Regional Distribution of the Plants on Dawson Saddle Trail
The purpose for making this chart is to see how many of the plants on the Dawson Saddle Trail, 7901' to 9134', in the San Gabriel Mountains of Los Angeles County, California, are found in other mountainous areas like the Sierra Nevada and the Rockies.
The six regions used for comparison are:
- the Dawson Saddle Trail [SGM];
- the remainder of the Transverse Ranges which includes the San Bernardinos and Mt. Pinos [TR];
- the Sierra Nevada [SN];
- the California Floristic Province, which includes everything west of the Sierra Nevada and parts of Oregon and Baja California [CA-FP];
- everything outside the CA-FP and the Sierra Nevada in North America [Other NA]; and
- the rest of the Earth outside the North American continent [Outside NA].
Initially a separate list was made for the Rockies when that area was specifically listed by Munz. The Rockies list turned out to be no different from the list for the region outside the California Floristic Province [CA-FP], so it was combined into that list, Other NA [North America]. It was also not judicious to assume that an entry for location in a flora for Colorado was or was not part of the Rockies.
There are 49 species on this chart. Of those, only one species, Peirson's lupine, Lupinus peirsonii, is unique to the San Gabriel Mountains and only one species, downy brome, Bromus tectorum, is found worldwide.
All together the Transverse Ranges share 48 of the 49 species found on the Dawson Saddle Trail.
Eight of these 48 shared species are found only in the Transverse Ranges, mainly the San Bernardinos, in addition to the San Gabriels. These unusual species are mostly found together on that part of the trail without shade and without trees and shrubs. The soil here is rubbly, broken up light-colored granite. This area is subject to intensive radiation, reflection and strong winds and deep cold. The list is in order seen using this page Dawson Saddle Trail Plant Guide.
The eight local endemics in addition to the Peirson's lupine are:
- San Bernardino rubber rabbitbrush; Chrysothamnus nauseosus ssp. bernardinus
- silky lupine; Lupinus elatus
- alpine sulfur-flowered buckwheat; Eriogonum umbellatum var. minus
- San Bernardino Mountain onion; Allium monticola
- southern alpine buckwheat; Eriogonum kennedyi var. alpigenum
- woolly mountain-parsley; Oreonana vestita
- Southern California draba; Draba corrugata var. corrugata
An additional two species
- Sierra mousetail; Ivesia santolinoides
- Burlew's onion; Allium burlewii
Five different species are shared with the CA-FP excluding the Sierra Nevada giving a total of 13 species unique to the combined Transverse Range and Other CA-FP. These are:
- Grinnell's beardtongue; Penstemon grinnellii var. grinnellii
- Davidson's lotus; Lotus nevadensis var. davidsonii
- santolina pincushion; Chaenactis santolinoides
- leafy daisy; Erigeron foliosus var. foliosus
- Tehachapi ragwort; Senecio ionophyllus
The Dawson Saddle Trail has 38 species in common with other parts of the CA-FP excluding the Sierra Nevada. This is somewhat surprising since we expected to find more exclusive species shared with the Sierra Nevada than with the Other CA-FP.
Munz explains this in A Flora of Southern California on page 5 under Plant Distribution:
One would expect much similarity between our higher mountains [including the Sierra Nevada] and the Rocky Mountains and this is not so great as it might be. Undoubtedly the summer dryness of our area compared with that of the Rocky Mountains means that many northern plants, which in many cases are circumpolar and have worked their way south, have disappeared in our dry region, and have survived in the Rockies with more summer rain.
The distribution data was taken from The Jepson Manual, A California Flora and A Flora of Southern California by Munz, and Norman Weeden's A Sierra Nevada Flora. The stated distributions in these floras often are not the same, and hence different analyses may obtain slightly different lists of shared flora. Additionally, Weeden doesn't use subspecies and doesn't report species such as Erigeron foliolosus in the Sierra while JM says Erigeron foliolosus var foliolosus in in the sSN. Jepson has dropped some of the data from Munz such as Arabis platysperma in the TR.
Common Name Latin Name SGM TR SN Other CA-FP Other NA Outside NA Jeffrey pine Pinus jeffreyi x x x x giant blazing star Mentzelia laevicaulis x x x x x San Bernardino rubber rabbitbrush Chrysothamnus nauseosus ssp. bernardinus x x rock buckwheat Eriogonum saxatile x x x x Grinnell's beardtongue Penstemon grinnellii var. grinnellii x x x California squirreltail Elymus elymoides ssp. californicus x x x x x beaked penstemon Penstemon rostriflorus x x x x x California brickellbush Brickellia californica x x x x one-seeded pussypaws Calyptridium monospermum x x x x silky lupine Lupinus elatus x x green-leaf manzanita Arctostaphylos patula x x x x x Davidson's lotus Lotus nevadensis var. davidsonii x x x santolina pincushion Chaenactis santolinoides x x x white catch-fly Silene verecunda ssp. platyota x x x x white fir Abies concolor x x x x x sugar pine Pinus lambertiana x x x x mountain whitethorn Ceanothus cordulatus x x x x curl-leaf mountain-mahogany Cercocarpus ledifolius var. intermontanus x x x x x one-sided bluegrass Poa secunda ssp. secunda x x x x x Parish's needlegrass Achnatherum parishii x x x x x alpine sulfur-flowered buckwheat Eriogonum umbellatum var. minus x x pine lousewort Pedicularis semibarbata x x x x lodgepole pine Pinus contorta ssp. murrayana x x x x x leafy daisy Erigeron foliosus var. foliosus x x x wax currant Ribes cereum var. cereum x x x x x Burlew's onion Allium burlewii x x x groundsmoke Gayophytum diffusum ssp. parviflorum x x x x x San Bernardino Mountain onion Allium monticola x x southern alpine buckwheat Eriogonum kennedyi var. alpigenum x x Sierra mousetail Ivesia santolinoides x x x woolly mountain-parsley Oreonana vestita x x Peirson's lupine Lupinus peirsonii x snow-plant Sarcodes sanguinea x x x x flat-seeded rock cress Arabis platysperma x x x x x Tehachapi ragwort Senecio ionophyllus x x x bitter root Lewisia rediviva x x x x x bush chinquapin Chrysolepis sempervirens x x x x San Bernardino beardtongue Penstemon caesius x x x x pinedrops Pterospora andromedea x x x x x limber pine Pinus flexilis x x x x x Sierra gooseberry Ribes roezlii var. roezlii x x x x x little-leaf creambush Holodiscus microphyllus var. microphyllus x x x x spineless horsebrush Tetradymia canescens x x x x mountain California-fuchsia Epilobium canum ssp. latifolium x x x x white hawkweed Hieracium albiflorum x x x x x *downy brome Bromus tectorum x x x x x x Additional species seen [collected] by Jane on previous trips Draba corrugata x x white-veined wintergreen Pyrola picta x x x x x Additional species seen by Tom mountain gooseberry Ribes montigeum x x x x x Not included in the distributional count because species is unknown goosefoot Chenopodium popcorn flower Cryptantha Total Species 49 48 35 38 21 1 SGM TR SN Other CA-FP Other NA Outside NA
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Copyright © 2002 by Jane Strong and Tom Chester.
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Updated 12 September 2002.