The Use of Isoenzymes in Tracing Evolution and in Classifying Drosophilidae

Abstract

Lakovaara, S. (Department of Genetics, University of Oulu, SF‐90100 Oulu 10, Finland), Saura, A., Lankinen, P., Pohjola, Liisa and Lokki, J. The use of isoenzymes in tracing evolution and in classifying Drosophilidae. Zool. Scr. 5 (3–4): 173–179, 1976.—Studies on the genetic constitution of natural populations of organisms have shown that these populations are extensively polymorphic at gene loci coding for enzymes. Much of this polymorphism detected by electrophoresing enzyme proteins is, however, not useful in classifying organisms, even though in general species differ from each other more than populations within a species. Good diagnostic characters are monomorphic species‐specific genes and their products. Finding these characters requires a thorough study of many populations of the species being studied. Once these characters have been found they can be used in assigning single individuals into different taxa. Electrophoresis of enzymes and allozyme differences between species can also be used in tracing the evolution of organisms. On the basis of allozymes a new phylogeny is proposed for the Drosophila obscura species group. Traditionally this group has been divided into two subgroups, obscura and affinis. Genetic characters divide this species group into three evolutionary lineages. The first lineage comprises the Eurasian obscura subgroup, the second the American affinis subgroup and the third the American obscura subgroup. D. alpina and D, helvetica, which belong to the obscura and affinis subgroups, respectively, are not appreciably related to any other species.

New African species in the Drosophila obscura species group: genetic variation, differentiation and evolution

“…between either local or geographically distant populations of these species. This is in good agreement with previous studies (Lakovaara and Saura, 1971;Lakovaara et al, 1976;Loukas et al, 1979;Pinsker and Buruga, 1982 Different trees can be constructed using either, or both, different measurements of genetic distance represents the data, although the "best fit" may not necessarily be the best hypothesis of evolutionary relationships. Therefore we have used several other criteria based on extraneous information concerning group taxonomy to judge tree reliability; these were, whether or not different populations of the same species clustered, the relative positions of D. madeirensis and D. guanche close to D. subobscura (Krimbas and Loukas, 1984) and the relative closeness of D. tristis and D. ambigua (Lakovaara et aL, 1972;Lakovaara and Keränen, 1980).…”

Evolution of the obscura group drosophila species. II. Phylogeny of ten species based on electrophoretic data

“…(b) To the utilization of electrophoretic techniques with very little discrimination efficiency. This is obvious from the very small differences in migration of the allozymes reported by Lakovaara et aL (1976) in comparison to those of the present study. The same cause could also explain the differences in electrophoretic phenotypes, between the present study and that of Cabrera et aL (1983) It could be argued that these differences are due to the fact that we used only one strain for D. madeirensis and one for D. guanche while Cabrera et aL (1983) used samples from natural populations.…”

“…Species which yielded allozymes with different mobilities are separated by semicolons, while a dash between two species denotes identical mobility of the corresponding allozymes. The data of Lakovaara et aL (1976) and Cabrera et aL (1983) presented here are restricted to the species in common with the present study: nine species for the first study [except for Acph, for which only seven species were studied (Lakovaara et aL, 1972) and Ao and Xdh, for which only eight species were studied (Lakovaara et aL, 1976)], and five species for the second study.…”

“…This is a further suggestion on the correctness of the phylogenetic topology presented here. Using the data presented by Lakovaara et aL (1976), concerning the nine species, common to both studies, we constructed a phylogenetic tree: this tree was found to be quite similar in topology to the tree depicted in fig. 1.…”

“…(These two loci are stained on the same slab by the same substrate). Lakovaara et aL (1976) in their latest paper on the phylogeny of the obscura group, which included nine of the ten species studied here, utilised 15 enzymatic systems corresponding to 21 loci, of which three were invariable between species. Cabrera et aL (1983) utilised 30 enzyme systems corresponding to 67 loci to study the electrophoretic relationships among six species of the obscura group, five of which were in common with the present study.…”