Search

Two Agrostis taxa occur in geothermal habitats of Yellowstone National Park: Agrostis rossiae is reported to be endemic to the thermal areas and A. scabra occurs both in thermal and nonthermal habitats. Thermal populations of both taxa are always surrounded by a nonthermal population of A. scabra that is reproductively isolated from the thermal plants by its later flowering time (summer rather than spring). Since Agrostis species are well known for their ability to form edaphic ecotypes, we used common garden and greenhouse experiments to test the hypothesis that “soil type” (a complex variable including factors such as soil chemistry and soil biotic community) was responsible for the separation of the thermal and nonthermal populations. In addition, field monitoring and growth chamber experiments were used to determine whether soil temperature affected the local distribution of these taxa. The results indicate that the thermal and nonthermal taxa are affected similarly by both soil temperature and soil t...