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

We examine the Digitaria filiformis complex, to determine the proper taxonomic rank and rarity of each taxon. The taxonomy of the D. filiformis complex is highly debated and includes two widespread species, D. filiformis and D. villosa; a possibly extinct species endemic to a single-site in New Hampshire, D. laeviglumis; and a rare species of southern Florida and the West Indies, D. dolichophylla. We conducted morphologic comparisons and molecular analysis of the four members of the D. filiformis complex, together with specimens from Mexico and Venezuela purportedly identified as D. laeviglumis (morphology only). Based on results of phylogenetic analyses of plastid and nuclear ITS sequences and morphologic comparisons, we recognize five species in the D. filiformis complex, including a newly described Mexican endemic D. glabrifloris. After field investigation we have moved the global rank of D. laeviglumis from globally historical (GH) to extinct (GX), as there is virtually no likelihood of rediscovery. Digitaria dolichophylla is much rarer than previously recognized, moving from secure (T5) to imperiled with extinction (G2).