Dubautia kalalauensis, a new species of the Hawaiian silversword alliance (Compositae, Madiinae) from northwestern Kaua'i, USA

Dubautia kalalauensis B. G. Baldwin & G. D. Carr is a newly described species of the Hawaiian silversword alliance (Compositate, Madiinae) from wet forests in the vicinity of the rim of Kalalau Valley, Kaua'i. The taxon has been treated within the circumscription of D. taxa Hooker & Arnott subsp. hirsuta (Hillebrand) G. D. Carr. but differs by having a more openly branching habit, softer leaf surfaces, greenish cream (rather than yellow) corollas, less glandular corolla tubes and throats, and longer pappus elements. Based on molecular phylogenetic data, D. kalalauensis is less closely related tot he widespread D. taxa than to other Kaua'i endemics, including D. imbricala H. St. John & G. D. Carr, D. kenwoodii G. D. Carr, D. laevigata A. Gray, D. syndetica G. D. Carr & Lorence, and D. waialealae Rock. Unlike all previously described taxa of Dubautia Gaudiehaud-Beaupre, D. kalalauensis combines opposite leaves, eglandular peduneles, receptacular bracts throughout the heads (one per floret), greenish cream corollas, and pappi of setiform scales ca. 4 mm long.