Blows M W, Sokolowski M B
Department of Biology, York University, North York, Ontario, Canada.
Genetics. 1995 Jul;140(3):1149-59. doi: 10.1093/genetics/140.3.1149.
Experimental lines of Drosophila melanogaster derived from a natural population, which had been isolated in the laboratory for approximately 70 generations, were crossed to determine if the expression of additive, dominance and epistatic genetic variation in development time and viability was associated with the environment. No association was found between the level of additive genetic effects and environmental value for either trait, but nonadditive genetic effects increased at both extremes of the environmental range for development time. The expression of high levels of dominance and epistatic genetic variation at environmental extremes may be a general expectation for some traits. The disruption of the epistatic gene complexes in the parental lines resulted in hybrid breakdown toward faster development and there was some indication of hybrid breakdown toward higher viability. A combination of genetic drift and natural selection had therefore resulted in different epistatic gene complexes being selected after approximately 70 generations from a common genetic base. After crossing, the hybrid populations were observed for 10 generations. Epistasis contributed on average 12 hr in development time. Fluctuating asymmetry in sternopleural bristle number also evolved in the hybrid populations, decreasing by > 18% in the first seven generations after hybridization.
从一个在实验室中已分离了约70代的自然种群衍生而来的黑腹果蝇实验品系进行了杂交，以确定发育时间和活力方面加性、显性和上位性遗传变异的表达是否与环境相关。对于这两个性状，在加性遗传效应水平和环境值之间均未发现关联，但在发育时间的环境范围的两个极端，非加性遗传效应均增加。在环境极端情况下高水平的显性和上位性遗传变异的表达可能是某些性状的普遍预期。亲本品系中上位基因复合体的破坏导致杂种衰败倾向于更快的发育，并且有一些迹象表明杂种衰败倾向于更高的活力。因此，遗传漂变和自然选择的结合导致在大约70代后从共同的遗传基础中选择了不同的上位基因复合体。杂交后，对杂种群体进行了10代观察。上位性在发育时间上平均贡献12小时。杂种群体中胸骨侧鬃毛数的波动不对称性也发生了进化，在杂交后的前七代中减少了超过18%。
