SPECIES FACT SHEET
Common Name: Tuberous hornwort
Scientific Name: Phymatoceros phymatodes (Howe) Duff, Villarreal, Cargill, et
Renzaglia.
Division: Anthocerotophyta (Stotler and Crandall-Stotler 2005)
Class: Anthocerotopsida
Order: Notothyladales
Family: Notothyladaceae
Taxonomic Note: There is some debate about the correct name for this
species. The name Phymatoceros phymatodes is based on Duff et al. (2007)
belief that ours is distinct and recognizes Howe's specific epithet for the Pacific
coast plants. However, the name given by Stotler, Doyle, and Crandall-Stotler
(Phymatoceros bulbiculosus) assumes that the material from western North
America is conspecific with a European taxon. Both ITIS and the Oregon
Biodiversity Information Center use Phymatoceros phymatodes as the
appropriate name; NatureServe uses Phymatoceros bulbiculosus.
Technical Description: Plants thalloid, dark green, frequently and irregularly
branched. Cells contain solitary chloroplasts that vary from angular to spindle
shaped, to rounded, to dumbbell shaped. Female plants are up to 2.5 mm
wide, somewhat grayish green and often with slightly raised wing margins.
Stalked ventral tubers develop early on female thalli without sporophytes. Male
plants are smaller than the female plants, generally less than 1 mm wide. Male
plants develop a cluster of antheridia and then become vegetative and initiate
development of long stalked, ventral tubers. When sporophytes develop they
are short, less than 2 cm tall, straight to slightly curved, changing from green
to orange to dark brown or blackish as they mature. Young spores are yellow,
mature spores are dark brownish-black (Doyle & Stotler 2006).
Distinctive Characters: This is the only hornwort with stalked tubers arising
from the bottom of the thallus. The tubers are numerous and impossible to
miss once a plant is lifted from the substrate.
"The tubers of A. phymatodes are formed at the apex of the costa, but
their peduncles become strictly ventral in their attachment by the
continued onward growth of the segment. Two or three tubers
successively older and larger as one passes backward may often be seen
from a single branch. The tuber consists of a cortex of 2–4 layers of
nearly empty cells enclosing a central mass of smaller cells so densely
filled with oil drops or nearly colorless granules that the cell boundaries
in a section are rendered obscure." (Howe 1899)
Similar species: Other hornworts are superficially similar but all regional
species lack the stalked, ventral tubers. Note that 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. It
is active during the typical growing season for bryophytes, November - May,
and then becomes dormant, perenniating by means of subterranean tubers.
They are all but invisible during the dry season. 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: Accepting taxonomic rank in the
narrow sense (as P. phymatodes ), this species is characteristic of the California
floristic province, from the central coast and Sierra Nevada of California to
Curry and Douglas Counties, Oregon. Very rare in Oregon, apparently more
common in California. Oregon Natural Heritage Information Center lists only
Curry County for distribution in Oregon; there are two Douglas County records
as of May, 2010, one based on a collection in the herbarium at the California
Academy of Sciences and the second a 2010 collection from near Scottsburg.
Schuster (1992) reports he has collected this (as Anthoceros phymatodes) from
Baja California and Arizona.
Habitat Associations: This species grows on bare, mineral soil which remains
moist until late spring or summer. 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, habitats such as roads, trail cuts or roadside ditches which
support populations of ephemerals like this are continually being created.
Conservation Considerations: Relocate and monitor known colonies to
evaluate natural population fluctuations and reproductive potential.
BLM: Documented on Coos Bay District; suspected on Roseburg and
Medford Districts.
USFS: Suspected on Rogue River-Siskiyou National Forest.
ORNHIC list 3. Rank G5/S1 (Global rank based on European range of P.
bulbiculosus ).
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.
Preparer: David H. Wagner, Ph.D.
Edited by: Rob Huff
Date Completed: 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).
ATTACHMENTS:
(1) Photos
References:
Christy, J.A. & D.H. Wagner. 1996. Guide for the identification of rare,
threatened or sensitive bryophytes in the range of the northern spotted owl,
western Washington, western Oregon and northwestern California. USDI
Bureau of Land Management, Oregon-Washington State Office, Portland. 222
pp.
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.
Howe, M.A. 1899. The Hepaticae and Anthocerotes of California. Memoirs of
the Torrey Botanical Club 7: 1–208, plates 88–122.
ITIS. 2008. Integrated Taxonomic Information System (official government
database of scientific names)
http://www.itis.gov/index.html
Accessed August 2008.
Oregon Natural Heritage Information Center. 2007. Rare, threatened and
endangered species of Oregon. Oregon Natural Heritage Information Center,
Oregon State University. Portland. 100 pp.
http://oregonstate.edu/ornhic/2007_t&e_book.pdf
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.
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
Attachment 1 – 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 fresh male plants.