Conservation Action Plan
Chamaecrista lineata var. keyensis
Species Name: Chamaecrista lineata (Sw.) Greene var. keyensis (Pennell) H.S. Irwin
& Barneby
Common Name(s): Narrowpod sensitive pea, Keys partridge pea, Big Pine partridge
pea
Synonym(s): C. keyensis (Pennell), Cassia keyensis (Pennell) J.F. Macbr.
Family: Fabaceae
Species/taxon description: Prostrate perennial herb with one to multiple stems rising
from one rootstock. It has alternate, pinnately compound leaves, 2-3 cm long. Leaves
have 4-7 pairs of oblong leaflets, each 6-8 mm long. Flowers are axilary with only 1
subtended per leaf. Peduncle is slender and curves upward, 1-1.5 cm long and has 2
small linear bracts at the apex. 5 sepals. Orbicular flower petals are yellow with small
orange markings near the base. Ten stamen and the anthers are enlarged at the base and
taper upward to form a long neck (poricidal anthers). Legume is slender and poricidal
dehiscent containing up to 13 seeds (Ward, 1979).
Legal Status: Florida endangered, federal candidate
Biogeographic Value: Native, Endemic
Prepared by: Adrianna Muir, Conservation of South Florida Endangered and
Threatened Flora (ETFLORA) Project, Research Department, Fairchild Tropical
Garden and Hong Liu, Florida International University
Last Updated: 9 June 2003 (Liu and Muir)
Hong Liu
Background and Current Status
Range-wide distribution – past and present
{CONFIDENTIAL}
Population and reproductive biology/life history
Annual/Perennial: Perennial
Habit: Herb
Average Life Span: Lifespan may be up to 5 years.
Pollinators: Xylocopa micans and Melissodes spp., three bee species that successfully
perform buzz pollination, a specialized type of pollination (Liu and Koptur, 2003).
Flowering Period: May-August
Fruiting: June-September
Annual variability in Flowering: Flowers may appear out of season if a recent fire has
burned the habitat (Liu, personal observation).
Growth Period: Year-round; growth is more active in the summer.
Dispersal: Seeds are released by poricidal dehiscence; there are no known dispersers.
Seed Maturation Period: 1 month
Seed Production: 0-13 seeds per fruit
Seed Viability: Greenhouse experiments have shown up to 90% germination; a very
small percentage of seeds will remain viable up to 2 years in the wild population (Liu,
2003).
Regularity of Establishment: Establishment of seedlings can be found throughout the
year, with the majority of seedlings established in the fall immediately following seed
dispersal (Liu, personal observations).
Germination Requirements: There are no specific germination requirements except
for the addition of water (Liu, unpublished data).
Establishment Requirements: Plants are most likely found in canopy openings; plants
are also capable of colonizing disturbed areas (i.e. dirt roads in pineland habitat) where
they can flower, set fruit, and disperse prolifically.
Population Size: There are approximately 10,000 adult (reproducing) individuals. The
entire population (including seedlings) is significantly larger.
Annual Variation: Fires usually reduce population size, but populations increase
rapidly during the 5-7 years post-fire. Net population growth rate will drop below zero
for populations that have not been burned for more than 10 years resulting in a slow
decline of population size (Liu and Koptur, 2003).
Number and Distribution of Populations: {CONFIDENTIAL}
Habitat description and ecology
Type: PINE ROCKLAND Open areas in the uplands of the pine rockland.
Physical Features:
Soil: This species has been observed not to persist in damp soil (Liu, personal
observation).
Elevation: This species will not persist in depressions (Liu, personal
observation).
Aspect: Not a significant factor
Slope: Not a significant factor
Moisture: This species prefers dry to moderate moisture levels (Liu, personal
observation).
Light: Full to partial shade. This species is very shade intolerant; it cannot
persist in a habitat with greater than 70% canopy cover (Liu, unpublished data).
Biotic Features:
Community: Often associated with Centrosema virginianum, Galactia
parvifolia, Linum arenicola, Melanthera parvifolia, Polygala grandiflora,
Thrinax morrissii, Tragia saxicola
Interactions:
Competition: Unknown
Mutualism: Nitrogen-fixing root nodule bacteria, pollinating bee species
.
Mycorrhizae Association: Unknown
Parasitism: None
Host: None
Other:
Animal use: None
Natural Disturbance:
Fire: C. lineata var. keyensis depends upon fire to create sunny openings
in the pine rockland landscape; in the post-fire environment, it can take
advantage of more light and less competition. Performance is best after
fires in the early summer or winter and the ideal frequency of fires is
every 7 years (Liu, 2003).
Hurricane: Unknown
Slope Movement: Unknown
Small Scale (i.e. Animal Digging): Unknown
Temperature: Unknown
Protection and management
Summary: {CONFIDENTIAL}
Availability of source for outplanting: {CONFIDENTIAL}
Availability of habitat for outplanting: {CONFIDENTIAL}
Threats/limiting factors
Natural:
Herbivory: A leaf-tying insect has been observed (Liu, personal observation).
Disease: unknown
Predators: Two unidentified seed predators have been observed (Liu, personal
observation).
Succession: This species is an early to mid successional herb, however seeds are
able to germinate in later successional stands (Liu, 2003).
Weed invasion: The non-native invasive tree Schinus terebinthifolius poses a
threat to the integrity of the natural areas where this species grows.
Fire: Although this species is fire dependent, fires occurring too frequently
(more than every 4-7 years) can have adverse effects (Liu, 2003).
Genetic: The remaining population suffers from inbreeding depression, e.g.
reduced seed set and seed germination if self-pollination occurs.
Anthropogenic
On site: Fire suppression is the most immediate threat to C. lineata var. keyensis
and to its remaining habitat. Because this population exists in an urban-wildland
interface, it is very difficult to gain support for prescribed fires. Without more
frequent burns, succession will transform remaining pine rocklands into
hardwood hammocks, making habitat loss another significant threat.
Another possible anthropogenic threat to this species is the insecticide currently
sprayed over its range to control the mosquito populations. Currently, an aerial
insecticide (1,2-dibromo-2,2-dichloroethyl dimethyl phosphate) and ground
insecticide (Permethrin) are applied sometimes as frequently as daily. This
management practice is targeted toward mosquitoes, but if used without caution,
it may adversely affect the bees that pollinate C. lineata var. keyensis.
Off site: If urbanization continues to expand over C. lineata var. keyensis’
range, remaining pine rockland habitat may be lost. As well, off-site sea-level
rise and salt-water intrusion may soon threaten this rare species that is suited to
upland conditions.
Conservation measures and actions required
Research history:
From 1998 to 2003, Hong Liu has been conducting population viability analyses
on Chamaecrista lineata var. keyensis as her dissertation work (Liu, 2003). In her
dissertation, she studied the effects of an urban-wildland interface on the breeding
system and pollination of C. lineata var. keyensis (Liu and Koptur, 2003). She found
that this species was self-compatible, but relied on bees, particularly those capable of
buzz pollination (Xylocopa micans and Mellisodes spp.), for seed set. In addition, the
population of C. lineata var. keyensis in more urban habitat was seen to suffer higher
seed predation and therefore set fewer seeds than the pineland interior population.
Furthermore, the aerial mosquito spray might have a negative impact on populations of
Mellisodes spp., one of the two effective pollinators of C. lineata var. keyensis on Site
65.
Liu’s dissertation research focused mainly on the effects of fire at different times
of the year, summer (wet) vs. winter (dry). She found that the C. lineata var. keyensis
population recovered faster after winter burns and early summer burns (May-June) than
after late summer burns (July-September). In addition, C. lineata var. keyensis
population had lower extinction risk and population decline probability if burned in the
winter than in the late summer. A fire frequency of more or less 7 years would sustain
the lowest extinction probability for C. lineata var. keyensis. Finally, she concluded that
a fire management regime including a wide range of burning season may be essential
for the continued existence of C. lineata var. keyensis and other endemic species of pine
rockland on Site 65.
Liu has also studied several other aspects of C lineata var. keyensis ecology,
such as the microhabitat requirements, and the effects of key deer and insect herbivory
on population dynamics. These studies will be published separately in peer-reviewed
journals. In addition to ecological work, Liu has conducted some preliminary trials to
quantify the genetic diversity of C. keyensis using allozymes and RAPDs.
Significance/Potential for anthropogenic use: Unknown
Recovery objectives and criteria: There are no existing official objectives to augment
this C. lineata var. keyensis population. The present objective is to emphasize protection
and preservation of the intact pine rockland on federal, state, and private properties
upon which this species occurs. The remnant population is already very fragmented,
therefore maintaining or increasing its current state of cohesiveness is a priority.
Management options:
Prescribed Burns
It has been proven that without regularly occurring fires, suitable open pine rockland
habitat for C. lineata var. keyensis becomes overgrown and will no longer support this
rare species. Therefore, an ideal management option for this species would be to
simulate the natural fire disturbance regime with prescribed burns every 7-10 years.
Based on its phenology, it has been found that C. lineata var. keyensis responds best
after early summer or winter burns; however, an ecosystem approach to management
would consider the phenology of all native species and conduct burns on a rotation
cycle at different times of the year. In comparison to other management techniques,
prescribed burns are relatively low in cost. However, prescribed burns can be difficult
to implement, especially in an area close to residential buildings with fire codes
Fire Analogues
Due to the aforementioned reasons against the feasibility of prescribed burns, fire
analogues should be considered as another management option. These analogues, such
as limb cutting or selective thinning, may serve to open the canopy and reestablish the
conditions necessary for the existence of C. lineata var. keyensis. The response of C.
lineata var. keyensis to these fire alternatives is unknown and should be researched.
Limiting Insecticide
It is possible that the frequency of aerial mosquito spraying (i.e. at least every other
day) may negatively affect the existing buzz-pollinating bee populations and thereby the
number of pollination visits to C. lineata var. keyensis.
Outplanting
Although the existing population covers a large area, it is very fragmented and
vulnerable to chance events that may lead to extinction. Therefore, outplantings to other
locations, such as other neighboring islands of the Lower Florida Keys would be
favorable. These sites would have to be made suitable for the outplanting by restoration
and management. Moreover, propagation methods would need to be established to
prepare seeds or plants for outplanting.
Removal of non-native invasives
Brazilian pepper (Schinus terebinthifolius) has been observed in some of the pine
rockland habitat on Site 65. This non-native species is known to extirpate native species
by allelopathy and competition. At the present, this non-native invasive is not a critical
problem, however, its seeds are dispersed by native and non-native bird species so its
range may soon encroach upon the C. lineata var. keyensis population.
Maintain current management
At present, there is no active management in place. Taking no action may increase this
species’ rate of extinction. C. lineata var. keyensis requires management intervention,
especially to thwart the encroachment of hardwood species into its habitat and to protect
against chance extinction events.
Next Steps:
Clarify the taxonomic state of C. lineata var. keyensis in relation to C. lineata var.
lineata and other varieties of the species complex (to begin 2004)
Research the genetic diversity that exists in the wild population
Develop successful horticultural methods
Prepare other pine rockland sites for outplantings
Research the effects of fire analogues
Collaborate with the Mosquito Control District of Monroe County to reduce the
frequency of insecticide application
Incorporate prescribed burns into the management of the natural areas in the range of C.
lineata var. keyensis.
References
Gann, G.D., K.A. Bradley, S.W. Woodmansee, 2002. Rare Plants of South Florida:
Their History, Conservation, and Restoration. Institute for Regional Conservation,
Miami.
Irwin, H.S. and R.C. Barenby. 1982. The American Cassiinae, a synoptical revision of
Leguminosae, tribe Cassieae, subtribe Cassiinae in the New World. Memoirs of the New
York Botanical Garden 35:1-918.
Liu, H. 2003. Population viability analysis of Chamaecrista keyensis, a narrowly
endemic herb of the Lower Florida Keys. Ph.D. Dissertation. Florida International
University.
Liu, H., S. Koptur. 2003. Breeding System and Pollination of a Narrowly Endemic Herb
of the Lower Florida Keys: Impacts of the Urban Wildland Interface. American Journal
of Botany. 90(8) (no. pages to be determined).
Ross, M. S., and P. Ruiz. 1996. A study of the distribution of several South Florida
endemic plants in the Florida Keys. Report to the USFWS. Florida International
University, Southeast Environmental Research Program, Miami, Florida, USA.
Ward, D. (Editor) 1979. Rare and Endangered Biota of Florida. Volume 5, Plants.
University Presses of Florida, Gainesville.