title: Phylogenetic Relationships among DROSOPHILA LONGICORNIS, DROSOPHILA PROPACHUCA and DROSOPHILA PACHUCA, a Triad of Sibling Species.
abstract: Drosophila longicornis, D. propachuca and D. pachuca comprise a triad of sibling species. They are morphologically indistinguishable, sympatric forms that, under laboratory conditions, are capable of exchanging genes through the production of fertile F(1) females. However, we have no evidence for introgressive hybridization in nature. The chromosomal constitution of our strains indicates that the ancestral species had the Primitive E gene sequence, and therefore differed from the standard repleta sequence by being Xabc; 2abcg; 3abc. This Primitive E sequence is found in both D. propachuca and D. longicornis. Each of these two species has its own unique rearrangements. D. pachuca is a derived species, which evolved from propachuca. It is cytologically more advanced and has, as its most primitive gene arrangement, one of the more advanced arrangements found in propachuca.
authors.affiliation: Department of Biology, Queens College of the City University of New York, Flushing, New York 11367.
authors.forename: M
authors.initials: M
authors.lastname: Wasserman
authors.forename: H R
authors.initials: HR
authors.lastname: Koepfer