1. Previous theoretical work has highlighted the potential for natural enemies to mediate the coexistence of species with similar life histories via density‐dependent effects on survivorship. For plant pathogens to play this role, they must differ in their ability to infect or induce disease in different host plant species. In tropical forests characterized by high diversity, these effects must extend to phylogenetically closely related species pairs. Mortality at the seed and seedling stage strongly influences the abundance and distribution of tropical tree species, but the host preferences and spatial distributions of fungi are rarely determined.
2. We examined how host species identity, relatedness and seed viability influence the composition of fungal communities associated with seeds of four co‐occurring pioneer trees (Cecropia insignis, C. longipes, C. peltata and Jacaranda copaia). Seeds were buried in mesh bags in five common gardens in the understorey of a lowland tropical forest in Panama and retrieved at intervals from 1 to 30 months. A subset of the seeds in each bag was used to determine germination success. One half of each remaining seed was tested for viability; and the other half was used to culture and identify seed‐infecting fungi.
3. Seeds were infected by fungi after burial. Although fungal communities differed in viable versus dead seeds, and across burial locations, community composition primarily varied as a function of plant species identity (30.7% of variation in community composition vs. 4.5% for viability and location together), even for congeneric Cecropia species. Phylogenetic reconstruction showed that relatedness of fungi mostly reflected differences between Jacaranda (Bignoniaceae) and Cecropia (Urticaceae).
4. Although the proportion of germinable seeds decreased gradually over time for all species, intraspecific variation in survival was high at the same location (e.g. ranging from 0% to 100% for C. peltata) suggesting variable exposure or susceptibility to seed pathogens.
5. Synthesis. Our study provides evidence under field conditions that congeneric tree species with similar life history traits differ markedly in seed‐associated fungal communities when exposed to the same soil‐borne fungi. This is a critical first step supporting pathogen‐mediated coexistence of closely related tree species.

中文翻译：

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密切相关的树种为低地热带森林中的种子相关真菌提供了独特的群落

1. 先前的理论工作强调了天敌通过对生存率的依赖于密度的作用来介导具有相似生活史的物种共存的潜力。为了使植物病原体发挥这种作用，它们在不同宿主植物物种中感染或诱导疾病的能力必须有所不同。在以高度多样性为特征的热带森林中，这些影响必须扩展到系统发育上密切相关的物种对。种子和幼苗期的死亡率强烈影响热带树木物种的丰富度和分布，但是很少确定宿主的喜好和真菌的空间分布。
2. 我们研究的宿主物种的身份，相关性和种子活力如何影响与四个共现先驱树木的种子相关的真菌群落的组成（天蚕荚，C.长柄，C.盾叶和蓝花楹copaia）。将种子埋在巴拿马低地热带森林底层的五个常见花园中的网眼袋中，每隔1到30个月取一次。每个袋子中的种子的子集用于确定发芽成功。测试每个剩余种子的一半的生存力；另一半用于培养和鉴定感染种子的真菌。
3. 埋葬后，种子被真菌感染。尽管真菌群落的存活种子与死种子以及埋葬地点之间存在差异，但群落组成主要随植物物种身份而变化（群落组成的变化为30.7％，而生存力和位置则为4.5％），即使是同种Cecropia物种也是如此。 。系统发育重建表明，真菌的相关性主要反映了蓝花car（Bignoniaceae）和盲目的（Cercopia）（荨麻科）之间的差异。
4. 尽管所有物种的可萌芽种子比例均随时间逐渐降低，但同一位置的种内存活差异很高（例如，C。peltata范围从0％到100％），表明种子病原体的暴露量或易感性不同。
5. 综合。我们的研究提供了在野外条件下证据，即具有相似生活史特征的同类树种，在与种子相关的真菌群落中，暴露于相同的土壤传播真菌中，其差异显着。这是支持病原体介导的近缘树种共存的关键的第一步。