Overview

Brief Summary

Helianthus bolanderi (synonym: Helianthus exilis) is a rare forb species endemic to California's North Coast Ranges. This plant is restricted to areas within serpentine outcrops, where it occurs in insular metapopulations.

Also known as Serpentine sunflower, this annual forb achieves a height of 60 to 150 centimeters. The erect stems are hispid to hirsute. Leaves are chiefly cauline and typically alternate. Leaf petioles are one to four centimeters in length.
  • * Amy Wolf, Paul A.Brodmann and Susan Harrison. 1999. Distribution of the rare serpentine sunflower, Helianthus exilis (Asteraceae): the roles of habitat availability, dispersal limitation and species interactions. OIKOS 84: 69-76. Copenhagen
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Distribution

National Distribution

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

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Physical Description

Morphology

Description

Annuals, 60–150 cm. Stems erect, hispid to hirsute. Leaves mostly cauline; mostly alternate; petioles 1–4 cm; blades lance-linear or lance-ovate to ovate, 3–15 × 2–6 cm, bases cuneate to truncate, margins usually serrate, abaxial faces sparsely hirsute, gland-dotted . Heads 1–3. Peduncles 3–13 cm. Involucres hemispheric, 17–25 mm diam. Phyllaries 10–18, usually lanceolate to lance-ovate, 9–27 × (3–)3.5–5 mm (often surpassing discs), apices gradually attenuate, abaxial faces hirsute. Paleae 9.5–10.5 mm, 3-toothed (middle teeth subulate, surpassing discs, apices glabrous). Ray florets 12–17; laminae 14–20 mm. Disc florets 75+ (discs usually 2+ cm diam.); corollas 5–7 mm, lobes usually reddish; anthers dark, appendages dark (style branches reddish). Cypselae 3.5–4.5 mm, glabrate; pappi of 2 lanceolate scales 1.7–3 mm. 2n = 34.
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Type Information

Type collection for Helianthus bolanderi A. Gray
Catalog Number: US 323498
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Original publication and alleged type specimen examined
Preparation: Pressed specimen
Collector(s): H. N. Bolander
Year Collected: 1864
Locality: Clear Lake, The Geysers., Lake, California, United States, North America
  • Type collection: Gray, A. 1865. Proc. Amer. Acad. Arts. 6: 544.
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Conservation

Conservation Status

National NatureServe Conservation Status

United States

Rounded National Status Rank: NNR - Unranked

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NatureServe Conservation Status

Rounded Global Status Rank: G4 - Apparently Secure

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Notes

Comments

Helianthus bolanderi and H. exilis form a closely related pair of sister species that share the distinctive feature of having the middle teeth of the paleae glabrous and relatively elongated, surpassing the disc florets. As treated here, H. bolanderi corresponds to the "valley weed race" (C. B. Heiser 1949; L. H. Rieseberg et al. 1988); it is separated from the "serpentine foothill race," here recognized as H. exilis. Heiser proposed that H. bolanderi originated through hybridization between H. annuus and H. exilis; molecular studies by Rieseberg et al. do not support this scheme. In an ironic twist, it appears that H. bolanderi may be undergoing "genetic assimilation" through hybridization with H. annuus (S. E. Carney et al. 2000).
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