Flora of North America species comparison

Endolepis covillei was treated within the synonymy of Atriplex phyllostegia (Torrey) S. Watson by H. M. Hall and F. E. Clements (1923).

H. C. Stutz et al. (1993) placed Atriplex covillei within Endolepis, based in large part on the presence of a perianth subtending the pistil within the fruiting bracteoles and on the lack of Kranz anatomy in the leaves. The pattern of venation is, nevertheless, very similar to that in species with Kranz anatomy. The presence of perianth scales in the pistillate flowers of A. covillei has been regarded as evidence of relationship with A. suckleyi. Despite placement of these taxa within Endolepis by Stutz et al. Atriplex covillei is possibly more closely allied to the morphologically similar and partially sympatric A. phyllostegia than it is to strongly dissimilar and the distantly disjunct A. suckleyi. Stutz and his associates placed great emphasis on the presence of reduced perianth segments subtending the pistil within the fruiting bracteoles of A. covillei. Calyces per se, otherwise known only in A. suckleyi and A. pleiantha, probably have arisen independently. Their presence does not necessarily indicate a close relationship. Stutz et al. pointed to other differences aside from the calyx of the pistillate flowers, and it is apparent that the two entities can stand as distinct species. To segregate A. covillei within a separate genus and to ally it with a species to which its relationships are obscure at best, stretches logic beyond reason.

(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.)