水蚤滞育的数量遗传学研究:遗传与环境控制及遗传作用

在单性生殖循环水蚤群体中,滞育卵由有性生殖产生．在一系列实验中用到了不同种群和种类的水蚤,通过这些实验来观察：1)有性生殖和滞育卵复苏的遗传和环境控制;2)生活在相同区域中,但有不同生存微环境的近缘种类的有性生殖的光周期反应;3)在群体遗传结构上有性生殖的遗传效应(基因型均值和生活史性状遗传方差)．结果发现：1)遗传作用和环境作用,以及两者的相互作用都对有性生殖和滞育卵的孵化有显著的影响．GE显著的相互作用对环境中观察到的有性生殖来说,有助于维持其较高的遗传方差;2)在相同区域中,不同生存微环境的近缘种类的有性生殖的光周期反应有所不同．这有助于进一步区别近缘的水蚤种类,这也可能是一个水环境中同素异形的物种形成的例子;3)在有性生殖上,生活史性状平均值和遗传方差变化与前代选择造成的均值和遗传方差相反(遗传滑阻),这会造成暂时的适应不良(遗传滑阻和隐藏的遗传变异的表达),应对它补偿滞育的进化优势．

Quantitative Genetic Studies of Diapause in Daphnia:Genetic and Environmental Control and Genetic Consequences

Diapausing eggs (ephippia) in cyclical parthenogenetic Daphnia populations are produced by sexual reproduction(SR). A series of experiments were performed in different populations and species of Daphnia to investigate: 1) genetic and environmental controls of SR and revival of diapausing eggs; 2) the photoperiodic responses of SR in closely related species inhabiting overlapping but different micro habitats; 3) the genetic consequences of SR on populations' genetic architecture (genotypic mean and genetic variance of life history traits). The main findings are: 1) Genetic and environmental effects, and G*E interaction all have significant effects on SR and hatching of resting eggs. Significant G*E interaction may help maintain the high genetic variation for SR observed within environments; 2) Photoperiodic responses of SR are distinct in closely related species inhabiting overlapping but different micro habitats. This contributes to further differentiate closely related Daphnia species and is likely to be an example of allotropic speciation in aquatic systems; 3) Means and genetic variances for life history traits change significantly upon SR in the opposite direction to that promoted by the previous selection (genetic slippage). This causes temporary maladaptation (genetic slippage and release of hidden genetic variance), which must have been compensated by the evolutionary advantage of diapause.