Plants of Southern California: Chrysothamnus nauseosus ssp. consimilis and mohavensis
Separating these two subspecies is problematic in the San Gabriel Mountains. See Chrysothamnus nauseosus subspecies for our attempts in years 2003-2004 to separate them.
Since then, both the Jepson Manual Second Edition (JM2) and the Flora of North America (FNA) have been published, with these two species treated as Ericameria nauseosa varieties oreophila (FNA and JM2) and mohavensis (FNA and JM2). Table 1 gives a summary of the characteristics they claim distinguish these two subspecies.
Oddly, despite the clear presence of abundant consimilis in the San Gabriel Mountains, from our observations and from vouchers, and the mention of a vouchered occurrence in the San Antonio Mountains at an altitude of 8000 feet, I.M. Johnston, no. 1706 in Hall's 1919 paper on Chrysothamnus nauseosus and Its Varieties, SnGb is not listed in its geographic distribution in the JM1 or JM2. (San Antonio Mountains is an older name for the portion of SnGb that includes Mt. San Antonio.)
Table 1. Characteristics that are claimed to distinguish ssp. consimilis and mohavensis in the Floras
mohavensis Stem at flower time leafy leafless* Leaf length 2-6 cm 1.5-3 cm* Involucre spiraled, weakly keeled strongly keeled Involucre length 6-10 mm 8.5-12 mm # Phyllaries 11-20 20-26 Phyllary surface glabrous glabrous to tomentose Corolla length 6-9 mm* 7-11 mm Corolla tube hairs glabrous* puberulent Style appendage length compared to stigma length ≤ 1* > 1 Pappus Length 4.2-7.6 mm 6.3-9.8 mm
* Characteristics that don't seem to fit the southern California plants in part or in all cases.
One problem in trusting what the floras say about consimilis is that the southern California plants are not actually consimilis in the strict sense. In Hall's 1919 paper, he gave the variety of the southern California plants as viridulus. Subspecies consimilis was only extended into southern California by synonymizing consimilis with viridulus.
Often when two taxa are synonymized, the floras never get updated to include all the characteristics of the subsumed taxon. In particular, Hall gives the corolla tube of viridulus as being glabrous or sparsely pubescent. The sparsely pubescent characteristic was lost when these two varieties were synonymized. He also gives the corolla as being 8-10 mm, so the upper range was lost as well.
Also, since the type specimen of consimilis is from Nevada, and the type specimen of viridulus is from Mono County, California, it is quite possible that specimens from southern California might be different in a number of respects from either type specimen. In fact, for viridulus, Hall says almost every valley exhibits forms not exactly like those in any other.
I measured six of my vouchers taken in 2004 to see if a PCA could separate the plants into two taxa. Perhaps not surprisingly, two of those plants came out as clear consimilis; two as clear mohavensis; and two appear to be dead intermediates.
Measured characteristics for the PCA
I measured a number of characteristics, but no matter how I experimented with putting all or a subset into the PCA, the results didn't change. Table 2 gives the essential characteristics used for the PCA given below.
Table 2. Measured characteristics
Plant # # Phyllaries Phyllaries sharply keeled (0=no;1=yes) Invol length (mm) Corolla length_(mm) Pappus max length(mm) Determination 1 17 0 7.8 8 7.2 consimilis 2 13 0 7.1 9.9 7.2 consimilis 6 17 0.5 8.85 9.2 8.7 ?? 4 18 0.5 9.05 7.7 7.2 ?? 3 22 1 10.3 10 8.1 mohavensis 5 23 1 9.4 9.5 9.1 mohavensis
Note that the table is in order of the determinations, in order to more easily see the relationships of the measured characteristics, and hence the Plant # is not sequential in the table.
Plants #1 and #2 are perfect consimilis, with # phyllaries less than 20, phyllaries that are not sharply keeled, and have the shortest involucre lengths of this set of plants.
Plants #3 and #5 are perfect mohavensis, with # phyllaries greater than 20, phyllaries that are sharply keeled, with the longest involucre lengths of this set.
Plants #4 and #6 appear to be intermediate, with # phyllaries less than 20 like consimilis, longer involucre lengths like mohavensis, and phyllaries with intermediate degree of being sharply keeled.
Geographic and Elevation plots
Note the three landmarks I put in the plot for reference points.
The two clear consimilis are from Glendora Ridge Road and from Dawson Saddle. All the plants from Mt. Baldy road are also clear consimilis.
The two clear mohavensis are from near Shortcut and from Buckhorn. All the plants from the Wrightwood area are also clear mohavensis.
The two plants that appear to be intermediates are from SR2 at Kratka Ridge and from the hairpin turn on SR2 between Cloudburst Summit and Winston Spring, on the westernmost ridge of Winston Peak.
PCAThe results of the PCA are in the next figure:
Each point is labeled by the plant #, as given below. Plants #1 and #2 are clear consimilis, and separate out well in the PCA at the extreme left. Plants #3 and #5 are clear mohavensis, and separate out well at the extreme right. Plants #4 and #6 appear to be intermediates, plotting between the two subspecies.
The labeled red lines are the characters the best separate the points. The invol length, # phyllaries, degree of phyllary keel, and the maximum pappus length are the best separators. Corolla length doesn't seem to separate the subspecies much.
Pictures of the involucres
These pictures were taken on 5 October 2013 of plants pressed in 2004.
Note that as given in the Munz key, and mentioned in the JM2, the phyllaries for mohavensis are all sharply keeled, which makes them appear to be in very distinct vertical rows. Some of the phyllaries of consimilis are also sharply keeled, but the innermost phyllaries, seen at the tip of the involucre, are much less keeled.
The pictures were taken under two different lighting conditions. One was light shining directly on the involucre using a microscope. The other was sunlight illuminating the involucre from the side.
Specimen Pix with straight-on lighting Pix with side lighting consimilis, TC406, #1 consimilis, TC421, #2 ??, TC417, #4 ??, TC419, #6 mohavensis, #3, TC413 mohavensis, #5, TC425
Copyright © 2013 by Tom Chester
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Last update: 6 October 2013