ABSTRACT
A new species, Leitneria pilosa, and a new subspecies, L. pilosa subsp. ozarkana, are described based on leaf morphology, ISSR polymorphisms, ITS sequence character, and geographical isolation. Our infrageneric assessment of populations of Leitneria showed that L. pilosa, which occurs as western disjunct populations in Missouri, Arkansas, and Texas, has undergone species-level divergence from plants of Leitneria floridana indigenous to Florida and Georgia. Leitneria pilosa differs from L. floridana in the presence of dense trichomes on both abaxial and adaxial leaf surfaces, while trichomes are sparse to absent on the leaf surfaces of L. floridana. Leaves of L. pilosa are smaller, about half the length, and have a lower length : width ratio than leaves of L. floridana. Within L. pilosa, subsp. ozarkana indigenous to Arkansas and Missouri differs from subsp. pilosa indigenous to Texas by its consistently larger, elliptic to slightly oblanceolate or obovate leaves with longer petioles. Leaves of L. pilosa subsp. pilosa are narrower and lanceolate. These new taxonomic designations are supported strongly by data from molecular analyses and by the geographic disjunction of the taxa.