作为风靡全球的重要观赏鱼类，人类对孔雀鱼（Poecilia reticulata）的体型、体色和体表色素排列模式进行了一系列的选择，从而产生出多个品系。孔雀鱼的体色与色素排列模式是受到体内多个基因控制的，因而人工选择对此类表型的选择必然对其基因组产生影响。我们选择8个微卫星标记对11个不同体色和色素排列模式的品系进行遗传多样性和遗传结构的研究。另外，从进化生物学的角度来看，对某些表型特征强烈的人工定向选择，可能会导致物种的适合度下降。有研究表明，盐度耐受性是孔雀鱼稳定的适合度指标之一。故我们采用该指标研究10个品系孔雀鱼的适合度差异，分析人工选择对孔雀鱼适合度的影响。同时，由于孔雀鱼存在性二色（sexual dichromism）现象，而雌雄孔雀鱼受人工选择压力的程度是否存在差异尚无研究报道，因此我们对雌雄孔雀鱼的盐度耐受性差异也进行了比较。

Colorful guppies ( Poecilia reticulata ) have been introduced to the whole world as an ornamental fish and have experienced a series of artificial selections upon their body shape, color and pigment patterns. Consequentially, there exist multiple domesticated guppy stains with various phenotypes. Since the body color and pigment color under artificial selection were heritable, we used 8 microsatellite DNA loci to analyze the genetic diversity and differentiation among 11 guppy strains distincted by these two characters. Meanwhile, it is hypothesized that along with the change of phenotypes, the fitness of guppies has also been altered. We tested this hypothesis using salinity tolerance, a fitness-related trait of guppy. 10 domesticated guppy strains were investigated by their survival time after transferring from fresh water to 35 ppt seawater. Considering the sexual dichromism in guppies, the variation between male and female guppies was also examined.