Plants in coastal and geothermal habitats rely on symbiotic fungal endophytes for stress tolerance. Geothermal endophytes confer heat tolerance, while coastal endophytes confer salt tolerance. These endophytes are specific to their habitats and do not confer the opposite stress tolerance. Agricultural endophytes, however, confer disease resistance but not stress tolerance. The study defines this habitat-specific symbiotic relationship as "habitat-adapted symbiosis," which may explain how plants survive in high-stress environments. The endophytes also colonize tomato and rice, conferring disease, salt, and heat tolerance, respectively. They provide drought tolerance regardless of the plant's habitat. Stress tolerance is linked to reduced water consumption or reactive oxygen sensitivity, not increased osmolyte production. Fungal endophytes may offer a novel strategy to mitigate climate change impacts on plants. The study highlights the role of class 2 endophytes in plant survival under stress, with F. culmorum being a key species. Field experiments showed that FcRed1, a F. culmorum isolate, enhances salt tolerance in dunegrass, rice, and tomato. The endophyte's ability to colonize various plants suggests a broad host range. The study also found that FcRed1 is more salt-tolerant than Fc18, an isolate from a non-geothermal habitat. The endophyte's growth is influenced by environmental stress, with FcRed1 showing lower growth in salt conditions. The study concludes that habitat-specific symbiosis is a key adaptation for plant survival in extreme environments.Plants in coastal and geothermal habitats rely on symbiotic fungal endophytes for stress tolerance. Geothermal endophytes confer heat tolerance, while coastal endophytes confer salt tolerance. These endophytes are specific to their habitats and do not confer the opposite stress tolerance. Agricultural endophytes, however, confer disease resistance but not stress tolerance. The study defines this habitat-specific symbiotic relationship as "habitat-adapted symbiosis," which may explain how plants survive in high-stress environments. The endophytes also colonize tomato and rice, conferring disease, salt, and heat tolerance, respectively. They provide drought tolerance regardless of the plant's habitat. Stress tolerance is linked to reduced water consumption or reactive oxygen sensitivity, not increased osmolyte production. Fungal endophytes may offer a novel strategy to mitigate climate change impacts on plants. The study highlights the role of class 2 endophytes in plant survival under stress, with F. culmorum being a key species. Field experiments showed that FcRed1, a F. culmorum isolate, enhances salt tolerance in dunegrass, rice, and tomato. The endophyte's ability to colonize various plants suggests a broad host range. The study also found that FcRed1 is more salt-tolerant than Fc18, an isolate from a non-geothermal habitat. The endophyte's growth is influenced by environmental stress, with FcRed1 showing lower growth in salt conditions. The study concludes that habitat-specific symbiosis is a key adaptation for plant survival in extreme environments.