Neotyphodium fungal endophytes are keystone species in temperate grasslands: impacts from population ecology to ecosystem functioning

北美各地使用的牧草和草坪草大多是非本土物种。这些草经常逃避人类的管理，入侵自然和未管理的生态系统，在这些生态系统中，它们被广泛认为是重要的入侵物种。当这些植物被内生真菌感染时，这些草对它们入侵的生态系统的影响被认为是更显著的。农业和草坪草通常是系统共生真菌内生菌的宿主，这些内生菌驻留在气生植物部分，并通过受感染的草的种子垂直传播。理论表明，垂直传播的共生体必须以某种方式增强寄主植物的适应性，才能保持它们在种群中的地位。内生真菌的侵染被认为是通过提高对非生物胁迫(如干旱)的耐受性，增强生长和竞争能力，以及由于内生植物衍生生物碱的产生而增强对草食的抗性，从而使寄主牧草受益。事实上，这最后的好处导致许多人将这种互动描述为防御互惠。所有这些好处使内生真菌感染的草更有可能成功入侵自然社区，并在它们入侵这些社区时产生更大的影响。

Pasture and turfgrasses used throughout North America are mostly non-native species. These grasses routinely escape their human management and invade natural and unmanaged ecosystems where they are widely considered to be significant invasive species. The impact that these grasses have on the ecosystems that they invade is thought to be more significant when those plants are infected with endophytic fungi. Agricultural and turfgrasses are often hosts of systemic symbiotic fungal endophytes which reside in aerial plant parts and are vertically transmitted through the seeds of infected grasses. Theory suggests that the vertically transmitted symbionts must, in some way, enhance the fitness of the host plant if they are to be maintained in the population. Endophyte infection is proposed to benefit their host grasses through increased tolerance to abiotic stress (e.g. drought), enhanced growth and competitive ability, and increased resistance to herbivory due to the production of endophyte-derived alkaloids. Indeed, this last benefit has led many to describe the interaction as a defense mutualism. All of these benefits make endophyte-infected grasses more likely to succeed in invading natural communities and to have greater impact when they do invade such communities.