Another New, Nearly Extinct Species of Hibiscadelphus (Malvaceae) from the Hawaiian Islands

Abstract

Four individuals of a new species of Hibiscadelphus (Malvaceae: Hibisceae) have been discovered on Kaua'i, the oldest of the major Hawaiian Islands. Hibiscadelphus woodii is described and illustrated, and its status and basal relationship within the genus are discussed. The imperiled status of the other six species is reviewed, and a key to the genus is given. Hibiscadelphus Rock consists of seven species endemic to the Hawaiian Islands (Bates, 1990), including the one described herein. The genus was originally established by Joseph F. Rock (Radlkoffer & Rock, 1911) to accommodate three species of shrubs or small trees that he had collected from dryland forests: two species on the island of Hawai'i, H. giffardianus Rock (Mauna Loa) and H. hualalaiensis Rock (Hualalai), and H. wilderianus Rock from Auwahi on East Maui. Four additional species were subsequently described: H. bombycinus C. Forbes from the Kohala Mountains on the island of Hawai'i (Forbes, 1920), H. distans L. Bishop & Herbst from the Koai'e Canyon of Kaua'i (Bishop & Herbst, 1973), H. crucibracteatus Hobdy from Puhielelu Ridge on Lana'i (Hobdy, 1984), and the new species, H. woodii, described herein from Kalalau Valley, Kaua'i. Hibiscadelphus is a member of the tribe Hibisceae, represented in the Hawaiian Islands by the indigenous genus Hibiscus L., following Fryxell's (1968) classification. Although closely related to Hibiscus (the generic name means brother of Hibiscus), Hibiscadelphus is clearly a distinct monophyletic group based on its curved and narrowly convolute zygomorphic corollas with the lower two lobes shorter than the other three, calyces that are circumscissily deciduous in fruit, and relatively thick, woody capsules (Hobdy, 1984; Bates, 1990). The green, yellow, or magenta flowers with tubular, curved corollas are presumably adapted to pollination by native Meliphagid and Drepanidine birds, known a the honeyeaters and honeycreepers (Hobdy, 1984). The Hawaiian name for members of the genus is hau kuahiwi, meaning upland or mountain hau, because of their resemblance to the common lowland hau, Hibiscus tiliaceus L. (Rock, 1913; Bates, 1990). Due to the destruction and severe alteration of the diverse dry and mesic forest habitats and loss of all of the Meliphagid birds in the Hawaiian Islands (Hobdy, 1984), five of the seven Hibiscadelphus species have become extinct in the wild, although at least two of these are maintained through cultivated plants: H. giffardianus and H. hualalaiensis. Only H. distans, a U.S. federally listed endangered species, and the new species described in this paper have naturally occurring wild populations (Table 1; Bates, 1990). The status of the genus is extremely precarious at present. In March 1991 an unusual species of Hibiscadelphus not corresponding with any of the described taxa was discovered on Kaua'i by Kenneth R. Wood, staff member of the National Tropical Botanical Garden, along with M. Query and S. Montgomery. Four plants were found growing on a steep slope below the rim of Kalalau Valley in northwestern Kaua'i (K. R. Wood, 1992, unpublished). Study of flowering specimens has revealed that they represent a new species. Hibiscadelphus woodii Lorence & W. L. Wagner, sp. nov. TYPE: Hawaiian Islands. Kaua'i: Hanalei District, Kalalau Rim, N of Kahuama'a Flat, steep diverse lowland mesic forest, 9901020 m, 3 Mar. 1991, K. R. Wood, M. Query & S. Montgomery 629 (holotype, PTBG, a flower also in spirit collection; isotypes, BISH, K, MO, NY, US). Figure 1. Species foliis glabratis vel venis sparsim stellato-puberulis, pagina abaxiali laminae axillis venarum trichomatibus stellatis instructis, calyce trichomatibus stellatis cum radiis 5-8 ornatis, corolla cerina cupreo-suffusa atropurpurescentia distinguibilis. NovoN 5: 183-187. 1995. This content downloaded from 207.46.13.131 on Sun, 16 Oct 2016 05:12:04 UTC All use subject to http://about.jstor.org/terms