Sandlace

Polygonella myriophylla

Description

Sandlace, Polygonella myriophylla, is a sprawling shrub with reddish-brown bark that looks somewhat like the ornamental creeping juniper (Juniperus horizontalis ). Its many branches zigzag along the ground and root at the nodes, forming low mats. The lower parts of the creeping branches have bark that cracks and partly separates in long, flat, interlacing strips. The short lateral branches end in flowering racemes. Sandlace has the sheathing leaf stipules (ocreae and ocreolae) typical of the jointweed family. The leaves are needlelike and are 0.01-0.4 in (0.3-10 mm) in length. The small, white or cream-colored flowers have white petal-like sepals up to 0.13 in (3.4 mm) long.

This species reproduces sexually and asexually. Pollinators of sandlace include small halictid bees (Perdita polygonellae ), a genus-specific pollinator. Pollinators of another Polygonella include Eumenidae wasps and Glagellula spp. and may also be responsible for pollination of sandlace. The species also reproduces by suckering and/or adventitious rooting of decumbent stems. Information on seed production and germination is not available for this species. It is known, however, that because of the allelopathic effects of this species, seedlings do not survive in the vicinity of mature plants.

Habitat

This low, spreading shrub thrives in areas of bare white or yellow sand created by moderate disturbance. It is not known whether regular fires are needed to maintain bare sand habitat for this species or whether the allelopathic nature of the species creates and maintains sufficient bare sand for the species to persist. Where found, sandlace is a dominant part of the groundcover vegetation in young scrubs. In many localities, however, the herbaceous layer is poorly developed because of the xeric conditions. The shrub layer of this habitat is dominated by oaks and ericaceous plants. Any overstory trees are usually widely spaced, forming an open canopy.

Distribution

Sandlace occurs within scrub habitats that covered about 24,700 acres (10,000 hectares) in the late 1980s. It is found in three sites in western Orange County where it occurs with the endangered scrub lupine and at one site in Osceola County near Interstate 4. In Polk County sandlace is found on the Lake Wales Ridge from the Davenport-Poinciana area south to the Highlands County line. It is absent from the southern tip of the Lake Wales Ridge. It is also found well west of the Lake Wales Ridge in a highly altered area just southeast of Bartow. In Highlands County, sandlace is found on the Lake Wales Ridge south to Archbold Biological Station.

Threats

Sandlace was known from about 119 scrubs as of the late 1980s. These habitats covered about 24,700 acres (10,000 hectares) of scrub habitat along the Central Florida Ridge. Like most other endemic plants, habitat for this species is being acquired for conservation purposes. Unfortunately, only a small fraction of remaining habitat will be preserved with the limited conservation funds available. About 15 sites are protected or will be protected through acquisition, conservation, and management. These sites represent a small fraction of the historic numbers and range of this species. By the late 1990s, sandlace probably occupied 300-475 scrub sites. Protection of 15 sites, therefore, represented conservation of only 4% of the sites that historically contained sandlace.

Conservation and Recovery

Sandlace persists in scrub habitats with substantial bare ground. These patchy habitats are commonly found after intense fires in sandpine scrub. This habitat condition is also common within rosemary scrub due to extreme xeric conditions and allelopathic features of several species that limit vegetative growth. Persistent, patchy, open sands are not prevalent in oak dominated scrubs, since fires are more frequent and less devastating.

Management for sandlace will probably require development of long-term burning regimes that mimic the 50-100 year natural fire cycles of sand-pine/rosemary scrub and rosemary balds. The interaction of allelopathic affects and fire frequency needs to be investigated. If allelopathic affects are sufficient to maintain open sand patches in some areas, fire may not be necessary as a management tool. The effects of fire timing and intensity on other scrub endemics, however, should be considered before excluding fire.

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

References

Christman, S. 1988. "Endemism and Florida's Interior Sand Pine Scrub." Final project report, Project No. GFC-84-101. Submitted to Florida Game and Fresh Water Fish Commission, Tallahassee, Florida.

Christman, S., and W. S. Judd. 1990. "Notes on Plants Endemic to Florida Scrub." Florida Scientist 53: 52-73.

Hawkes, C. V. and E. S. Menges. 1995. "Density and Seed Production of a Florida Endemic, Polygonella basiramia, in Relation to Time since Fire and Open Sand." American Midland Naturalist 133: 138-148.

Lewis, P. O., and D. J. Crawford. 1995. "Pleistocene Refugium Endemics Exhibit Greater Allozymic Diversity than Widespread Congeners in the Genus Polygonella (Polygonaceae)." American Journal of Botany 82: 141-149.

Small, J. K. 1924. "Plant Novelties from Florida." Bulletin of the Torrey Botantical Club 51: 379-393.

U. S. Fish and Wildlife Service. 1996. "Recovery Plan for 19 Central Florida Scrub and High Pineland Plants (Revised)." U. S. Fish and Wildlife Service, Atlanta.