CPC Plant Profile: Trailing Tick-trefoil
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Plant Profile

Trailing Tick-trefoil (Desmodium humifusum)

Description
  • Global Rank: G1 - Critically Imperiled
  • Legal Status: N/A
  • Family: Fabaceae
  • State: PA, CT, DE, IN, MA, MD, MO, NJ, NY
  • Nature Serve ID: 136935
  • Date Inducted in National Collection: 03/08/1989

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.

Participating Institutions
Updates
  • 09/08/2020
  • Genetic Research

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).

  • 09/08/2020
  • Propagation Research

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.

  • 09/08/2020
  • Seed Collection

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.

Nature Serve Biotics
  • 05/02/2017

Poorly known but thought to have been widespread in the northeast at one time. Extirpated (state historic) in DE, MD, NJ, and NY. Now reduced to about 6 scattered remnant populations. Threats include development, ORVs, suppression of fire which maintains favorable habitat, and invasive species. Likely a hybrid of Desmodium paniculatum and D. rotundifolium, which reliably co-occur with D. humifusum. Allozyme studies support this hypothesis (Raveill 2002).

Elizabeth J. Farnsworth
  • 01/01/2010

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

Elizabeth J. Farnsworth
  • 01/01/2010

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).

Elizabeth J. Farnsworth
  • 01/01/2010

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.

Elizabeth J. Farnsworth
  • 01/01/2010

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).

Elizabeth J. Farnsworth
  • 01/01/2010

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

Elizabeth J. Farnsworth
  • 01/01/2010

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

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Nomenclature
Taxon Desmodium humifusum
Authority (Muhl.) Beck
Family Fabaceae
CPC Number 7633
ITIS 502018
USDA DEHU3
Common Names spreading tick-trefoil | tick trefoil | trailing tick-trefoil | eastern trailing ticktrefoil | ground-spreading tick-trefoil
Associated Scientific Names Desmodium humifusum | Meibomia humifusa | Hedysarum humifusum
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
State Rank
State State Rank
Connecticut S1
Delaware SH
Indiana S1
Massachusetts S1
Maryland SH
Missouri SNA
New Jersey S1
New York SH
Pennsylvania SNA
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).

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.

Pollinators
Common Name Name in Text Association Type Source InteractionID

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