No abstract

No abstract

Drosophila littoralis is a latitudinally widespread European species of the Drosophila virilis group. The species has ample genetic variation in photoperiodism (adult diapause) and circadian rhythmicity (pupal eclosion rhythm), with adaptive latitudinal clines in both of them. The possible common genetic basis between the variability of photoperiodism and circadian rhythms was studied by a long-term crossing experiment. A northern strain (65 degrees N) having long critical day length (CDL = 19.9 h) for diapause, early phase of the entrained rhythm in LD 3:21 (psi(LD3:21) = 12.3 h), and short period (tau= 18.8 h) of the free-running rhythm for the eclosion rhythm was crossed with a southern strain (42 degrees N) having short CDL (12.4 h), late eclosion phase (psi(LD3:21) = 20.2 h), and long period (tau= 22.8 h). After 54 generations, including free recombination, artificial selection, and genetic drift, a novel strain resulted, having even more "southern" diapause and more "northern" eclosion rhythm characteristics than found in any of the geographical strains. The observed complete separation of eclosion rhythm characteristics from photoperiodism is a new finding in D. littoralis; in earlier studies followed for 16 generations, the changes had been mostly parallel. Evidently, the genes controlling the variability of the eclosion rhythm and photoperiodism in D. littoralis are different but closely linked. To test for the possible gene loci underlying the observed geographical variability, the period gene was studied in 10 strains covering all the known clock variability in D. littoralis. The authors sequenced the most suspected Thr-Gly region, which is known to take part in the adaptive clock variability in Drosophila melanogaster. No coding differences were found in the strains, showing that this region is not included in the adaptive clock variability in D. littoralis.

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.