Pacific Science, vol. 64, no. 1 (2010)

Pacific Science 64.1 cover
Potential Economic Damage from Introduction of Brown Tree Snakes, Boiga irregularis (Reptilia: Colubridae), to the Islands of Hawai‘i
Stephanie A. Shwiff, Karen Gebhardt, Katy N. Kirkpatrick, and Steven S. Shwiff, 1-10

The Brown Tree Snake (Boiga irregularis) has caused ecological and economic damage to Guam, and the snake has the potential to colonize other islands in the Pacific Ocean. This study quantifies the potential economic damage if the snake were translocated, established in the state of Hawai‘i, and causing damage at levels similar to those on Guam. Damages modeled included costs of medical treatments due to snakebites, snake-caused power outages, and decreased tourism resulting from effects of the snake. Damage caused by presence of the Brown Tree Snake on Guam was used as a guide to estimate potential economic damage to Hawai‘i from both medical- and power outage–related damage. To predict tourism impact, a survey was administered to Hawaiian tourists that identified tourist responses to potential effects of the Brown Tree Snake. These results were then used in an input-output model to predict damage to the state economy. Summing these damages resulted in an estimated total potential annual damage to Hawai‘i of between $593 million and $2.14 billion. This economic analysis provides a range of potential damages that policy makers can use in evaluation of future prevention and control programs.

Potential Distribution of the Alien Invasive Brown Tree Snake, Boiga irregularis (Reptilia: Colubridae)
Dennis Rödder and Stefan Lötters, 11-22

The Brown Tree Snake (Boiga irregularis) is native to Southeast Asia and Australia and has been introduced to Guam. There it causes major ecological and socioeconomic problems and is considered to belong to the 100 worst alien invasive species worldwide. We used a maximum entropy-based Climate Envelope Model to identify worldwide areas outside the species’ known range that are potentially suitable under current climatic conditions. Projections revealed that this invasive alien species potentially occurs in tropical and some subtropical regions. In the closer vicinity of the snake’s known distribution, highest suitability was found for the Northern Mariana Islands, Hawaiian Islands, Madagascar, New Caledonia, and Fiji Islands. If predictions are interpreted as depicting invasiveness potential of B. irregularis, strategies to prevent invasion should focus on these regions. An analysis of potential distributions under different future anthropogenic climate-change scenarios showed that the Fiji Islands, Hawaiian Islands, and Northern Mariana Islands will remain overall most suitable habitat for the Brown Tree Snake. In addition, we noted an increase of suitability in New Zealand.

Rapid Invasion Despite Lack of Genetic Variation in the Erythrina Gall Wasp (Quadrastichus erythrinae Kim)
Daniel Rubinoff, Brenden S. Holland, Alexandra Shibata, Russell H. Messing, and Mark G. Wright, 23-31

The erythrina gall wasp, Quadrastichus erythrinae Kim, has recently and rapidly invaded a broad swath of the tropical and subtropical Pacific Basin, causing severe damage to most species of coral trees (Erythrina spp.). This small (length ~1.5 mm) wasp attacks the photosynthetic tissue (leaves, buds, stems, flowers) of ornamental and native Erythrina, often killing the trees. This invasion poses an immediate extinction threat to native Erythrina spp. throughout Asia, Australia, and a number of Pacific archipelagos, including Hawai‘i, where populations of the endemic E. sandwicensis have been devastated. Although this pest is known to occur naturally in East Africa, the precise geographic origin of the invasions remains unknown. In this study, 1,623 base pairs of mitochondrial (cytochrome c oxidase subunit I) and nuclear DNA (elongation factor alpha) were used to confirm systematic identity and to examine genetic divergence among invasive populations from Hawai‘i, Guam, American Samoa, Japan, Singapore, Taiwan, and China. Samples from all invasive populations included in our study showed a complete lack of genetic diversity. Molecular findings confirm that a single species, Q. erythrinae, is involved in this dramatic, recent range expansion and that introductions may have been associated with population bottlenecks that have reduced genetic diversity in populations sampled. Although reductions in genetic diversity are generally considered detrimental to fitness, this study provides an example of invasion success despite a lack of detectable genetic variation. The monomorphic genetic pattern observed also suggests that Q. erythrinae initially may have been introduced to one location, and this invasive population may have subsequently served as a source for additional secondary invasions by unknown introduction vectors.

A Native Besieged: Effects of Nonnative Frugivores and Ground Vegetation on Seed Removal in a Highly Endangered Hawaiian Shrub, Delissea rhytidosperma (Campanulaceae)
Tracy L. Erwin and Truman P. Young, 33-43

Nonnative species can have serious negative effects on regeneration and restoration of rare plant taxa, particularly in insular ecosystems. An endangered Hawaiian shrub, Delissea rhytidosperma (Campanulaceae), produces fruits and viable seeds, but no regeneration has been observed in the wild. We used cages and vegetation removal to explore direct and indirect effects of three groups of nonnative species on suspected seed predation of this endangered plant: a mat-forming grass (Oplismenus hirtellus), rats (Rattus spp.), and invertebrates. Substantial seed removal occurred in all treatments. Both rat exclusion and clearing of nonnative vegetation had strong significant negative effects on seed removal. Highest removal rates occurred with rats not excluded and vegetation present, and lowest removal occurred when rats were excluded and vegetation cleared. Without rat exclosures, 100% of seeds were removed within 15 days. Even when protected from rats, most seeds were removed by smaller herbivores, unless ground vegetation was cleared. Vegetation appears to harbor invertebrates that eat seeds, including nonnative slugs. These results revealed that different nonnative species combine to greatly increase rates of seed removal in endangered D. rhytidosperma.

Reproductive and Pollination Biology of the Endemic Hawaiian Cotton, Gossypium tomentosum (Malvaceae)
John M. Pleasants and Jonathan F. Wendel, 45-55

Gossypium tomentosum is a cotton species endemic to the Hawaiian Islands. We studied several aspects of its reproductive biology, including potential pollinators, floral biology, and diurnal and seasonal flowering phenology. Flower visitors were observed in G. tomentosum populations on O‘ahu, Kaho‘olawe, and Maui. Primary visitors were introduced species, honeybees and carpenter bees, both of which were pollinating the flowers. No native bee species were seen visiting flowers. In examining floral biology we found that in some cases 10% of flowers had styles that were as short as the anthers or were recurved toward the anthers. In the greenhouse, in the absence of pollinators, these flowers were the only ones that set fruit. Flowering of G. tomentosum commences in January and February, following the rainy season, peaks in May, and may continue into August and September. In one year, after higher than average precipitation during the rainy season, there was a greater abundance of flowering, and flowering persisted later into the year. Transgenic varieties of commercial cotton, G. hirsutum, are grown in Hawai‘i and are interfertile with G. tomentosum. Honeybees and carpenter bees are also known pollinators of commercial cotton. Because these pollinators are long-distance foragers, we estimate that transgenic cotton fields would have to be greater than 10 km from a G. tomentosum population to prevent gene flow.

Methane Emission from a Tropical Wetland in Ka‘au Crater, O‘ahu, Hawai‘i
Maxime Grand and Eric Gaidos, 57-72

Natural tropical wetlands constitute an important but still poorly studied source of atmospheric methane, a powerful greenhouse gas. We measured net methane emission, soil profiles of methane generation and oxidation, and related environmental parameters in a tropical wetland occupying the Ka‘au extinct volcanic crater on the Hawaiian island of O‘ahu. The wetland has a fluctuating water table with dynamics that can be reproduced using precipitation data and a simple model. Median net methane flux was 117 mg m-2 day-1 and is consistent with measurements at other tropical sites. Net methane flux in the Commelina diffusa–dominated vegetation pattern (honohono) was significantly higher than that of the invasive Psidium cattleianum–dominated pattern (strawberry guava). Net methane emission in the honohono vegetation pattern was also significantly higher during the “wet” season compared with the “dry” season, although we did not find a clear correlation between net methane emission, water table level, or precipitation. We show that the measured fluxes are consistent with the integrated potential methane generation over the uppermost 30 cm of soil and consumption of ~50% of that methane in the soil. Absence of a correlation between net methane emission and water table level may be due to suppression of the activity of strictly anaerobic methanogens by dynamic redox conditions in the upper layers of soil and varying rates of methane oxidation by facultive methanotrophs.

Climate and Vegetation Changes at Coringa-Herald National Nature Reserve, Coral Sea Islands, Australia
George N. Batianoff, Gillian C. Naylor, John A. Olds, Nigel A. Fechner, and V. John Neldner, 73-92

Climatic changes at Coringa-Herald National Nature Reserve (CHNNR) in the last 82 yr include a 0.7ºC rise in mean minimum winter temperatures and increases in drought duration and frequency. Between 1991 and 2002, a plague of the scale insects Pulvinaria urbicola (Cockerell), together with attendant ants destroyed Pisonia grandis R.Br. rain forest at South-West Coringa Islet. Scale insect damage of P. grandis has also been recorded at North-East Herald Cay. This study explored the reasons for vegetation dieback during current climate. Woody species such as Argusia argentea (L.) Heine, Cordia subcordata Lam., and the grasses Lepturus repens (G. Forst.) R.Br. and Stenotaphrum micranthum (Desv.) C. E. Hubb. have also declined at CHNNR. Ximenia americana L. and Digitaria ctenantha (F. Muell.) Hughes were found to be locally extinct. Dieback of forests results in reduction of canopy-breeding seabirds and burrowing shearwaters (Puffinus pacificus [Gmelin)]. Dieback species were replaced by the shrub Abutilon albescens Miq. and/or fleshy herbaceous plants such as Achyranthes aspera L., Boerhavia albiflora Fosberg, Ipomoea micrantha Roem. & Schult, Portulaca oleracea L., and Tribulus cistoides L. Increasing duration of droughts and increased temperatures, together with damage caused by exotic insect pests, appear to be the key drivers of the current vegetation changes.

Twig Cutting by the Black Rat, Rattus rattus (Rodentia: Muridae), on the Ogasawara (Bonin) Islands
T. Yabe, T. Hashimoto, M. Takiguchi, M. Aoki, and M. Fujita, 93-97

Introduced black rats (Rattus rattus) have been reported to damage endemic plants of the Ogasawara Islands by gnawing. This study used seasonal field observations of plants together with analysis of rat stomach contents and age structure to help understand the cause or mechanism of black rat twig-cutting activities. Twigs of Ochrosia nakaiana and Hibiscus glaber were found to be cut by black rats on the islands of Nishijima, Anijima, and Mukojima in March and April 2006 and 2007. Fragments of twig tissues in rat feces proved that the rats ate twigs, rather than only gnawing or cutting them. Age compositions of trapped black rats showed that the season of plant damage corresponded with that of low breeding activities of the rats and scarcity of preferred foods (January–March). We assume a link between low breeding activities of the black rats and food shortage, which motivated the rats to consume twig tissues.

Temporal Changes in Reef Community Structure at Bintan Island (Indonesia) Suggest Need for Integrated Management
Loke Ming Chou, Danwei Huang, Karenne P. P. Tun, Jeffrey T. B. Kwik, Ywee Chieh Tay, and Angie L. Seow, 99-111

Reefs in Southeast Asia, such as those in Indonesia’s Riau archipelago, are among the most diverse habitats in the sea, but limited baseline data pose a severe challenge for their conservation. Here, we surveyed five reef sites along the northern coast of Bintan Island to determine the most recent condition of the benthic and fish communities. Fourteen years of resort development on the island have elapsed since the last survey in 1993. Using several diversity measures to compare the reefs then and in 2007, we found that abundances of hard corals and fish remained high (average of >50% coral cover and >0.7 fish/m3), but taxonomic richness was compromised. The most common taxa now account for greater proportions of fish counts at all sites and of coral cover at three of four comparable sites. These shifts in coral and fish assemblages may be explained by freshwater influences and development along the north coast of Bintan Island. Because the local community and tourism industry still rely heavily on the reefs, we advocate implementing a comprehensive, integrated coastal management plan that mitigates further reef declines and promotes sustainable use.

Water-Quality Variables across Sekisei Reef, A Large Reef Complex in Southwestern Japan
Naoko Morimoto, Yasuo Furushima, Masayuki Nagao, Takahiro Irie, Akira Iguchi, Atsushi Suzuki, and Kazuhiko Sakai 113-123

At Sekisei Reef in southwestern Japan (24º N), coral cover dramatically decreased in the mid-1980s, probably due to a population outbreak of the coral predator Acanthaster planci. Coral communities subsequently recovered well outside the semiclosed lagoon, but recovery has been poor inside it. Hence, water-quality degradation including eutrophication has been a concern inside the lagoon. In addition, temporal variation in eutrophication parameters is common among high-latitude coral reefs, resulting in difficulties in evaluating them. Therefore, to address these issues, we monitored temperature, salinity, turbidity, chlorophyll-a, NOx-N (NO3-N+NO2-N), and NH4-N concentrations year-round across the lagoon at Sekisei Reef. Turbidity and NOx-N concentration increased with increasing wind velocity, suggesting that variation in turbidity and NOx-N concentrations was attributed to resuspension of bottom sediments, and NOx-N release through regeneration processes of microorganisms from the sediments and reef frameworks, respectively. In contrast, variation in chlorophyll-a and NH4-N concentrations appears to be mainly controlled by the seasonality of temperature and irradiance. Long retention time of seawater inside the lagoon seems to have enhanced NH4-N assimilation and increase of phytoplankton during summer. Inside the lagoon, turbidity, NOx-N, and summer chlorophyll-a concentrations were higher, and variation in temperature was larger than outside it. Although water quality appears not to be seriously degraded, multiple effects of these water-quality variables might have negatively affected recovery of coral communities inside the lagoon. Recent expansion of land use on nearby islands might have contributed to water-quality degradation inside the lagoon.

Immature East Pacific Green Turtles (Chelonia mydas) Use Multiple Foraging Areas off the Pacific Coast of Baja California Sur, Mexico: First Evidence from Mark-Recapture Data
Jesse Senko, Melania C. López-Castro, Volker Koch, and Wallace J. Nichols, 125-130

Since 2001, Grupo Tortuguero has been conducting monthly in-water monitoring of East Pacific green turtles (Chelonia mydas), also known as black turtles, at four neritic foraging areas (Bahía Magdalena, Laguna San Ignacio, Punta Abreojos, Laguna Ojo de Liebre) along the Pacific coast of Baja California Sur, Mexico. Extensive tagging (883 turtles tagged of 1,183 turtles captured) and recaptures (154 tagged turtles recaptured at least once) at these four areas suggest that immature East Pacific green turtles show strong site fidelity to their neritic foraging grounds. However, in 2007, we recaptured two immature turtles, one in Laguna San Ignacio and the other in Bahía Magdalena, that were both originally captured in Punta Abreojos. To our knowledge, this represents the first direct evidence of immature East Pacific green turtles using multiple foraging areas along the Baja California Peninsula. This report highlights the importance of long-term monitoring efforts that encompass several habitats on a relatively large spatial scale (~80 km between Punta Abreojos and Laguna San Ignacio and ~300 km between Punta Abreojos and Bahía Magdalena) to better understand the movements and habitat use of immature East Pacific green turtles on their neritic foraging areas.

Helminths of Ten Species of Geckos (Squamata: Gekkonidae) from Papua New Guinea, with Comparisons between Immigrant and Endemic Geckos
Stephen R. Goldberg, Charles R. Bursey, and Fred Kraus, 131-139

Two hundred three individuals representing 10 species of gekkonid lizards from Papua New Guinea collected from 2002 to 2005 were examined for helminths: Cyrtodactylus epiroticus (n = 2), C. klugei (n = 2), C. loriae (n = 7), C. novaeguineae (n = 3), C. sermowaiensis (n = 30), Gehyra mutilata (n = 22), G. oceanica (n = 27), Gekko vittatus (n = 41), Hemidactylus frenatus (n = 29), and Lepidodactylus lugubris (n = 40). One species of Digenea, one species of Cestoda, 18 species of Nematoda, as well as three taxa of nematode larvae (in cysts) were found. Thirty-one new host records and six new locality (= country) records are reported. Prevalence in endemic geckos was significantly higher than in nonendemic geckos.

Pantala flavescens (Insecta: Odonata) Rides West Winds into Ngulu Atoll, Micronesia: Evidence of Seasonality and Wind-Assisted Dispersal
Donald W. Buden, 141-143

Observations of the dragonfly Pantala flavescens (Fabricius) on Ngulu Island during early August 2008 constitute the first report of Odonata on Ngulu Atoll, Yap State, Federated States of Micronesia; no other odonate is documented on the atoll, but descriptions by local residents of a larger, rarely encountered, blue dragonfly may pertain to Anax guttatus (Burmeister). The sudden appearance of P. flavescens on Ngulu after its apparent absence during the previous two and a half weeks of this study, together with the absence of exuviae at potential breeding sites and remarks by local residents alluding to its appearance each year around August and September, suggests that it occurs regularly in migration and that there is no permanent resident population. Its appearance often coincides with winds from a westerly direction.

Association Affairs, 145