Revision of Brighamia (Campanulaceae: Lobelioideae) a Caudiciform Succulent Endemic to the Hawaiian Islands

Abstract

Brighamia is a genus of caudiciform succulents endemic to coastal cliffs on four of the Hawaiian Islands. Aside from its habit, the genus is also unusual among Lobelioideae in its sal- verform corolla and few-flowered axillary inflorescences. The four species and two non-autonymic infraspecific taxa previously recognized are reduced to two allopatric species: Brighamia insignis of Ni'ihau and Kaua'i, with deltate to ovate calyx lobes 0.2-1 mm long, pedicels 10-30 mm long, papillose seeds, and yellow to pale cream (rarely white) corollas; and B. rockii of Moloka'i and Maui (and possibly Lana'i), with oblong to elliptic calyx lobes 2.5-8 mm long, pedicels 6-12 mm long, smooth seeds, and white corollas. The relationships of Brighamia to other genera are obscure. Possibly, it is most closely related to the endemic Australian genus Isotoma. The floral nectar is rich in sucrose, supporting suggestions based on floral morphology that the genus is pollinated by hawkmoths (Lepidoptera: Sphingidae).