Abstract
Townsendialemhiensis (Asteraceae) is described from the Lemhi Valley of east-central Idaho. From a genus with weak intrinsic isolating barriers, T.lemhiensis remains distinct apparently due to apomixis and to its isolation and habitat specialization on spatially limited occurrences of ashy white soils in the Lemhi Valley. Despite similarities to T.spathulata, this new species differs in its persistent pappus, fewer series of phyllaries and sericeous rather than long woolly hairs.