Distance and the Allelism of Lethals in a Tropical Population of Drosophila melanogaster

Abstract

Ninety three autosomal lethals (2nd and 3rd chromosomes tested simultaneously) were recovered from 4 collections of Drosophila melanogaster in Columbia, S. A. The collection sites were spaced at 30 m intervals and the entire collection required less than 2 hrs. Eighty three allelic combinations were observed among 2255 crosstests of these lethals, an average frequency of allelism of 3.7%. It is estimated (through the use of a theoretical model which states that the logarithm of allelism from common descent should decline linearly with the square root of distance) that the frequency of allelism of lethals carried by flies found simultaneously at a given spot is approximately 4.7%. In this Colombian population, the elimination of lethals by homozygosls seems to equal or exceed mutation rate.