Santa Cruz Island Bushmallow

Malacothamnus fasciculatus var. nesioticus

Description

Malacothamnus fasciculatus var. nesioticus (Santa Cruz Island bushmallow) was described in 1897 as Malvastrum nesioticum from material collected in 1886. The plant has had a complicated taxonomical history, being assigned to several different genera. In 1910 it was named Malacothamnus nesioticus ; and again renamed, in 1925, Sphaeralcea nesiotica. In 1936 it became Sphaeralcea fasciculata var. nesiotica ; and in 1951 it was referred to as Malvastrum fasciculatum var. nesioticum. The same year the combination Malacothamnus fasciculatus var. nesioticus was published. In 1993, var. nesioticus was not recognized as being distinct, noting that Malacothamnus fasciculatus is a highly variable species "with many indistinct and intergrading local forms."

It was noted var. nesioticus was essentially indistinguishable from the mainland var. nuttallii. However, later studies on the genetics of Malacothamnus have determined that var. nesioticus is a distinct variety, and it is recognized as such in the Flora of Santa Cruz Island.

Malacothamnus fasciculatus var. nesioticus is a small soft-woody shrub in the mallow (Malvaceae) family. The plant reaches up to 2 m (6 ft) tall, and has slender branches covered with star-shaped hairs. The palmately shaped leaves are dark green on the upper surface and gray on the lower surface. The rose-colored flowers are up to 3.75 cm (1.5 in) broad and scattered along the ends of the branches. It is differentiated from the mainland var. nuttallii by its bicolored leaves and genetic distinction.

Habitat

The Santa Cruz Island bushmallow inhabits the coastal sage scrub community on Santa Cruz Island, offshore of southern California.

Distribution

Malacothamnus fasciculatus var. nesioticus was already very uncommon around 1900 when Greene wrote that the plant was "rare; only two bushes seen, and these under the protection of large opuntias; perhaps thus kept from the sheep". Malacothanmus fasciculatus var. nesioticus is currently known from two small populations on Santa Cruz Island, where it occurs within a coastal sage scrub community. One population of less than 50 individuals (10 clones) is located on the west shore of the island near the historic Christy Ranch. The second population was discovered in 1993 in the Central Valley near the University of California Field Station. Subsequent genetic analyses of the Central Valley population indicated that, although there are 19 individual shrubs, they consist of only three genotypes or three clones.

Threats

Malacothamnus fasciculatus var. nesioticus is threatened by soil loss, habitat alteration, and feral pig rooting.

The soil from around the roots of Malacothamnus fasciculatus ssp. nesioticus on Santa Cruz Island is actively eroding.

The collection of whole plants or reproductive parts of Malacothamnus fasciculatus var. nesioticus could adversely affect the genetic viability and survival of this taxa.

Conservation and Recovery

The Santa Cruz Island bushmallow only survives as a perilously small population of about 70 shrubs (but representing only 13 genotypes). Although its habitat is being protected from development, the rare shrub is still severely threatened by soil loss, the feeding of feral pigs, and habitat alteration by invasive alien plants and other causes. The western 90% of Santa Cruz Island is owned and managed by The Nature Conservancy, a private environmental organization, and the other 10% is federal land managed by the National Parks Service. The survival of this endangered plant requires strict protection from the feeding of herbivorous mammals. This could be done by securely fencing the plants, or by eradicating the mammals from its critical habitat. The abundance of competing non-native plants must also be managed. The populations of the Santa Cruz Island bushmallow should be monitored, and research undertaken into its basic biology and ecological requirements. It should be propagated in captivity to produce stock for out-planting to supplement the tiny wild population, and to establish new populations in suitable habitat.

Contact

U.S. Fish and Wildlife Service
Ventura Fish and Wildlife Office
2493 Portola Road, Suite B
Ventura, California 93003-7726
Telephone (805) 644-1766

Reference

U.S. Fish and Wildlife Service. 31 July 1997. "Endangered and Threatened Wildlife and Plants; Final Rule for 13 Plant Taxa From the Northern Channel Islands, California." Federal Register 62 (147): 40954-40974.