| Botanical name: |
Aeschynomene
virginica |
| Common
name: |
Sensitive
joint-vetch |
| Group: |
Dicot |
| Family: |
Fabaceae
(pea family) |
| Growth
Type: |
Forb/herb |
| Duration: |
Annual |
| Plant
height |
3-6' |
| Flower
size |
1/2" |
| Flower
color: |
Yellow
with prominent red veins |
| Flowering/Fruiting
time: |
Flowers
late July into October. Fruit August & September, pods app. 3"
long. |
| Habitat: |
freshwater
to slightly tidal marshes, prefering lower edge of intertidal marsh
zone, receiving daily inundations. An obligate wetland species. |
| Range in
New Jersey: |
Manumuskin
River |
| Heritage
ranking
if any: |
G2,
S1, T, E, LP |
|
|
Sensitive
joint-vetch gets it names from its leaves, which fold
slightly when touched. It
has compound leaves that alternate along the stem, with each leaf
consisting of 30-56 leaflets.
Historically, sensitive joint-vetch was known from
New
Jersey, Delaware, Pennsylvania, Maryland, Virginia, and North Carolina.
It has been extirpated from Delaware and Pennsylvania; current North
Carolina populations are small, unstable, and unprotected. Populations
still exist in Virginia and a single population is known to exist in
New Jersey. Historical records for
A.
virginica occur in Atlantic,
Burlington, Camden, Cape May,
Cumberland, Gloucester, and Salem counties.
"Aeschynomene
virginica is native to freshwater tidal marshes of the
mid-Atlantic states (USFWS 1992). These marshes exhibit twice-daily
tides, but occur far enough upstream that they are nearly fresh or
barely brackish in water chemistry. Salinity of one site in New Jersey
ranges from 0.7 to 0.8 ppt with an average pH of 4.4. (NatureServe
2001). Only a small group of plants can tolerate this tidal inundation;
thus, freshwater tidal marshes are home to many specialized and rare
species. Aeschynomene
virginica
grows low in the intertidal zone where soils may be mucky, sandy, or
gravelly (Department of Conservation and Recreation 1997). Aeschynomene virginica
may perform
best in areas of the marsh where competition with other plants is
reduced -- for example, newly accreting shores or openings created by
wrack deposition or muskrat activity (Department of Conservation and
Recreation 1997).
In North Carolina, A.
virginica
has been found in a few road-side ditches and wet corn fields, but
these are not considered stable populations (Leonard 1985, USFWS 1992).
Biological inventories of available freshwater tidal marsh habitat in
North Carolina did not turn up additional populations, so the outlook
for the taxon in that state is uncertain.
Plant species commonly associated with A. virginica
include: Zizania
aquatica, Peltandra virginica,
Pontederia cordata,
Bidens
laevis, Polygonum arifolium, P. sagittatum, and Leersia oryzoides,
and, in southern
areas, another similar legume, Chamaecrista
fasciculata var. macrosperma
(Department of Conservation and Recreation 1997, NatureServe
2001).Interestingly, Aeschynomene virginica has frequently been
confused in the scientific literature with the invasive weed,
Aeschynomene indica, and referred to erroneously as an agricultural
pest! Recent genetic and taxonomic studies have resolved this confusion
(Carulli and Fairbrothers 1988, Isley 1990).
Insects are the primary pollinators: bumblebees (Bombus spp.),
leaf-cutter bees (family Megachilidae), and the least skipper
(Ancylozypha numitor) have been observed on plants in New Jersey,
according to Dr. Joeseph Patt of The Nature Conservancy.
• Seeds are produced in pods, and segments of the pods can
float
and potentially disperse in water. However, seeds commonly fall very
close to the parent plant (Griffith 2001). Seedlings may preferentially
germinate in rafts of floating plant material that have been deposited
on the river bank (Bruederle and Davison 1984). Such floating wrack may
kill existing plants and open new bare space that can be colonized by
A. virginica. Muskrats may also create such openings (Department of
Conservation and Recreation 1997). As an opportunistic colonizer of
bare space, an apparently poor competitor with other plants, and a
plant that occurs in periodically disturbed, riparian sub-populations
that may exchange propagules, A. virginica may exhibit metapopulation
dynamics where it occurs (Griffith 2001).
• Like its more common relatives, A. indica and A. americana
(Grant 1996), Aeschynomene virginica may form nodules with symbiotic,
nitrogen-fixing bacteria, but these dynamics have not been studied. If
so, the species may be very sensitive to changes in the nitrogen
content of wetland soils due to increasing nutrient inputs in water and
rising atmospheric nitrogen deposition, problems that are especially
severe in the mid-Atlantic region."
Center
for Plant Conservation
USF&W Endangered Species Federal
recovery plan
for Aeschynomene
virginica
|
|
