Allozyme variation in the milkweed butterflies (Lepidoptera: Danainae)

Seventeen enzyme systems, representing 22 zones of activity, are surveyed in 20 species of Danainae (some represented by multiple samples) and one species of Acraeinae, by the technique of horizontal starch gel electrophoresis. Descriptions of each of the enzyme systems is given, including a brief review of their use in previous lepidopteran electrophoretic investigations. Each currently recognized danaine taxon is considered from the viewpoint of whether or not it can be characterized using allozymes. Enzyme polymorphism in relation to average heterozygosity and population structure is discussed, as are the possible reasons for the observed allozymic differences between the N American and Australian populations of the monarch, Danaus plexippus. Finally, the potential for allozymic data in the classification of the Danainae is examined and it is concluded that such data are likely to be of most use at the generic level and below.