Eriocaulon albosetaceum: a new species of Eriocaulaceae from the Brazilian Cerrado

ABSTRACT Eriocaulon is a predominantly pantropical and monophyletic genus, with aquatic or amphibian species and a high endemism rate. The number of nerves in the leaves varies widely among the species of the genus, but up to now only four have one-nerved leaves: Eriocaulon araguaiense, E. cylindratum, E. huanchacanum and E. setaceum. These species are exclusive to South America, except E. setaceum, which is broadly distributed. Eriocaulon setaceum is easily recognised by its aquatic habit, linear, one-nerved leaves, and the cucullate sepals of the pistillate flowers. However, it has characters with wide variation, including the scape number, stem length, and the presence or absence of trichomes, which make the species difficult to delimit. Here, we describe a new species from the Cerrado: Eriocaulon albosetaceum that is similar to E. setaceum. To clarify the differences between them, we present tables of distinguishing characters, including the seed coat and anatomical data. Also, we describe the seed coat and the scape anatomy of vouchers of E. setaceum collected in Brazil. The results show a different kind of seed projection when compared with specimens from Asia, corroborating the idea that E. setaceum is a complex of at least two species that occur in both the Old and New Worlds.