A New Species of Sabatia (Gentianaceae) from the Chihuahuan Desert

Abstract

Sabatia tuberculata J. E. Williams, a gypsophilous endemic from the Cuatro Ciene- gas basin in central Coahuila, is distinguished from the wide-ranging S. stellaris Pursh of the eastern United States, Caribbean and central Mexico by its larger habit, larger flowers and the presence of a basal rosette of distinctly tuberculate leaves. Sabatia stellaris Pursh is a wide-ranging herbaceous species of saline marshes to sandy, often littoral, wetland habitats from the Atlantic and Gulf Coastal plain from Massachusetts to Lousiana, to the Bahamas, Cuba as well as inland Florida. It also occurs in marshes and lake, river margins in central Mexico from Jalisco, Michoacan to San Luis Potosi and Tamaulipas (Wilbur, 1955). Due to the broad disjunction of these populations and the differences in habitats (i.e. coastal v. inland wetlands) one would tend to predict the Mexican populations might be a distinct species, and three such species have been described. However, Wilbur (1955) could find no morpho- logical distinctions between the Mexican specimens and plants from the sou- theastern United States and Caribbean, other than a tendency towards longer calyx tubes and capsules in some Mexican populations. An examination of the holotype of S. palmeri Gray (Palmer 668 (GH) from Jalisco) and an iso- type of S. purpusii Brandegee (Purpus 5345 (GH) from San Luis Potosi) corroborates this observation but with one exception. Plants from the gypseous Cuatro Cienegas basin in central Coahuila pre- viously included in S. stellaris by Wilbur (1955), however, are morphologi- cally distinct from that species-a point initially recognised by Pinkava (unpubl.). These Coahuilan plants differ from S. stellaris in their more robust habit with greater height, thicker stems, more branched inflorescences with shorter pedicels, larger calyces and corollas with shorter filaments,