School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, United Kingdom.
Evolution. 2010 Sep;64(9):2643-52. doi: 10.1111/j.1558-5646.2010.00999.x.
Understanding the reasons why different parasites cause different degrees of harm to their hosts is an important objective in evolutionary biology. One group of models predicts that if hosts are infected with more than one strain or species of parasite, then competition between the parasites will select for higher virulence. While this idea makes intuitive sense, empirical data to support it are rare and equivocal. We investigated the relationship between fitness and virulence during both inter- and intraspecific competition for a fungal parasite of insects, Metarhizium anisopliae. Contrary to theoretical expectations, competition favored parasite strains with either a lower or a higher virulence depending on the competitor: when in interspecific competition with an entomopathogenic nematode, Steinernema feltiae, less virulent strains of the fungus were more successful, but when competing against conspecific fungi, more virulent strains were better competitors. We suggest that the nature of competition (direct via toxin production when competing against the nematode, indirect via exploitation of the host when competing against conspecific fungal strains) determines the relationship between virulence and competitive ability.
了解为什么不同的寄生虫会对其宿主造成不同程度的伤害，是进化生物学的一个重要目标。一组模型预测，如果宿主同时感染了一种以上的寄生虫株或物种，那么寄生虫之间的竞争将选择更高的毒力。虽然这个想法有直观的意义，但支持它的经验数据却很少且存在争议。我们研究了昆虫真菌寄生虫拟青霉在种间和种内竞争中，适应性和毒力之间的关系。与理论预期相反，竞争有利于毒力较低或较高的寄生虫株，具体取决于竞争者：当与一种昆虫病原线虫斯氏线虫竞争时，真菌的毒力较低的菌株更成功，但当与同种真菌竞争时，毒力较高的菌株则是更好的竞争者。我们认为，竞争的性质（当与线虫竞争时通过毒素产生直接竞争，当与同种真菌菌株竞争时通过利用宿主间接竞争）决定了毒力和竞争能力之间的关系。
