Molecular and Taxonomic Reevaluation of the Digitaria filiformis Complex (Poaceae), Including a Globally Extinct, Single-Site Endemic from New Hampshire, USA, and a New Species from Mexico

Abstract

Abstract— We examine the Digitaria filiformis complex to determine the proper taxonomic rank and conservation status of each member. The taxonomy of the D. filiformis complex is debated and includes two widespread taxa, D. filiformis var. filiformis and D. filiformis var. villosa; a rare taxon of southern Florida and the West Indies, D. filiformis var. dolichophylla; and a possibly extinct taxon that supposedly is a single-site endemic in New Hampshire, USA, D. filiformis var. laeviglumis. We conducted molecular analyses and morphologic comparisons of the four members of the D. filiformis complex, together with specimens from Venezuela (morphology only) and Mexico purportedly identified as D. filiformis var. laeviglumis. Based on results of phylogenetic analyses of plastid and nuclear ITS sequences and morphologic comparisons, we elevated taxonomic ranks, recognizing four species in the D. filiformis complex, and circumscribe the Mexican species D. glabrifloris (sp. nov.). Digitaria dolichophylla is much rarer than previously recognized, moving from Secure Globally to Imperiled with extinction (G2). After research and field investigations, we changed the global rank of D. laeviglumis from Globally Historical (GH) to Globally Extinct (GX), as there is virtually no likelihood of rediscovery.