Sairocarpus is a genus of flowering plants in the family Plantaginaceae, placed within the tribe Antirrhineae. It comprises around ten to twelve species of small-flowered plants commonly known as snapdragons — a name inspired by the personate (two-lipped, closed-mouth) flowers that snap open when laterally squeezed, resembling the mouth of a dragon or animal.
The genus was formally described by D.A. Sutton in his 1988 monograph A Revision of the Tribe Antirrhineae (Oxford University Press). Sutton recognised these plants as a distinct New World group, separating them from the Old World genus Antirrhinum with which they had long been combined. Molecular phylogenetic studies published by Vargas et al. (2004) confirmed this separation, demonstrating that the New World snapdragons form a lineage independent of the Mediterranean Antirrhinum sensu stricto. Under this treatment, 11 of the species that Sutton placed in Sairocarpus are accepted; the remainder were assigned to the closely related genera Howelliella and Neogarrhinum.
Species in the genus are mostly annual herbs, mostly native to California, with a collective range extending from Oregon south through Baja California Sur and eastward to Utah and Arizona. They are ecologically diverse, occupying rocky and arid habitats in western North America, and are tetraploid (chromosome number n = 15–16), which distinguishes them from the diploid Old World Antirrhinum.
All species share the characteristic personate corolla with an inferior gibbous (pouched) base that typifies tribe Antirrhineae. The genus belongs to the same family, Plantaginaceae, into which Scrophulariaceae was merged following DNA-sequence-based reclassification.
Etymology
The genus name Sairocarpus was coined by D.A. Sutton in 1988 to accommodate the New World snapdragon species he segregated from Antirrhinum. These plants share the common name "snapdragon" with Antirrhinum, a name that refers to the personate flowers, which open and close like an animal's mouth when squeezed — likened to a dragon's face. The earlier section name applied to this group within Antirrhinum was Saerorhinum (Thompson 1988).
Distribution
Species of Sairocarpus are native to western North America, ranging from Oregon south through California and Baja California Sur, and east to Utah and Arizona. The majority of species are concentrated in California. They tend to grow in rocky, arid, and semi-arid environments typical of the Pacific coast ranges and the Sonoran Desert borderlands.
Taxonomy Notes
The circumscription of Sairocarpus has been contentious. Under the broad view, the New World snapdragons were included within Antirrhinum as section Saerorhinum (Thompson 1988). Sutton (1988) was the first to formally separate them as Sairocarpus. Molecular phylogenetic work by Oyama & Baum (2004) and Vargas et al. (2004) confirmed the New World group is monophyletically distinct from Old World Antirrhinum, and recommended placement of most species in Sairocarpus, with a minority in Howelliella and Neogarrhinum. The genus is tetraploid (n = 15–16), contrasting with the diploid Old World species. The Plants of the World Online lists approximately ten accepted species; GBIF records 12 descendants.
