Loeseliatsrum and Langloisia are sister genera native to southwestern North America. The clade is comprised of four species. Specific assignment within each genus has had a tortuous taxonomic history. Timbrook (1977, 1986) cites morphological, palynological, chromosomal, and phytochemical evidence to support the segregation of the two genera. However, Lo. depressum was not treated by Timbrook as it remained in Ipomopsis at that time. Molecular evidence clearly places Lo. depressum in this clade and as a result Timbrook’s circumscription no longer holds true. As of yet, molecular evidence has not provided a clear resolution of this problem (see below). As a result, both genera are treated on the same page for the time being.
Langloisia was defined by Timbrook based on the following combination of characters: clustered bristles on upper leaves, actinomorphic corollas, erect stamens of equal length, white to blue pollen, branched trichomes, and capsule valves three times as long as wide and convex across the back. By contrast, Loeseliastrum was defined by Timbrook based on the following combination of characters: only single bristles on upper leaves, zygomorphic corollas, declined stamens of unequal length, yellow pollen, unbranched trichomes, and capsule valves two times as long as wide and concave across the back. Lo. depressum possesses no lateral bristles, zygomorphic corollas, erect stamens of unequal length, and white to blue pollen and is therefore morphologically intermediate between the two genera sensu Timbrook. However, Timbrook placed most emphasis on the clustering of bristles, stating that the: “infallible character of leaf bristles allows ready separation of Langloisia and Loeseliastrum” (Timbrook 1977 p. 31) yet this character is somewhat variable as bristles (when clustered) may be single or clustered on the same leaf. Furthermore, Timbrook (1977) demonstrates crossability (however slight) between his two genera which sometimes resulted in more seed set per capsule than intraspecific crosses!
Johnson et al. (2008) recover Loeseliatsrum and Langloisia as a monophyletic group sister to Eriastrum. Within this clade however, the monophyly of Loeseliatsrum is uncertain (less than 50 percent parsimony bootstrap and 0.55 posterior probability). Unpublished evidence using more genes and more taxa indicates some support for a monophyletic Loeseliatsrum (71 percent maximum likelihood bootstrap), though the genera are poorly defined morphologically (see above). The decumbent anthers and yellow pollen indicative of Loeseliatsrum (sensu Timbrook) appears to be a derived condition in this clade.
Both genera (with one exception) are restricted to desert regions of southwestern North America (United States as well as Baja California and Sonora, Mexico). La. setosissima subsp. punctata occurs in both southern California and Nevada and reappears again as a disjunct in southern Idaho and eastern Oregon in the Snake and Salmon River valleys (Timbrook 1977, 1986). The disjunct populations posses several morphological differences and might be best treated as separate taxon but this warrants further study.
- Langloisia setosissima (Torr. & A. Gray)
- La. setosissima (Torr. & A. Gray) subsp. punctata (Coville) Timbrook
- La. setosissima (Torr. & A. Gray) subsp. setosissima
- Loeseliastrum depressum (M.E. Jones) J.M. Porter & L.A. Johnson
- Loeseliastrum matthewsii (A. Gray) Timbrook
- Loeseliastrum schottii (Torr.) Timbrook
Timbrook (1977) rejects recognizing La. punctata as a distinct species based on supposed overlap in morphological features. However, the corolla coloration is distinctly different in the two (purple with maroon streaks in La. setosissmia compared to white with maroon dots and yellow nectar guides in La. punctata) suggesting reproductive isolation. Furthermore, within La. setosissima subsp. punctata the disjunct populations in southern Idaho and eastern Oregon posses several morphological differences and might be best treated as separate taxon.
KEY TO LANGLOISIA AND LOESELIASTRUM (modified from Timbrook 1977)
1. Corolla actinomorphic; bristles of the upper cauline leaves clustered (La. setosissima)
2. Corolla lobes 0.3-0.5 X length of the tube; filaments > 3 mm long…La. s. setosissima
2′. Corolla lobes 0.5-1 X length of the tube; filaments ca. 5 mm long…La. s. punctata
1′. Corolla zygomorphic; bristles of the upper cauline leaves solitary or none
3. Corolla 5-8 mm long; leaves entire to slightly bristly with a long apical bristle…Lo. depressum
3′. Corolla 8-21 mm long; leaves with conspicuous lateral bristles
4. Corolla 11-21 mm long, upper lip 0.75-1.5 X length of the tube; longest filaments equal to upper lip of corolla, calyx 0.5-0.75 length of the corolla tube…Lo. matthewsii
4′. Corolla 8-15 mm long, upper lip 0.5-0.75 X length of tube; longest filaments shorter than the upper lip of corolla; calyx 0.75-1 X length of corolla tube...Lo. schottii
Timbrook, S. 1986. Segregation of Loeseliastrum from Langloisia (Polemoniaceae). Madroño 33: 157–174.
Timbrook, S.L. 1977. Biosystematic Studies of Langloisia and Loeseliastrum. PhD Thesis University of California Santa Barbara.