Grafting the molecular phylogenetic tree with morphological branches to reconstruct the evolutionary history of the genus Zaprionus (Diptera : Drosophilidae)

A molecular phylogeny for the drosophilid genus Zaprionus was inferred using a mitochondrial (CO-II) and a nuclear (Amyrel) gene using 22 available species. The combined molecular tree does not support the current classification, dubbed phylogenetic, based entirely upon a morphocline of forefemoral ornamentation. For species for which DNA was not available, phylogenetic positioning was only assigned using morphological characters. In order to avoid conflict between DNA and morphology in the combined analyses (supermatrix method), we developed a new method in which few morphological characters were sampled according to an a priori homoplasy assessment on the consensus molecular tree. At each internal node of the tree, a number of synapomorphies was determined, and species with no molecular sequences were grafted thereon. Analogously to tree vocabulary, we called our method 'morphological grafting'. New species groups and complexes were then defined in the light of our findings. Further, divergence times were estimated under a relaxed molecular clock, and historical biogeography was reconstructed under a maximum likelihood model. Zaprionus appears to be of recent origin in the Oriental region during the Late Miocene (similar to 10 MYA), and colonization of Africa started shortly after (similar to 7 MYA) via the maritime route of the Indian Ocean Islands. Most of the morphological and ecological diversification took place, later, in Western Africa during the Quaternary cyclic climatic changes. Furthermore, some species became recent invaders, with one, Zaprionus indianus, has successfully invaded South and North America during the last decade. (C) 2008 Published by Elsevier Inc.47390391

Data from: X-chromosome meiotic drive in Drosophila simulans: a QTL approach reveals the complex polygenic determinism of Paris drive suppression

Meiotic drivers are selfish genetic elements that promote their own transmission into the gametes, which results in intragenomic conflicts. In the Paris sex-ratio system of Drosophila simulans, drivers located on the X chromosome prevent the segregation of the heterochromatic Y chromosome during meiosis II, and hence the production of Y-bearing sperm. The resulting sex-ratio bias strongly impacts population dynamics and evolution. Natural selection, which tends to restore an equal sex ratio, favors the emergence of resistant Y chromosomes and autosomal suppressors. This is the case in the Paris sex-ratio system where the drivers became cryptic in most of the natural populations of D. simulans. Here, we used a Quantitative Trait Locus (QTL) mapping approach based on the analysis of 152 highly recombinant inbred lines (RILs) to investigate the genetic determinism of autosomal suppression. The RILs were derived from an advanced intercross between two parental lines, one showing complete autosomal suppression while the other one was sensitive to drive. The confrontation of RIL autosomes with a reference XSR chromosome allowed us to identify two QTLs on chromosome 2 and three on chromosome 3, with strong epistatic interactions. Our findings highlight the multiplicity of actors involved in this intragenomic battle over the sex ratio