An allozyme study of two sibling species of Lemna (Lemnaceae) with comments on their morphology, ecology and distribution

CRAWFORD, D. J. (Department of Plant Biology, The Ohio State University, Columbus, OH 43210), E. LANDOLT (Geobotanisches Institut ETH, Zurichbergstrasse 38, CH-8044, Zurich, Switzerland) AND D. H. LES (Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269). An allozyme study of two sibling species of Lemna (Lemnaceae) with comments on their morphology, ecology and distribution. Bull. Torrey Bot. Club 123: 1-6. 1996.-Enzyme electrophoresis was employed to examine divergence between Lemna mninuta H.B.&K. and L. valdiviana Phil., two nearly indistinguishable species comprising sect. Uninerves of Lemna. Fifteen presumptive loci were resolved for 25 clones of Lemna minuta and 26 of L. valdiviana. Genetic identity between the two species is 0.70, which is near the mean value for congeneric species of flowering plants, but is much higher than values reported for other species of Lemnaceae. With the exception of two clones, the taxonomic designations of the strains correlated with monomorphism for alternative alleles at two MDH loci. The two species are highly differentiated at two other loci as well. Although the taxa are morphologically similar, they differ in geographic distribution, flavonoid chemistry, and certain physiological and ecological attributes. The relatively high identity at allozyme loci compared to other Lemnaceae suggests that L. minuta and L. valdiviana are closely related and recently diverged sister species.