title: Evolution of male genitalia: environmental and genetic factors affect genital morphology in two Drosophila sibling species and their hybrids.
abstract: BACKGROUND
  The rapid evolution of genital morphology is a fascinating feature that accompanies many speciation events. However, the underlying patterns and explanatory processes remain to be settled. In this work we investigate the patterns of intraspecific variation and interspecific divergence in male genitalic morphology (size and shape) in the cactophilic sibling species Drosophila buzzatii and D. koepferae. Genital morphology in interspecific hybrids was examined and compared to the corresponding parental lines.
  
  
  RESULTS
  Despite of being siblings, D. buzzatii and D. koepferae showed contrasting patterns of genital morphological variation. Though genitalic size and shape variation have a significant genetic component in both species, shape varied across host cacti only in D. buzzatii. Such plastic expression of genital shape is the first evidence of the effect of rearing substrate on genitalic morphology in Drosophila. Hybrid genital morphology was not intermediate between parental species and the morphological resemblance to parental strains was cross-dependent.
  
  
  CONCLUSIONS
  Our results suggest the evolution of different developmental networks after interspecific divergence and the existence of a complex genetic architecture, involving genetic factors with major effects affecting genital morphology.
authors.affiliation: Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina. soto@ege.fcen.uba.ar
authors.forename: Ignacio M
authors.initials: IM
authors.lastname: Soto
authors.forename: Valeria P
authors.initials: VP
authors.lastname: Carreira
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Fanara
authors.forename: Esteban
authors.initials: E
authors.lastname: Hasson
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D005075:Biological Evolution; D003433:Crosses, Genetic; D004330:Drosophila / Q000235:genetics* / Q000254:growth & development; D018507:Gene Expression Regulation, Developmental; D005837:Genitalia, Male / Q000254:growth & development*; D008297:Male; D009929:Organ Size; D013045:Species Specificity