An electrophoretic study of two closely related species of Isoetes L. from the Southern Appalachians

Allozyme electrophoresis, spore morphology, and vegetative morphology were used to analyze the relationship of Isoetes caroliniana (A. Eaton) Taylor and Leubke to I. engelmannii A. Braun. Allozyme electrophoresis was applied to twenty-nine populations of I. engelmannii and I. caroliniana and related taxa. It was found that sixteen populations of I. caroliniana can be distinguished from six populations of I. engelmannii by four loci; AAT-1, 6-PGD, LAP-1, and TPI-2. Three populations of what were putatively thought to represent I. engelmannii were determined to be probable examples of natural hybrids between I. engelmannii and I. caroliniana, and I. engelmannii and I. melanopoda. Descriptions of spore ornamentation and vegetative morphology are recorded and discussed for each of the populations collected for electrophoresis. Examination of spore ornamentation revealed that I. caroliniana could be distinguished from I. engelmannii with the former having cristate to echinate ornamentation whereas the latter has a reticulate ornamentation. The amount of variability of morphological characters is discussed with respect to the other available data and the two taxa are described within a range of that observed variability.