Lessingianthus pseudoglabratus (Asteraceae, Vernonieae), a new species of the L. glabratus Complex from southern South America

Abstract

A new species of Lessingianthus (Asteraceae, Vernonieae) from Mato Grosso do Sul (Brazil) and northeastern Paraguay is described and illustrated. The species was identified during a taxonomic revision of the genus based on herbarium material combined with detailed morphological, micromorphological (LM and SEM), and palynological analyses. It is morphologically similar to L. glabratus but differs by its pedunculate capitula (vs. sessile), 20–30 florets per head (vs. 35–40), 6–7-seriate involucre with linear-lanceolate, uniformly long-acuminate and brownish phyllaries (vs. ovate-lanceolate, purplish phyllaries with variable apices), and by the absence of conical, non-glandular trichomes on the corolla lobes. It further differs from L. carduoides and L. subcarduoides in leaf shape and margin, number of florets per capitulum, and the trichome complement of the corolla lobes and cypsela. Pollen grains are radially symmetric, 3-colporate, echinolophate (type B), consistent with the diagnostic pollen type of the genus. The new species occurs in the Cerrado, Alto Paraná Atlantic Forest, and Humid Chaco ecoregions, where it grows on sandy, well-drained soils. Based on available occurrence data, it is preliminarily assessed as Vulnerable (VU: B1ab(ii,iii)+B2ab(ii,iii)) according to the IUCN Red List criteria.