Sexual dimorphism of body size and sternopleural bristle number: a comparison of geographic populations of an invasive cosmopolitan drosophilid |
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Authors: | Jean R David Luciana O Araripe Blanche C Bitner-Mathé Pierre Capy Beatriz Goñi Louis Bernard Klaczko Hélène Legout Marlucia B Martins Joseph Vouidibio Amir Yassin Brigitte Moreteau |
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Institution: | (1) CNRS, Lab. Populations, Génétique et Evolution, Gif sur Yvette Cedex, 91198, France;(2) Departamento de Genetica, I.B., Unicamp, Campinas, SP, Brazil;(3) Departamento de Genetica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21944–970, Brazil;(4) Sección Genética Evolutiva, Facultad de Ciencias, Montevideo, 11400 Uruguay;(5) Museu PE., Goeldi, Belem, Brazil;(6) Département de Génétique, Université de Brazzaville, Brazzaville, Congo;(7) Department of Genetics, University of Alexandria, Alexandria, Egypt |
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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. |
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Keywords: | Drosophila melanogaster female/male ratio genetic drift intra-class correlation isofemale lines stabilizing selection thorax length wing length Zaprionus indianus |
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