(Vol. 05, 2002-12) Natural Populations of Hesperaloe (Agavaceae) in Texas

Abstract

Starr provided a classically oriented systematic treatment of the genus Hesperaloe in which five species were recognized; only one of these, H. parviflora (including H. engelmannii) was said to be native to Texas (and closely adjacent Mexico). Unfortunately, he did not examine populations of this species complex in the field so as to assess morphoecogeographical patterns in the taxon. We have undertaken a field study of living populations of this complex in Texas and conclude that there are two, and possibly three, taxa of Hesperaloe native to Texas. Two of these, H. parviflora and H. engelmannii, have long been known to occur in Texas. The former is largely confined to the northern Chihuahuan Desert (mostly occurring with Larrea tridentata, Agave lechugilla and associated thorny shrubs) while the latter occurs mostly beneath oaks and associated shrubs and trees of the Edwards Plateau. A third, exceedingly rare, mostly Mexican species, H. funifera, has recently been suggested as being native to the state by Butterwick and Poole. According to Starr, Hesperaloe funifera is composed of two infraspecific taxa (H. f. subsp. funifera and H. f. subsp. chiangii), but these are treated as species in the present paper necessitating the following new name: Hesperaloe chiangii (Starr) B. L. Turner, comb. & stat. nov. Texas material belongs to H. funifera. A discussion of these several taxa is provided along with a map showing their distribution in Texas.