USE OF PROTEIN ELECTROPHORESIS IN EVOLUTIONARY SYSTEMATICS

Summary

This paper explores the use of genotypic data derived by protein electrophoresis in taxonomic and phylogenetic research. Variation in the electrophoretic mobilities of proteins can be used as a measure of nucleotide sequence variation in nuclear DNA. The resulting Mendelian data are useful for identifying morphologically cryptic species and for inferring phylogenetic relationships among congeneric species or closely related genera. Two methods, phenetics and cladistics, can be used to make phylogenetic inferences. In the phenetic approach, genetic distances are calculated between all possible pairs of taxa and a clustering algorithm is used to produce a tree-like phenogram. Cladistic methods, on the other hand, attempt to identify phylogenies on the basis of shared derived character states. Electrophoretic data can be used cladistically on the basis of: (1) tissue distributions of gene expression, (2) the occurrence of tandem or genomic gene duplications, (3) the ability of multimeric proteins to form heteropolymers between duplicated proteins, (4) alleles as characters, and (5) loci as characters and alleles as states. We illustrate the use of some of these methods to infer phylogenetic relationships among the taxa of two gastropod genera, Bullia and Burnupena. In comparison with other molecular techniques, protein electrophoresis is a relatively inexpensive, ‘low-technology’ method that does not require sophisticated equipment and has a large potential for solving taxonomic problems in southern Africa.