SPECIES FACT SHEETCommon Name: Tuberous hornwortScientific Name: Phymatoceros phymatodes (Howe) Duff, Villarreal, Cargill & Renzaglia.Division: Anthocerotophyta Class: AnthocerotopsidaOrder: Phymatocerotales Family: Phymatocerotaceae

Taxonomic Note: There is some debate about the correct name and systematic placement for this species. ITIS.gov uses the above taxonomy and classifies the North American Phymatoceros phymatodes as distinct from the European Phymatoceros bulbiculosus (Brot.) Stotler, W.T. Doyle & Crand.-Stotl. (Duff, et al. 2007, Söderström, et al 2016). Stotler and Crandall- Stotler (2005) consider the two taxa synonymous and place gave it a different systematic placement. David Wagner (2011) includes it in Phymatoceros bulbiculosus.

Technical Description: Hornwort. Plants thalloid, terrestrial, dark green, frequently and irregularly branched, made of homogeneous cells; cells contain solitary chloroplasts that vary from angular to spindle shaped, rounded, or dumbbell shaped. Female plants up to 2.5 mm wide, somewhat grayish green, often with slightly raised wing margins; stalked ventral tubers develop early on female thalli without sporophytes. Male plants smaller, generally less than 1 mm wide; after developing a cluster of antheridia they become vegetative and develop long-stalked, ventral tubers. Reproduction: Dioicous. Sporophytes are elongated and cylindrical; they mature gradually from the tip down and eventually split into two twisted thread-like valves; when present they are less than 2 cm tall, straight to slightly curved, changing from green to orange to dark brown or blackish as they mature. Spores yellow when young, dark brownish-black when mature.

Distinctive Characters: Hornworts are ribbon-like plants with tall, narrow sporophytes that split into two thread-like valves when mature. Phymatoceros phymatodes is the only hornwort in western North America with stalked tubers arising from the bottom of the thallus. The tubers are numerous, yellow-green, maturing golden-brown and obvious once a plant is lifted from the substrate.

Similar species: Other hornworts are superficially similar but all regional species lack the stalked ventral tubers.

Phaeoceros pearsonii has lateral tuberous thickenings on its thalli but these are not stalked and are not hidden beneath the thallus.

Life History: This species has a strong annual cycle even though perennial. Its thallus on the soil surface is active during the typical November - May bryophytes growing season, and then becomes all but invisible during the dry season. The plant perenniates by subterranean tubers. Because the species is dioicous, populations may consist of a single sex. In these populations reproduction is solely by the perenniating tubers.

Range, Distribution, and Abundance: Phymatoceros phymatodes is known from western North America in Oregon, California, Mexico, and Arizona.

Very rare in Oregon, apparently more common in California. There are collections from Curry and Douglas Counties, and reports of sites in Coos and Lane counties (Exeter et al. 2015).

BLM Districts and National Forests: Documented on Coos Bay BLM District; suspected on Roseburg, Medford District and by the Northwest Oregon BLM Districts. Documented on Rogue River-Siskiyou National Forest.

Habitat: Grows on bare mineral soil (riparian banks, road and trail-sides, sloping meadows) that remains moist until late spring or summer. The Coos county site occurs in a steep (80% slope) grass-dominated meadow of less than 1 acre, within a Douglas fir forest situated in an area of south-facing slopes on a dissected ridge. The meadow is bordered by poison oak and has shallow, thin, fragile soils and areas of exposed bedrock. Associated vascular plants include Mimulus alsinoides, Mimulus guttatus, Nemophila menziesii and grasses. Associated bryophytes include: Asterella, Cephaloziella, Fossombronia, Imbribryum miniatum, Phaeoceros, Riccia, and Weissia. Similar meadows dominated by Racomitrium elongatum may prove to be too dry. From near sea level to 650 m (2100 feet) elevation (Doyle and Stotler 2006).

Threats: Threats include replacement by later successional plant communities because plants like this tend to be colonizers of recently disturbed soil. On the other hand, bare soils along roads, trail cuts or roadside ditches which support populations of ephemerals are continually being created. Small isolated populations could be threatened if an extreme soil disturbance (landslide, road construction, etc.) destroyed or buried the propagules of the entire site.

Conservation Considerations: Relocate and monitor known colonies to evaluate natural population fluctuations and reproductive potential. Conservation Rankings and Status:Global: G2/G3; Oregon: S1, ORBIC List 2; Washington: NR.

Forest Service and BLM Sensitive species in Oregon.

Other pertinent information:Survey Protocol: Suitable habitat should be searched quite early in the year, February to May, when vegetative growth is nearing a maximum and the plants are most visible.

Key to Identification of the Species: Doyle and Stotler (2006), Wagner (2011).

Photos and/or line drawings: Exeter et al. (2016, p. 245); Wagner (2011)

Preparer: David H. Wagner, Ph.D., January, 2010

Updated: David Wagner, May, 2010 (General editing of text; photos of herbarium specimens attached; also attached are new images prepared from recently collected material); Rob Huff, April, 2011 (Documented and suspected status, taxonomic note, and conservation ranks); and February 2018 by Michael Russell based information in Exeter et al. (2016) and including taxonomic updates.

References:

Doyle, W. T. & R.E. Stotler. 2006. Contributions toward a bryoflora of California III. Keys and annotated species catalogue for liverworts and hornworts. Madroño 53: 89–197.

Duff, R.J., J.C. Villarreal, D.C. Cargill, and K.S. Renzaglia. 2007. Progress and challenges toward developing a phylogeny and classification of the hornworts. The Bryologist 110: 214–243.

Exeter, R. L., J. Harpel, D. Wagner. 2016. Rare Bryophytes of Oregon. Salem District, Bureau of Land Management. Salem, Oregon. 97306. ISBN-13: 978-0-9791319-4-2. 378 p.

ITIS. 2018. Integrated Taxonomic Information System (official government database of scientific names) http://www.itis.gov/index.html Accessed February 2018.

Oregon Biodiversity Information Center. 2016. Rare, Threatened and Endangered Species of Oregon. Institute for Natural Resources, Portland State University, Portland, Oregon. 130 pp. http://inr.oregonstate.edu/sites/inr.oregonstate.edu/files/2016-rte-book.pdf Accessed February 2018.

Paton, J.A. 1999. The liverwort flora of the British Isles. Harley Books, Colchester, U.K. 626 pp.

Schuster, R.M. 1992. The Hepaticae and Anthocerotae of North America. Volume 6. The Field Museum of Natural History, Chicago.

Söderström, L., A. Hagborg, M. von Konrat, S. Bartholomew-Began, D. Bell, L. Briscoe, E. Brown, D. C. Cargill, D. P. Costa, B. J. Crandall-Stotler, E. D. Cooper, G. Dauphin, J. J. Engel, K. Feldberg, D. Glenny, S. R. Gradstein, X. He, J. Heinrichs, J. Hentschel, A. L. Ilkiu-Borges, T. Katagiri, N. A. Konstantinova, J. Larraín, D. G. Long, M. Nebel, T. Pócs, F. Puche, E. Reiner-Drehwald, M. A. M. Renner, A. Sass-Gyarmati, A. Schäfer-Verwimp, J. G. Segarra Moragues, R. E. Stotler, P. Sukkharak, B. M. Thiers, J. Uribe, J. Váňa, J. C. Villarreal, M. Wigginton, L. Zhang, R. Zhu 2018. World Checklist of Hornworts and Liverworts. PhytoKeys 59 : 1 – 828.

Stotler, R. E. & B. Crandall-Stotler. 2005. A revised classification of the Anthocerotophyta and a checklist of the hornworts of North America, north of Mexico. Bryologist 108: 16-26. http://bryophytes.plant.siu.edu/anthocerotophyta.html Accessed March 2018.

Wagner, D.H. 2011. Hornworts of Oregon. November 2011 edition. Northwest Botanical Institute. Eugene, Oregon. http://fernzenmosses.com/hornworts_of_oregon/allhorns.htm Accessed March 2018.

Photos All photos by Dr. David Wagner, under contract with the Oregon/Washington Bureau of Land Management.

Rehydrated thallus from herbarium specimen; mature tubers present

Rehydrated thallus from herbarium specimen; mature tubers present

Fresh thalli of male plants. Note tubers at right edge of patch.

Fresh thalli of male plants. Note tubers on upturned thallus at bottom.

Young tubers on lower side of fresh male plants.