Allophyllum is a small genus of five species of glandular-pubescent annuals endemic to western and southwestern North America. Species delimitation in genus has been problematic, not only due to the fact that all species can interbreed to form fertile offspring but that they may all occur in sympatry, including all species found together “in small areas in the San Gabriel and San Bernardino Mountains” (Grant & Grant 1955).
Phylogeny
Allophyllum is sister to a clade comprised of Collomia and Navarretia. This is in line with the hypothesis of a close relationship between Allophyllum and Collomia based on morphological similarity (Grant & Grant 1955). Grant and Grant (1955) recognized two “series” within Allophyllum. One series was comprised of small plants similar to A. gilioides with linear leaf segments, sparsely pubescent stems, and slightly irregular flowers. The second series was comprised of of more robust plants similar to A. divaricatum with broad leaf segments, villous stems, and more or less regular flowers. However, molecular sequence data indicates that these series are not monophyletic. More data are needed to confirm these results.
Biogeography
Allophyllum is endemic to the western United States and Baja California. It is most diverse in California with five of the six species in the genus found in that state. Allophyllum giliodies shows a disjunct distribution on either side of the Mojave Desert. The worldwide distibution and partitioning of species richness in geographic space within Allophyllum is shown below.
Taxonomy
- Allophyllum divaricatum (Nutt.) A.D. Grant and V.E. Grant
- Allophyllum gilioides (Benth.) A.D. Grant and V.E. Grant
- Allophyllum glutinosum (Benth.) A.D. Grant and V.E. Grant
- Allophyllum integrifolium (Brand) A.D. Grant and V.E. Grant
- Allophyllum violaceum (A. Heller) A.D. Grant and V.E. Grant
KEY TO ALLOPHYLLUM (modified from Grant & Grant [1955])
1. Cauline leaf segments 3-15 mm wide; corolla 6-22 mm long; stamens exserted or included; herbage distinctly glandular…2
1′. Segments of cauline leaves < 3 mm wide; corolla 2-9.5 mm long; stamens included; herbage not distinctly glandular…4
2. Stamens unequal in length; lower leaves pinnate to bipinnately lobed; capsules 6- to 9-seeded…A. glutinosum
2′. Stamens equal in length; lower leaves entire to pinnately lobed; capsules 3-seeded…3
3. Corolla tube 6-16 mm long; inflorescence 4- to 8-flowered…A. divaricatum
3′. Corolla tube 5-8 mm long; inflorescence 2-flowered…A. integrifolium
4. Inflorescence head-like, 4-8 flowered; plant with many pinnately lobed leaves; inflorescence branches arising above the middle of the plant…A. gilioides
4′. Inflorescence loose, 2-3 flowered; plant with few pinnately lobed leaves; inflorescence branches arising throughout the plant…A. violaceum
References
Grant, A., and V. Grant. 1955. The genus Allophyllum (Polemoniaceae). Aliso 3: 93–110.
Porter, J. M. and L. A. Johnson. 2000. A phylogenetic classification of Polemoniaceae. Aliso 19: 55-91.
Evolution of the Phlox Family 