Fellowes M D, Kraaijeveld A R, Godfray H C
Department of Biology, Imperial College at Silwood Park, Ascot, UK.
Proc Biol Sci. 1998 Aug 22;265(1405):1553-8. doi: 10.1098/rspb.1998.0471.
Costs of resistance are widely assumed to be important in the evolution of parasite and pathogen defence in animals, but they have been demonstrated experimentally on very few occasions. Endoparasitoids are insects whose larvae develop inside the bodies of other insects where they defend themselves from attack by their hosts' immune systems (especially cellular encapsulation). Working with Drosophila melanogaster and its endoparasitoid Leptopilina boulardi, we selected for increased resistance in four replicate populations of flies. The percentage of flies surviving attack increased from about 0.5% to between 40% and 50% in five generations, revealing substantial additive genetic variation in resistance in the field population from which our culture was established. In comparison with four control lines, flies from selected lines suffered from lower larval survival under conditions of moderate to severe intraspecific competition.
人们普遍认为，抗性成本在动物寄生虫和病原体防御的进化中起着重要作用，但通过实验证明这一点的情况却很少。内寄生蜂是一类昆虫，其幼虫在其他昆虫体内发育，在那里它们要抵御宿主免疫系统的攻击（尤其是细胞包囊化）。我们以黑腹果蝇及其内寄生蜂布氏丽蝇茧蜂为研究对象，在果蝇的四个重复种群中选择增强抗性。在五代之内，遭受攻击后存活的果蝇百分比从约0.5%增加到40%至50%之间，这表明我们所培育果蝇的野外种群在抗性方面存在大量可加性遗传变异。与四个对照品系相比，在中度至重度种内竞争条件下，选择品系的果蝇幼虫存活率较低。
