title: Hawaiian Drosophila genomes: size variation and evolutionary expansions.
abstract: This paper reports genome sizes of one Hawaiian Scaptomyza and 16 endemic Hawaiian Drosophila species that include five members of the antopocerus species group, one member of the modified mouthpart group, and ten members of the picture wing clade. Genome size expansions have occurred independently multiple times among Hawaiian Drosophila lineages, and have resulted in an over 2.3-fold range of genome sizes among species, with the largest observed in Drosophila cyrtoloma (1C = 0.41 pg). We find evidence that these repeated genome size expansions were likely driven by the addition of significant amounts of heterochromatin and satellite DNA. For example, our data reveal that the addition of seven heterochromatic chromosome arms to the ancestral haploid karyotype, and a remarkable proportion of ~70 % satellite DNA, account for the greatly expanded size of the D. cyrtoloma genome. Moreover, the genomes of 13/17 Hawaiian picture wing species are composed of substantial proportions (22-70 %) of detectable satellites (all but one of which are AT-rich). Our results suggest that in this tightly knit group of recently evolved species, genomes have expanded, in large part, via evolutionary amplifications of satellite DNA sequences in centric and pericentric domains (especially of the X and dot chromosomes), which have resulted in longer acrocentric chromosomes or metacentrics with an added heterochromatic chromosome arm. We discuss possible evolutionary mechanisms that may have shaped these patterns, including rapid fixation of novel expanded genomes during founder-effect speciation.
authors.affiliation: Natural Sciences Building, Purchase College, State University of New York, 735 Anderson Hill Road, Purchase, NY, 10577, USA. elysse.craddock@purchase.edu.
authors.forename: Elysse M
authors.initials: EM
authors.lastname: Craddock
authors.affiliation: Department of Embryology, Carnegie Institution for Science, Baltimore, MD, USA.
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Gall
authors.affiliation: Natural Sciences Building, Purchase College, State University of New York, 735 Anderson Hill Road, Purchase, NY, 10577, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Jonas
mesh_terms: D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D004276:DNA, Satellite / Q000235:genetics; D004330:Drosophila / Q000235:genetics*; D005260:Female; D059646:Genome Size; D049750:Genome, Insect; D006254:Hawaii; D006570:Heterochromatin; D007621:Karyotyping; D008297:Male; D014921:Wings, Animal
chemical_list: D004276:DNA, Satellite; D006570:Heterochromatin
keywords: Dot chromosome; Genome size evolution; Hawaiian Drosophila; Heterochromatin; Karyotypic change; Satellite DNA; X chromosome