Genetic Architecture of Hybrid Male Sterility in Drosophila: Analysis of Intraspecies Variation for Interspecies Isolation

Background: The genetic basis of postzygotic isolation is a central puzzle in evolutionary biology. Evolutionary forces causing hybrid sterility or inviability act on the responsible genes while they still are polymorphic, thus we have to study these traits as they arise, before isolation is complete. Methodology/Principal Findings: Isofemale strains of D. mojavensis vary significantly in their production of sterile F 1 sons when females are crossed to D. arizonae males. We took advantage of the intraspecific polymorphism, in a novel design, to perform quantitative trait locus (QTL) mapping analyses directly on F1 hybrid male sterility itself. We found that the genetic architecture of the polymorphism for hybrid male sterility (HMS) in the F1 is complex, involving multiple QTL, epistasis, and cytoplasmic effects. Conclusions/Significance: The role of extensive intraspecific polymorphism, multiple QTL, and epistatic interactions in HMS in this young species pair shows that HMS is arising as a complex trait in this system. Directional selection alone would be unlikely to maintain polymorphism at multiple loci, thus we hypothesize that directional selection is unlikely to be the only evolutionary force influencing postzygotic isolation

Spin Transfer in Exclusive Lambda Production from pp Collisions at 3.67 GeV/c

We report the first polarization transfer measurements for exclusive hyperon production reactions. The normal spin transfer coefficient DNN for pp -> p K+ Lambda is large and negative for forward Lambda production at a beam momentum of 3.67 GeV/c, a result qualitatively consistent with expectations for a mechanism dominated by kaon-exchange and rescattering. The sign of DNN is opposite to that observed in the fragmentation regime for inclusive Lambda production at much higher energies

INELASTIC REACTIONS INDUCED BY PIONS ON HE-4 AT 68, 120, 135, 156, 174 AND 208 MEV

16nonenoneBALESTRA F; BOSSOLASCO S; BUSSA MP; BUSSO L; FERRERO L; PANZIERI D; PIRAGINO G; TOSELLO F; FALOMKIN IV; LYASHENKO VI; PONTECORVO GB; SHCHERBAKOV YA; CAUZ D; GARFAGNINI R; SANTI L; MAGGIORA ABalestra, F; Bossolasco, S; Bussa, Mp; Busso, L; Ferrero, L; Panzieri, D; Piragino, G; Tosello, F; Falomkin, Iv; Lyashenko, Vi; Pontecorvo, Gb; Shcherbakov, Ya; Cauz, Diego; Garfagnini, R; Santi, Lorenzo Gianni; Maggiora, A