1997 Volume 82 Pages 61-75
A total of 810 bryophyte taxa have been reported from the interior Columbia River Basin and northern Great Basin, a study area encompassing all or parts of seven U.S. states. Of these taxa, 409 have five or fewer occurrences in the study area. Exclusion of “problem” taxa and incompletely identified subspecific material produces a list of 296 potentially rare taxa. Of seven ecological provinces present in the study area, the northern Rocky Mountains host the most taxa, dominated by circumpolar and disjunct elements, with a strong showing of eastern North American elements. The east slope of the Cascade Range has the greatest number of endemic and Mediterranean taxa. The arid lowlands of the Intermountain region have the greatest number of southern arid taxa, but are very poorly collected bryologically.