title: Sexual dimorphism of body size and sternopleural bristle number: a comparison of geographic populations of an invasive cosmopolitan drosophilid.
abstract: Zaprionus indianus is a cosmopolitan drosophilid, of Afrotropical origin, which has recently colonized South America. The sexual dimorphism (SD) of body size is low, males being almost as big as females. We investigated 10 natural populations, 5 from America and 5 from Africa, using the isofemale line technique. Three traits were measured on each fly: wing and thorax length and sternopleural bristle number. Two indices of SD were compared, and found to be highly correlated (r > 0.99). For the sake of simplicity, only the female/male (F/M) ratio was further considered. A significant genetic variability of SD was found in all cases, although with a low heritability (intra-class correlation of 0.13), about half the value found for the traits themselves. For size SD, we did not find any variation among continents or any latitudinal trend, and average values were 1.02 for wing length and 1.01 for thorax length. Bristle number SD was much greater (1.07). Among mass laboratory strains, SD was genetically much more variable than in recently collected populations, a likely consequence of laboratory drift. Altogether, SD, although genetically variable and prone to laboratory drift, is independent of size variations and presumably submitted to a stabilizing selection in nature.
authors.affiliation: CNRS, Lab. Populations, Génétique et Evolution, Gif sur Yvette Cedex, 91198, France. david@pge.cnrs-gif.fr
authors.forename: Jean R
authors.initials: JR
authors.lastname: David
authors.forename: Luciana O
authors.initials: LO
authors.lastname: Araripe
authors.forename: Blanche C
authors.initials: BC
authors.lastname: Bitner-Mathé
authors.forename: Pierre
authors.initials: P
authors.lastname: Capy
authors.forename: Beatriz
authors.initials: B
authors.lastname: Goñi
authors.forename: Louis Bernard
authors.initials: LB
authors.lastname: Klaczko
authors.forename: Hélène
authors.initials: H
authors.lastname: Legout
authors.forename: Marlucia B
authors.initials: MB
authors.lastname: Martins
authors.forename: Joseph
authors.initials: J
authors.lastname: Vouidibio
authors.forename: Amir
authors.initials: A
authors.lastname: Yassin
authors.forename: Brigitte
authors.initials: B
authors.lastname: Moreteau
mesh_terms: D017954:Africa South of the Sahara; D000825:Animal Structures / Q000033:anatomy & histology; D000818:Animals; D049628:Body Size / Q000235:genetics; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000235:genetics; D018428:Drosophilidae / Q000033:anatomy & histology* / Q000235:genetics*; D005260:Female; D005828:Genetics, Population; D008297:Male; D012727:Sex Characteristics; D013020:South America; D013045:Species Specificity; D014921:Wings, Animal / Q000033:anatomy & histology