Chrysothamnus nauseosus (=Ericameria nauseosa) Subspecies With Glabrous Involucres At And Near The Grand Canyon, Arizona


Table of Contents

Properties of the Subspecies
Distribution of the Subspecies
New Names for These Subspecies


This page discusses the properties and plots the distribution of the four Chrysothamnus nauseosus (= Ericameria nauseosa) subspecies in Coconino County that have non-tomentose involucres. The analysis done for this page was to help me determine the subspecies of the plants near the Bright Angel Trailhead. (See also var. junceus on the Bright Angel Trail.)

The subspecies analyzed here are consimilis (=E.n. oreophila), graveolens, junceus and leiospermus (=abbreviatus). For the names used in the Flora of North America and USDA Plants, see New Names for These Subspecies.

Properties of the Subspecies

The Kearney and Peebles key to these subspecies, with the subspecies names used under C. nauseosus, is:

1.  Involucre glabrous, or the margins of the phyllaries sometimes ciliate (2)

2.  Achenes glabrous                             ..........ssp. leiospermus 
2'. Achenes densely pubescent   (3)

3.  Leaves linear, 1-2 mm wide, persistent           ....   ssp. graveolens
3'. Leaves linear-filiform, less than 1 mm wide, soon deciduous in ssp. junceus  (4)

4.  Plants essentially leafless [in bloom]; phyllaries in very distinct vertical rows;
    corolla teeth thinly long-pilose, at least when young ...  ssp. junceus
4'. Plants leafy [in bloom]; phyllaries in less distinct vertical rows;
    corolla teeth glabrous                             ...  ssp. consimilis

With this key, the plants in Grand Canyon Village, and along the upper Bright Angel Trail, clearly key to ssp. consimilis, since the leaves near the inflorescence are ~0.5 mm wide and the plants have their leaves when they are blooming. (Although I haven't checked the achenes for these plants, a determination of ssp. leiospermus is ruled out on the height of the plants, the length of the involucre, the length of the corolla lobes, and the fact that the plants are leafy at bloom time; see the table below.)

However, using the Flora of North America key, these same plants key to ssp. graveolens! The following key is the Flora of North America key, modified to key only the subspecies considered here and using those subspecies names:


1.  Achenes glabrous                                      ..........ssp. leiospermus 
1'. Achenes hairy   (2)

2.  Corolla lobes villous (sometimes sparsely)                     .... ssp. junceus
2'. Corolla lobes glabrous  (3)

3.  Corolla lobes 0.6-1.5 mm; corolla tubes puberulent or glabrous ..  ssp. graveolens
3'. Corolla lobes 1.5*-2.5 mm; corolla tubes glabrous              ...  ssp. consimilis

The corolla lobes of the plants in Grand Canyon Village, and along the upper Bright Angel Trail, are 1.0-1.4 mm long and glabrous, keying them unambiguously to ssp. graveolens!

At this point, I was stumped. The best way to resolve such difficulties is to visit a good herbarium that has a number of samples of both species, including one from this area, and study them to resolve the discrepancy here.

But being in southern California, a full day's drive from a herbarium with lots of Arizona vouchers, and wanting the get the answer right now, I did the next best things.

First, I consulted the detailed descriptions of these subspecies in the Flora of North America treatment, and compared them. The following table gives the characteristics of all four subspecies directly from the treatments, in a format so that I could easily compare sspp. consimilis and graveolens.

Descriptions of Four Chrysothamnus nauseosus subspecies from the Flora of North America treatments

SubspeciesHeight (cm)StemsLeavesInvolucre length (mm)PhyllariesCorollasAchenes (cypselae)Pappus length (mm)
consimilis (oreophila)70-250greenish, usually leafy, compactly tomentoseyellowish green; blades 1-nerved, filiform to linear, 20-50 0.8-1 mm, faces glabrate6.5-10 11-20, apices erect , acute, glabrous6-9 mm, tubes glabrous, lobes 1.5*-2.5 mm, glabrous; style appendages shorter than or equaling stigmatic portionshairy (sometimes glabrous in Idaho populations)4.2-7.6
graveolens50-160yellowish green to nearly white, leafy, compactly, smoothly tomentosegreenish; blades 3-nerved, broadly linear, 30-90 1-3 mm, faces often tomentulose.6-814-18, apices erect, acute, abaxial faces usually glabrous, outer sometimes sparsely hairy.7-9+ mm, tubes puberulent or glabrous, lobes 0.6-1.5 mm, glabrous; style appendages longer than stigmatic portions.densely hairy4.9-6.5
junceus40-70yellowish green, usually leafless at flowering, compactly tomentoseyellowish green; blades 1-nerved, filiform, 10-30 0.7-1 mm, faces compactly tomentose9.5-1222-25, apices erect , acute, abaxial faces tomentose or glabrate7-8.5 mm, tubes hairy, lobes 0.7-0.9 mm, villous; style appendages longer than stigmatic portionshairy5.6-7.6
leiospermus (abbreviatus)25-60 yellowish green, often leafless at flowering, densely, compactly tomentoseyellowish green; blades 1-nerved, filiform, 10-30 0.8-1 mm, faces glabrate8-11.517-31, apices erect, acute to obtuse, abaxial faces glabrous5-8.5 mm, tubes mostly glabrous, lobes 0.5-1.1 mm (erect to incurved), glabrous; style appendages longer than stigmatic portionsglabrous3-6.6

Unfortunately, a detailed comparison of what I knew about these plants to these characteristics didn't result in a clear determination. The stems look a bit whitish-green in my pictures, which tends to go with graveolens. But the leaf width of ~0.5 mm clearly goes to consimilis (albeit outside the range given in the treatment), and the phyllary lengths of 6-9 mm fit consimilis slightly better. Including the characteristic of the corolla lobe lengths, the score is tied, with each species having two characteristics that match my plants best. However, color comparisons are notoriously unreliable, and my pictures are certainly not definitive in giving the color of the stems, making the score 2 to 1 in favor of consimilis.

I then consulted the 1987 Grand Canyon Flora by Phillips et al. This does not even list ssp. consimilis as occurring at the Grand Canyon! It gives locations for ssp. graveolens of 2 miles south of Yaki Point, and Yavapai Point, South Rim, both of which are immediate neighbors to the Bright Angel Trail. This made a determination of my plants as ssp. graveolens seem clear.

Finally, I analyzed online vouchers for these subspecies, to try to understand the distributions of each of these subspecies and confirm the Grand Canyon Flora reports. My analysis of the voucher distribution is reported in the next section.

Surprisingly, the only vouchers near the Bright Angel Trail are ssp. consimilis, including a voucher from that trail by the famous Alice Eastwood! Furthermore, there are a lot of vouchers of ssp. consimilis in the pine forests of Coconino County; it is by far the dominant subspecies at elevations of 6000-8000 feet. Within 20 miles of the Bright Angel Trail, there are four vouchers of ssp. consimilis but only a single voucher of ssp. graveolens, from Cape Royal on the North Rim.

The dominance of ssp. consimilis in the pine forests here should not have been a surprise to me, since Kearney and Peebles state that its type locality is the base of the San Francisco Peaks. One should expect that there would be a lot of specimens near its type locality. (However, Abrams (1960) says that the type locality is Deeth, Elko County, Nevada, which is the farthest northeast county in Nevada. This Nevada voucher was probably for C. oreophilus, which beat out the name C. consimilis by three years, 1899 vs 1902.)

In contrast, vouchers of ssp. graveolens in Coconino County are very widely scattered, but appear to dominate only north of the latitude of Grand Canyon Village. Since the type locality of ssp. graveolens is ~1,000(?) miles away, on the banks of the Missouri [River] in denudated soils, it might be expected that this taxon would not be very abundant here at the edge of its range.

I could find no online vouchers to confirm the Phillips et al 1987 report of this subspecies at Yaki and Yavapai Points. (Note that it is possible that voucher specimens of ssp. consimilis were previously determined as ssp. graveolens, accounting for the Phillips et al 1987 report. It is also possible that specimens observed in spring were misdetermined, since the early leaves are wider than later leaves, and it is the width of the later leaves that are used in the floras.)

As I was analyzing the voucher distributions, I finally remembered that I had studied ssp. consimilis in southern California, and consulted my analysis of Chrysothamnus nauseosus subspecies in southern California. Within seconds, I found that the corolla lobes for ssp. consimilis can be much shorter than reported in the Flora of North America, down to 1.0 mm.

Munz, in his 1974 Flora of southern California, states that the corolla lobes of ssp. consimilis are 1.0-2.5 mm, not 1.5-2.5 mm. In fact, all specimens I measured of ssp. consimilis in the San Bernardino Mountains had lobe lengths of 1.1-1.5 mm. Furthermore, there is no possibility of these southern California measurements coming from plants of ssp. graveolens, since everyone agrees that subspecies does not exist in California.

I should have been skeptical of the Flora of North America key for the corolla lobes in the beginning, but being in a different state (Arizona vs. my home state of California) apparently suspended my usual skepticism. Keys that have a magic dividing line in a numeric characteristic, such as the 1.5 mm length here, often are erroneous. Nature doesn't often supply us with taxa that divide so neatly. Such keys are often the result of a well-intentioned human trying to make a key that seems to clearly differentiate such taxa.

With this error corrected, the determination of ssp. consimilis for these Grand Canyon plants is clear. In particular, every reference, including the Flora of North America, agrees that the leaves of ssp. consimilis have widths of less than 1.0 mm, whereas the leaves of ssp. graveolens are wider than 1.0 mm.

Of the four characteristics mentioned above, the three numeric measurements all fit ssp. consimilis, and two of them clearly rule out ssp. graveolens. The fourth is the subjective estimate of the color of the stem, which was not a definitive measurement.

After I completed the above analysis, I found a picture of one plant near the Visitor Center which showed that the length of the stigma is equal to or slightly exceeds the length of the style. This is consistent with the description of var. oreophila in the Flora of North America, and is another confirmation of this determination. In contrast, the length of the stigma is less than the length of the style for var. graveolens.

By the way, I would love to know where the original report came from that ssp. consimilis grows in saline valleys. This description of its habitat appears in Kearney and Peebles 1960 (often in saline soil), the Flora of North America (alkaline valleys and plains); the Jepson Manual 1993 (gen alkaline soils); Munz 1974 (open alkaline valleys); Abrams 1960 (alkaline valleys and plains); and Jepson 1925 (alkaline flats). I have yet to see a ssp. consimilis growing in such a habitat!

The most-frequently-associated species in the Coconino County vouchers for ssp. consimilis is ponderosa pine, yet no one goes around saying that ponderosa pine grows in saline valleys. The new name for this subspecies much better fits its preferred habit: oreophila means mountain-loving.

Distribution of the Subspecies

I plotted the vouchers collected in Coconino County, Arizona, which contains most of the Grand Canyon, for these subspecies, and analyzed the elevation distribution for these subspecies. I also included ssp. hololeucus simply because that taxon is a favorite of mine, and I wanted to see where it lived in Arizona. (Jane Strong and I call it the white ghost because of its ghostly appearance when not in bloom.) That turned out to be an interesting inclusion.

I searched the Southwest Environmental Information Network (SEINet) on 25 September 2007 for all vouchers of these subspecies in Coconino County. I downloaded the data, which were missing the elevations, and then manually retrieved the elevation for each voucher. For vouchers near the Grand Canyon Village area, I georeferenced five vouchers that did not have coordinates, and estimated elevations for those and several additional vouchers from that area that had locations precise enough to produce a good estimate.

The following maps shows the geographic distribution of the voucher specimens by determination. Keep in mind that many vouchers have very imprecise coordinates, due to voucher labels that do not precisely give the position. Specific positions should never be trusted precisely without examination of the voucher locality information (see example below).

The first map shows all the vouchers in Coconino County. Humphrey Peak, the highest point in the San Francisco Peaks, is noted, since its foothills is the type location for ssp. consimilis. The second map zooms in on the Grand Canyon Village area from Hermits Rest to Grandview, outlined in red.

The single ssp. graveolens voucher in the Grand Canyon Village area originally plotted at the trailhead for the Bright Angel Trail. When I examined that voucher, I found it was from Cape Royal, North Rim, so I corrected its coordinates.

The following plot gives the elevation versus latitude for vouchers with elevations. Note that not all mapped vouchers have elevations, so this plot includes only a subset of the mapped vouchers.

The distributions of sspp. consimilis and junceus are very clear from these maps and plot.

Subspecies consimilis is the dominant subspecies in the pine forests at elevations of 6000 to 8000 feet, although it is found as low as 5200 feet elevation. If I overlayed the pine forest distribution on the map, it would appear essentially only where ssp. consimilis appears, as well as extending a bit to the north. In particular, the pine forest is in a band along latitude 35.4° in Coconino County, then disappears to the north until it reappears just south of Grand Canyon National Park.

Subspecies junceus is the dominant subspecies in lower elevation areas from 3000 to 5000 feet, which are mostly found in the Grand Canyon and hence surround and follow the Colorado River in the above plots. (Note that the geographic coordinates are imprecise for the voucher that plots at the Bright Angel Trailhead, since the elevation there is 6845 feet. In fact, the locality for that voucher is just Grand Canyon.) Ssp. junceus is also found up to 6300 feet in the winter rain shadow of the San Francisco Peaks.

Vouchers of ssp. graveolens are few and very widely scattered. It is difficult to draw firm conclusions from their distribution, since small number statistics, and the lack of collections from the Arizona Strip may be responsible for any apparent pattern. With that caution, ssp. graveolens may dominate only north of the latitude of Grand Canyon Village.

No conclusions can be drawn about the distribution of ssp. leiospermus, since it has only two vouchers in the above plot.

Subspecies hololeucus has its niche at even higher elevations in the winter rain shadow of the San Francisco Peaks.

The distribution of these three subspecies is nearly identical to their distributions in the San Gabriel Mountains of southern California, except that ssp. junceus is replaced by ssp. mohavensis in southern California. Subspecies consimilis is found on the coastal (wetter) side of the San Gabriel Mountains, ending at the mountain ridgeline, with ssp. hololeucus beginning at the ridgeline, and being replaced by ssp. mohavensis at the drier lower elevations on the rain shadow side.

New Names for These Subspecies

It was recently recognized that the traditional genus Chrysothamnus contained a number of species that were not closely related to the others in that genus. As a result, those species were transferred to other genera. In this case, C. nauseosus was transferred to Ericameria, hence the new name of E. nauseosa. If the former subspecies had been transferred over directly in a new botanical publication, it would have been straightforward to get the new names for all the subspecies.

Unfortunately, that didn't happen. Name-wise, things were made immensely confusing when G. L. Nesom and G. I. Baird (1993) changed all the former subspecies into varieties under just two subspecies: subspp. nauseosa and consimilis. (They may have had a perfectly good scientific reason for doing so, but there is no doubt it has made a mess for the names.) Every name got lengthened since the variety name was then appended after the subspecies name. Fortunately, the Flora of North America did not use these subspecies, and just used the variety name. Unfortunately, USDA Plants uses the longer name with both subspecies and variety.

Worse, the former C. n. ssp. consimilis got renamed to var. oreophila, probably because C. oreophilus was defined three years earlier than the name C. consimilis, and thus had precedence. (One then wonders why the E. n. ssp. consimilis also wasn't changed to ssp. oreophila, but it presumably has to do with the arcane rules for botanical nomenclature.)

The bottom line is that C. n. ssp. consimilis is now known as Ericameria nauseosa var. oreophila in the Flora of North America, and Ericameria nauseosa ssp. consimilis var. oreophila at USDA Plants. If you want a real mouthful, here is the full name as used by USDA Plants with the authors:

Ericameria nauseosa (Pallas ex Pursh) Nesom & Baird ssp. consimilis (Greene) Nesom & Baird var. oreophila (A. Nels.) Nesom & Baird

!!

What makes this new name scheme especially unfortunate is that in my opinion, many of the former subspecies are so distinctive that it seems there is a good argument to make at least some of the former subspecies into species in their own right. Anyone who sees a ssp. hololeucus can hardly believe it is the same species as ssp. bernardinus. I can't think of any other species that has 21 subspecies. Most species have just a handful of subspecies at most; as far as I know, Astragalus lentiginosus comes the closest, with 19 varieties in California and perhaps a few more outside of California. Turning these 21 subspecies into varieties is going in the wrong direction, since a variety is generally considered a weaker taxonomic separation than a subspecies.


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Copyright © 2007 by Tom Chester.
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Last Update: 27 September 2007