Erythranthe thermalis

Annuals, taprooted, rarely with a basal, runnerlike stem. Stems erect, simple or branched from basal nodes, 1.5–10(–15) cm, villous-glandular proximally, moderately to densely stipitate-glandular, sometimes hirtellous and eglandular distally. Leaves basal and cauline, cauline 2–5 pairs; petiole: basal and proximal cauline 3–20 mm, distals 0 mm; blade palmately 3–5-veined, suborbicular to ovate, depressed-ovate, ovate-deltate, or reniform, 4–15(–20) × 4–20 mm, base cuneate to truncate or subcordate, margins evenly crenate-dentate to subentire, apex acute to obtuse or rounded, surfaces moderately to densely stipitate-glandular, sometimes hirtellous and eglandular. Flowers plesiogamous, 1–5(–9), usually at distal nodes, chasmogamous. Fruiting pedicels 7–12 mm, moderately to densely stipitate-glandular, sometimes hirtellous and eglandular. Fruiting calyces ovate-campanulate, inflated, sagittally compressed, 8–11 mm, moderately to densely stipitate-glandular, sometimes hirtellous and eglandular, throat closing, adaxial lobe longer than others. Corollas yellow, red-dotted or not, bilaterally symmetric, strongly bilabiate; tube-throat funnelform, 8–12 mm, exserted 1–2 mm beyond calyx margin; limb expanded 12–15 mm, throat open, palate villous. Styles hirtellous. Anthers included, glabrous. Capsules included, 5–6 mm. 2n = 28.

Phenology: Flowering Mar–Aug.
Habitat: Hot, shallow, quick-drying soils around thermal pools and vents.
Elevation: 2200–2600 m.

Distribution

• Generated Map
• Legacy Map

Wyo.

Discussion

Erythranthe thermalis is endemic to Yellowstone National Park in northwestern Wyoming. The species is recognized by its annual duration (without rhizomes), reduced stature and leaf size, and short, but broad-limbed, corollas with autogamous fertilization. Typical E. guttata (rhizomatous, herkogamous) also grows in the immediately surrounding areas but apparently not in hot soils. Each species maintains distinctions in growth form, phenology and mating system in common garden experiments (Y. Lekberg et al. 2012).

Selected References

Lekberg, Y. et al. 2012. Phenotypic and genetic differentiation among yellow monkeyflower populations from thermal and non-thermal soils in Yellowstone National Park. Oecologia 170: 111–122.

Lower Taxa

None.