Flora of the Santa Rosa Mountains From Vouchers


Checklist of the Vascular Flora of the Santa Rosa Mountains From Vouchers


This checklist is a first attempt at producing a flora of the Santa Rosa Mountains above an elevation of 2000 feet (600 m) from online vouchers.

This checklist was made possible through the work of all the botanists who have vouchered species and deposited them in herbaria, as well the considerable efforts of the major herbaria in California to digitize their collections and georeference the localities on the labels. This digitization is a huge task, which is still ongoing. I and many other botanists are deeply grateful for the immense amount of work done on this task.

The lower elevation of 2000 feet was somewhat arbitrarily chosen to exclude taxa normally found only on the desert floor below the Mountains. The desert edge of the Santa Rosa Mountains ranges from roughly 0 to 1000 feet in elevation, and hence 2000 feet elevation eliminates nearly all of that desert floor vegetation.

The choice to eliminate desert floor vegetation was done since my only objective in producing the list was to help me identify the plants found on the Cactus Spring Trail at roughly 4000 feet elevation. My original intent was also to toss all records above 6000 feet elevation, but I decided in the end to keep the higher elevation species so that this could serve as a first draft of a flora of the Santa Rosa Mountains. The higher elevations do not add many species to the list.

I have put this list online since it will undoubtedly prove interesting and/or useful to others.

The flora here has been constructed almost entirely from vouchers that I have not examined. Hence I make no promises that the identifications are all correct, although a cursory analysis shows that the overwhelming majority of the vouchers are indeed correctly identified.

There are probably at least some incorrect determinations in the list presented here. Perhaps the biggest source of error results from taxa that were once known by a name widely applied throughout southern California, but which are now split into several names, and the vouchers have not yet been redetermined. One example is Quercus dumosa, which is now known to be restricted to just a few places along the coast. Two vouchers from this area still retain that name. A list of such taxa that have been excluded from the flora is given below. I hope readers will scan this list for similar taxa that should be removed.

As far as I know, no one has ever published a flora of the Santa Rosa Mountains. All lists and all floras have to start with something; this first attempt will serve to begin the process. I know very little about the flora of the Santa Rosa Mountains, and have not critically examined the following list for completeness or reliability except cursorily (see below). If you can contribute constructive criticism of the list, with additions, deletions or corrections, I'll be happy to incorporate your comments. If enough people familiar with the area, or with the taxa, contribute their comments, the list might evolve into a good flora of the area.

This list was compiled in roughly the following way:

I communicated all typos and other errors that I noticed in the vouchers to the appropriate Herbaria. In general, I was quite impressed by the high quality of the voucher records; I did not find very many typos or clearly-incorrect determinations.

Note that the list here does not represent all vouchers in southern California herbaria. My understanding is that the UC and UCR herbaria have been completely databased, but that the RSA/POM is about 50% databased and SD is about 25% databased. The UCR collection has been nearly entirely georeferenced for Riverside County, but the southern California portion of the UC and RSA/POM databases have not yet been georeferenced for the bulk of the data.

The resulting list contained 1,893 vouchers. Of those, 621 (33%), were georeferenced. There were 629 unique determinations among the 1,893 vouchers, including separately determinations made using an older taxon name as well as a new taxon name, and determinations only to the genus level as well as those to the species level, and to the species level when subspecies were also present.

These vouchers were collected by a total of 320 unique collectors. 15 collectors contributed half of the 1,893 vouchers:

Collector# Vouchers% of All VouchersCumulative % of all Vouchers
From Top of Table
P. A. Munz30115.9%15.9%
A. C. Sanders1035.4%21.3%
W. L. Jepson834.4%25.7%
G. K. Helmkamp663.5%29.2%
H. M. Hall643.4%32.6%
L. B. Ziegler522.7%35.3%
J. C. Roos502.6%38.0%
F. C. Vasek331.7%39.7%
Mitch Provance321.7%41.4%
Marjorie D. Clary311.6%43.1%
R. S. Woglum291.5%44.6%
W. L. Jepson and H. M. Hall281.5%46.1%
Lauramay T. Dempster and G. L. Stebbins271.4%47.5%
R. H. Whittaker, W. A. Niering271.4%48.9%
Craig Reiser241.3%50.2%

It is possible that Munz collected twice as many vouchers, since the RSA database is only ~half digitized.

162 collectors contributed a single voucher.

These botanists should get the bulk of the credit for the checklist presented here, since it could not have been compiled without their work. Note that if you go out and collect 25 or more vouchers, your name will appear here in the next iteration of this flora.

The list of 629 unique determinations was then compared to my database of names of taxa in southern California. At this point, some voucher determinations were changed in order to update names or provide subspecies when the choice of subspecies was clear. Determinations that could not be matched to a specific taxon name were tossed. Almost all of these were determinations just to the genus level.

The final list contains 546 taxa.

When the Cactus Spring Trail plant list is more complete, I will compare it against this list and note which taxa are found on that trail. If I have time in the future, I will step through these taxa individually and examine all their vouchers to make sure they are actually found in this area.

With the above-mentioned incompleteness in mind, the following plot shows the coverage of the 621 georeferenced vouchers for the Santa Rosa Mountains area:

The map above gives the major roads and trails in the area, the major drainages, and the 2000 foot elevation contour. The southwestern boundary of the Santa Rosa Mountains is taken as the trace of the San Jacinto Fault, which is in two main strands south of the Thomas Mountains.

The rejection of vouchers below the 2000 foot contour appears fairly complete. The few vouchers that plot below that contour may not have had recorded elevations, or their elevations were incorrect, or I simply failed to reject them; I haven't checked them yet.

Note that many of the vouchers have the same location, and hence plot on top of each other. Thus although there are 621 vouchers plotted above, there are far fewer than 621 unique locations.

The georeferenced vouchers are, almost without exception, only taken along roads and trails. The vast majority of the area of the Santa Rosa Mountains is apparently unsampled.

One example of how under-botanized this area is the discovery of Arctostaphylos parryana ssp. deserticum along Santa Rosa Mountain Road in 1997 by Jon Keeley, Laura Boykin and Allen Massihi. This taxon lines the road in places, and differs from previously-known Arctostaphylos parryana by the presence of an obvious burl. Surely other discoveries like this await botanists here.

Of course, firm conclusions about the sampling must await the georeferencing of the remaining two-thirds of the vouchers.

The checklist is at the following link:

Checklist of the Vascular Flora of the Santa Rosa Mountains From Vouchers

Taxa Unique to the Santa Rosa Mountains Checklist

The following taxa are found only in the Santa Rosa Mountains Checklist, and in none of the other 64 southern California flora I have digitized:

TaxonGeographic Distribution# Vouchers
Arctostaphylos parryana ssp. deserticumnew taxon; SnJt, Santa Rosa Mountains14
Chamaesyce revolutaUncommon; DMtns1
Ditaxis claryanaCoachella Valley1
Eriophyllum ambiguum var. paleaceumTeh, D2
Machaeranthera canescens var. ziegleriSanta Rosa Mtns15
Marina orcuttii var. orcuttiiSanta Rosa Mountains; RARE3
Saltugilia latimerinewly separated from Gilia australis; San Bernardino, Riverside and Inyo Counties1
Salvia dorrii var. dorriin Dmoj (JM); Mojave Desert (Los Angeles and San Bernardino Counties; Munz)1
Silene verecunda ssp. andersoniiDMtns1
Tridens muticusDMtns2
Woodsia plummeraeDMtns; RARE in California1

The Geographic Distribution is from the Jepson Manual except for the two taxa not present there, Arctostaphylos parryana ssp. deserticum (distribution from Keeley, Boykin and Massihi 1997) and Saltugilia latimeri (distribution from the Jepson Interchange).

A list like this would be expected to pick up taxa endemic to the Santa Rosa Mountains, as well as any misdeterminations. The only obvious candidate for misdetermination that came from this search was Linanthus nuttallii (SBBG89085), which is most likely the incompletely-determined name for Linanthus nuttallii ssp. floribundus, now Linanthus floribundus ssp. hallii. Hence it was dropped from the final list.

Voucher Taxa Removed From the Santa Rosa Mountains Checklist

The following taxa have been removed from the Checklist, for the stated reasons:

Scientific NameReason For Exclusion
Delphinium variegatum ssp. variegatumOnly in Northern California and ChI (JM). Jeffrey Greenhouse checked the voucher, UC118590. The taxon turned out to be true Delphinium variegatum from Santa Rosa in Sonoma County. The record was assigned to Riverside Co. by mistake. The label just has "Santa Rosa" without a county or date.
Eleocharis montanaNot in California according to FNA. This voucher, UC838982, has a duplicate, POM14329, which is determined as Eleocharis montevidensis var. montevidensis and will be added to the next version of the Checklist. See both vouchers.
Linanthus nuttalliiProbably the incompletely-determined name for Linanthus nuttallii ssp. floribundus, now Linanthus floribundus ssp. hallii
Machaeranthera canescens var. canescensThere are 15 vouchers of var. ziegleri that completely surround this voucher, making it seem likely that this is a misdetermination
Opuntia acanthocarpa var. coloradensisFound only in narrow corridor along Colorado River. This voucher, UC718131, has a duplicate, RSA22788, which is determined as Opuntia acanthocarpa var. ganderi, which is in the checklist as O. ganderi. See both vouchers.
Quercus berberidifoliaFound only inland of Santa Rosa Mountains
Quercus dumosaFound only along coast
Quercus engelmanniiFound only ~30 miles away. This specimen is Q. acutidens
Quercus john-tuckeriIt seems likely this voucher by Hall is a misidentified Q. cornelius-mulleri, which is the extremely common scrub oak here. The nearest location with multiple vouchers of Q. john-tuckeri is in the Little San Bernardino Mountains, ~30 miles away.

Notes On Some Taxa

Scientific NameNotes
Boechera californicaTreated as synonymous with Boechera sparsiflora (Nuttall) Dorn var. californica Rollins, which is synonymous with Arabis sparsiflora var. californica
Eriogonum nodosumTreated as synonymous Eriogonum wrightii var. nodosum
Polygonum sawatchense ssp. sawatchenseNew (and old) name for Polygonum douglasii ssp. johnstonii

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Copyright © 2006 by Tom Chester.
Permission is freely granted to reproduce any or all of this page as long as credit is given to me at this source:
Comments and feedback: Tom Chester
Updated 1 December 2006.