Species: Erigeron basalticus

Basalt Daisy

Species

Encyclopedia of Puget Sound

Taprooted perennial herb with one to several sprawling or pendent stems per plant. The stems are 4-6 inches long, leafy especially toward the tip. Most of the leaves are about 1 inch in length, wedge-shaped in outline, and three-lobed at the tip. The herbage is glandular and covered with stiff, spreading hairs. Branches are terminated by a single flower. The flowers are typically daisy-like, with white to lilac ray flowers, about 1/4 inch long, surrounding a cluster of small disk flowers (Gamon 1988, after Alverson and Sheehan 1986).

Classification

Kingdom

Plantae

Phylum

Anthophyta

Class

Dicotyledoneae

Order

Asterales

Family

Asteraceae

Genus

Erigeron

NatureServe

Source:
ELEMENT_GLOBAL.2.156390

Classification

Informal Taxonomy

Plants, Vascular - Flowering Plants - Aster Family

Formal Taxonomy

Plantae - Anthophyta - Dicotyledoneae - Asterales - Asteraceae - Erigeron

Ecology and Life History

Short General Description

A perennial herb, up to 1 dm tall, with tri-lobed leaves and flower heads with white to lavender rays surrounding a yellowish disc. Blooms May-October.

Reproduction Comments

Little is known about the reproductive biology of Erigeron basalticus. It presumably begins its yearly growth as the daily minimum temperatures increase to above the freezing level, sometime in late March or early April. Flowering has been reported as early as the first week of May, when daily temperatures and the number of daylight hours are increasing. Peak anthesis occurs typically from late May to the middle of June. Although a majority of individuals have flowered by the end of July, when rainfall reaches its lowest monthly average, occasional individuals can be found flowering throughout the summer. Although the mode of pollination has not been documented, it is presumed to be accomplished primarily by insect vectors. The achenes of Erigeron basalticus are adapted for wind dispersal. This mechanism is perhaps enhanced by the plants' location on cliffs and within canyons through which there is often a breeze blowing. Rainwater may also wash seeds down slope. The only known germination tests have been conducted by the Berry Botanic Garden in Portland, Oregon (Kierstead, pers. comm. 1987). Seeds were divided into two groups. The first group of ten seeds were stratified for 40 days and then planted. Only one of these plants germinated. A second group of 10 seeds were planted without stratification. No individuals from this group germinated. No information is available on the seed and seedling ecology of Erigeron basalticus. Although there would appear to be a fair amount of suitable unoccupied habitat within and adjacent to the known range of this species, it may be that the amount of habitat with sufficient light, moisture and substrate requirements for seed germination and seedling growth and survival is limiting. It is also possible that Erigeron basalticus does not successfully disperse its seeds to these sites. The number of known sites and the size of populations occupying those sites are both quite small. However, as evidenced by the size-class distribution of individuals, the populations appear to be stable.

Ecology Comments

The habitat for Erigeron basalticus is exposed basalt cliffs and outcrops. Such sites undergo gradual weathering and continual fracturing of the basalt. This fracturing creates the microsites within which the species roots. There is no evidence to suggest that the taxon is dependent on other natural disturbances, at least within the time frame which we tend to think about for such disturbances. Erigeron basalticus occurs in microsites that are relatively devoid of other vascular vegetation. There are occasional grasses, herbs and small shrubs present, but the total cover of vascular vegetation is 1% or less. The range of Erigeron basalticus occurs within Bailey's (1980) Sagebrush-Wheatgrass (3131) section of the Intermountain Sagebrush Province and within the area mapped by Daubenmire (1970) as the Artemisia tridentata / Agropyron spicatum Association. However, the habitat within which E. basalticus grows is specialized and is not properly considered part of this association. Although Erigeron basalticus typically occurs by itself, other species are commonly found nearby on the basalt cliffs and outcrops. These species include: Haplopappus resinosus, Heuchera cylindrica, Penstemon richardsonii, Mimulus sp., Achillea millefolium, Thelypodium laciniatum, Poa secunda and Bromus tectorum. No quantitative data exist on the dominance or frequency of Erigeron basalticus. However, where E. basalticus occurs, it is generally conspicuous, though it never provides more than 1% cover. Erigeron basalticus is restricted to sites (basalt cliffs) which are undergoing primary succession. The only suitable habitat for this and other species is the cracks in the basalt. The vegetation present in these cracks may contribute to the fracturing of the basalt. The deposition of plant litter in these cracks and its subsequent decomposition undoubtedly contribute to the soil development. It is not known what role interspecific competition for space plays in the overall biology of Erigeron basalticus.

Conservation Status

NatureServe Global Status Rank

Global Status Last Reviewed

2007-09-26

Global Status Last Changed

2004-02-10

Other Status

(USFWS 2007).

Distribution

Conservation Status Map

Global Range

Erigeron basalticus is known from an area approximately 17 x 4.5 km in and adjacent to the Yakima River Canyon in Yakima and Kittitas Counties, Washington. The species' range is entirely within the Columbia Basin Province of Franklin and Dyrness (1973) and within the Columbia Plateau Ecoregion (TNC 1997).

ELEMENT_GLOBAL.2.156390