Gilia is a genus of approximately 39–40 accepted species of flowering plants in the family Polemoniaceae, native to the Americas. The genus was described by Ruiz and Pavón in 1794, with the name honouring Felipe Luis Gil, a Spanish botanist.
Plants in the genus are predominantly summer annuals, though perennial forms exist. They grow from 10 to 120 cm tall on simple to branched, taprooted stems that range from glabrous to glandular-pubescent. Leaves are arranged spirally or alternately, entire to deeply pinnately lobed, and many species produce basal rosettes. The inflorescence is terminal and paniculate — open to congested — bearing 2–7 pedicelled flowers subtended by a bract. Flowers are actinomorphic with funnelform to salverform five-lobed corollas appearing in blue, white, pink, or yellow; the calyx membrane is usually ruptured in fruit. Fruits are ovoid to spheroid capsules with 2 to many seeds per locule.
The genus is centred in western North America, ranging from British Columbia south through California, Arizona, and Colorado into northern Mexico, with an eastern outlier population reaching Ohio. A disjunct South American range extends from Ecuador and Peru south through Bolivia and Chile to Argentina. Species occupy predominantly desert and semi-desert habitats in sunny, well-drained soils. Several Lepidoptera larvae — notably the moths Schinia aurantiaca and Schinia biundulata — use Gilia as a host plant; S. biundulata feeds exclusively on G. cana.
Well-known members include G. achilleifolia (California gilia), G. capitata (bluehead gilia), and G. tricolor (bird's-eye gilia). The genus has undergone significant taxonomic revision; Ipomopsis aggregata (scarlet gilia) was formerly placed within Gilia, and three heterotypic synonyms are recognised: Aegochloa Benth. (1833), Brickellia Raf. (1808), and Rossmaesslera Rchb. (1841).
Etymology
The genus name Gilia honours Felipe Luis Gil (died 1821), a Spanish botanist and apothecary. The name was bestowed by the Spanish botanists Hipólito Ruiz López and José Antonio Pavón Jiménez, who published the genus in their Flora Peruviana et Chilensis Prodromus in 1794.
Distribution
Gilia species are native to the Americas in two disjunct ranges. The main range spans western North America from British Columbia south through the Pacific states and into northern Mexico, with eastward extensions reaching Texas and Ohio. A separate South American range runs from Ecuador and Peru through Bolivia, Chile, and Argentina. Individual species are recorded from Arizona, California, and Colorado in the United States, reflecting a strong concentration in the arid and semi-arid western states.
Ecology
Gilia species are characteristic plants of desert and semi-desert habitats, favouring open, sunny sites with well-drained soils in both temperate and tropical zones of the Americas. As predominantly annual herbs, they complete their life cycles rapidly in seasonally dry environments. The genus supports specialist insect herbivores: larvae of the noctuid moths Schinia aurantiaca and Schinia biundulata feed on Gilia; S. biundulata is an obligate feeder on G. cana.
Taxonomy
Gilia Ruiz & Pav. was established in Flora Peruviana et Chilensis Prodromus (p. 25, October 1794) and is accepted by Kew's Plants of the World Online. Three heterotypic synonyms are recognised: Aegochloa Benth. (1833), Brickellia Raf. (1808), and Rossmaesslera Rchb. (1841). The genus belongs to the family Polemoniaceae, order Ericales. Significant reshuffling has occurred: Ipomopsis aggregata (scarlet gilia) and other species once placed in Gilia have been moved to segregate genera. GBIF recognises approximately 121 descendant taxa across all datasets, while POWO accepts 39 species.
