Gayophytum heterozygum

Herbs usually glabrous or strigillose, rarely villous. Stems erect, usually unbranched near base, branched at each of several nodes proximal to first flower, less branched distally, branching dichotomous, 15–80 cm. Leaves much reduced distally, 15–60 × 1–5 mm; petiole 0–10 mm; blade narrowly lanceolate to sub­linear. Inflorescences with flowers arising usually as proximally as first 10–20 nodes from base. Flowers: sepals 1–1.8 mm, reflexed singly or in pairs; petals 2–3(–4) mm; pollen ca. 50% fertile; stigma hemispheric to subglobose, surrounded by anthers at anthesis. Capsules ascending or reflexed, terete to ± flattened, 6–15 × 0.8–1.1 mm, with conspicuous irregular constrictions between seeds, valve margins undulate, all valves free from septum after dehiscence, septum sinuous; pedicel (2–)3–12 mm. Seeds 2–10, ca. 1/2 aborted, arranged± parallel to septum and in alternating pattern between locules, adjacent seeds not overlapping, irregularly well spaced from each, forming a single row in capsule, brown or gray mottled with brown, 1.4–2 × 0.6–0.8 mm, glabrous or puberulent. 2n = 14.

Phenology: Flowering Jun–Oct.
Habitat: Open montane forests.
Elevation: 800–3000 m.

Distribution

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• Legacy Map

Calif., Nev., Oreg., Wash.

Discussion

Gayophytum heterozygum is the only species of Onagraceae outside of Oenothera that is a permanent translocation heterozygote (PTH) (W. L. Wagner et al. 2007), in which the chromosomes form a ring of 14 at meiosis rather than the seven pairs characteristic of all other self-pollinating diploid species of the genus. As is true for other PTH species, G. heterozygum produces only about fifty percent fertile pollen and a correspondingly reduced number of fertile seeds. All other species have less than ten percent of the pollen sterile.

It is not clear whether one or two species were involved in the parentage of Gayophytum heterozygum (H. Lewis and J. Szweykowski 1964; L. B. Thien 1969). This species is morphologically intermediate between G. eriospermum and G. oligospermum and has been suggested by Lewis and Szweykowski to be a PTH species derived by hybridization between them, much like the PTH species in 17. Oenothera.

Selected References

None.

Lower Taxa

None.