POPULATION GENETICS OF DROSOPHILA NASUTA NASUTA, DROSOPHILA NASUTA ALBOMICANA AND THEIR HYBRIDS. I. KARYOTYPIC MOSAICISM IN THE HYBRID POPULATIONS

D. n. nasuta and D. n. albomicana constitute a pair of chromosomal races with 2n=8 and 2n=6, respectively. The F₁ of these has 2n=7 and it is fertile. There exists a state of karyotypic mosaicism as evidenced by the presence of 26 types of chromosome combinations in F₂, F₃, and F₁₀ populations. In the midst of this karyotypic noise, the karyotype similar to that of F₁ reached 51% of the population. Implications of these findings are discussed.