An endophyte is an endosymbiont, often a bacterium or fungus, that lives within a plant for at least part of its life cycle without causing apparent disease. Endophytes are ubiquitous and have been found in all species of plants studied to date; however, most of the endophyte/plant relationships are not well understood. Endophytes are also known to occur within lichens and algae. Many economically important grasses (e.g., Festuca spp. and Lolium spp.) carry fungal endophytes in genus Epichloë, some of which may enhance host growth, nutrient acquisition and may improve the plant's ability to tolerate abiotic stresses, such as drought, and enhance resistance to insects, plant pathogens and mammalian herbivores.