Department of Biology HS104, University of Montana, 32 Campus Drive, Missoula, Montana 59812, USA.
Ecology. 2012 Jan;93(1):3-8. doi: 10.1890/11-1347.1.
Competitive outcomes among plants can vary in different abiotic and biotic conditions. Here we tested the effects of two phylotypes of Alternaria endophytes on the growth, competitive effects, and competitive responses of the exotic invasive forb Centaurea stoebe. Centaurea stoebe was a better competitor against North American grass species than grasses from its European home range in the absence of endophytes. However, one endophyte both increased the biomass of C. stoebe and reduced the competitive effect of North American grasses on C. stoebe. The competitive effects of C. stoebe on grass species native to North America were enhanced by both fungal endophytes, but not for native European grasses. We do not know the mechanism by which endophytes increased C. stoebe's competitive ability, and particularly against biogeographically new neighbors, but one endophyte increased the competitive ability of C. stoebe without increasing its size, suggesting mechanisms unrelated to increased growth. We tested only a fraction of the different endophytic fungi that have been found in C. stoebe, only scratching the surface of understanding their indirect effects. However, our results are the first to demonstrate such effects of a fungal endophyte infecting an invasive forb, and one of the few to show that endophyte effects on competition do not have to be mediated through herbivory.
植物之间的竞争结果可能因不同的非生物和生物条件而异。在这里，我们测试了两种Alternaria 内生真菌对入侵外来植物矢车菊的生长、竞争效应和竞争响应的影响。在没有内生真菌的情况下，矢车菊相对于来自其欧洲原生范围的草种具有更好的竞争力。然而，有一种内生真菌既能增加矢车菊的生物量，又能降低北美草对矢车菊的竞争效应。两种内生真菌都增强了矢车菊对北美本地草种的竞争效应，但对欧洲本地草种没有这种作用。我们不知道内生真菌如何增强矢车菊的竞争能力，特别是对来自生物地理上不同地区的新邻居，但有一种内生真菌在不增加其大小的情况下增强了矢车菊的竞争能力，这表明其与生长无关的机制。我们只测试了在矢车菊中发现的不同内生真菌的一小部分，只是对它们的间接影响有了初步的了解。然而，我们的结果是首次证明内生真菌感染入侵性外来植物会产生这种影响，也是少数几个表明内生真菌对竞争的影响不一定通过食草作用来介导的结果之一。
