Multi‐infections may result in either competitive exclusion or coexistence on the same host of pathogen genotypes belonging to the same or different species. Epidemiological consequences of multiple infections, particularly how the development and transmission of a pathogen can be modified by the presence of another pathogen, are well documented. However, understanding how life history strategies of each pathogen modulate co‐infection outcomes remains quite elusive. To analyze how co‐infection drives changes in life history traits and affects co‐existence in epidemic pathogens, we infected detached pea stipules with two fungal species, Peyronellaea pinodes and Phoma medicaginis var. pinodella (considering two strains per species), part of the ascochyta blight complex but presenting different life history strategies. All pairwise combinations (including self‐pairs) between two strains of each species were tested. Strains were inoculated simultaneously, but apart from one another on the stipule. For each strain, four life history traits were measured: incubation period, necrosis area six days after inoculation, latent period and offspring production. Results show that, in co‐infection, when resources are highly allocated to lesion development, the time between inoculation and the appearance of reproduction structures (latent period) and offspring production decreased, and vice‐versa relative to single infections. The direction and/or magnitude of these responses to co‐infection depend on the co‐infecting strains. Moreover, these changes were always higher in self‐pairs than in mixed co‐infections. These results suggest facilitation between co‐infecting strains, resulting in the selection of an intermediate level of virulence (here measured as the lesion development) at the expense of pathogen offspring production. This strategy allows the development and reproduction of each co‐infecting strain when sharing limited resources. However, the direction and strength of these life history traits variations in co‐infection depend on the life history strategy of the co‐infecting strains, with a clear difference between ‘opportunists', ‘scavengers' and ‘pioneer colonisers'.

中文翻译：

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真菌植物寄生虫之间的竞争和促进会影响其生活史特征

多重感染可能导致相同或不同物种的同一病原体基因型竞争排斥或共存。多重感染的流行病学后果，尤其是病原体的发生和传播如何通过存在另一种病原体而得到改善的证据已得到充分证明。但是，了解每种病原体的生命史策略如何调节共同感染的结果仍然很遥远。为了分析共同感染如何驱动生活史特征的改变以及如何影响流行病原体的共存，我们用两种真菌物种（Peyronellaea pinodes和Phoma medicaginis var）感染了分离的豌豆托叶。皮诺德拉（考虑到每个物种两个菌株），是草枯病疫情的一部分，但呈现不同的生活史策略。测试了每个物种的两个菌株之间的所有成对组合（包括自配对）。同时接种菌株，但在托叶上彼此分开。对于每种菌株，测量了四个生命史特征：潜伏期，接种后六天的坏死面积，潜伏期和后代的产生。结果表明，在共感染中，当资源大量分配用于病变发展时，接种与生殖结构出现（潜伏期）和后代生产之间的时间减少，相对于单次感染而言，反之亦然。这些对共感染反应的方向和/或强度取决于共感染菌株。而且，在自我配对中，这些变化总是比在混合感染中更高。这些结果表明，在共感染菌株之间的促进作用，导致选择了中等水平的毒力（此处称为病灶发展），而以病原体后代的生产为代价。当共享有限的资源时，此策略允许每种共感染菌株的开发和繁殖。然而，这些共同感染中生活史特征变化的方向和强度取决于共同感染菌株的生命史策略，“机会主义者”，“清道夫”和“先锋殖民者”之间存在明显的差异。导致以致病菌后代的生产为代价，选择了中等水平的毒力（此处称为病灶发展）。当共享有限的资源时，此策略允许每种共感染菌株的开发和繁殖。但是，这些共同感染中生活史特征变异的方向和强度取决于共同感染菌株的生命史策略，“机会主义者”，“清道夫”和“先锋殖民者”之间存在明显差异。导致以致病菌后代的生产为代价，选择了中等水平的毒力（此处称为病灶发展）。当共享有限的资源时，此策略允许每种共感染菌株的开发和繁殖。然而，这些共同感染中生活史特征变化的方向和强度取决于共同感染菌株的生命史策略，“机会主义者”，“清道夫”和“先锋殖民者”之间存在明显的差异。