Little Amphianthus

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Little Amphianthus

Amphianthus pusillus

Status	Threatened
Listed	February 5, 1988
Family	Scrophulariaceae (Snapdragon)
Description	Tiny, ephemeral aquatic plant with long-stemmed, floating lance-shaped leaves.
Habitat	Granite outcrops, sandy-silty soils in rock-rimmed vernal pools.
Threats	Quarrying, recreational traffic, livestock grazing.
Range	Alabama, Georgia, South Carolina

Description

Little amphianthus, Amphianthus pusillus, is a diminutive fibrous-rooted, annual aquatic plant with both floating and submerged leaves. Submerged leaves are lance-shaped, less than 0.4 in (1 cm) in length, and appear to be arranged in a rosette at the base of the plant. The smaller ovate floating leaves are oppositely arranged and attached by long, delicate stems. White flowers occur in the axils of both types of leaves. Floating flowers open, but submerged flowers remain closed except when exposed to air. Leafing occurs December to January, budding in February, blooming in March or April, fruiting April to May, and seed dispersal May to June. Germination seems to be dependent on the presence of light and sufficient standing water or soil saturation.

Habitat

The species grows in shallow, flat-bottomed rock pools that retain a thin bottom deposit of sandy-silty soil. These seasonal pools are filled by winter and spring rains and dry up as the hot summer progresses. Such pools are characteristic of the flatrocks areas of the southeast, often extensive expanses of granite outcroppings that occur as large isolated domes or as gently rolling extrusions. A few populations of this species have been found in atypical habitats such as stream banks and seepage areas.

Other federally listed plants that occur in this habitat are black-spored quillwort (Isoetes melanospora ) and mat-forming quillwort (I. tegentiformans ).

Distribution

Little amphianthus was first collected in 1836 in present-day Rockdale County, Georgia. The species is historically known from the Piedmont region of Georgia, Alabama, and South Carolina.

Of 50 historic population sites in Georgia, 11 have been destroyed. Most remaining sites are limited to fewer than five closely grouped pools each; only six habitat areas are considered extensive, with 15-25 pools each. The number of individual plants in these pools range from as few as a dozen to as many as several thousand. Most pools contain several hundred plants when rainfall is adequate. Georgia counties with extensive populations are DeKalb, Greene, Heard, Hancock, and Columbia. Little amphianthus is found at three sites in South Carolina: Lancaster, Saluda, and York Counties.

Threats

Georgia's granite flatrocks are mined at a rate that makes this state the world's largest granite producer and destruction of outcrops is expected to continue unabated. Quarrying companies now own about 20% of the granite outcrops known to contain habitat pools for little amphianthus.

Outcrops are also popular as recreation sites, and many of the pools with little amphianthus populations have been damaged by vehicles, fire building, or trash dumping. Cattle drinking from the pools have caused damage both by trampling plants and by adding nutrients to the water. Changing the nutrient balance of the pools then favors the growth of other species.

Conservation and Recovery

Little amphianthus receives no protection under state laws in South Carolina or Alabama. A population is protected at Forty-Acre Rock Preserve in Lancaster County, South Carolina, owned by the South Carolina Wildlife and Marine Resources Department. The Nature Conservancy owns and manages Heggie's Rock Preserve in Columbia County, Georgia, which supports 10 pools with amphianthus populations.