Overview

Comprehensive Description

Dicerandra frutescens grows in dry, sandy soils where physical disturbances have created gaps in the canopy (Menges et al. 2006: 1992, 1999).

Dicerandra frutescens generates monoterpenes such as pulegone that may prevent herbivory (Smedley et al. 1990: 156, 158). The larval stage of the moth Pyrausta panopealis can ingest the leaves despite the presence of the compound (Smedley et al. 1990: 158). The moth may produce enzymes that can neutralize its effects (Smedley et al. 1990: 158). The larva applies regurgitated droplets of the consumed leaf on their silken enclosures to take advantage of its anti-insectan properties (Smedley, et al. 1990: 158-9).

Dicerandra frutescens requires physical disturbance such as fire to create gaps in the canopy layer (Menges et al. 2006: 121). At Archbold Biological Station in Highlands County, Florida, extinction risks are predicted to be minimal when fires occurred every 6-12 years (Menges et al. 2006: 121, 127). Without this relatively frequent burning there is a risk that the open, sunlit habitats favorable to D. frutescens will be dominated by shrubs that will close these critical gaps (Menges, et al., 2006: 123). Controlled-burns were recommended (previous burns were done once every 15-100 years) to minimize potential for extinction of D.fructescens populations (Menges et al. 2006: 125).

References

Menges, E. S., Quintanan Asencio, P. F., Weekley, Carl W. & Gaouge, O. G. 2006. Population viability analysis and fire return intervals for an endemic Florida scrub mint. Biological Conservation 127: 115-127.

Smedley, S. R., McCormick, K. D. & Eisner, T. 1990. Interaction of Pyrausta Panopealis (Pyralidae) with a newly-reported host, the endangered mint Dicerandra fructescens (Labiatae). Journal of the Lepidopterists’ Society 44:156-172.

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Distribution

National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

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Global Range: Dicerandra frutescens is endemic to a very limited portion of the Lake Wales Ridge in Highlands County, Florida, and is found at four localities. The mint occurs at Archbold Biological Station; in the Sun 'n' Lakes Estates subdivision east of US highway 27 and southeast of the town of Lake Placid; at YMCA Camp Florida on the west side of Grassy Lake southeast of the town of Lake Placid; and on a sand ridge along the northwest shore of Lake Placid. All four of these areas are native vegetation which are surrounded by agricultural and residential areas.

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Historic Range:
U.S.A. (FL)

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Physical Description

Diagnostic Description

The most striking feature of this plant, upon first encountering it in the field, is the very powerful minty odor with which it releases into the surrounding atmosphere. The crushed plant is even more strongly aromatic. The source of this odor appears to be the small glands with which the foliage and parts of the flower are covered.

Four species of Dicerandra are perennial and shrubby. This taxon differs from D. immaculata in its denser growth, its narrower and fleshier leaves, its purple-dotted (rather than spotless) corollas and its smooth (rather than minutely puberulent) anther horns. Differs from D. christmanii in corolla color (white to pink, vs. cream), anther color (purplish yellow, vs. bright yellow), and odor (peppermint, vs. mint-camphor). Distinguished from D. cornutissima by wider leaves, flower color (purple-rose in D. cornutissima), style hairy (vs. naked or with a few hairs), and anther appendage usually less than 1 mm long (vs. usually more). Moreover, the species are allopatric. (USFWS 1987, Paradiso & Martin 1985, Wunderlin 1982, Martin 1989)

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Ecology

Habitat

Comments: SUMMARY: Well-drained soils of scrub or sandhill vegetation. Locally abundant in and around the sand pine-evergreen oak scrub, where it may occur in the low shrub layer or in open stands, clearings, or adjacent sandy places. END SUMMARY. The tree layer is comprised of Pinus clausa. The shrub layer is comprised of Persea humilus, Carya floridana, Quercus chapmanii, and Q. geminata. Widely spaced species like Asimina obovata, Bumelia tenax, Ceratiola ericoides, Palafoxia feayi, Sabal etonia, and Ximenia americana also occur in the shrub layer. The herbaceous layer may include various bunchgrasses in the genera Panicum, Andropogon, and Aristida, and other species adapted to xeric soils such as Lechea deckertii, Nolina brittoniana, Polygonella myriophylla, Liatris tenuifolia, Paronychia patula, Petalostemun feayi, Galactia volubilis, and Sisyrinchium solstitiale.

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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 1 - 5

Comments: Eleven occurrences recorded as of 10/90.

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General Ecology

Dicerandra frutescens is locally abundant in and around the sand pine evergreen oak scrub, where it may occur in the low shrub layer or in open stands, clearings, or adjacent sandy places. The tree layer is comprised of Pinus clausa. The shrub layer is comprised of Persea humilus, Carya floridana, Quercus chapmanii, and Q. geminata. Widely spaced species like Asimina obovata, Bumelia tenax, Ceratiola ericoides, Palafoxia feayi, Sabal etonia, and Ximenia americana also occur in the shrub layer. The herbaceous layer may include various bunchgrasses in the genera Panicum, Andropogon, and Aristida, and other species adapted to xeric soils such as Lechea deckertii, Nolina brittoniana, Polygonella myriophylla, Liatris tenuifolia, Paronychia patula, Petalostemun feayi, Galactia volubilis, and Sisyrinchium solstitiale.

Clear-cutting of the sand pine overstory affects the species favorably, as probably does fire, as both remove shade and competing vegetation. The fact that plants are often abundant along plowed firelanes, fencerows, and roadbanks, is an indication that it spreads readily into such exposed sites. It is not, however, found in areas cleared for pasture, or areas in which wholesale site preparation has taken place.

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Life History and Behavior

Life Cycle

Persistence: PERENNIAL

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Reproduction

D. frutescens reproduces entirely by seed and insects must trigger the spurred anthers in order for pollen to be released (Huck 1984).

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Conservation

Conservation Status

National NatureServe Conservation Status

United States

Rounded National Status Rank: N1 - Critically Imperiled

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NatureServe Conservation Status

Rounded Global Status Rank: G1 - Critically Imperiled

Reasons: A very narrow Florida endemic. The Florida Natural Areas Inventory contains 12 occurrence records in its database. The species is threatened by rapid residential, commercial, and agricultural development on and around the Central Ridge.

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Current Listing Status Summary

Status: Endangered
Date Listed: 11/01/1985
Lead Region:   Southeast Region (Region 4) 
Where Listed:


Population detail:

Listing status: E

For most current information and documents related to the conservation status and management of Dicerandra frutescens, see its USFWS Species Profile

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Dicerandra frutescens is listed as federally endangered and endemic to central Florida (Smedley et al. 1990: 156).

References

Smedley, S. R., McCormick, K. D. & Eisner, T. 1990. Interaction of Pyrausta Panopealis (Pyralidae) with a newly-reported host, the endangered mint Dicerandra fructescens (Labiatae). Journal of the Lepidopterists’ Society 44:156-172.

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Global Short Term Trend: Relatively stable (=10% change)

Comments: The populations at the Archbold Biological station seem to be stable and are not decreasing, but the status of populations can change rapidly.

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Threats

Comments: The destruction of remaining habitat is the primary threat to the existence of the remaining mints. In Highlands County, 74.4 percent of the xeric vegetation (scrubs, scrubby flatwoods, and sandhills) present before settlement had been destroyed or disturbed by 1981. This is due to the development of residential subdivisions and citrus groves (Peroni and Abrahamson 1985). The species thrives on bare open sand, but also is found in moderate shade. The pollinators, however, which are necessary for reproduction, are attracted to open, sunny sites (Huck pers. comm. to USFWS 1986). There is no apparent disease or predation threatening the species.

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Management

Restoration Potential: The USFWS has determined that recovery and delisting could be considered for the species if 20 separate, self-sustaining populations are established at secure sites in Florida. These numerical goals are subject to change based on new information gathered during the recovery process.

From root cuttings, a nursery in Aiken, S.C. has successfully propagated D. frutescens (R. McCartney pers. comm. to USFWS 1986). This is very important in that new populations may be introduced to sites where D. frutescens previously occurred.

Preserve Selection and Design Considerations: Dicerandra frutescens is protected at the Archbold Biological Station where it is most abundant on the edges of fire lanes. Two privately owned sites are highly vulnerable to development; they sites should be preserved in order to protect the existing populations of D. frutescens.

Management Requirements: Clear-cutting of the sand pine overstory affects the species favorably, as probably does fire, as both remove shade and competing vegetation. The fact that plants are often abundant along plowed firelanes, fence-rows, and roadbanks, is an indication that it spreads readily into such exposed sites. It is not, however, found in areas cleared for pasture, or areas in which wholesale site preparation has taken place.

The existing sites where D. frutescens occurs must be protected and managed in order to initiate recovery. Access to the habitat where the species occurs must be controlled. Access to pedestrians and\or off road vehicles must be prevented or limited where feasible. Destruction of scrub vegetation, trash dumping, or site disturbance should be prevented. On road right-of-way, mowing should be deferred until after flowering and seed set. The protected sites must be monitored for tree and shrub encroachment. Prescribed burning, cutting, or bush hogging may be necessary to prevent such encroachment. Fire should be the primary management tool used since the sandhill and scrub habitats are fire maintained. Educational and consulting support in the form of written materials should be provided to landowners that are interested in protecting sites. Dormancy testing of seeds is needed to determine whether storage is feasible. New populations should be established from plants propagated from seeds or cuttings in protected sites that contain the historic ranges of the species.

Management Programs: The USFWS for the Southeast Region located in Atlanta, Georgia has prepared a recovery program which has provided the information stated in management procedures.

Monitoring Programs: The USFWS office located in Jacksonville, Florida should be contacted to discuss any monitoring programs which are in effect.

Management Research Needs: The need for localized soil disturbance and\or fire should be documented.

Biological Research Needs: Investigate plants relations to fire and disturbance.

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Relevance to Humans and Ecosystems

Risks

Stewardship Overview:

1. Locate and preserve habitats where Dicerandra frutescens exists.

2. Implement management program proposals at each site, especially the management of the species via fire.

3. Initiate new populations of D. frutescens at sites where it formerly occurred.

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Wikipedia

Dicerandra frutescens

Dicerandra frutescens is a rare species of flowering plant in the mint family known by the common names scrub mint and scrub balm. It is endemic to Highlands County, Florida, where it is known only from the Lake Wales Ridge. Its habitat is quickly being lost as it is converted to residential and agricultural use. It was federally listed as an endangered species of the United States in 1985.[1]

This shrub grows about half a meter tall from a deep taproot. It is glandular and strongly aromatic with a mint scent. The oblong leaves are roughly 2 centimeters long, smooth-edged, oppositely arranged, and dotted with visible oil glands. The inflorescence is a pair of flowers each roughly 1.5 centimeters long. The flower has a tubular throat and a lobed, lipped mouth. The corolla is white to light pink and dotted with darker pink on the lips. The protruding stamens are tipped with tiny horned anthers.[1][2] Blooming occurs in August through October.[3] The flowers are pollinated by the bee-fly Exprosopa fasciata.[3]

A number of other Dicerandra have been separated from D. frutescens and elevated to species status, including Dicerandra cornutissima in 1981,[4] Dicerandra christmanii in 1989,[5] and Dicerandra modesta in 2008.[6]

This plant grows in endangered Florida scrub habitat on the botanically unique Lake Wales Ridge. It is estimated that 74.4% of the native habitat in this area was destroyed or altered by 1981, and the process continues today.[7] There are fourteen occurrences, and nine of them are located on private property that may be slated for development; their status is uncertain and some of them may have been destroyed. The scrub where the plant grows is yellow sand scrub dominated by either sand pine or a mix of oaks (Quercus spp.) and scrub hickory (Carya floridana), or both types.[3] This kind of habitat is maintained by periodic wildfire, a process which is required to clear large and woody vegetation and provide gaps that the smaller plants, including this species, require. Fire suppression is a threat to these species.[2]

There is little damage from disease or predation on the plants,[3] but one species of moth does use it as a larval host. The larva of Pyrausta panopealis is not disturbed by the aromatic oils that keep most other insects from consuming the plant.[8] Furthermore, the moth larva might protect itself from other insects by vomiting quantities of the irritating oil all over itself.[8]

References[edit source | edit]

  1. ^ a b USFWS. Determination of endangered status for two Florida mints. Federal Register November 1, 1985.
  2. ^ a b Dicerandra frutescens. Center for Plant Conservation.
  3. ^ a b c d USFWS. Dicerandra frutescens Five-year Review. August 2009.
  4. ^ Huck, R. B. (1981). Dicerandra cornutissima, a new woody Labiate from Florida. Phytologia 47:313-315.
  5. ^ Huck, R. B., et al. (1989). A new Dicerandra (Labiatae) from the Lake Wales Ridge of Florida, with a cladistic analysis and discussion of endemism. Systematic Botany 14:2 197-213.
  6. ^ Huck, R. B. (2008). Dicerandra modesta (Lamiaceae): Raise in rank for a disjunct perennial in a new coastal clade in Florida. Journal of the Botanical Research Institute of Texas 2:2 1163-4.
  7. ^ Dicerandra frutescens. The Nature Conservancy.
  8. ^ a b Smedley, S. R., et al. (1990). Interaction of Pyrausta panopealis (Pyralidae) with a newly reported host, the endangered mint Dicerandra frutescens (Labiatae). Journal of the Lepidopterists' Society 44(3) 156-62.
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