General Information

Habitat Requirements

Hesperomannia lydgatei is found in the Wahiawa Mountains between 207 and 1,570 meters (680 and 5,151 feet) elevation along streambanks and forested slopes in rich brown soil and silty clay in Metrosideros polymorpha (ohia) wet forest with Adenophorus spp., Antidesma platyphyllum (hame), Bidens forbesii (kookoolau), Bobea brevipes (akahea lau lii), Boehmeria grandis (akolea), Cheirodendron sp. (olapa), Cibotium spp. (hapuu), Cyanea spp. (haha), Cyrtandra longifolia (haiwale), Dicranopteris linearis (uluhe), Diplopterygium pinnatum (uluhe lau nui), Dubautia spp. (naenae), Elaphoglossum spp. (ekaha), Hydrangea arguta (kanawao), Ilex anomala (kawau), Kadua affinis (manono), Labordia lydgatei (kamakahala), Machaerina angustifolia (uki), Melicope feddei (alani), Myrsine lessertiana (kolea lau nui), Peperomia spp. (ala ala wai nui), Perrottetia sandwicensis (olomea), Pipturus spp. (mamake), Platydesma rostrata (pilo kea lau lii), Polyscias oahuensis (ohe mauka), Pritchardia flynii (loulu), Psychotria mariniana (kopiko), Sadleria spp. (amau), Scaevola spp. (naupaka), Syzygium sandwicense (ohia ha), and Wikstroemia spp. (akia).

Movement / Home Range

Genetic studies conducted on the Hawaiian Hesperomannia species indicated that plants that occur on west Maui and Molokai are H. arborescens, those on Oahu are H. swezeyi (Koolau mountains) and H. oahuensis (Waianae mountains), and those individuals on Kauai remain H. lydgatei. Hesperomannia arbuscula is no longer a valid species. The Kauai populations show low genetic variation with some degree of inbreeding and genetic drift, with some reduction in fitness (Ching Harbin 2003). Hesperomannia lydgatei is currently restricted to a single large population of fewer than 100 individuals in the Wahiawa–Kanaele Bog Drainage Basin of southern Kauai at 660 to 774 m (2,165 to 2,540 ft).

Reproductive Strategy

The purple flower heads with long, tubular yellow florets of this species suggest pollination by long-tongued insects such as moths or butterflies. The plume-like hairs crowning the fruit strongly suggests dispersal by wind, as in many members of the sunflower family. This species grows almost exclusively along streams, so dispersal by water currents is also likely. Flowering material was collected from July to November. No mature fruits have been observed, and it is possible that Hesperomannia lydgatei is self-incompatible and fails to set seed unless cross-pollinated with other individuals. The abortive fruits are covered by a plume-like crown of light brown hairs 2 cm (0.8 in) long. Recent information about H. lydgatei biology and life history suggests that the species has high pollen viability, but low germination rates (Ching Harbin 2003). Most of the fruit are aborted, and few have embryos (Tangalin 2008).

Other

Pollen grains of Hesperomannia lydgatei (and H. arborescens) measure 45 micrometers in diameter, have a cylindrical shape and isolated spines, unlike other Asteraceae genera (Wortley et al. 2007). The species is distinguished from other members of this endemic Hawaiian genus by its pendant flower heads, longer and narrower hairless flower stalks, and shorter involucral (floral) bracts.