Species delimitation in the Sporobolus aeneus complex (Zoysieae, Chloridoideae, Poaceae) using the phylogenetic species concept

Abstract

The "Sporobolus aeneus complex" constitutes a morphologically well-defined group of species with lax, exerted, pyramidal panicles with verticillate branches, and comprises 14 species and six infraspecific taxa in southern South America (eastern Bolivia, eastern Paraguay, Uruguay, southern Brazil, northeastern Argentina). Species delimitation in the complex remains unresolved. To clarify the taxonomy of the group, multivariate analyses of qualitative and quantitative characters from herbaria specimens were performed. We applied the phylogenetic species concept and we used a modified "population aggregation analysis." Five species (S. aeneus, S. cubensis, S. linearifolius, S. multinodis, S. recurvatus) ar e recognized by unique combinations of qualitative character states, and three varieties based on significant mean value differences of quantitative characters. We conclude that leaf blade pilosity, widely used as a diagnostic character in the complex, is affected by external conditions like fire or blade age and is taxonomically unreliable. Two new cominations, Sporobolus aeneus var. angustifolia (Döll) S. Denham & Aliscioni and S. aeneus var. eximius (Nees ex Trin.) S. Denham & Aliscioni are made. Vilfa acuminata Trin. and Vilfa eximia Nees ex Trin. are lectotypified.