银额果绳(Drosophila albomicans)B染色体对繁殖的影响

利用遗传背景一致的３类含有不同Ｂ染色体数目的银额果蝇（Ｄｒｏｓｏｐｈｉｌａ ａｌｂｏｍｉｃａｎｓ）品系，对繁殖的２个参数，即净繁殖量和性比进行了比较研究。结果表明Ｂ染色体对净繁殖量有着显著的影响，其影响依赖于Ｂ染色体数目的不同而不同；低数目增加其携带者的净繁殖量，而在高含量时有使其携带者净繁殖量下降的趋势。Ｂ染色体对繁殖的影响还具有一定的时间分布特征，即３类品系净繁殖量的差异主要集中在雌蝇繁殖的早期。因为雌蝇繁殖的后期产生的后代数占总后代数的比例很低且对种群发展贡献较小，Ｂ染色体的这种时间效应使得其携带者在自然界的生存竞争中更具优势。这些结果支持关于Ｂ染色体的杂合优势模型，但不支持目前占主导地位的寄生模型。

The Effect of B Chromosome on the Reproduction of Drosophila albomicans

By using three strains with different number of B chromosome (l--2Bs,OB, > 2Bs) on the same genetic background, the effect of B chromosome on the reproduction of Drosophila albomicans was studied. Comparison of net reproduction and sex ratio among three strains showed that Bs has significantly effect on flies' net reproduction. The net reproduction of flies with l~ 2Bs, OB, > 2Bs is 196,157,147, respectively. Significant difference among three strains exists in the early stage of reproduction. The sex ratios of three strains are all close to 1:1, no significant difference was observed. The results indicated that lower dose of Bs enhances the flies' reproduction and fitness, while higher dose of Bs slightly reduces flies reproduction and fitness. These results lend the first strong support to the heterotic model.