Variability is the nature of the endophyte-grass interaction

Studies of systemic endophyte in grasses have skyrocketed in the past two decades. However, the vast majority of these studies still occur in agroecosystems. We show that ecological and evolutionary concepts derived from these systems may be misleading because they fail to incorporate the enormous variability found in endophyte-host grass interactions in wild grass populations. This variability stems from 1) genetic differences in host plants and endophytes, 2) environmental factors such as light and soil nutrients and moisture, and 3) the tangled web of interacting species in natural communities, such as conspecific and interspecific plants, multiple generalist and specialist herbivore species, and the third trophic level, predators and parasites. Studies of natural populations and communities continue to lag far behind those involving agronomic grass systems. However, we argue that additional studies of infected wild grass populations and communities are essential to advance ecological and evolutionary concepts of endophytegrass interactions. Keywords: endophytes, herbivore resistance, grasses, natural populations and communities, natural enemies, Neotyphodium, pathogens, plant defenses, variability