Plants of Southern California:
Schismus barbatus and S. arabicus
This page was stimulated by a discussion as to whether we actually have both of these species in southern California, and if so, how to recognize them. It does not present any conclusions on my part; it only presents information about these two species. I hope it stimulates someone to work on the Schismus plants in southern California to actually see what is going on with them.
I suspect, but do not know for sure, that the central problem here is that these species have been freely interbreeding in southern California for a hundred years or more. Although both of these species are self-fertile, they can interbreed, and the hybrids are fully fertile (Faruqi and Quraish, 1979). However, as far as I know, no one has studied the plants in California to see whether they morphologically separate into two semi-distinct forms, with a smattering of intermediate forms, or whether they morphologically group into a single widely-variable clump.
Gould 1951, in his Grasses of the southwestern United States, stated that they broadly intergrade.
Felger 1990 treated S. arabicus as a synonym for S. barbatus in his account of Sonoran plant species. But in his 2000 Flora of the Gran Desierto, and his 2014 Flora of Ajo Peak to Tinajas Altas, he gave them as separate species, albeit with "subtle differences".
In looking at different keys from around the world as to how to separate the species, it became apparent that different people were using different characteristics to determine specimens, so much so that it is probably not possible to use voucher determinations to study these species in areas where they are non-native.
I wrote Kelly Allred, the Jepson Manual author for Schismus about the massive confusion I was seeing, and he kindly replied with the following, which he granted permission for me to place online here:I understand perfectly your frustration with the Schismus species. I haven't really had anything to do with the Jepson Flora since the first edition (1993), being heavily involved with other projects closer to home (New Mexico).
I have since that time backed away from recognizing two species, because, at least in western U.S., the distinctions do not hold consistently. That said, one can be misled by analyzing only variation in exotic habitats, and not accounting for what is going on in the native habitats (Eurasia).
Also, it is important to look at mature florets near or at the base of the spikelet, ones with grains. One does easily find plants that fall out pretty well into the two groups, so the situation might be a bit more complex than just a wholesale merging of the two entities. (As my son, a plant ecologist, would say, there's nothing like variation!)
Here is a copy of my treatment for Schismus barbatus for our revision of Flora Neomexicana, a manual of New Mexico vascular plants, to give you an idea of how I'm treating them now, in New Mexico.Teeth at tip of lemma narrowly triangular, clearly longer than broad; palea reaching at most to the middle of the lemma teeth, usually only as far as the base of the cleft; lower glumes equaling or exceeding the distal florets…var. arabicus (Nees) J.P. Smith [Schismus arabicus Nees].
Teeth at tip of lemma broadly triangular, about as broad as long; palea reaching at least as far as the lemma teeth and often projecting well beyond; lower glumes shorter than the distal florets…var. barbatus [Festuca barbata Loefling ex Linnaeus].
Kelly made the important point that for the names for these two species, or varieties, to make sense, one needs to compare what we see here to what is seen in the native habitats of this species. The plants could well have morphed into something different with the ability to freely interbreed in habitats that are very different from where they evolved. If that is the case, botany does not have a good way of handling that situation, since the names are tied to the type specimens from their native lands. The only kluge to deal with this situation, if that is the case, is to call our plants by the oldest name, which is S. barbatus, but recognizing that they may not in some or most cases actually correspond to the type specimen of S. barbatus, since this kluge lumps the two species together.
Fortunately, Conert & Türpe wrote an exhaustive manuscript on these species in their native ranges in 1974, Abh Senckenberg Naturf Ges 532:1--81. This monograph is not available online, but fortunately Travis Columbus was able to get a copy of it. The monograph is written entirely in German, which I cannot read, but the figures are extremely valuable in showing what these species are like in their native land.
Excerpts from Conert & Türpe Monograph
Lateral lobes of lemmas broad-triangular, not longer than broad. Palea at least to the middle of the lemma teeth, usually reaching their peak or even superior. Hair of lemmas often club-shaped ... barbatus
Lateral lobes narrow-triangular, much longer than wide. Palea slightly outstretch the incision between the lobes and at most to the middle of the lemma teeth. Hair of lemmas pointed, never club-shaped ... arabicus
Separation of Samples Using Palea and Lemma Lengths, Shape of Lemma Teeth, and presence of Club-Shaped Hairs or not
Variation in Lemma Teeth and Relative Palea Length
Illustration of S. arabicus
Illustration of S. barbatus
I thank Travis Columbus for obtaining a copy of the Schismus monograph and sharing it with me.
Copyright © 2018 by Tom Chester
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Last update: 22 March 2018