Fig. 3

Distribution of the Sgs1 and Sgs3x genes across the 24 studied Drosophila species and most parsimonious scenario for gene gains and losses. The species tree is from [33]. Branch distances are not on scale. Green, pink and gray arrows represent, respectively, Sgs1, Sgs3x and their adjacent neighboring genes. Gene lengths and intergenic distances are not to scale. “R” means that internal repeats are present. The cross ‘X’ on top of the D. triauraria Sgs1 gene indicates the presence of six premature stop codons in the published genome sequence, which may be genuine stop codons or sequence assembly artifacts. * indicates a premature stop codon present in the published coding sequence of D. rhopaloa and D. biarmipes, which we consider as an artifact (see text for details). Minus signs on tree branches indicate gene deletion events for Sgs1 in green and for Sgs3x in pink. Minus sign followed by ‘?’ indicates a presumed loss of a functional gene coding region that has not been confirmed by resequencing