Allozyme Electrophoresis and the Taxonomy of Two Species of Isoetes in the Southeastern Appalachians

Abstract

Recent research in the genus Isoetes has included both a continued effort to locate and describe new and little understood taxa as well as a new effort to understand their population biology and mechanisms of speciation. Gel electrophoresis has only recently been used to aid in the latter research. Taylor et al. (1985) and Taylor and Luebke (1988) have compared North American taxa using several enzyme systems, and Hickey et al. (1989b) have used electrophoresis to examine species relationships and population biology in Isoetes. Although electrophoresis may be utilized to distinguish taxa of Isoetes, practical methods of species sorting and identification in the genus continue to utilize characters of spore morphology, habitat preference, and geographical location. The purpose of the present study was to utilize the techniques of gel electrophoresis to explore the relationship between I. engelmannii A. Br. var. engelmannii and var. caroliniana Eaton (1900a). Data gathered as part of this study were also used to better understand the population biology of both taxa and to investigate the usefulness of electrophoresis for examining relationships between presumably closely and more distantly related taxa. Braun (1846) originally described I. engelmannii (Engelmann's quillwort) from specimens collected by Engelmann in 1842 from a Missouri pond near St. Louis. Later Engelmann (1867, 1882) described several varieties of the species: var. valida from Pennsylvania and Delaware, var. gracilis for small plants from southern New England, and var. georgiana for extremely large and robust plants from Floyd County, Georgia. Eaton (1905) recognized var. fontana for plants with accessory bast bundles in the leaves, spotted sporangia, and larger spores with broken reticulations. Isoetes engelmannii var. caroliniana was described by Eaton (1900) from Mitchell County, North Carolina, based on a wide velum covering up to two-thirds of the sporangia and megaspores with jagged crests to a broken reticulate pattern. This variety of I.