Spring Creek Bladderpod

Lesquerella perforata

Description

Spring Creek bladderpod, Lesquerella perforata, is a winter annual that is 8-16 in (20-40 cm) tall. Its auriculate leaves are oblong to ovate in shape. The flowers have petals that are 0.3 to 0.4 in (7-10 mm) long and are white to lavender in color. It has a broadly ovoid-shaped fruit that is hairless on the outside and densely pubescent on the inside. An internal partition between the two halves of the fruit is "perforated" or missing.

Spring Creek bladderpod is a winter annual that germinates in early fall, over-winters as small rosettes of leaves, and flowers the following spring. Flowering usually occurs in March and April. Soon after, the flowers wither, the fruits mature, and the plants die. The fruits split open and the enclosed seeds fall to the ground and lay dormant until the fall, when the cycle starts over again. If conditions are not suitable for germination the following fall, the seeds can remain dormant, though viable, for several years.

Habitat

This species is typically found growing on flood plains. It requires annual disturbance in order to complete its life cycle. Historically, this disturbance was probably provided by periodic flooding of the streams along which it occurs. This flooding is thought to have removed the perennial grasses and woody plants that quickly invade the flood plains without regular natural or artificial disturbances. Cultivation of annual crops like corn provides an excellent means of artificially maintaining the habitat, provided there is no fall plowing and herbicide use is limited. No-till farming techniques are believed to adversely affect the species because of the extensive use of herbicides required to successfully implement the technique. Row-crop cultivation, which avoids the use of fall plowing and delays spring plowing until the majority of the plants have set fruit, does not seem to adversely affect the species.

Distribution

Spring Creek bladderpod is known from four populations consisting of 13 extant sites in Wilson County, in the vicinity of Lebanon, Tennessee. Three additional sites no longer support the species. One of the extant populations occurs along Spring Creek and consists of five groups of plants. Another, consisting of four groups of plants, is found along Lower Bartons Creek. Two sites are located farther upstream and are designated the Middle Bartons Creek population. The fourth population consists of two sites and is located along a tributary of Bartons Creek. All of the known sites for the species are found within a few miles of each other. With only one exception, sites are within the flood plains of Spring and Bartons Creeks or within the floodplain of a Bartons Creek tributary. The only non-flood-plain location is within a gladey area slightly above the floodplain of Spring Creek. All of the known sites supporting L. perforata are privately owned, and none are protected through cooperative management agreements with the State of Tennessee or the U. S. Fish and Wildlife Service.

Sites 1-5 are in Spring Creek. Site 1 is the largest known site for the species (population here is 100,000+), and it is also the L. perforata type locality. Site 2 is a small field and its population is about 500, and Site 3's population is between 25,000 and 50,000. Site 4 is a swath measuring 90 ft (27 m) long and 43 ft (13 m) wide, and its population is 1,000-5,000. Site 5, the only non-floodplain location for the species, is a triangular-shaped glade that is about 150 ft (46 m) long and 100 ft (30 m) wide at its widest point, and its population is between 500 and 1,000 individuals. This last site was discovered during 1992 field work to update the status of L. perforata.

Sites 6 through 9 occur in the Lower Bartons Creek population. Site 6 numbers about 1,000 plants. Site 7 is a small location that supported two 30-ft by 5-ft (9-m by 1.5-m) clumps of this taxon in 1992. Site 8 supports only a few plants, while Site 9 is a medium-sized location that supports about 10,000 plants.

Sites 10 and 11 occur in the Middle Bartons Creek population; the first being a small tract in an industrialized area near Lebanon that supports about 600 plants, and the latter being an area near site 10 that supports a larger colony of about 5,000 plants.

Sites 12 and 13 occur in the Bartons Creek Tributary population. Site 12, a group of about 450 plants, is located along 1,000 ft (305 m) of the flood-plain of an ephemeral tributary of Bartons Creek. Site 13 is a small area located near site 12, so overgrown with dense herbaceous growth that it contained only a few individuals in 1992.

Threats

The primary threat to Spring Creek bladderpod, known only from a limited area within Tennessee's Central Basin, is direct destruction of habitat for commercial, residential, or industrial development. The other significant threats to this species, also directly related to habitat alteration, are the conversion of land to uses other than cultivation of annual crops, conversion of its limited habitat to pasture, habitat encroachment by woody vegetation and herbaceous perennials, and livestock grazing.

Residential, business, or industrial construction directly removes Spring Creek bladderpod habitat, thereby causing extirpation of the plants that occurred in the newly developed areas, and it can also indirectly damage populations of this taxon by creating an environment ripe for alien plant succession. As the degraded habitat becomes less conducive to Spring Creek bladderpod, it becomes more congenial to invasive plants, the most competitive of which will usurp the territorial position formerly held by L. perforata. Most of the known locations for this species are threatened by the encroachment of more aggressive herbaceous vegetation and woody plants, some induced by the aforementioned development and some by the loss of the controlling factor of natural flood regimes.

The habitat for this species has historically been maintained by periodic flooding; now annual crop production is apparently the primary mechanism by which essential habitat is kept suitable for L. perforata. Conversion of sites to pasture or other uses that maintain a perennial cover crop are a significant threat. In order for this annual plant to complete its life cycle each year, it is essential that the sites not be plowed or disked after the seeds have germinated in the fall and that spring plowing and planting be delayed until the plants have matured in the spring. This requirement is easily met through the production of crops such as corn, provided that traditional cultivation methods are used. The use of no-till cultivation techniques does not appear to maintain L. perforata habitat, probably because the soil is not physically disturbed using this technique and that it relies so heavily upon the liberal use of herbicides.

There is little or no commercial trade in Spring Creek bladderpod at this time. Many of the populations are very small and cannot support the collection of plants for scientific or horticultural purposes. Inappropriate collecting for scientific purposes or as a novelty would definitely threaten this species.

Conservation and Recovery

The Spring Creek bladderpod only survives in four populations consisting of 13 sites. All of the known sites are privately owned and are potentially at risk from conversion to other land-uses or other threats. These critical habitats should be protected. This could be done by acquiring the habitats and establishing ecological reserves, or by negotiating conservation easements with the landowners. The populations of the Spring Creek bladderpod should be monitored, and studies made of its habitat needs.

Contacts

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

Asheville Field Office
U.S. Fish and Wildlife Service
160 Zillicoa Street, Asheville, NC 28801-1082
Telephone: (828) 258-3939
Fax: (828) 258-5330

References

Baskin, J. M., and C. C. Baskin. 1990. "Seed Germination Biology of the Narrowly Endemic Species Lesquerella stonensis (Brassicaceae)." Plant Species Biology 5: 205-213.

Kral, R. 1983. "A Report on Some Rare, Threatened, or Endangered Forest-related Vascular Plants of the South." USDA, Forest Service Technical Publication R8-TP2, Vol. 1. 718 pp.

Rollins, R. C. 1952. "Some Crucifers of the Nashville Basin, Tennessee." Rhodora 54:182-192.

Rollins, R. C. 1955. "The Auriculate-leaved Species of Lesquerella (Cruciferae)." Rhodora 57:241-264.

Somers, P., A. Shea, and A. McKerrow. 1993. "Status Survey Report on Lesquerella perforata Rollins (Spring Creek Bladderpod)." Unpublished report to the Asheville Field Office, U. S. Fish and Wildlife Service, Asheville, NC. 81 pp.

U. S. Fish and Wildlife Service. 23 December 1996. "Determination of Endangered Status for Lesquerella perforata (Spring Creek Bladderpod)." Federal Register 61 (247):67493-67497.