Flora of North America species comparison

Problems with prior applications of the name Atriplex mucronata lie in the mistaken determination of the place of publication as Amer. Monthly Mag. & Crit. Rev. 2: 176. 1818 (where the name is only mentioned), instead of 2: 119. 1817 (where accompanied by a description and notes). H. M. Hall and F. E. Clements (1923) evidently relied on P. C. Standley’s (1916) interpretation, which indicated the wrong citation (see also A. dioica Rafinesque as an identical example). Hall and Clements applied the name mucronata to their interpretation of A. patula subsp. hastata or to A. hastata (i.e., to A. prostrata according to this treatment).

The treatment of Obione by C. H. B. A. Moquin-Tandon (1849) included “A. mucronata Rafin.!” as a synonym of O. arenaria. Possibly a sheet in the Prodromus herbarium at Geneva was the basis for that decision. It has two mounted specimens, one labeled A. arenaria Nuttall, collected by Nuttall in “N. Jersey, 1826,” and a second labeled “Atriplex mucronata Rafinesque (A. arenaria Nuttall, N. Jersey) Maritime NY, Rafinesque 1819.” From that information (although the year is 1819, not 1817), and from the description of the taxon, it seems clear that A. arenaria Nuttall is a later synonym of A. mucronata Rafinesque by at least half a year.

H. A. Gleason and A. Cronquist (1991) indicated that this taxon, by whatever name, is “perhaps better treated as a variety of the more tropical Atriplex pentandra (Jacquin) Standley, but the proper nomenclatural combination not yet made.” The present writer agrees with that conclusion, but such subjugation might indicate further contraction into the species of additional closely related taxa, e.g., A. wrightii, which is clearly closely allied as well.

Plants from the coastal states from New England south to New Jersey are much alike and seldom, if ever, display prominent, terminal, naked spikes or panicles with beadlike glomerules of staminate flowers. Plants from Florida westward sometimes have such staminate spikes or panicles.

Specimens from Florida and some from Texas can be distinguished from Atriplex pentandra only with difficulty, especially those individuals with entire leaves. However, the fruiting bracteole length-width ratio and overall shape, with some allowance for overlap, can serve to distinguish most specimens; those of A. mucronata are proportionately longer than broad and, on average, larger.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

H. M. Hall and F. E. Clements (1923) placed great emphasis on the inferior radicle, dioecious habit, and free bracts in stating that there are no close relatives of Atriplex californica in North America. P. C. Standley (1916) regarded the radicle as lateral or superior, not inferior, and placed the species at the beginning of his treatment of the American species. Plants of A. californica, however, form a mirror-image, matched pair with A. watsonii, with which they share habit, leaf conformation, staminate glomerules arranged, at least partially, in terminal interrupted spikes, and Kranz anatomy, but from which they differ in the radicle position, valves of the fruiting bracteoles free beyond the middle, monoecious habit, and mostly alternate leaves. The interpretation by Hall and Clements of radicle position as fundamental is made problematic by the apparent random occurrence of a great many morphologic features from place to place within the genus and often within the taxon. Each character fails individually as having definitive taxonomic importance, making difficult or impossible an ultimately satisfactory phylogenetic arrangement. It is not, however, the character that makes the species, rather, it is the entire syndrome of features that constitutes the taxon. Most certainly A. californica is more closely allied to American taxa than to those from other regions of the world.

(Discussion copyrighted by Flora of North America; reprinted with permission.)