Pacific Science, vol. 65, no. 2 (2011)

Pacific Science 65.2 cover

Floristic Composition and Natural History Characteristics of Dry Forests in the Pacific
Thomas W. Gillespie, Gunnar Keppel, Stephanie Pau, Jonathan P. Price, Tanguy Jaffré, Jean-Yves Meyer, and Kristin O’Neill, 127-141

We compare the floristic composition of tropical dry forests at the stand level using Gentry’s transect method (0.1 ha) in some of the largest and highest-quality remaining fragments in the Pacific (Hawai’i, 15 sites; Fiji, 9; the Marianas, 3; the Marquesas, 6; New Caledonia, 7) and compare results with neotropical dry forests. A total of 299 species or morphospecies ≥2.5 cm diameter at breast height were identified from all 40 sites in the Pacific. Rubiaceae (28 spp.), Euphorbiaceae (25 spp.), Fabaceae (23 spp.), Sapindaceae (18 spp.), and Myrtaceae (17 spp.) were the most speciose families in Pacific dry forest; however, no family dominated across regions in the Pacific. The most common species by frequency and density in each region were native with the exception of Hawai’i, which contains a high number of nonnative species. Observed and estimated (Chao 2) levels of native species richness show that New Caledonia and Fiji contain the highest species richness followed by Hawai’i, the Marianas, and the Marquesas. There is very little overlap at the native species level among regions, with Hawaiian dry forests the most dissimilar at the native species, genus, and family level and New Caledonia and Fiji the most similar. Unlike mainland neotropical dry forest, dry forests in the Pacific contain very few deciduous species and a low proportion of wind-dispersed species. There is a high proportion of dioecious species in Hawai’i, which is similar to the neotropics; however, other Pacific regions have fewer dioecious species.

Plant Dispersal, Introduced Species, and Vegetation Change in the South Pacific Kingdom of Tonga
Patricia L. Fall and Taly Dawn Drezner, 143-156

Dispersal guilds hold key ecological implications for the vegetation history of islands. This study considers dispersal vectors in conjunction with species origin and growth form to characterize vegetation dynamics on the islands of Tonga in the South Pacific. Data for over 700 species compiled from published literature on the plants of Tonga support a comparative study of dispersal mechanisms and growth forms for native flora, species brought by Polynesian settlers, and taxa introduced since European contact. The indigenous flora, predominantly trees, is characterized primarily by endozoochorous (internal) dispersal through birds and bats. European introductions, primarily herbs, disperse commonly through epizoochorous (external) animal dispersal. Bat dispersal is most important for overstory indigenous and Polynesian trees and vines. In addition, rodents commonly eat seeds of native rain forest trees. The understory, which is overwhelmingly introduced, consists of wind-dispersed and externally animal-dispersed species, which are often early successional. Rain forest thinning encourages establishment of wind-dispersed species and nonnatives. Thus, the prospect of sustained native flora in Tonga would be enhanced by the preservation of bats, a particularly important dispersal vector for indigenous and endemic species, and by the eradication of introduced rats.

Primary Succession along an Elevation Gradient 15 Years after the Eruption of Mount Pinatubo, Luzon, Philippines
Thomas E. Marler and Roger del Moral, 157-

We determined vegetation structure and environmental variables in the Pasig-Potrero and Sacobia River systems on the east flank of Mount Pina-tubo, Luzon, Philippines, to define growth form and taxonomic groups that have influenced primary succession during the 15 yr since the eruption. We selected eight sites within an east-west range of 11.5 km, a north-south range of 7 km, and an elevation gradient of ca. 500 m. The 58 plant taxa we encountered among 63 sampled plots belonged to 21 families. Cover was dominated by Parasponia rugosa (tree) and Saccharum spontaneum (large grass). Cover of these two species was inversely related at the plot level. Exotic species represented nearly 60% of this flora but only 32% of the vegetation cover. Family richness was high for Asteraceae, Fabaceae, and Poaceae. Elevation, distance to the caldera, and distance to human settlement exhibited the most control over the vegetation. The influence of elevation on cover, species composition, and structure differed in these adjacent canyons. Plot species richness, cover, and diversity indices were greatest at the highest elevation of the Pasig-Potrero River. On a small scale, current dominant species may control progression of species assemblages as mediated by geophysical, chemical, facilitative, and competitive changes. Our findings indicate that ongoing anthropogenic disturbances and the prevalence of exotic species may prevent the vegetation from returning to its preeruption state. The invasive Pennisetum setaceum and Chromolaena odorata were widespread in this landscape, and their negative influence on vegetation recovery is probable. Ours is the first detailed survey of vegetation on newly created volcanic surfaces in the region and provides a baseline for understanding the landscape-level processes determining continuing succession.

Runoff, Sediment Transport, and Effects of Feral Pig (Sus scrofa) Exclusion in a Forested Hawaiian Watershed
Dashiell O. Dunkell, Gregory L. Bruland, Carl I. Evensen, and Creighton M. Litton, 175-194

Browsing and trampling by nonnative feral pigs (Sus scrofa) negatively impact native flora and fauna in forested ecosystems and cause soil compaction. However, their impact on runoff and erosion is largely unknown. This study addressed this knowledge gap by investigating effects of feral pigs on runoff volume and total suspended solids (TSS) in runoff from the upper forested area of a Hawaiian watershed. Correlations between TSS, runoff, and other environmental variables were also examined. Runoff was collected monthly after 11 individual storm events from June 2008 to April 2009 at seven sites in the Mānoa watershed on the island of O’ahu. Each site consisted of paired runoff plots (5.04 m2) with one plot located inside a fenced pig exclosure (exclosures 1 yr old at study initiation) and the other located in an adjacent area open to feral pigs. Forest composition and structure (stem density, stand basal area, and seedling/ sapling counts) were quantified at each site. Soil moisture, throughfall, runoff volume, and TSS in runoff were sampled for each storm event. The seven sites varied considerably in terms of forest structure, with stem densities ranging from 1,500 to 9,000 stems ha-1 and basal areas ranging from 20 to 132 m2 ha-1. Vegetation at all sites was dominated by nonnative species. Runoff volumes from fenced and unfenced plots were highly variable, ranging from <1 to >128 liters. TSS levels in runoff ranged from <0.01 to 7.05 g liter-1. TSS levels were generally higher in wet-season months, but this pattern was not consistent across all sites. TSS in runoff was significantly correlated with throughfall, soil moisture, and coarse woody debris cover. Although pig exclusion did not reduce TSS, significant reductions in runoff volume from pig exclusion plots were observed at one site, and two other sites showed a similar trend. Longer-term studies may reveal stronger or more consistent impacts of feral pigs. Using paired fenced versus unfenced runoff plots to study erosion impacts of feral pigs is a novel approach, and results from this study will help forest managers better understand and manage runoff and erosion dynamics.

Stream Nutrient Concentrations on the Windward Coast of Hawai‘i Island and Their Relationship to Watershed Characteristics
Jene Michaud and Tracy Wiegner, 195-217

Dissolved inorganic and organic nutrients and physiochemical parameters were measured in 24 Hawai‘i Island streams. Particulate nutrients and instantaneous nutrient and sediment fluxes were measured in half of these streams. Stream waters were dilute and slightly alkaline and had low concentrations of ammonium, orthophosphate, dissolved organic phosphorus, and total suspended solids. Particulate matter comprised 45%, 73%, and 28% of nitrogen, phosphorus, and carbon pools, respectively. Dissolved nitrogen was comprised primarily of organic nitrogen (54%) and nitrate (34%). In some streams, nitrate and total nitrogen concentrations were slightly elevated relative to Hawai‘i Department of Health (HDOH) water quality standards. Instantaneous nitrate yields for the streams plus 26 HDOH stations were calculated, and the average from the combined data set was 7.1 (SD 11.1) moles N day-1 km-2. Nitrate concentrations and yields were 2.1 and 3.5 times higher, respectively, in Kohala watersheds than in Mauna Kea watersheds. Regression analysis was used to evaluate whether water quality parameters are predicted by watershed area, mean annual rainfall, population density, or percentage of agricultural land. Many water quality parameters were not predicted by these variables. In Mauna Kea streams, concentrations of dissolved organic nitrogen and dissolved organic carbon increased with increasing watershed area, nitrate concentrations increased with increasing population density, and both specific conductivity and nitrate yield increased with increasing percentage of agricultural lands. In Kohala streams, nitrate concentrations and yields were not predicted by watershed characteristics. Overall, watershed characteristics, as quantified in this study, were not strong predictors of water quality.

Chemical Ecology of Red Mangroves, Rhizophora mangle, in the Hawaiian Islands
Brian Fry and Nicole Cormier, 219-234

The coastal red mangrove, Rhizophora mangle L., was introduced to the Hawaiian Islands from Florida 100 yr ago and has spread to cover many shallow intertidal shorelines that once were unvegetated mudflats. We used a field survey approach to test whether mangroves at the land-ocean interface could indicate watershed inputs, especially whether measurements of leaf chemistry could identify coasts with high nutrient inputs and high mangrove productivities. During 2001–2002, we sampled mangroves on dry leeward coasts of southern Moloka’i and O’ahu for 14 leaf variables including stable carbon and nitrogen isotopes (δ13C, δ15N), macronutrients (C, N, P), trace elements (B, Mn, Fe, Cu, Zn), and cations (Na, Mg, K, Ca). A new modeling approach using leaf Na, N, P, and δ13C indicated two times higher productivity for mangroves in urban versus rural settings, with rural mangroves more limited by low N and P nutrients and high-nutrient urban mangroves more limited by freshwater inputs and salt stress. Leaf chemistry also helped identify other aspects of mangrove dynamics: especially leaf δ15N values helped identify groundwater N inputs, and a combination of strongly correlated variables (C, N, P, B, Cu, Mg, K, Ca) tracked the mangrove growth response to nutrient loading. Overall, the chemical marker approach is an efficient way to survey watershed forcing of mangrove forest dynamics.

Community Composition of Elasmobranch Fishes Utilizing Intertidal Sand Flats in Moreton Bay, Queensland, Australia
Simon J. Pierce, Tracey B. Scott-Holland, and Michael B. Bennett, 235-247

Thirteen elasmobranch species were collected during a 4-yr survey of the intertidal margins of Moreton Bay, a large subtropical embayment in southeastern Queensland, Australia. Stingrays were the most common large predators in the intertidal zone, with total catch dominated numerically by blue-spotted maskray, Neotrygon kuhlii (53.8%); estuary stingray, Dasyatis fluviorum (22.2%); and brown whipray, Himantura toshi (10.2%). There was a significant female bias within intertidal populations of N. kuhlii and D. fluviorum. Courtship behaviors were observed in July and September in D. fluviorum and in January for white-spotted eagle ray, Aetobatus narinari. Dasyatis fluviorum, a threatened Australian endemic stingray, remains locally abundant within the bay. Overall, the inshore elasmobranch fauna of Moreton Bay is relatively species rich compared with similar studies elsewhere in Australia, emphasizing the regional importance of this ecosystem.

New Records of Commercially Valuable Black Corals (Cnidaria: Antipatharia) from the Northwestern Hawaiian Islands at Mesophotic Depths
Daniel Wagner, Yannis P. Papastamatiou, Randall K. Kosaki, Kelly A. Gleason, Greg B. McFall, Raymond C. Boland, Richard L. Pyle, and Robert J. Toonen, 249-255

Mesophotic coral reef ecosystems are notoriously undersurveyed worldwide and particularly in remote locations like the Northwestern Hawaiian Islands (NWHI). A total of 37 mixed-gas technical dives were performed to depths of 80 m across the NWHI to survey for the presence of the invasive octocoral Carijoa sp., the invasive red alga Acanthophora spicifera, and conspicuous megabenthic fauna such as black corals. The two invasive species were not recorded from any of the surveys, but two commercially valuable black coral species, Antipathes griggi and Myriopathes ulex, were found, representing substantial range expansions for these species. Antipathes griggi was recorded from the islands of Necker and Laysan in 58–70 m, and Myriopathes ulex was recorded from Necker Island and Pearl and Hermes Atoll in 58–70 m. Despite over 30 yr of research in the NWHI, these black coral species had remained undetected. The new records of these conspicuous marine species highlight the utility of deepdiving technologies in surveying the largest part of the depth range of coral reef ecosystems (40–150 m), which remains largely unexplored.

Newly Collected Specimens of the Sleeper Eleotris acanthopoma (Teleostei: Eleotridae) from French Polynesia Indicate a Wide and Panmictic Distribution in the West and South Pacific
Ken Maeda, Takahiko Mukai, and Katsunori Tachihara, 257-264

The morphology of Eleotris acanthopoma collected from Moorea in French Polynesia is described. This is the first record of this species from French Polynesia, greatly expanding the known range, which was previously only considered to extend from southern Japan to New Caledonia. Nucleotide sequences of the mitochondrial ND5 gene of several Eleotris species and related genera indicate that E. acanthopoma from Moorea belongs to the same lineage as E. acanthopoma from Japan and the Philippines. Despite being separated by a distance of approximately 10,000 km, two of the specimens from Moorea and one from the Philippines had identical nucleotide sequences. Results of this study indicate that extensive dispersal occurs during the pelagic larval stage of this species.

Acanthurus nigros Günther, a Valid Species of Surgeonfish, Distinct from the Hawaiian A. nigroris Valenciennes
John E. Randall, Joseph D. DiBattista, and Christie Wilcox, 265-275

The Blueline Surgeonfish, Acanthurus nigroris Valenciennes, formerly considered as wide-ranging in the central and western Pacific, is restricted to the Hawaiian Islands. Acanthurus nigros Günther, type locality Vanuatu, is available for the sister species from the Pitcairn Islands west to the Great Barrier Reef and Caroline Islands. Although these two species are very similar in color, there are fin-ray and gill-raker differences, and the genetic difference (i.e., 4.12 % mtDNA cytochrome b sequence divergence) alone warrants species recognition.

Reptiles of Fais Island, Yap State, Federated States of Micronesia
Donald W. Buden, 277-283

Eleven species of reptiles (six skinks, four geckos, one monitor lizard) are recorded from Fais Island, Micronesia, four of them (Gehyra mutilata, Lepidodactylus moestus, L. sp., and Eugongylus albofasciolatus) for the first time. The skinks Emoia caeruleocauda and E. jakati are the most common species; G. mutilata is the most common gecko in edificarian habitats, and L. moestus is the most common outside the areas of human habitation. Nearly all of the species are widespread in the western Pacific region, although Eutropis sp. is at the easternmost limits of its distribution in the Caroline Islands on Fais. The monitor lizard Varanus indicus was introduced during the Japanese administration. The other species may have arrived by natural dispersal, or by human assistance, or a combination of the two.

Association Affairs, 285