依频自然选择与果蝇性状的高低替位

Density-Dependent Natural Selection and Trade-offs in Life History Traits

本文通过在保持于低密度下约200代的6种黑腹果蝇(Drosophila malanogaster)群体(r群体)中抽取随机样本,并将其养殖于拥挤的培养环境中,从而得到K群体。25代后,K群体在高密度下的生长速度和繁殖力明显高于对照。由于K群体在低密度下的生长速度和繁殖力低于对照,这显然是性状的高低替位现象。本研究不仅确证了生活史性状演化中高低替位现象的作用,而且促进了高低替位现象的遗传与生理基础的研究工作。

Theories of density-dependent natural selection have generally claimedthat evolution at extreme population densities will produce alternative life-histories due to trade-offs. The trade-offs are presumed to arise becausethose genotypes with highest fitness at high population densities will notalso have high fitness at low density and vice-versa. These predictions havebeen tested by taking samples from six populations of Drosophila melanoga-ster kept at low population densities (γ-populations) for nearly 200 genera-tions and by placing them in crowded oultures (K-populations). After 25generations in these crowded cultures the K-populations showed elevatedgrowth rates and productivity at high densities relative to the controls.Moreover, a trade-off was observed in the direction predicted since thegrowth rates and productivity of the K-populations were depressed at lowdensities relative to the controls. This study confirms the utility of the ideaof trade-offs in life-history evolution and motivates continued research onthe genetic and physiological basis of these trade-offs.