AN ANALYSIS OF GENETIC STRUCTURE IN THE MONARCH BUTTERFLY, DANAUS PLEXIPPUS L.

Abstract

The genetic structure of a set of populations is a consequence of the patterns of mating within, and the magnitude of gene exchange among the populations of interest. Mathematically, this can be expressed as the deviation from Hardy-Weinberg proportions within, and the amount of differentiation or variance in allele frequencies among populations. High rates of gene flow among populations and tendencies toward random mating within populations will decrease the amount of genetic structuring, while obstructions to movement, restraints upon random mating such as develop in social systems, and even physical distance in the absence of real barriers will all generate genetic differentiation and structure. It is often assumed that in the absence of selection (mutuation is generally ignored) genetic structure will reflect parameters of population structure, such as population size, amount of gene exchange, and breeding pattern. In the last decade, electrophoretic techniques have been extensively employed in studying the genetic structure of natural populations. Many studies have been concerned with inferring population structure from the variation and geographic pattern of electrophoretic variant frequencies. As the non-selective nature of these variants cannot be simply assumed, the definition of population structure by this procedure often becomes framed in the arguments of the selectionist-neutralist debate (see Lewontin, 1974). In few studies can the observed genetic differentiation as described by electrophoretic variants be safely as-