https://phaidra.vetmeduni.ac.at/o:3471 The influence of GC-biased gene conversion on nonadaptive sequence evolution in short introns of Drosophila melanogaster Yıldırım, Burçin Burçin Yıldırım 0000-0003-4606-2867 University of Veterinary Medicine Vienna / Vienna Graduate School of Population Genetics Vogl, Claus Claus Vogl 0000-0002-3996-7863 University of Veterinary Medicine Vienna / Vienna Graduate School of Population Genetics Oxford University Press text eng Population genetic inference of selection on the nucleotide sequence level often proceeds by comparison to a reference sequence evolving only under mutation and population demography. Among the few candidates for such a reference sequence is the 5' part of short introns (5SI) in Drosophila. In addition to mutation and population demography, however, there is evidence for a weak force favouring GC bases, likely due to GC-biased gene conversion (gBGC), and for the effect of linked selection. Here, we use polymorphism and divergence data of Drosophila melanogaster to detect and describe the forces affecting the evolution of the 5SI. We separately analyse mutation classes, compare them between chromosomes, and relate them to recombination rate frequencies. GC-conservative mutations seem to be mainly influenced by mutation and drift, with linked selection mostly causing differences between the central and the peripheral (i.e., telomeric and centromeric) regions of the chromosome arms. Comparing GC-conservative mutation patterns between autosomes and the X chromosome showed differences in mutation rates, rather than linked selection, in the central chromosomal regions after accounting for differences in effective population sizes. On the other hand, GC-changing mutations show asymmetric site frequency spectra, indicating the presence of gBGC, varying among mutation classes and in intensity along chromosomes, but approximately equal in strength in autosomes and the X chromosome. Codon Usage Bias; Effective Population-Size; Recombination Rate; Base Composition; Directional Selection; Noncoding Sequences; Molecular Evolution; Natural-Selection; Moran Model; Patterns http://creativecommons.org/licenses/by/4.0/ https://phaidra.vetmeduni.ac.at/api/object/o:3471/download 10.1093/jeb/voae015 https://phaidra.vetmeduni.ac.at/o:605 application/pdf Journal of Evolutionary Biology 37(4), 383-400 (2024) Journal of Evolutionary Biology 37 4 383 400 1.20 MB 2024