Geographic distribution, morphological and molecular characterization, andrelationships of Lathrocasis tenerrima (Polemoniaceae)

Lathrocasis is a recently recognized genus of Polemoniaceae that circumscri bes the species first named Gilia tenerrima A. Gray. This species, distribu ted primarily in the Great Basin and Rocky Mountain floristic regions, has previously escaped thorough taxonomic scrutiny. Surveys of herbarium specim ens and living material show that some features of this species have been i naccurately characterized in die past, while other characteristics have not been previously considered in assessing its relationships. Lathrocasis pos sesses a distinct suite of morphological features that, considered as a who le, distinguish this taxon at the generic level. This suite of characters i ncludes the mostly entire, non-mucronate leaves, effuse branching: with div erging to retrorse and threadlike pedicels, uniformity of short stipitate g lands throughout, uniovulate locules, spiriliferous seeds with verrucate se ed coats, minute funnelform flowers with simple vasculature, and stamens eq ually inserted approximately mid-tube. ParsiInony analyses of ITS, trnL, an d,matK genes recover similar trees that place Lathrocasis in Gilieae with p ossible sister relationships to Gilia, a group composed of Allophyllum, Col lomia, and Navarretia. or both of these groups combined. A detailed descrip tion of L. tenerrima, a review of its taxonomic history, and notes on the t ype collection are presented.