Nuttallanthus is a small genus of herbaceous annuals and perennials in the family Plantaginaceae (the plantain family), comprising four species. It was traditionally placed in Scrophulariaceae (the foxglove family), but molecular phylogenetic research prompted its transfer to the greatly expanded Plantaginaceae, which now encompasses many former Scrophulariaceae genera.
The genus was formally described in 1988 by botanist David A. Sutton. Its taxonomic standing remains disputed: it is treated as an accepted genus in World Plants and the World Flora Online, but Plants of the World Online (POWO) considers it a synonym of Linaria. Prior to the 1980s, its species were included within a broadly circumscribed Linaria; that genus is now considered restricted to the Old World. Closely related genera include Linaria (Eurasian toadflaxes), Antirrhinum (snapdragons), and Cymbalaria (ivy-leaved toadflaxes).
Three of the four species are native to North America, ranging from Canada south through the United States to Mexico, with Nuttallanthus floridanus restricted to the southeastern United States. A fourth species, Nuttallanthus subandinus, occurs in the Andean regions of Colombia, Ecuador, and Peru, though the World Flora Online treats it as a synonym of Nuttallanthus canadensis. The North American species reproduce predominantly by self-fertilization, with occasional outcrossing; no interspecific hybrids are known. Members of the genus are commonly called toadflax, a vernacular name shared with several related genera.
Etymology
The genus name Nuttallanthus honors Thomas Nuttall (1786–1859), the English-American botanist and ornithologist who made extensive collections across North America. The common name "toadflax" is shared with several related genera in the tribe Antirrhineae, including Linaria and Cymbalaria.
Distribution
Three species of Nuttallanthus are native to North America, collectively ranging from Canada south through the United States to Mexico, with Nuttallanthus texanus extending to the Dominican Republic and Nuttallanthus floridanus confined to Alabama, Florida, Georgia, and Mississippi. A fourth species, Nuttallanthus subandinus, is native to the Andes of Colombia, Ecuador, and Peru.
Taxonomy Notes
Nuttallanthus was described as a distinct genus in 1988 by David A. Sutton, separating it from a broadly circumscribed Linaria. Its status remains contested: World Plants and the World Flora Online accept it as a valid genus, while Plants of the World Online treats it as a synonym of Linaria, which is now considered an Old World genus. The genus belongs to family Plantaginaceae (formerly Scrophulariaceae) based on molecular phylogenetic evidence.
