Saxifraga bryophora var tobiasiae

Tobias' Saxifrage

Taxonomy

General Description: Saxifraga bryophora var. tobiasiae (Tobias' saxifrage) is a diminutive annual with one main stem (rarely 2 - 3) that has several lateral branches. The main stem is terminated by a prominent white flower, as is an occasional lateral branch. The remaining flowers are replaced with numerous bulbils. The herbage is covered with glandular hairs. Although Grimes and Packard (1981) noted the branches are never terminated by a flower, further field investigations have found that one to several of the branches can bear terminal flowers (Moseley 1989).

Technical Description: Glandular-pubescent annual, 4 - 20 cm tall; stems usually one, rarely more, much branched, terminated by a single flower, other flowers replaced by bulbils; leaves to 15 mm long, ciliate with multicellular hairs; petals 4 - in number, 4 - 6 x 2 mm, with sagittate bases up to 0.25 mm long (modified from Grimes and Packard 1981).

Diagnostic Characteristics: Diagnostic characters for Tobias' saxifrage include its annual habit, the main stem being terminated by a single flower, and most other flowers replaced by bulbils.

Infraspecific Taxa: Saxifraga bryophora var. tobiasiae is the only infraspecific taxa of S. bryophora occurring in Idaho.

Similar-appearing Taxa: Five other species of Saxifraga have been observed in the vicinity of Tobias' saxifrage populations on the Payette National Forest. All five are perennial species. In addition, they occur in different habitats.

S. arguta occurs along perennial streams and rivulets.

S. debile is restricted to steep, north-facing outcrops that rarely receive direct sunlight.

S. ferruginea generally is found on north-facing rock outcrops or moist slopes with thin soil over bedrock.

S. tolmiei var. ledifolia is restricted to the immediate vicinity of late-lying snowbanks on north-facing slopes.

S. rhomboidea usually occurs on moist, north-facing slopes with more organic material at the surface. Saxifraga rhomboidea has been observed sympatric with Tobias' saxifrage in one place (Moseley 1989).

Identification of this Taxon in Idaho: The combination of its annual habit, and the main stem being terminated by a single flower with most other flowers being replaced by bulbils, distinguishes Tobias' saxifrage.

Global Comments:

Idaho Comments: When originally discovered at Fisher Creek Saddle in 1978, specimens were identified as Saxifraga foliolosa var. foliolosa, a taxon whose distribution is mainly arctic. The taxonomic disposition of this population was later reevaluated and found to be an undescribed variety of S. bryophora, a species previously thought to be endemic to California (Grimes and Packard 1981).

Status

Global: Tobias' saxifrage is endemic to the western Salmon River mountains north of McCall, Idaho, where it is known from five populations, all on the Payette National Forest. It was originally discovered by Nelle Tobias in 1978, and is one of the rarest taxa in the state. One population is large, containing more than 10,000 plants over approximately 200 acres. Another population covers approximately 10 acres and supports an estimated 1500 plants. Three small populations contain an estimated 200 - 250 widely scattered plants each. One of these small population may have been recently extirpated. In 1989, it was estimated to be one acre in size and contain 200 plants.

Four populations of Tobias' saxifrage are located within the perimeters of the large Corral and Blackwell fires, which burned during August through October 1994. Surveys by Moseley in 1995, found that habitat containing three populations actually burned, and one was in an unburned portion of the Blackwell Fire (Moseley 1996). His preliminary assessments indicate that two of the burned populations were not greatly affected because of the low intensity or spotty burn pattern of the fires. One population (North Fork Pearl Creek, 002) was not found, and may be extirpated. A combination of the plant's life history characteristics and the severe intensity of the burn and subsequent erosion may have contributed to its disappearance from the site. This site will have to be revisited to verify whether the population is extirpated, or if more than one year of post-fire recovery of the habitat is needed.

Aside from erosion and other deleterious effects to the species' habitat due to high-magnitude disturbances such as severe wildfires, no factors have been identified which threaten Tobias' saxifrage. Populations occur on high elevation ridges in areas of low productivity and high amounts of exposed bedrock that are generally unsuitable for timber harvest. Past, and possibly ongoing sheep grazing takes place in some populations, but does not appear to negatively affect Tobias' saxifrage (Moseley 1989).

Until the U. S. Fish and Wildlife Service revised their candidate system in early 1996, Tobias' saxifrage was a Category 2 (C2) candidate for listing under the Endangered Species Act. Under the revised system it is no longer considered a candidate species. Tobias' saxifrage is a U. S. Forest Service Region 4 Sensitive Species for the Payette National Forest. The Idaho Conservation Data Center ranks Tobias' saxifrage as G5T1 S1 [G5 = Saxifraga bryophora is demonstrably secure; T1 = var. tobiasiae is critically imperiled globally because of rarity or because of some factor of its biology making it especially vulnerable to extinction; because it is endemic to Idaho, the state (S) rank is the same as the taxon's global (T) rank]. Tobias' saxifrage is on the globally rare plant list maintained by the Idaho Native Plant Society, and was recommended for federal candidate status at the 1996 Idaho Rare Plant Conference.

Idaho: Tobias' saxifrage is on the globally rare plant list maintained by the Idaho Native Plant Society. At the 1996 Idaho Rare Plant Conference, it was recommended for reinstatement as a federal candidate species.

Distribution

Global: Tobias' saxifrage is endemic to the western Salmon River Mountains, north of McCall, Idaho.

Idaho: See Global Distribution comments.

Habitat

Saxifraga bryophora tobiasiae habitat

Elevation (Global): 7400 to 8400 feet

Elevation (Idaho): 7400 to 8400 feet

Global: Tobias' saxifrage occurs in openings in subalpine forest communities, classified as the Vaccinium globulare phase of the Abies lasiocarpa/Xerophyllum tenax habitat type. Within this community it occurs in microhabitats characterized by considerable amounts of bare soil and substrate instability. The cause of the instability has two sources: earth cores created by pocket gopher activity and meltwater channels between bedrock or areas stabilized by perennial vegetation. Plants are found on the flat to gently sloping portions of the meltwater channels. It does not occur in the steeper channel sections, where the substrate is continually subject to downslope movement, nor in gravelly depressions where ephemeral ponding takes place.

Although saturated early in the growing season, soils at all sites are dry by about mid-July. Populations occur mostly on aspects other than north. Elevations of known populations range from 7,400 to 8,400 feet. The underlying geology is uniformly intrusive, although several rock-types are present, including quartz monzonite, granodiorite, and quartz diorite.

Associated species include Lewisia triphylla, Hypericum formosum, Polygonum phytolaccifolium, Polygonum austiniae, Castilleja miniata, Antennaria lanata, Erythronium grandiflorum, Arenaria capillaris, Trisetum spicatum, Poa gracillima, Vaccinium scoparium, Mimulus breweri, Phlox diffusa, Cymopterus glaucus, Suksdorfia ranunculifolia, and Pinus albicaulis (Moseley 1989).

Idaho: See Global Habitat comments.

Ecology

Global: Tobias's saxifrage is rarely found beneath the forest canopy, suggesting a relatively high light requirement. Tobias' saxifrage occurs in sites characterized by considerable amounts of exposed bare soil and substrate instability (Moseley 1996). Competition for space and resources appears to limit plants to these open soil areas (Moseley 1989). Like many annuals, these observations indicate Tobias' saxifrage is adapted to and probably requires periodic disturbance to maintain open habitats. However, high-magnitude disturbance events may be detrimental, at least on a local scale. Evidence for this comes from a recent resurvey of populations located in areas where large wildfires occurred in 1994. Preliminary indications are that one population may have been extirpated, perhaps due to a combination of the species' life history characteristics and the severe intensity of the burn and subsequent erosion. Tobias' saxifrage puts most of its reproductive energy into producing bulbils as a means of propagation. These bulbils may not be able to withstand burial by high levels of sediment such as after a severe fire, or other major disturbance event.

Idaho: See Global Ecology comments.

Reproduction

Global: Most flowers in the inflorescence are modified into bulbils, and it appears that Tobias' saxifrage places most of its reproductive energy into asexual propagation rather than sexual reproduction by seeds. Nothing is known about seed longevity, seed banking, or other aspects of the species' reproductive biology.

Idaho: See Global Reproductive comments.

Phenology (Idaho): Seeds probably germinate in early summer. Plants flower later in the summer, usually beginning around mid-July, and continuing well into August at some sites. The species reproduces largely via vegetative propagules (bulbils). These drop off the parent plant, overwinter, then resume growth early the next summer.

Management

Global: All known populations are located on the Payette National Forest. A small portion of the Fisher Creek Saddle population occurs within the Bruin Mountain Research Natural Area. Moseley (1996) has recommended the North Fork Pearl Creek population (002) be resurveyed (in 1996) to determine if it is extirpated, or if more than one year of post-fire recovery is needed for plants to become apparent above-ground. A graduate student is researching aspects of the population biology and reproductive ecology of Tobias' saxifrage. This research has important implications regarding conservation management and planning for the species, and should continue to receive adequate funding. Research plots should be made permanent for long-term post-fire population and habitat monitoring. There are considerable amounts of potentially suitable habitat remaining to be surveyed on the Payette National Forest. Sensitive plant clearances should be conducted for all projects that occur in areas of suitable habitat on the Forest.

Idaho: See Global Management comments.

Inventory

General Comments (Idaho): Prior to 1989, two populations had been discovered opportunistically. The type locality at Fisher Creek Saddle was discovered in 1978, and another in the North Fork Pearl Creek in 1988. Moseley (1989) conducted a systematic inventory of potential habitat in the Payette River drainage in 1989, and discovered three additional populations. One of these was later found to be connected by intermediate subpopulations to the type locality and now considered one large population. One new population was discovered during a revisit to the Payette National Forest in 1995 to assess the effects of recent wildfires on previously known sites (Moseley 1996).

Inventory Needs (Idaho): A considerable amount of suitable-appearing habitat remains to be surveyed on the Payette National Forest. Further searches should include the Granite Mountain-Hard Butte-Patrick Butte divide, Squaw Point-Bear Pete Mountain divide, and the Payette Crest east of McCall.

References

Atwood, D., and N. Charlesworth. 1987. Status report for Saxifraga bryophora var. tobiasiae. Unpublished report. Not paged.

Grimes, J. W., and P. L. Packard. 1981. New taxa of Apiaceae, Hydrophyllaceae and Saxifragaceae from Oregon and Idaho. Brittonia 33: 430-434.

Moseley, R. K. 1989. Field investigations of Saxifraga bryophora var. tobiasiae (Tobias' saxifrage) a Region 4 Sensitive Species, on the Payette National Forest, with notes on Campanula scabrella (rough bellflower). Idaho Department of Fish and Game, Conservation Data Center, Boise. 13 pp. plus appendices.

Moseley, R. K. 1996. Effects of the 1994 Blackwell and Corral fires on populations of the rare endemic, Saxifraga bryophora var. tobiasiae, Payette National Forest. Report prepared for the Payette National Forest. Conservation Data Center, Idaho Department of Fish and Game. 7 pp.

Author: M. Mancuso
Updated: 96-04-29
Produced by The Nature Conservancy, the Natural Heritage Network, and the Idaho Conservation Data Center.