Lankinen P
Department of Genetics, University of Oulu, Finland.
J Biol Rhythms. 1986 Summer;1(2):101-18. doi: 10.1177/074873048600100202.
Populations of Drosophila littoralis are known to be latitudinally highly variable in photoperiodic adult diapause and pupal eclosion rhythm. Phenotypic correlations between the two time-measuring systems among the strains from different latitudes are, however, weak. In the present study, two differing strains were crossed reciprocally in order to search for causal (genetic) correlations between the two traits in the strains. Segregation in the F2 generations showed that variation in each trait was based on a few variable loci only. In the F2, flies having different eclosion times also differed in their diapause. This association was not complete and could have been due to genetic linkage between the traits. For that reason, the hybrid generations were raised for eight generations more to allow recombination between the traits. In F8, selection against diapause was started in the lines by raising them in a light-dark cycle of 15:9, where only females of the southern type reproduce. After eight selected generations, the lines were studied for the traits. Diapause was completely of the southern type, and the eclosion rhythm had also changed in parallel. The change in the phase of the free-running rhythm was not complete. From the present experiment, and from earlier knowledge of the geographical variation in D. littoralis, I conclude that the same pacemaker that is seen in the eclosion rhythm could also participate in daylength measurement for diapause. However, there are also noncorrelated variable parts in the measuring systems of both traits, which may mask the correlated variation.
海滨果蝇种群在光周期诱导的成虫滞育和蛹羽化节律方面存在显著的纬度差异。然而，不同纬度品系的这两种计时系统之间的表型相关性较弱。在本研究中，对两个不同的品系进行了正反交，以寻找品系中这两个性状之间的因果（遗传）相关性。F2代的分离情况表明，每个性状的变异仅基于少数可变位点。在F2代中，羽化时间不同的果蝇在滞育方面也存在差异。这种关联并不完全，可能是由于性状之间的遗传连锁。因此，将杂交后代再饲养八代，以使性状之间发生重组。在F8代，通过在15:9的明暗周期中饲养果蝇，对品系进行了抗滞育选择，在这种条件下只有南方类型的雌蝇能够繁殖。经过八代选择后，对品系的性状进行了研究。滞育完全变为南方类型，羽化节律也相应发生了变化。自由运行节律的相位变化并不完全。从本实验以及之前对海滨果蝇地理变异的了解，我得出结论，在羽化节律中观察到的同一个起搏器也可能参与了滞育的日长测量。然而，这两个性状的测量系统中也存在不相关的可变部分，这可能掩盖了相关变异。
