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CPC National Collection Plant Profile

Desmodium humifusum

Family:	Fabaceae
Common Names:	spreading tick-trefoil, tick trefoil, trailing tick-trefoil
Author:	(Muhl.) Beck
Growth Habit:	Perennial
CPC Number:	7633

Distribution
Protection
Conservation
References

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Desmodium humifusum is Fully Sponsored

Primary custodian for this plant in the CPC National Collection of Endangered Plants is:

New England Wild Flower Society

Elizabeth J. Farnsworth contributed to this Plant Profile.

Desmodium humifusum

Desmodium humifusum is a prostrate, trailing, perennial herb in the pea family. It is found in dry, sandy, inland forests, ranging from Massachusetts south to Pennsylvania and west to Indiana. Once known from 35 herbarium collections from 19 sites in the northeast, the number of populations has declined, and the species is now ranked as historic in several states: Delaware, Maryland, New Jersey, and New York. Reasons for its demise are largely unknown, but conversion of its habitat, which is conducive to home building, is a likely cause. Its status as a true species or as a hybrid form remains to be resolved, but recent molecular evidence indicates that it is a likely hybrid of Desmodium paniculatum and Desmodium rotundifolium.

This species takes its name, "humifusum" from the words for "earth/ground/soil" (humi) and for "spread out or extended" (fusum), which describe it well. It trails along the ground, with prostrate, hairy stems reaching 1 to 2 m (3.26 to 6.5 ft) in length. "Trefoil" is a French expression referring to its compound groups of three leaves (hairy on both sides) that branch off the stem on slender petioles 2.5 to 5 cm (1 to 2 in) long. Seven to nine small, purple flowers are produced on racemes in July and August.

Distribution & Occurrence

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State Range

Connecticut
Delaware
Indiana
Maryland
Massachusetts
Missouri
New Jersey
New York
Pennsylvania

Habitat

Desmodium humifusum inhabits open, dry woods on sandy, acidic soils that have formed from a parent bedrock of sandstone or chert (Gleason and Cronquist 1991, Hanson 2001, NatureServe 2001). As such, the canopy of these woods is likely dominated by oaks (Quercus spp.) and pines (Pinus spp.), and other understory vegetation is probably sparse. It can also occur in power line rights of way (NatureServe 2001).

Distribution

Desmodium humifusum ranges from central Massachusetts and patchily down the east coast to Pennsylvania. The species also extends west to Indiana and putatively to Missouri, but its status as a hybrid in Missouri is uncertain (Missouri Botanical Garden 2001, NatureServe 2001). Confusion has existed about the distribution of Desmodium humifusum because the name has been previously misapplied to Desmodium glabellum and Meibomia glabella (Gleason and Cronquist 1991, Shetler and Orli 2000, Eckel 2001). Historical localities have been searched for in the past decade, but not successfully relocated for the most part. However, Rawinski (1990) discovered three new populations during a concerted survey.

Number Left

Described as "a few scattered remnant populations" (NatureServe 2001). Reported from: Worcester and Suffolk Counties in Massachusetts (Sorrie and Somers 1999); Perry County in Indiana (Indiana Department of Natural Resources 1999); and historically from Bronx, Orange, and Westchester Counties in New York (Young 2001). However, recent analyses of allozymes indicate that the extant D. humifusum populations encompass only 8 genetic individuals, rather than the hundred or so genets previously estimated (Raveill 2002).

Protection

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Global Rank:	G1G2Q	12/24/1997	Guide to Global Ranks
Federal Status:	SC		Guide to Federal Status
Recovery Plan:	No

State/Area Protection

State/Area	Rank	Status	Date

Conservation, Ecology & Research

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Ecological Relationships

� Specific ecological studies have not been published on this species.
� Pollinators are unrecorded, but may include bees, given the flower color and pollinators recorded for congeners.
� As a legume, this taxon may form nodules with nitrogen-fixing bacteria, as do other members of its genus.
� According to the Association for Biodiversity Information (NatureServe 2001), plants have been known to withstand herbiciding where they occur in power line cuts.
� From allozyme evidence, it is now considered likely that Desmodium humifusum is a hybrid of two parent taxa with which it always co-occurs: D. rotundifolium and D. paniculatum (Raveille 2002). The species also shows morphological characteristics intermediate between these two taxa, lending credence to its hybrid origin.

Threats

� Habitat conversion: particularly forest clearing
� Habitat manipulation in rights-of-ways
� Destruction by off-road vehicles
� Shading caused by succession to a dense tree canopy or invasive shrubs

Current Research Summary

� The New England Wild Flower Society (Framingham, Massachusetts) has collected seed and conducted germination trials. Seed needed no pre-treatment in order to germinate. Inspection of many intermediate characters shown by the resulting seedlings, however, raises questions about the distinct identity of putative Desmodium humifusum populations.

Current Management Summary

� No information has been published on management of this species.
� A mention has been made of positively affecting one population of Desmodium humifusum in Indiana through a proposed land acquisition and forest management in the Hoosier National Forest, Perry County, Indiana. (Hanson 2001).

Research Management Needs

� More research is needed to determine the taxon's status as a distinct species or as a hybrid.
� An analysis of the distribution of Desmodium humifusum with respect to environmental variables (e.g., edaphic features, canopy cover, water availability)
� Identification of other plant species with which Desmodium humifusum co-occurs
� Characterization of plant-animal interactions (pollination, herbivory) and nitrogen-fixing symbionts
� Precise counts of plants in each population and measurements of reproductive output

Ex Situ Needs

� Common garden experiments to quantify variability in morphology and habitat requirements within and among taxa, to help work out taxonomic relationships

References

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Books (Single Authors)

1986. A Checklist of New York State Plants. Contributions of a Flora of New York State, Checklist III. Albany, New York: New York State Museum.

Brown, M.L.; Brown, R.G. 1984. Herbaceous plants of Maryland. Baltimore, MD: Port City Press, Inc.

Gleason, H.A.; Cronquist, A. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. Bronx: The New York Botanical Garden.

Gray, A.; Fernald, M.L. 1987. Gray's manual of botany: a handbook of the flowering plants and ferns of the central and northeastern United States and adjacent Canada. Portland, Or.: Dioscorides Press. 1632p.

Isely, D. 1990. Vascular flora of the southeastern United States. Chapel Hill, NC: University of North Carolina Press. 258p.

Rhoads, A.F.; Klein, W.M., Jr. 1993. The vascular flora of Pennsylvania: Annotated checklist and atlas. Philadelphia, PA: American Philosophical Society. 636p.

Shetler, S.G.; Orli, S.S. 2000. Annotated checklist of the vascular plants of the Washington-Baltimore area. Part I. Ferns, fern allies, gymnosperms, and dicotyledons. Washington, D.C.: National Museum of Natural History.

Sorrie, B.A.; Somers, P. 1999. The vascular plants of Massachusetts: a county checklist. Westborough, Massachusetts: Massachusetts Natural Heritage and Endangered Species Program.

Steyermark, J.A. 1977. Flora of Missouri. Ames, IA: Iowa State University Press. 1728p.

Tatnall, R.R. 1946. Flora of Delaware and the Eastern Shore. The Society of Natural History of Delaware. 313p.

Wherry, T.E.; Fogg, J.M.; Wahl, H.A. 1979. Atlas of the flora of Pennsylvania. Philadelphia, Pennsylvania: Morris Arboretum.

Electronic Sources

Eckel, P. M. (2001). MADCAPHORSE: A revised checklist of the Niagara Frontier Region. Buffalo Academy of Natural Sciences, Buffalo, New York. http://www.sciencebuff.org/BOTANYCATALOGUE/WNYCheck.htm. Accessed: 2001.

INDNR. (1999). Endangered, threatened, and rare species documented from Perry County, Indiana. Indiana Department of Natural Resources. http://www.in.gov/dnr/naturepr/species/perry.pdf. Accessed: 2002.

NatureServe. (2008). NatureServe Explorer: An online encyclopedia of life [web application]. [Internet].Version 7.0. NatureServe, Arlington, Virginia. http://www.natureserve.org/explorer. Accessed: (June 17, 2008).

Journal Articles

Kucera, C.L.; Martin, S.C. 1957. Vegetation and Soil Relationships in the Glade Region of the Southwestern Missouri Ozarks. Ecology. 38: 285-291.

Raveille, J.A. 2002. Allozyme evidence for the hybrid origin of Desmodium humifusum (Fabaceae). Rhodora. 104: 253-270.

Reports

Dowhan, J.J. 1979. Preliminary Checklist of the Vascular Flora of Connecticut (growing without cultivation). Hartford. Connecticut: State Geological and Natural History Survey of Connecticut, Natural Resources Center, Department of Environmental Protection.

Hanson, D. 2001. Environmental Assessment: Edwards Exchange Proposal. Perry County, Indiana: Tell City Ranger District, Hoosier National Forest. p.44 + appendices.

Mitchell, R.S.; Sheviak, C.J. 1981. Rare Plants of New York State. Bull. No. 445. Albany, N.Y.: New York State Museum. University of the State of New York. p.96.

Rawinski, T.J. 1990. Final Status Survey Report: The distribution and abundance of ground-spreading tick-trefoil (Desmodium humifusum). Newton Corner, Massachusetts: Report to the U. S. Fish and Wildlife Service, Region 5.

Young, S.M. (Editor). 2001. New York rare plant status list. Albany, New York: New York Department of Conservation.

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This profile was updated on 3/4/2010