Final Comprehensive Conservation Plan - U.S. Fish and Wildlife ...

4.9.16 Silene hawaiiensis
Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
Silene hawaiiensis is a sprawling shrub federally listed as threatened. The climbing stems are
typically 6-16 in long and slightly hairy. The leaves are slender, with hairs concentrated along the
margins and toward the base. The flowers, which are arranged in branched inflorescences, are
greenish white and maroon below. These clusters are extremely sticky. Pale brown seeds are
enclosed in a capsule (dry fruit) that is 0.26-0.31 in in length. The enlarged root is spindle-shaped.
Silene hawaiiensis is endemic to the Island of Hawai„i from 3,352-7,915 ft. It occurs within montane
and subalpine dry shrubland on weathered lava, on various aged lava flows, and cinder substrates
(Federal Register 2003b). Historically, S. hawaiiensis could be found on the western slope of Mauna
Kea, the Humu„ula Saddle, near Kīlauea Crater, and along the slopes of Mauna Loa. Current
populations exist in the Hāmākua District, on Humu„ula Saddle, at PTA, north of Pu„u Keanui, and
in Hawai„i Volcanoes National Park (Federal Register 2003, Mitchell et al. 2005). In 2003, there are
156 occurrences of S. hawaiiensis. From 5,651-5,751 individuals were found at Hawai„i Volcanoes
National Park. The specimen identified on the KFU is currently pending verification. The shrub is
found in association with the following native flora: „ōhi„a, māmane, „a„ali„i, pūkiawe, pāwale, and
„ōhelo (Federal Register 2003b).
Two critical habitat units covering 6,908 ac were designated for the species within Hawai„i
Volcanoes National Park. These areas contain portions of Kīlauea Crater, Kīpukakulalio, Uwēkahuna
Bluff, Halema„uma„u Crater, and segments of the lava flows of 1919, 1921, and 1961 (Federal
Register 2003b).
Significant threats to S. hawaiiensis include grazing and trampling by goats, pigs, and sheep.
Ungulates easily break the branches and stems of this species. Competition with nonnative plants,
especially fountain grass, is another issue. The populations are also susceptible to human impacts
such as fire and disturbance due to military exercise (USFWS 1996a, Mitchell et al. 2005). No S.
hawaiiensis are known from Refuge lands, however it is known to be above the HFU at
approximately 7,000 ft.-10,000 ft in elevation
4.10 Other Native Plants
The plants now considered native to Hawai„i arrived to the archipelago via natural means such as
wind, water, or birds. According to Wagner et al. (1999), the native Hawaiian flora is comprised of
roughly 956 species within 87 families. Approximately 89 percent of these species are endemic
(found only in Hawai„i), while the remainder are indigenous (naturally found in Hawai„i and
elsewhere). Table 4-6 lists the native plant species found on either Refuge unit.
4-70 Chapter 4. Refuge Biology and Habitats