Lysimachia barcae (Primulaceae), a new endemic shrub from Wainiha, Kaua‘i, Hawaiian Islands

A new endemic species of Lysimachia from Kaua‘i, Hawaiian Islands, is described and illustrated with notes on its distribution, ecology, conservation status and phylogenetic relationships. A modification to the existing key for Hawaiian Lysimachia is provided. Lysimachia barcae sp. nov., differs from its Hawaiian congeners by its unique combination of mature stems villous to tomentose, petioles 1–3 mm long, leaves ovate, cordate to subcordate or rounded at base, with primary and secondary veins conspicuous, purple-red, raised on abaxial surface, often densely hirsute to pilose and pedicels 35–70 mm long.

Only ten mature individuals are known from a single colony along steep, precipitous slopes of Wainiha Valley, Kaua‘i. Lysimachia barcae represents a new Critically Endangered (CR) single-island endemic species and is the focus of concerted conservation efforts to prevent its extinction.