MORPHOLOGICAL AND ALLOZYMIC EVIDENCE FOR SABATIA FORMOSA (GENTIANACEAE) IN THE SECTION CAMPESTRIA

An investigation of eleven populations of Sabatia, utilizing twelve morphological traits and fifteen allozymic loci, revealed the presence of three species in the section Campestria. Currently, the section has two recognized species, S. campestris Nutt. and S. arenicola Greenm. A stepwise discriminant analysis of the morphological data indicated the presence of the third previously described species, S. formosa Buckl. Eight of the loci were either monomorphic or there were no allozyme frequency differences among the three species. An analysis of the allozyme frequencies of the seven polymorphic loci substantiated the presence of S. formosa. Ecological and phenological phenomena further separate the three species. A distribution map of the populations analyzed, populations observed, and populations represented in herbarium specimens indicates that the ranges of the three species are separate although sympatry does occur. Thus, the morphological form described and designated S. formosa by Buckley in 1862 is a separate species. THE GENUS Sabatia has been treated taxonomically (Wilbur, 1955) and biosystematically (Perry, 1971). These studies include S. arenicola Greenm. and S. campestris Nutt., the only species in the section Campestria currently recognized. Wilbur's (1955) description of S. campestris reveals a high level of morphological diversity, raising the question of whether more than one species is included in the taxon. Buckley (1862) described a new species, Sabatia formosa, from Llano County, Texas. Subsequent criticism by Asa Gray concerning most of Buckley's new species resulted in Buckley's proposal being rejected and the specimen being designated S. campestris. However, many of Buckley's described species have since been recognized as valid taxa. For example, Mahler (1973) credits Buckley with seventeen species and one variety from Taylor County, Texas. Wilbur (1955) was 1 Received for publication 24 May 1979; revision accepted 20 December 1979. We would like to thank B. A. Schaal for many discussions during the beginning phases of this study; B. L. Turner for use of the UT herbarium; Wm. F. Mahler for use of the SMU herbarium and for obtaining the type specimens from the Philadelphia Museum of Natural History; and many others for assisting with collecting. We are grateful to B. A. Schaal, R. L. Wilbur, Wm. F. Mahler, L. K. Medlin, and two reviewers for critically reading the manuscript. This research was supported by grants from the University of Houston Coastal Center, the Moody Foundation, and a Grant-in-Aid from Sigma Xi to NBB. Facilities were made available by the Galveston Laboratory of the National Marine Fisheries Service to LJL. Carol Arian provided the illustrations. unable to substantiate the existence of S. formosa by using measurements taken from herbarium sheets. Perry's (1971) biosystematic study did not investigate further subdivision within the section. Taxonomic descriptions of the two species can be found in Appendix 1. In Galveston County, Texas, two morphological forms of Sabatia campestris have been observed. Although the two morphs are usually ecologically isolated, they occasionally occur sympatrically. Differences in flower color, in size of vegetative and reproductive parts, and in flowering phenology are very evident when the two morphs are sympatric. However, characteristics of both morphs fall within the description of S. campestris presented by Wilbur (1955). We will confirm the existence of Sabatia formosa Buckl. by using morphological measurements and isozyme patterns obtained by starch-gel electrophoresis. Our data prove that the species S. campestris as it is described in Wilbur's (1955) taxonomic revision actually contains two species, S. campestris and S. formosa. Because S. arenicola is the only other Sabatia species in the general vicinity and the only other species in section Campestria, we will perform the same analyses on individuals of that species. By utilizing our collection data and that of herbaria specimen localities, the approximate distribution of S. campestris and S. formosa in Texas is delineated. For this study, a species is defined as a set of individuals that interacts reproductively as a genetic system. The species exhibits genetic differentiation from other genetic systems as the result of temporal and ecological isolating