Santa Cruz Island Malacothrix
Santa Cruz Island Malacothrix
|July 31, 1997
|An annual, herbaceous wildflower.
|Exposed coastal flats.
|Soil loss and disturbance by introduced mammalian herbivores, competition with invasive alien plants, and effects of nesting seabirds.
Malacothrix indecora (Santa Cruz Island malacothrix) was described in 1886 from specimens collected from "islets close to the northern shore" of Santa Cruz Island. The combination Malacothrix foliosa var. indecora was pubished in 1957. Subsequently the taxon was synonymized with Malacothrix foliosa. Later taxonomists continued to recognize the taxon as a separate species with the name Malacothrix indecora. The latter nomenclature was retained in the most recent treatment of the genus.
Malacothrix indecora is an annual herb in the aster (Asteraceae) family. The 8 to 16 in (20 to 40 cm) tall stems support numerous broadly lobed fleshy leaves with blunt tips. The greenish-yellow flowers are in hemispheric heads surrounded by linear bracts. Two other annual species of Malacothrix occur on the same islands as Malacothrix indecora ; however, the achenes (seeds) of Malacothrix similis are topped with 18 teeth and one bristle and Malacothrix squalida is topped with irregular teeth and no bristle, whereas Malacothrix indecora has neither of these features.
The Santa Cruz Island malacothrix occurs in exposed, naturally disturbed, coastal flats.
Historical collections of Malacothrix indecora were made from several locations on the northeast shore of San Miguel Island and on Prince Island off of the north shore of San Miguel Island. There were three populations observed in 1979. Researchers reported finding this species at one location during surveys in 1988 and 1989, but no collections were made to confirm identification of the taxon. Malacothrix indecorawas collected near Twin Harbor on Santa Cruz Island in 1939, but this population has not been relocated.
Malacothrix indecora is currently known from two populations. A population was discovered in 1980 at Black Point on the west end of Santa Cruz Island. Several hundred individuals were observed at this site by Junak in 1985 in exposed coastal flats, where it was associated with Santa Cruz Island buckwheat (Eriogonum grande var. rubescens ) and ice plant (Mesembryanthemum nodiflorum ). On a subsequent trip in 1989, only 50 plants were observed in the same location, and fewer than 100 plants in 1996. The second population of Malacothrix indecora, also comprised of fewer than 100 plants, was discovered on Santa Rosa Island in 1996 at the mouth of Lobo Canyon.
Malacothrix indecora is threatened by soil loss, habitat alteration and herbivory resulting from feral pig rooting, cattle grazing and trampling, and seabird activity. Historical habitat for Malacothrix indecora on San Miguel Island and Prince Island has been altered by seabird nesting activity.
A discovery, in the 1990s, of Malacothrix indecora on Santa Rosa Island included the observation that the prehistoric midden that the plants were growing on was being eroded from damage by livestock.
Seabirds occur in historic habitat for Malacothrix indecora on San Miguel Island and its offshore islet Prince Island. The nesting activities of these birds can disturb local plants and soils, promoting coastal cliff erosion and creating conditions conducive to alien plant invasion. The degree of harm they do to this taxa has not yet been determined.
The collection of whole plants or reproductive parts of Malacothrix indecora could adversely affect the genetic viability and survival of this taxa.
Conservation and Recovery
The Santa Cruz Island malacothrix survives only as tiny populations on the northeast shore of San Miguel Island, on nearby Prince Island, and on the west end of Santa Cruz Island. Although its habitat is being protected from development, the rare malacothrix is still 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. The other 10% of the island and San Miguel and Prince Islands are federal land managed by the National Parks Service. The survival of this endangered plant requires strict protection from the feeding of pigs. This could be done by securely fencing the plants, or by eradicating the pigs from its critical habitat. The abundance of competing non-native plants should also be managed. The populations of the Santa Cruz Island malacothrix should be monitored, and research undertaken into its basic biology and ecological requirements.
U.S. Fish and Wildlife Service
Ventura Fish and Wildife Office
2493 Portola Road, Suite B
Ventura, California 93003-7726
Telephone: (805) 644-1766
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.