Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, California, United States of America.
Rocky Mountain Biological Laboratory, Crested Butte, Colorado, United States of America.
PLoS One. 2019 Oct 30;14(10):e0224482. doi: 10.1371/journal.pone.0224482. eCollection 2019.
Climate change is affecting interactions among species, including host-parasite interactions. The effects of warming are of particular interest for interactions in which parasite and host physiology are intertwined, such as those between parasitic plants and their hosts. However, little is known about how warming will affect plant parasitic interactions, hindering our ability to predict how host and parasite species will respond to climate change. Here, we test how warming affects aboveground and belowground biomass of a hemiparasitic species (Castilleja sulphurea) and its host (Bouteloua gracilis), asking whether the effects of warming depend on the interaction between these species. We also measured how warming affected the number of haustorial connections between parasite and host. We grew each species alone and together under ambient and warmed conditions. Hosts produced more belowground biomass under warming. However, host biomass was reduced when plants were grown with a hemiparasite. Thus, parasitism negated the benefit of warming on belowground growth of the host. Host resource allocation to roots versus shoots also changed in response to both interaction with the parasite and warming, with hosts producing more root biomass relative to shoot biomass when grown with a parasite and when warmed. As expected, hemiparasite biomass was greater when grown with a host. Warmed parasites had lower root:shoot ratios but only when grown with a host. Under elevated temperatures, hemiparasite aboveground biomass was marginally greater, and plants produced significantly more haustoria. These findings indicate that warming can influence biomass production, both by modifying the interaction between host plants and hemiparasites and by affecting the growth of each species directly. To predict how species will be affected, it is important to understand not only the direct effects of warming but also the indirect effects that are mediated by species interactions. Ultimately, understanding how climate change will affect species interactions is key to understanding how it will affect individual species.
气候变化正在影响物种之间的相互作用，包括宿主-寄生虫相互作用。对于寄生虫和宿主生理相互交织的相互作用，如寄生植物与其宿主之间的相互作用，变暖的影响尤其受到关注。然而，对于变暖将如何影响植物寄生相互作用，我们知之甚少，这阻碍了我们预测宿主和寄生虫物种将如何应对气候变化的能力。在这里，我们测试了变暖如何影响半寄生物种（Castilleja sulphurea）及其宿主（Bouteloua gracilis）的地上和地下生物量，询问变暖的影响是否取决于这些物种之间的相互作用。我们还测量了变暖如何影响寄生虫和宿主之间的吸器连接数量。我们在环境和变暖条件下单独和一起种植每个物种。在变暖条件下，宿主产生更多的地下生物量。然而，当植物与半寄生植物一起生长时，宿主生物量减少。因此，寄生否定了宿主地下生长对变暖的益处。宿主对根和茎的资源分配也会对与寄生虫的相互作用和变暖做出响应，当与寄生虫一起生长或变暖时，宿主产生更多的根生物量相对于茎生物量。正如预期的那样，当与宿主一起生长时，半寄生植物的生物量更大。在温暖条件下生长的寄生虫根：茎比例较低，但仅当与宿主一起生长时。在高温下，半寄生植物的地上生物量略有增加，植物产生的吸器数量明显增加。这些发现表明，变暖可以通过改变宿主植物和半寄生植物之间的相互作用以及直接影响每个物种的生长来影响生物量的产生。为了预测物种将受到怎样的影响，了解变暖的直接影响以及物种相互作用介导的间接影响非常重要。最终，了解气候变化将如何影响物种相互作用是理解它将如何影响单个物种的关键。
