Lathrocasis is a monotypic genus of an annual endemic to the western United States. It occurs in open areas including gravelly slopes, sagebrush scrub, and pinyon pine-juniper woodlands and rarely into aspen-conifer zones at elevations from 1525-3000 m.
Lathrocasis is sister to a clade comprised of Allophyllum, Collomia, Gilia, and Navarretia (Johnson et al. 2008). However, support for this relationship is weak (66 percent parsimony bootstrap and 0.92 posterior probability). Unpublished analyses including more taxa and more genes continue to indicate an uncertain relationship at this node. This difficulty may be in part due to the fact that Lathrocasis is on a long branch with many putatively homoplasious substitutions (Johnson and Weese 2000).
Lathrocasis occurs in both the Great Basin and Rocky Mountains in the northwestern North America in the US states of California, Colorado, Idaho, Montanta, Nevada, Oregon, Utah, Washington, and Wyoming as well as in British Columbia, Canada.
Lathrocasis appears to be autogamous (Grant and Grant 1965, Johnson and Weese 2000) as the anthers and stigma mature at the same time, the anthers make contact with the stigma, and the flowers are only open for one day.
- Lathrocasis tenerrima (A. Gray) L.A. Johnson
Johnson, L. A. and T. L. Weese. 2000. Morphological and molecular characterization, geographic distribution, and relationships of Lathrocasis tenerrima (Polemoniaceae). Western North American Naturalist 60:355-373.