Two lineages of Lemna aequinoctialis sensu lato (Araceae, Lemnoideae) based on physiology, morphology, and phylogeny

Abstract Lemna aequinoctialis Welw. is a widely spread species that has diverse physiological and molecular properties. In this study, physiological and morphological analyses were conducted by inducing flowering, and molecular analysis was done based on two chloroplast DNA loci (atpF − atpH intergeneric spacer, matK) of L. aequinoctialis sensu lato from 70 strains found in 70 localities in Japan, Korea, Thailand, and the US. 752 flowering fronds from 13 strains were observed based on axenic conditions. Two different trends in flower organ development, protogyny and adichogamy, were detected in these strains. Their physiological traits were divided into two groups, showing different morphological features based on frond thickness, root cap, and anther sizes. Molecular analysis showed two lineages corresponding to two physiological groups. These were identified as L. aequinoctialis sensu Beppu et al. (1985)d aoukikusa Beppu et Murata based on the description of the nomenclature of L. aoukikusa. These were concluded as independent taxa and can be treated as different species. Furthermore, the distribution of L. aoukikusa is not only limited to Japan.