Many-flowered Navarretia

Navarretia leucocephala ssp. plieantha

Description

Navarretia plieantha was described from the margin of Bogg's Lake in Lake County, California by Mason in 1946. Day reduced the taxon to a sub-species of N. leucocephala in her revised treatment of 1993. Navarretia leucocephala ssp. plieantha is distinguished from N. leucocephala ssp. pauciflora by its more numerous and multi-flowered heads (20-60 flowers versus 2-15), and in having three or more pairs of outer bracts with the bract lobes being forked or three-four branched from the base. It is distinguished from other navarretias in the region by stature and degree of hairiness, as well as by the size, number, or lobing of floral parts.

Many-flowered navarretia is a low growing annual herb in the phlox family (Polemoniaceae) that forms a mat 2-8 in (5-20 cm) wide. The 1.0-1.6 in (2.5-4 cm) long leaves are linear or have a few widely spaced linear lobes. The inflorescence is a head composed of 20-50 white or blue flowers. Each head is 0.6-0.8 in (1.5-2 cm) across and is subtended by three to four leaf-like bracts that are simple-pinnate or compound-pinnate and extend outward one to two times the radius of the head. The bracts within the head are shorter. The funnel-shaped corolla is 0.20-0.24 in (5-6 mm) long with five lobes each 0.7 in (17.5 mm) long. The stigma is two-cleft. Many-flowered navarretia flowers in May and June.

Habitat

Many-flowered navarretia is found in dry meadows, along the margins of volcanic ash substrate vernal pools and lakes, and in wet ground in forest openings. It occurs over a 1,000 sq km (390 sq mi) area at elevations of 2,300-3,000 ft (690-900 m).

Distribution

Many-flowered navarretia is historically known from eight locations in Lake and Sonoma counties, California. Two historical populations in Sonoma County, possibly hybrids between N. leucocephala ssp. plieantha and N. leucocephala ssp. bakeri, are considered potentially extirpated. All five extant populations are found in Lake County. Four of the extant populations are located on private land; one of these is located on The Nature Conservancy preserve at Bogg's Lake. The fifth population is an intercross between N. leucocephala ssp. plieantha and N. leucocephala ssp. pauciflora that occurs on State land at Loch Lomond. As discussed earlier, as an intercross population resulting from two listed species, this population could receive protection under the Act if the proposed hybrid policy is finalized. This site is managed as an ecological reserve by the California Department of Fish and Game (CDFG).

Threats

Many-flowered navarretia is endangered because of the vulnerability of its restricted habitat to threats posed by urbanization, agricultural land conversion, drainage, vernal pool and pond construction, ditch construction, off-highway vehicle use, road maintenance, and random natural events.

Attempted drainage of a pool in Lake County containing N. leucocephala ssp. plieantha has resulted in the invasion of two competitive weeds, Centaurea solstitialis and Taeniatherum caput-medusa.

Off-highway vehicle use has resulted and continues to result in the destruction of plants and habitat of many-flowered navarretia at four population sites in Lake County. The CDFG has provided fencing at the Loch Lomond site to prevent off-highway vehicle entry into the area.

Conservation and Recovery

Conservation of the many-flowered navarretia requires the protection of its critical habitat of ash-flow volcanic vernal pools and associated habitats. Only five of these critical habitats survive. One is protected on land owned by the CDFG at Loch Lomond. Another is protected in the Bogg's Lake Preserve of The Nature Conservancy, a private conservation organization. The other three habitats are on non-protected private lands and are potentially threatened by various human influences. These habitats should be protected by acquiring the land and designating ecological reserves, or by negotiating conservation easements with the owners. The populations of the many-flowered navarretia should be monitored, and research undertaken into its biology, habitat needs, and beneficial management practices. A program of public education should be developed to inform local people of the important of protecting vernal pools and their rare plants.

Contacts

U.S. Fish and Wildlife Service
Sacramento Fish and Wildlife Office
Federal Building
2800 Cottage Way, Room W-2650
Sacramento, California 95821-1846
Telephone: (916) 414-6600
Fax: (916) 460-4619

U.S. Fish and Wildlife Service
Office of the Regional Director
Eastside Federal Complex
911 N.E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

Reference

U.S. Fish and Wildlife Service. 18 June 1997. "Endangered and Threatened Wildlife and Plants; Endangered Status for Four Plants From Vernal Pools and Mesic Areas in Northern California." Federal Register 62 (117): 33029-33038.