the genome, suggests that genetic changes within inversions play an important role in adaptation.
authors.affiliation: cE3c - Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Lisboa, Portugal.
authors.forename: J
authors.initials: J
authors.lastname: Santos
authors.affiliation: Department of Genetics and IrBio, Facultat de Biologia, Universitat de Barcelona, Barcelona, España.
authors.forename: M
authors.initials: M
authors.lastname: Pascual
authors.affiliation: cE3c - Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Lisboa, Portugal.
authors.forename: I
authors.initials: I
authors.lastname: Fragata
authors.affiliation: cE3c - Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Lisboa, Portugal.
authors.forename: P
authors.initials: P
authors.lastname: Simões
authors.affiliation: cE3c - Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Lisboa, Portugal.
authors.forename: M A
authors.initials: MA
authors.lastname: Santos
authors.affiliation: cE3c - Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Lisboa, Portugal.
authors.forename: M
authors.initials: M
authors.lastname: Lima
authors.affiliation: cE3c - Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Lisboa, Portugal.
authors.forename: A
authors.initials: A
authors.lastname: Marques
authors.affiliation: cE3c - Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Lisboa, Portugal.
authors.forename: M
authors.initials: M
authors.lastname: Lopes-Cunha
authors.affiliation: cE3c - Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Lisboa, Portugal.
authors.forename: B
authors.initials: B
authors.lastname: Kellen
authors.affiliation: Department of Genetics and IrBio, Facultat de Biologia, Universitat de Barcelona, Barcelona, España.
authors.forename: J
authors.initials: J
authors.lastname: Balanyà
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, USA.
authors.forename: M R
authors.initials: MR
authors.lastname: Rose
authors.affiliation: cE3c - Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Lisboa, Portugal.
authors.forename: M
authors.initials: M
authors.lastname: Matos
mesh_terms: D000222:Adaptation, Physiological; D000483:Alleles; D000818:Animals; D007446:Chromosome Inversion; D002875:Chromosomes; D004330:Drosophila / Q000235:genetics*; D015810:Linkage Disequilibrium; D011110:Polymorphism, Genetic
keywords: Drosophila subobscura; chromosomal inversions; experimental evolution; genetic content; linkage disequilibrium; selection