Pacific Science, vol. 65, no. 1 (2011)

Pacific Science 65.1 coverEighty Years of Succession in a Noncommercial Plantation on Hawai‘i Island: Are Native Species Returning?
Joseph Mascaro, 1

Hawai‘i’s forest ecosystems are changing rapidly due to a high level of species introductions, and it is an open question whether native species will be maintained. Several studies have explored the potential for native species to succeed in future communities dominated by introduced species in Hawai‘i, but the results have been conflicting and most of the studies have been limited to relatively young forest (<30 yr old). I surveyed a remote, 80-yr-old noncommercial plantation on Hawai‘i Island to determine whether any native tree species were able to succeed in the planted forest. I compared abundance and composition of native species in the plantation to that in a relict, native-dominated forest adjacent to the plantation and located on the same substrate type. After 80 yr, native species constituted just 4.5% of basal area and 12.1% of stem density in the plantation. However, I found that the relative success of native species varied strongly by species. Of nine native species encountered in the relict forest, six were rare or absent in the planted forest. A seventh (Metrosideros polymorpha) dominated the relict forest but was unable to recruit in the planted forest. However, two shade-tolerant understory tree species (Psychotria hawaiiensis and Psydrax odorata) were at least as common in the plantation as in the relict forest, and the latter was significantly more abundant in the plantation. Thus, although I found no evidence that native species will dominate with continued succession, I found that at least two native species may remain important components of plantation-derived Hawaiian forests in the future.

Role of Fire in the Germination Ecology of Fountain Grass (Pennisetum setaceum), an Invasive African Bunchgrass in Hawai‘i
Edith Nonner, Susan Cordell, and Donald R. Drake, 17

Field and laboratory studies were carried out to test factors expected to be relevant for the germination of fountain grass: (1) light; (2) emergence of fountain grass seedlings from depths of 0, 2.5, and 5 cm; (3) fire passing over exposed and buried seeds; (4) laboratory heat treatment mimicking exposure to grass fire. Both fire in the field and heat applied in the laboratory killed fountain grass seeds. In the laboratory, some seeds were killed after exposure to 75°C for 3 min, and all seeds were killed at 100°C. During the prescribed burns, temperatures at the soil surface reached at least 204°C, but temperatures at depths of 2.5 and 5 cm showed no measurable change. Light is not essential for germination of fountain grass seeds, and seedlings can emerge from depths of at least 5 cm. Both of these traits contribute to the invasive capacity of the species. Because fountain grass seeds are killed at temperatures in excess of 100°C, the species depends on its ability to resprout and quickly set seed after fire for population growth and spread. Seeds buried beneath the soil may escape exposure to fire, and substrate heterogeneity may provide refuge from temperature extremes experienced during fire. The morphology of fountain grass seeds likely inhibits burial in the soil for the most part, but there are several potential burial mechanisms. Prescribed burns could prove to be a useful tool for fountain grass control in large, degraded sites where fountain grass has invaded but only when coupled with additional control measures.

Pattern of Twig Cutting by Introduced Rats in Insular Cloud Forests
Tetsuto Abe and Hiromi Umeno, 27

We examined seasonal patterns of twig cutting by the introduced black rat, Rattus rattus, on Haha-jima Island, an island in the Ogasawara (Bonin) group of Japan. Censuses were conducted along seven routes to count the number of trees damaged by twig cutting in each month. Overall, 42.6% (23/54 species) of woody species were damaged. Twig cutting was greatest in spring (March-May). Probability of damage by twig cutting was not correlated with species frequency in the vegetation. This suggests that twig cutting is associated with particular characteristics of target species. Endemic plants experienced a significantly higher probability of twig cutting than alien plants. This may be due to an evolutionary loss of plant defense mechanisms in the absence of herbivorous mammals. Because the overall proportion of individuals damaged by twig cutting was not high, the behavior is unlikely to influence the population dynamics of trees and cause vegetation change. But intense twig cutting was also found on critically endangered plants, so twig cutting by black rats could be a threat to those species.

Excluding Nontarget Species from Brown Tree Snake, Boiga irregularis (Reptilia: Colubridae), Bait Stations: Experimental Tests of Station Design and Placement
Tom Mathies, Russell Scarpino, Brenna A. Levine, Craig Clark, and Julie A. Savidge, 41

Bait stations with toxic baits are an emerging technology for eradication of the invasive brown tree snake (Boiga irregularis) on Guam, yet potential interferences by nontarget species are largely unknown. We tested the efficacies of three bait station designs together with three commonly used station support structures to exclude nonnative rats (roof rat, Rattus rattus; Norway rat, Rattus norvegicus; Polynesian rat, Rattus exulans) and native coconut crabs (Birgus latro). When directly presented, all species readily consumed the dead neonatal mouse baits (nontoxic) including those replicating decomposing baits in the field. When bait stations were made easily accessible by placement near ground level, all rat species were able to enter all station types, but some individual roof rats and Norway rats exhibited apparent neophobia. When stations were placed up on support structures, simulating those in the field (~1 m above ground level), numbers of station accessions by roof rats and Norway rats remained essentially unchanged, but Polynesian rats then showed almost no inclination to enter stations. However, ability to access entrances of stations (but not interiors) when on support structures was extremely high for roof rats and appreciable for the other rat species, including Polynesians. The station type currently in widest use, when placed on chain-link cyclone fence, had the highest probability of accession. Crabs readily accessed station entrances but never interiors. The two downward-angled station designs, when placed in simulated vegetation, had the lowest probabilities of accession. In areas where nontarget species are a concern, we recommend use of either of the downward-angled station designs and suspension from vegetation wherever possible.

Survival of European Mouflon (Artiodactyla: Bovidae) in Hawai‘i Based on Tooth Cementum Lines
Steven C. Hess, Robert M. Stephens, Tommy L. Thompson, Raymond M. Danner, and Ben Kawakami Jr., 59

Reliable techniques for estimating age of ungulates are necessary to determine population parameters such as age structure and survival. Techniques that rely on dentition, horn, and facial patterns have limited utility for European mouflon sheep (Ovis gmelini musimon), but tooth cementum lines may offer a useful alternative. Cementum lines may not be reliable outside temperate regions, however, because lack of seasonality in diet may affect annulus formation. We evaluated the utility of tooth cementum lines for estimating age of mouflon in Hawai‘i in comparison to dentition. Cementum lines were present in mouflon from Mauna Loa, island of Hawai‘i, but were less distinct than in North American sheep. The two age-estimation methods provided similar estimates for individuals aged ≤3 yr by dentition (the maximum age estimable by dentition), with exact matches in 51% (18/35) of individuals, and an average difference of 0.8 yr (range 0–4). Estimates of age from cementum lines were higher than those from dentition in 40% (14/35) and lower in 9% (3/35) of individuals. Discrepancies in age estimates between techniques and between paired tooth samples estimated by cementum lines were related to certainty categories assigned by the clarity of cementum lines, reinforcing the importance of collecting a sufficient number of samples to compensate for samples of lower quality, which in our experience, comprised approximately 22% of teeth. Cementum lines appear to provide relatively accurate age estimates for mouflon in Hawai‘i, allow estimating age beyond 3 yr, and they offer more precise estimates than tooth eruption patterns. After constructing an age distribution, we estimated annual survival with a log-linear model to be 0.596 (95% CI 0.554–0.642) for this heavily controlled population.

Prehistoric Birds and Bats from the Atiahara Site, Tubuai, Austral Islands, East Polynesia
Trevor H. Worthy and Robert Bollt, 69

The Austral Islands in French Polynesia have a depauperate land bird fauna and until recently have been little investigated archaeologically or paleontologically to know whether this is natural. Here we report an avifaunal assemblage and bones of bats of the genus Pteropus from the Archaic period (ca. A.D. 1000–1450) cultural site Atiahara, on Tubuai. Fifteen taxa are reported from the island, and a new species of rail in the genus Gallirallus is described. The data indicate that several petrel species have been extirpated from the island and that former land bird inhabitants included at least two small pigeons and a flightless rail.

Pelagic Larval Duration and Settlement Size of Apogonidae, Labridae, Scaridae, and Tripterygiidae Species in a Coral Lagoon of Okinawa Island, Southern Japan
Taiki Ishihara and Katsunori Tachihara, 87

Pelagic larval duration and settlement sizes in species of Apogonidae, Labridae, Scaridae, and Tripterygiidae in a coral lagoon in southern Japan were examined. Sampling was conducted monthly from July 2004 to June 2005 in the coral lagoon and channel of the Oh-do Beach on Okinawa Island, Japan. Pelagic larval duration was estimated by the number of otolith increments. Mean standard length at settlement of apogonids ranged from 7.7 to 13.9 mm, and mean pelagic larval duration ranged from 14.0 to 30.6 days (14 species, 418 individuals). In labrids, mean standard length at settlement and pelagic larval duration varied greatly (mean standard length: 5.4–11.0 mm; pelagic larval duration: 18–57 days, four species, four individuals). Scarids showed consistent mean standard length at settlement and pelagic larval duration (mean standard length: 7.1–7.6 mm; pelagic larval duration: 29–42 days, five species, 25 individuals). In tripterygiids, pelagic larval duration was more consistent (range: 18–29 days, mean: 22.2±2.1 days), but mean standard length at settlement ranged from 7.8 to 10.3 mm (six species, 32 individuals). These results suggest that the pelagic larval duration of Apogonidae and Tripterygiidae (nonpelagic egg spawning) is shorter than that of Labridae and Scaridae (pelagic egg spawning), and the dispersal strategy of labrids and scarids may include wider dispersal than that of apogonids and tripterygiids.

Trace Metal Partitioning in a Nearshore Tropical Environment: Geochemistry of Carbonate Reef Flats Adjacent to Suva Harbor, Fiji Islands
John D. Collen, Jane E. Atkinson, and John E. Patterson, 95

Namuka Reef is a broad fringing reef flat situated immediately adjacent to the populous and heavily industrialized areas surrounding Suva Harbor, Fiji Islands. Reef flat sediments are mainly very poorly to moderately sorted carbonate gravels and sands with occasional boulders and very little silt, with terrigenous sediments limited to a narrow, nearshore strip. Bulk sediment geochemical analyses show that trace metal concentrations are generally very low across the reef flat and closely similar to pristine reef areas offshore rather than to the nearby contaminated areas within Suva Lagoon. Exceptions occur close to villages, however, where sediments are enriched in Pb, As, and other trace metals, and possibly near wreck sites on the reef where Fe increases locally. These data together with those for major and minor oxides show that there is little or no movement of sediments from the rivers and deeper lagoon onto the carbonate reef flat even though extreme events such as tsunamis or cyclones affect the area. This indicates that the geomorphic separation of reef flats from adjacent contaminated environments is sufficient to prevent the introduction of solid contaminants. Reef flats may thus retain healthy ecosystems and provide resources to the community even though close to heavily contaminated areas.

Proposal of the Name Chaetomorpha vieillardii (Kütz.), n. comb., for a Large-Celled Tropical Chaetomorpha (Chlorophyta)
Michael J. Wynne, 109

Type material of Bangia vieillardii Kütz. from New Caledonia has been studied and determined to belong to the green algal genus Chaetomorpha. The name Chaetomorpha vieillardii (Kütz.), n. comb., is effected, and this binomial is proposed to serve for what has previously been known in tropical seas as C. crassa. Genuine C. crassa (C. Agardh) Kütz., based on European type specimens, has been treated by others to be conspecific with C. linum (O. F. Müll.) Kütz.

New Records of Butterflies from Yap Outer Islands, Micronesia: Fais Island and Ngulu, Ulithi, and Woleai Atolls
Donald W. Buden and W. John Tennent, 117

Eight species of butterflies are recorded from among four different island groups in Yap Outer Islands, Federated States of Micronesia (FSM). Five species (63%) belong to the family Lycaenidae; the three others to Nymphalidae. Hypolimnas bolina is the most ubiquitous species, being the only one recorded on all the islands. Ngulu Atoll, which has the smallest land area, also has one of the most depauperate butterfly faunas, with only two species recorded, but it is located between Palau and Yap proper, which host the richest butterfly faunas in southwestern Micronesia. Ulithi Atoll, which is nearest to potential source populations on Yap, has the largest number of species. Small island size, limited habitat diversity, and lack of sufficient host plants combined with distance from potential source populations are likely to be the main factors contributing to the small number of species on these low-lying coralline islands.

Association Affairs, 123

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