About the occurrence of Elatine macropoda and E. gussonei (Elatinaceae) in Sicily and lectotypification of their names

Morphological and nomenclatural investigations for two critical Mediterranean species of Elatine, i.e., E. macropoda and E. gussonei, as well as their correct distribution in Sicily, are discussed. These two names are lectotypified on herbarium specimens kept, respectively, at NAP and FI. The morphological investigations carried out on both the types, as well as on several living and dried material collected in southern Sicily, Lampedusa, and Malta (loci classici included), allowed to individuate reliable diagnostic characters that can be used for a correct identification of the two species. The most relevant differential features are: ratio petal/sepal, size and shape of the seed testa pits, and their arrangement in row number. According to our results, only E. macropoda occurs in the Hyblaean territory (Sicily), which is the locus classicus, whereas E. gussonei occurs on Lampedusa and Maltese islands only. However, further and in-depth morphological research is necessary to clarify their overall distribution in the Mediterranean area. Finally, an analytic key to the Mediterranean Elatine is provided.