Systematics of the Drosophila virilis species group as assessed by two-dimensional electrophoresis

A primary problem that often faces an evolutionary biologist trying to determine a phylogeny is finding enough characters to build the tree. Increasingly, molecular biology is solving this problem, but many shortcomings and limitations still exist with the techniques currently in use. For example, allozymic studies are very useful, but they constitute a time consuming task that often does not produce enough characters to fully resolve the branching diagram. Immunological and DNA hybridization techniques can often discern phenetic relationships between taxa, but they cannot be used in a phylogenetic analyses, because they are based on overall similarity (Entingh, 1970). Approaches such as DNA, RNA, and protein sequencing are very powerful techniques for phylogenetic reconstruction, but they are extremely time consuming and effectively cost prohibitive, particularly when one is working on lower taxonomic levels. The development of the mitochondrial DNA technology may solve many of these problems, although recent studies seem to indidcate that it may not be more effective than the current electrophoretic studies at producing phylogenetic trees (Kessler and Avise, 1984). However, this research is still in its infancy, so it is difficult to assess its final impact.