Zyzyura, a new genus of Eupatorieae (Asteraceae) from Belize

Abstract A new Genus, Zyzyura is named to accommodate Fleischmannia mayana Pruski that has an eximbricate involucre, a high-conical receptacle, a corolla with a slender base closely investing the style and with a broadly campanulate limb, enlarged elongate cells in the carpopodium, short and broad distally protruding cells in the corolla lobes, and broad rounded anther appendages.


Introduction
Th e recent description of Fleischmannia mayana Pruski (Pruski and Clase 2012) (Figs. 1,2) was based on material of a procumbent epilithic herb from the western slope of Victoria Peak in the Cockscomb Range of the Maya Mountains in Belize. Th e type specimen includes four segments of prostrate stems with ascending fl owering branches and accompanying photos of the plants in the fi eld. Details of the plants that are visible are essentially consistent throughout. In the initial study by Pruski and Clase (2012), using a manuscript key to the Eupatorieae of Mesoamerica (Robinson in press), the species was identifi ed as a member of the genus Fleischmannia, and it was described in that genus. Now the type specimen has been subjected to a more intense study by the present authors, and a number of characteristics have been seen that preclude a position in Fleischmannia Robinson 1987, Robinson 2001).
Th e concept of Fleischmannia Sch.Bip. has been well established since the redefinition of the limits of the genus Robinson 1966, 1970) and in subsequent studies (King and Robinson 1972, 1974, 1975, 1978, 1991, Robinson 2001, 2011. Th e concept is now based on more than 90 species showing great uniformity in fl oral characteristics. Four characteristics of Fleischmannia mayana are inconsistent with the characters that defi ne Fleischmannia or even its only recognized close relative, Sartorina R.M. King & H.Rob. (1987).
Th e involucre of the Belize species is eximbricate with mostly 2 series of equal, obovate bracts with broadly rounded tips (Fig. 2C). While Fleischmannia often has the superfi cial appearance of being eximbricate, an appearance allowed for in many keys (King and Robinson 1987), it is always actually subimbricate with the involucral bracts in more than two series.
Th e receptacle of the Belize species is highly conical as seen in two heads in which the receptacle shows without dissection (Fig. 1C), while that of Fleischmannia is plane to scarcely convex.
Th e corolla has a basal tube closely investing the style and an abruptly expanded campanulate limb, diff ering from consistently funnelform shape in Fleischmannia.
Th e carpopodium of the Belize plant has enlarged and elongate cells (Fig. 1F), a feature diff erent from the smaller subquadrate cells in Fleischmannia.
Th ere are a few more subtle distinctions from Fleischmannia: Th e anther thecae are very short, and the apical anther appendages are slightly broader than long (Fig. 1E).
Th e cells of the corolla lobes are shorter and broader than those of Fleischmannia ( Fig. 1D) Th e pappus bristles are ca. ten in number and separated at the base (Fig. 2), a feature true of some Fleischmannia, but the bristles of the pappus are broad at the base unlike those in the Fleischmannia species which have fi ve or ten non-contiguous bristles.
A few features are similar to those of Fleischmannia: the cells of the corolla lobes project at their distal ends on both surfaces of the lobes (Fig. 1D), the anther collars are very narrow and strongly transversely annulated, though the annulations do not completely obscure the crosswalls of the cells in the collars, the cells of the carpopodium have reasonably thick walls, and the style bases are neither enlarged nor papillose.
Th e most striking feature of the new genus is the high-conical and fi stulose receptacle (Fig. 1C). How this structure functions is hard to determine, since there is no evidence of raised central fl orets in the fl owering heads on the holotype. Careful examination of the photographs, however, shows a central cluster of corolla-like material and a possible exposed tip of receptacle in the center of the cluster (Fig. 1B). It seems possible that fl orets never fully develop on the distal part of the receptacle.
Th e position of the Belize species in the Eupatorieae is not resolved. Although a number of features are shared with Fleischmannia, and the two may have some phylo-genetic relationship, the distinction of the species from anything in Fleischmannia is now certain. Furthermore, the new genus, cannot be placed in any of the other genera presently recognized in the tribe. It is particularly notable that few members of the Eupatorieae have a highly conical receptacle: Isocarpha R. Br. in which the receptacle is paleate, and Praxelis Cass, and Eupatoriopsis Hieron., both members of the subtribe Praxelinae, that have completely deciduous involucral bracts. Th e latter two also have 3-costate or obcompressed achenes.
In the general key to all the Eupatorieae genera in King and Robinson (1987) the new genus runs to couplet 137 on the basis of the articulated bases of the involucral bracts, the more than fi ve fl orets in the capitula, the symmetrical corollas of the capitula, the well-developed apical anther appendage, the three to fi ve-ribbed prismatic cypsela, the pappus of ten, subequal capillary, non-plumose, persistent bristles, the persistent involucre, the pedunculate capitula, the epaleate receptacles and the leaves subtending the peduncles not in pseudowhorls. Of the three genera in couplet 137, Ageratina Spach, Gymnocondylus R.M.King & H.Rob. & Fleischmannia, all diff er from the new genus by their plane or slightly convex receptacles. Th e fi rst two diff er by their expanded style bases, and Fleischmannia diff ers as indicated above. Because of these characteristics and because of the generally distinctive aspect of the specimen, the species is placed here in another new genus of the Eupatorieae which we name Zyzyura.
Distribution. Th e genus contains only the single species that may be endemic to the type locality in the Maya Mountains of the Cockscomb range in Belize.