ESTIMATION OF THE PROPORTION OF DIPLOID MALES IN POPULATIONS OF HYMENOPTERA

Diploid males occur at low frequencies in natural populations of Hymen optera as a consequence of the sex-determination system. Routine elect rophoretic surveys will often reveal heterozygous diploid males. Maxim um likelihood estimates are given for phi, the proportion of males in the population that are diploid, when data are available from males on ly or from both males and females. In the simplest case, using male da ta only, phi ($) over cap = B-2/2pqT(2), where p and q are the gene fr equencies at the marker locus, B-2 is the number of heterozygous diplo id males and T-2 is the total number of males sampled. The variance V( phi ($) over cap) = phi[1 - 2pq phi - (1 - 4pq)phi(2)]/2pqT(2). When b oth male and female data are available then Phi, the proportion of dip loids that are male, can also be estimated. This allows the approximat e effective number of sex-determining alleles (assuming a single locus system) to be determined. Maximum likelihood estimates of phi have to be obtained numerically when data are available from multiple-allelic or multiple marker loci.