Local context drives infection of grasses by vector-borne generalist viruses

Host characteristics commonly determine infection risk, but infection can also be mediated by regional- or local-scale variation in the biotic and abiotic environment. Experiments can clarify the relative importance of these factors. We quantified drivers of infection by barley and cereal yellow dwarf viruses (B/CYDV), a group of generalist, vector-borne grass pathogens, at hierarchically nested spatial scales (105–1 m) by planting individuals of six common grass species into five Pacific Coast grassland sites spanning 7° of latitude (> 5000 total hosts) and applying a factorial combination of nitrogen and phosphorus fertilizer. Infection differed most among experimental blocks (102–103 m scale), suggesting that local factors control infection risk; infection increased with cover of long-lived hosts and phosphorus, but not nitrogen, fertilization. For B/CYDV, local context more strongly predicts infection risk than host species traits or regional context; such spatially nested experiments can clarify the factors underlying variation in infection risk.

宿主特征通常决定感染风险，但感染过程也可因生物与非生物环境在区域或局地尺度上的变异而受到调控。实验可阐明上述两类因素的相对重要性。我们在层级嵌套的空间尺度（10⁵–1 m）下，量化了大麦黄矮病毒与谷类黄矮病毒（Barley and Cereal Yellow Dwarf Viruses，B/CYDV）的感染驱动因子；该类病毒为泛宿主性、媒介传播的禾本科病原菌。本实验将6种常见禾本科植物的个体，种植于横跨7°纬度的5个太平洋沿岸草原样地（总宿主数量超5000），并施加氮、磷肥料的因子组合处理。研究发现，感染情况在实验样区（10²–10³ m尺度）间差异最为显著，表明局地因子调控感染风险；感染率随长寿命宿主盖度与磷素施肥水平升高而增加，而氮素施肥无此效应。对于B/CYDV而言，局地环境对感染风险的预测能力强于宿主物种特征或区域环境；此类空间嵌套实验可阐明感染风险变异背后的驱动因素。