Speciation and Evolution of Marine Fishes Studied by the Electrophoretic Analysis of Proteins

Abstract

Electrophoretic analysis of proteins can be utilized to clarify the taxonomic status of species as well as the evolutionary interrelationships of populations, species, and higher taxa. Electrophoretic data for over 50 gene loci in the bonefish Albula "vulpes" (Albulidae) demonstrate the existence of two discrete species in Hawaii and throughout the Indo-West Pacific. Similar studies of lizardfishes (Synodontidae) in the genera Synodus and Saurida reveal that several unreported and/or undescribed species occur in the Hawaiian Islands. Both of these studies emphasize the power of electrophoresis in distinguishing morphologically cryptic species. The interrelationships of species and genera of lizardfishes and of goatfishes (Mullidae) were investigated by using values of genetic distance derived from protein similarities and differences. These comparisons and the analysis of the two bonefish species, provide additional examples of the basic independence of the rates of biochemical and morphological evolution. Published electrophoretic investigations of fish speciation and evolution are reviewed and several guidelines for future applications of the technique are proposed. The importance of sympatric samples, the use of large numbers of gene loci, and the conservative interpretation of genetic distance values are emphasized. The utility of electrophoretic data for (a) identifying species (especially juvenile, larval, and embryonic stages, or isolated animal products such as fillets); (b) identifying F 1 interspecific hybrids; and (c) estimating absolute and relative divergence times between taxa are discussed. Finally, the combined use of electrophoretic data from fresh specimens together with multivariate morphometric analyses of both the fresh specimens and preserved museum type specimens is recommended as a robust approach for sorting out nomenclatural problems.