Independence of Genetic Geographical Variation between Photoperiodic Diapause, Circadian Eclosion Rhythm, and Thr-Gly Repeat Region of the Period Gene inDrosophila littoralis

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.

Genetic correlations and the evolution of photoperiodic time measurement within a local population of the pitcher-plant mosquito, Wyeomyia smithii

“…Herein, we answer this question by hybridizing the selected lines from Bradshaw et al (2003) and imposing antagonistic selection against the genetic correlation (Emlen, 1996;Roff, 1997;Conner, 2003;Lankinen and Forsman, 2006;Tigreros and Lewis, 2011) to test for the genetic independence of these traits. An inability to select against the genetic correlation would indicate a strong pleiotropic relationship, that is, a causal, necessary connection between the circadian clock and photoperiodism within this population.…”

Effects of altitude on circadian rhythm of adult locomotor activity in Himalayan strains of Drosophila helvetica

“…Latitude and altitude of origin are known to modify fundamental properties of the pacemaker controlling circadian rhythms of eclosion, oviposition and adult locomotor activity of naturally occurring clock phenotypes of Drosophila [1]. For example, latitude of origin dramatically altered the basic parameters of eclosion rhythm of the Japanese strains of D. auraria [2,3], the European strains of D. littoralis [4-6] and D. subobscura [7].…”

Physical mapping of the Period gene on meiotic chromosomes of South American grasshoppers (Acridomorpha, Orthoptera)

“…Most of the research done with this gene was the molecular characterization of the threonine-glycine repeating regions in some groups, mainly Diptera and Lepidoptera, allowing the use of this gene as a marker in phylogeographic studies, molecular systematics, and evolution. These studies demonstrated the considerable level of evolutionary conservation and feasibility of using this gene, alone or combined with other markers, for applications in systematic, taxonomic, and population studies of insect groups (Rosato and Kyriacou, 2001;Miyatake et al, 2002;Barr et al, 2005;Mazzotta et al, 2005;Lankinen and Forsman, 2006;Sawyer et al, 2006;Matsumoto et al, 2008).…”