Eastern Mojave Vegetation Tom Schweich
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Eastern Mojave Vegetation | Two occurrences of Desert Elkweed Swertia albomarginata (S. Watson) Kuntze Gentianaceae in the Mid Hills, Eastern Mojave Desert, San Bernardino County, California (Continued) |
| Tom Schweich |
 Topics in this Article: Introduction Literature Review Field Work and Methods Results Taxonomy Distribution Growth Habits Relationships to Soils and Other Plants Life History Discussion Summary Literature Cited Appendix A -- Field Data Communications Received. |
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| Taxonomy
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| Taxonomy
| Literature Cited: Locations: Saint George. The type specimen of Swertia
albomarginata
(S. E. Utah, 1870, Palmer (US))
is an entirely glabrous plant, as was indicated in Watson's description
of the species.
However, Watson's original description of Frasera albomarginata
gives the locality as "Near St. George in Southern Utah (Dr. Palmer, 1870)."
St. George is, of course, in southwestern Utah.
Specimens of the species examined in the
University and Jepson Herbaria
(University of California, Berkeley) include the type species and one
variety, S. a. var. induta.
Although, this variety is not recognized in
Hickman (1993).
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Variety albomarginata is the most common expression.
It is found mostly on dry, sagebrush foothills and alluvial fans,
extending into the pinyon-juniper zone, mostly from 4,500-7,600 ft.
| | Literature Cited: Locations: Clark Canyon. Harris Springs. Spring Mountains.
Variety induta (Tidestrom) Card, Ann. Mo. Bot. Gard., 18:275. 1931. is a rare expression in Nevada, ranging from Charleston Peak, Clark Canyon, Harris Springs and elsewhere in the Spring Mountains, Clark County; to southern Nye County. It is found in dry habitats, often with Cercocarpus and pinyon-juniper but extending into the yellow pine zone from 5,000-8,000 ft. (Kartesz, 1988). Kartesz states the variety is
easily separated from the above expression
by its glandular-hairy infloresence and unique foveae.
| |  Collection
No. 183, Wild Horse Mesa.  Collection No. 184, Coal Pits Wash, Utah.
Most of my collections of the
species are from the eastern Mojave. |
|
 Swertia albomarginata flower.
The nectaries in Swertia are prominently placed on the corolla
lobes, and called fovea.
This can be seen in the photograph of the flower at left.
Fovea is a Latin word for "small pit" and defined as, "a shallow
cuplike depression or pit, as in a bone (Websters II, 1984)."
Since we are speaking good Latin here, the plural is "foveae."
The foveae seem to be prospective characteristics for distinguishing
between subspecies of S. albomarginata and among species of
the genus Swertia.
In my examination of herbarium specimens of S. albomarginata,
there seem to be five different shapes of foveae.
These are diagrammed below.
| |  Fovae.
Adapting some of the terminology used in describing leaf bases and tips, these nectaries would be described as follows:
| (a) nectary linear pit, 2-lobed at tip, lobes rounded.
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I would like to be able to describe some sort of evolutionary order of increasing complexity and elaboration in the fovea from (a) to (e).
However, at this time, I'll have to leave that as a possible construct, awaiting a testable hypothesis and testing.
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From my examination of herbarium specimens, I agree with separation of the variety induta on the character of glandular-hairy infloresence.
Although, I would express the character as puberulent upper stems and bracts.
I don't, however, find that the shapes of the foveae are distinctive for the variety.
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I identify the eastern Mojave specimens as S. a.
var. albomarginata because the stems and bracts are glabrous,
not puberulent, and the foveae are not unique.
| | Literature Cited: Locations: Charleston Peak. Spring Mountains. Kartesz (1988) also states that
var. induta is the westernmost expression of the species,
with the type from rocky places in the pinyon and yellow pine belts, Spring (Charleston) Mountains, Clark County. This may be true. My eastern Mojave locations are just east of south
of the Spring Mountains and Charleston Peak. Unless there are occurrences of S. albomarginata west of the Mid Hills or Providence Mountains, then the Spring Mountains are the
westernmost location for the species.
| | Literature Cited: Both this species and the closely
related S. [Frasera] puberulenta are most likely evolved from Frasera speciosa (Kartesz, 1988).
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| | Date and time this article was prepared: 5/15/2008 12:35:43 PM |