Notes on Psychotria Subgenus Heteropsychotria (Rubiaceae: Psychotrieae) in Mexico and Northern Central America

Abstract

Expanded descriptions, comments on geographic ranges and infraspecific variation, and complete synonymy are presented for Psychotria minarum, P. galeottiana, and P. phanaerandra (Standley & Steyerm.) Lorence, a new combination made here that is based on Palicourea phanaerandra Standley & Steyerm. The new species Psychotriajuarezana C. M. Taylor & Lorence from southern Mexico is also described. Psychotria L. is a pantropical genus of about 1,500 species of herbs, shrubs, and small trees. It is represented by three subgenera in the Neotropics. All subtropical species are assignable subgenus Psychotria or subgenus Heteropsychotria Steyerm., except P. microdon (DC.) Urban. This species was included in subgenus Psychotria by Steyermark (1974) and other authors, but is better placed in subgenus Tetramerae (Hiern) E. Petit (Hamilton, 1989). Subgenus Tetramerae comprises species found in the Palaeotropics, plus this one. It is characterized by leaves that dry pale green, pyrenes with the abaxial (dorsal) surface smooth except for a median keel, persisting marcescent stipules, and lateral branches in opposite pairs (Hamilton, 1989; Verdcourt, 1976). In contrast, subgenus Heteropsychotria is characterized by leaves that dry dark green brown or gray, pyrenes with three or more ribs on the abaxial surface, stipules that may be persistent or deciduous but are not marcescent, and lateral branches that are usually not opposite. Psychotria microdon is found in the Antilles and adjacent continental lowlands, and probably represents an example of long-distance dispersal. Members of subgenus Tetramerae characteristically have bacterial nodules in their leaves (Verdcourt, 1976), a feature not found in the neotropical members of Psychotria (including P. microdon). The two other subgenera found in the Neotropics encompass at least 500 species. These have been studied in the framework of regional floras but have not been treated comprehensively. The species of subgenus Psychotria have recently been treated indepth for Mexico and Central America (Hamilton, 1989). This is the area of highest diversity for this subgenus, with about 60 species. Subgenus Heteropsychotria includes approximately twice as many pecies in this same area, and many more in South America. Cephaelis Sw. was studied by Steyermark (1972), who concluded that it comprised an assemblage of species that in many cases were more closely related various members of Psychotria than other members of Cephaelis. He therefore combined Cephaelis with Psychotria subg. Heteropsychotria, making the appropriate combinations for the floras of the Guayana Highlands (Steyermark, 1972) and Venezuela (Steyermark, 1974). Combinations remain be made for many species that are not found in Venezuela (e.g., Taylor et al., 1991). A modern infrageneric classification of Psychoria subg. Heteropsychotria (including Cephaelis) was also begun by Steyermark in his South American studies (1972), but was not extended the Mesoamerican species. Unfortunately, Steyermark's system did not include explicit diagnoses of his groups, but was intended instead to show apparent relationships between the taxa presented. The flora of northern Mesoamerica includes many of the species Steyermark classified, as well as endemic relatives of these species, so his classification can be extended in general the region. However, the flora of northern Mesoamerica is not simply a northward extension of the South American flora, but does have its own identity as a phytogeographic province (Takhtajan, 1986); the existing infrageneric classification for subgenus Heteropsychotria is inadequate allow us classify the species treated here. We present here expanded descriptions, comments on geographic range and infraspecific variNOVON 2: 259-266. 1992. This content downloaded from 157.55.39.105 on Fri, 13 Jan 2017 18:14:20 UTC All use subject http://about.jstor.org/terms