A Vascular Flora of the Selkirk Mountains, Bonner and Boundary Counties, Idaho

The vascular flora described here covers ∼2295 square kilometers (∼886 square miles) of the Selkirk Mountains that lie in the Idaho Panhandle, covering an elevational range of 540–2330 m (1770–7670 ft). The majority of the mountain range is underlain by granitic rock of the Kaniksu Batholith, and is diversified by the rich glacial history of the Panhandle. The study area contains multiple pockets of alluvial and glacial deposition that serve as specialized habitat for present-day floristic diversity within the range. The Idaho Selkirks are part of the Northern Rocky Mountains and have floristic influences from the Pacific coast, boreal north, the Columbia Basin, and the RockyMountains to the south and east. Despite notable collection interest over the last century in the northern Idaho Panhandle, a comprehensive checklist did not exist prior to this project, and previous collecting efforts were uneven, creating significant gaps in coverage and incomplete documentation of the area. A total of 108 collection days were spent in the field in 2019 and 2020, resulting in 4155 vascular plant collections from 665 collection sites, documenting 845 total unique taxa in 94 plant families. Taxa previously collected but not recovered were first verified by the author using historical specimens housed at multiple Pacific Northwest herbaria, and were then included in the final checklist. Sixty-two rare taxa and six state collection records were found in the study area, as well as numerous range extensions and county collection records. While the primary objective was to document and voucher all vascular plant taxa of the Selkirk Mountains of Idaho to create an annotated checklist of the vascular flora, additional objectives included formal assessments of the vegetation types and threats to the flora of the study area, as well as increasing documentation of sensitive, rare, and non-native species occurrences within the range.