Crawford, D. J., E. Landolt , D. H. Les, and R. T. Kimball. 2001. Allozyme studies in Lemnaceae: variation and relationships in Lemna sections Alatae and Biformes. Taxon 50: 987-999.

Allozyme variation was examined within and among three species of Lemna (Lemnaceae) that have been viewed as closely related based on morphological and DNA sequence data. These include L. aequinoctialis, L. perpusilla, and L. tenera, with the former two species the only members of sect. Alatae and the latter the sole species of sect. Biformes, Lemna aequinoctialis is widely distributed in tropical and subtropical regions whereas the other two species have much narrower distributions. Sampling from one population of L. aequinoctialis revealed several multilocus genotypes but a deficiency of heterozygotes, which agrees with observations that the species can self-fertilise and produce seed in addition to reproducing clonally. Two series of localized populations revealed several multilocus genotypes in each group, but no heterozygotes were detected at any of the variable loci. Twenty single clones from much of the geographic range of L. aequinoctialis contain the same alleles detected in the local populations. no pattern of large-scale geographic variation was detected. Allozyme data support the recognition of L. perpusilla as distinct from L. aequinoctialis, but the two species share much higher identities at allozyme loci than either does with any other species of Lemna, thus agreeing with morphological and plastid DNA sequence data indicating that the two are closely related yet distinct species. Lemna tenera shares very low allozyme identities with L. aequinoctialis and L. perpusilla. Neither allozymes nor plastid sequences support the hypothesis that L. perpusilla is a hybrid between L. aequinoctialis and L. turionifera. Molecular data indicate that the three species form a strongly supported monophyletic group, with the common ancestor of Lemna tenera and L. aequinoctialis-L. perpusilla having diverged first, much later divergence occurring between the common ancestor of L. aequinoctialis and L. perpusilla.