Plant Species of the Bright Angel Trail:
smooth spreading four o'clock, Mirabilis oxybaphoides
See Plant Guide to Bright Angel Trail for an introduction to this page.
Identification status: high confidence for the plants at the trailhead.
Mirabilis oxybaphoides and M. pumila are very similar species. To reliably separate these species, one must examine the fruit to see whether it is strongly ribbed or not. See illustration of the non-ribbed fruit of M. multiflora versus the illustration of the strongly-ribbed fruit of M. coccinea.
This is, of course, very annoying that one must use a relatively-obscure trait, that is not available most of the year, in order to discriminate these species. But that is a fact of life for a number of look-alike species, and sometimes even part of the fun in identifying species.
No fruit was available on my trips in 2006 and 2007, but fortunately Wayne Armstrong was able to check the fruit of the plants at the trailhead in October 2006, and reported that the fruit was not ribbed.
The keying in Kearney and Peebles is as follows, beginning at the Mirabilis / Oxybaphus couplet in the Nyctaginaceae Family on p. 270 (M. pumila was Oxybaphus pumilus in Kearney and Peebles):7a. Fruits not strongly 5-angled ... 4. Mirabilis 1a. Involucre subtending 3 flowers. Perianth purplish red 2a. Perianth not more than 1 cm long; involucre subrotate, 3-flowered; perianth campanulate-funnelform; stamens 3, the filaments distinct; herbage copiously viscid-villous to glabrate ... M. oxybaphoides
In their text, Kearney and Peebles say Apache, Navajo, and Coconino counties, 6,000 to 8,000 feet, August and September, apparently rare in Arizona.
The determination is supported by two other observations, but neither of these other observations can definitively give the determination. First, the flower color of the plants here is purplish red, fitting M. oxybaphoides, whereas the flower color of M. pumila can be either pale pink or purplish. The flowers look exactly like the ones in this picture of M. oxybaphoides, and not like the ones in this picture of M. pumila.
Second, the leaves on the plants here are cordate, which also fits M. oxybaphoides. Although M. pumila can also have cordate leaves, the SEINet picture shows wedge-shaped bases.
This species is not in McDougall 1964; it was either lumped in with the nearly-identical Mirabilis pumila, or not yet known to exist at the Grand Canyon then.
Phillips et al 1987 list only a single location for M. oxybaphoides: growing in bushes along the rim near Red Canyon Trail, South Rim. 7000 feet. They also quote the voucher Schmidt 026. As far as I know, this is the only species for which they cited a voucher in that flora.
From a SEINet search, there are only two vouchers of M. oxybaphoides from the Coconino County portion of the Grand Canyon: Tapeats narrows in the east arm of Clear Creek at 4100 feet, and Sumner Butte, upper Muav ls in gully toward Butte & Zoroaster Saddle, at 5000 feet. Oddly, the Schmidt voucher isn't listed online.
There are only four vouchers of M. pumila online: South Kaibab Trail, just below 'Tip Off' at 3231 feet; North Kaibab Trail, just above bridge at junction with Manzanita Canyon at 4600 feet; North Kaibab Trail, above Cottonwood Camp at 4215 feet; and Above Mooney Falls, Havasu at 2800 feet.
Note that there may be additional vouchers at other herbaria not available through SEINet.
First occurrence on Bright Angel Trail: mile 0.00, elevation 6845 feet (2086 m).
Number of plants along Trail: As discussed above, it is difficult for me to be sure how many of the similar-looking plants farther along the trail are also M. oxybaphoides. My usual philosophy is to assume that similar-looking plants are the same as previous species unless proven otherwise. Given that caveat, this taxon is quite widespread on this trail; at least 50 plants were found in at least 9 different locations in September 2007.
From 5 September 2007, mile 0.00, under the Quercus gambelii at the trailhead:
From 5 September 2007, mile ~0.08, in a completely different habitat (the fruit from these plants was not examined, so there is no guarantee this is the same species):
From 14 September 2006, mile 0.00, verified species at trailhead:
From 16 September 2006, unrecorded location perhaps around mile 0.5-1.0 (the fruit from these plants was not examined, so there is no guarantee this is the same species):
See Resources for Grand Canyon Flora for further information on most of these references. Entries in the second column are either the name used in that source or a page reference. The name is linked to online pages when available. If a given reference does not contain this taxon, the entry is either left blank or contains a hyphen.
Family Nyctaginaceae Scientific Name Mirabilis oxybaphoides 1987 Grand Canyon Flora Name Mirabilis oxybaphoides 1987 Grand Canyon Flora page 47 SEINet Image Page Mirabilis oxybaphoides USDA Plants Mirabilis oxybaphoides Flora of North America Mirabilis oxybaphoides Jepson Manual for California treatment Jepson Manual illustration page Kearney and Peebles Name Mirabilis oxybaphoides Kearney and Peebles Page # 272 Vascular Plants of AZ name Vascular Plants of AZ volume: page Huisinga et al 2006 name - Huisinga et al 2006 page numbers - Epple Name Mirabilis oxybaphoides Epple description page # 60 Epple pix # 621 McDougall 1964 name - McDougall 1964 page # - Brian 2000 Name Phillips 1979 name - Phillips 1979 page # - Stockert 1967 name - Stockert 1967 page # -
Copyright © 2007 by Tom Chester.
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Comments and feedback: Tom Chester
Last Update: 24 September 2007