Molecular phylogenetics, seed morphometrics, chromosome number evolution and systematics of EuropeanElatineL. (Elatinaceae) species

Abstract

The genusElatinecontainsca25 species, all of which are small, herbaceous annuals distributed in ephemeral waters on both hemispheres. However, due to a high degree of morphological variability (as a consequence of their amphibious life-style), the taxonomy of this genus remains controversial. Thus, to fill this gap in knowledge, we present a detailed molecular phylogenetic study of this genus based on nuclear (rITS) and plastid (accD-psaI,psbJ-petA,ycf6-psbM-trnD) sequences using 27 samples from 13 species. On the basis of this phylogenetic analysis, we provide a solid phylogenetic background for the modern taxonomy of the European members of the genus. Traditionally accepted sections of this tree (i.e., CryptaandElatinella) were found to be monophyletic; onlyE. borchoni—found to be a basal member of the genus—has to be excluded from the latter lineage to achieve monophyly. A number of taxonomic conclusions can also be drawn:E. hexandra, a high-ploid species, is most likely a stabilised hybrid between the main sections;E. campylospermamerits full species status based on both molecular and morphological evidence;E. gussoneiis a more widespread and genetically diverse species with two main lineages; and the presence of the AsianE. ambiguain the European flora is questionable. The main lineages recovered in this analysis are also supported by a number of synapomorphic morphological characters as well as uniform chromosome counts. Based on all the evidence presented here, two new subsections withinElatinellaare described: subsectionHydropiperaconsisting of the temperate species of the section, and subsectionMacropodaeincluding the Mediterranean species of the section.