Pacific Science, vol. 64, no. 2 (2010)

Pacific Science 64.2 coverBiogeographic Breaks in Vanuatu, a Nascent Oceanic Archipelago
Alison M. Hamilton, Elaine R. Klein, and Christopher C. Austin, 149-159

The study of distinct biogeographic demarcations has played a pivotal role in our understanding processes responsible for patterns of species distributions and, importantly, the role of geologic processes in promoting biotic diversification. Biogeographic barriers such as Wallace’s line have been shown to be the result of old geologic processes shaping ancient faunal or floral diversification events. Based on distributions of birds, bats, reptiles, plants, and invertebrates we identify a distinct biogeographic disjunction in Vanuatu, a geologically nascent oceanic archipelago. We discuss mechanisms contributing to this concordant pattern across these disparate taxonomic groups in light of geologic history, ocean currents, vegetation, soil, and bioclimatic data, and propose the name Cheesman’s line to indicate the faunal and floral discontinuity between the northern and southern islands of Vanuatu.

Diel and Seasonal Occurrence Patterns of Drifting Fish Larvae in the Teima Stream, Okinawa Island
Ken Maeda and Katsunori Tachihara, 161-176

Drifting fish larvae were collected with a plankton net in the lower reaches of a freshwater area of the Teima Stream, Okinawa Island, Japan, during 24 hr periods each month from June 1998 to October 1999 (except July 1998). Newly hatched larvae of several gobioid and two pipefish species were collected, and their morphology was described. The larval occurrences suggested that most species spawn mainly from spring to fall, with some Rhinogobius species spawning in winter. Larvae of all fishes occurred predominantly during hours after dusk throughout the year. It is suggested that larvae of amphidromous fishes spawned in freshwater streams on Okinawa Island begin to drift soon after hatching at dusk and complete their exit from freshwater areas into the estuary and sea by midnight.

Distribution of Virus-Infected Bacteria in the Western Equatorial Pacific
Chung Yeon Hwang and Byung Cheol Cho, 177-186

Viruses are generally considered an important agent of bacterial loss in diverse marine environments. However, the impact of viruses on bacteria is unknown in the western equatorial Pacific, where surface waters are warm and phytoplankton biomass is low (i.e., oligotrophic). Further, little is known about their importance in the mesopelagial, where bacteria and heterotrophic nanoflagellates are known to be metabolically active. To elucidate the ecological characteristics of viruses in the western equatorial Pacific, abundances of bacteria and viruses were measured, along with frequencies of visibly infected cells (FVIC) and frequencies of dividing cells (FDC) in epipelagic and mesopelagic samples at three stations near the equator from August to September 2002. Measurements of Secchi depth (20 m) and chlorophyll a concentrations (0.07–0.4 μg chl a liter-¹) indicated that the study area was oligotrophic during the investigation. FVIC ranged from 0.4% to 1.8% and 0.5% to 1.8% in the epipelagic and mesopelagic zones, respectively. Virally induced bacterial mortality was inferred to range from 4.5% to 20.8% in the epipelagic zone, suggesting that viruses contribute substantially to bacterial mortality in oligotrophic seawaters. In addition, these values were similar to those estimated for the mesopelagic zone (5.0%–21.2%). Overall, viruses appear to be an important factor in the loss of bacterial production in both oligotrophic epipelagic and mesopelagic zones in the study area.

Distribution and Performance of the Nonnative Sea Grass Zostera japonica across a Tidal Height Gradient on Shaw Island, Washington
Kevin H. Britton-Simmons, Sandy Wyllie-Echeverria, Elizabeth K. Day, Katherine P. Booth, Kelsey Cartwright, Susana Flores, Cheyenne C. Garcia, Tessa L. Higgins, Cynthia Montanez, Arielle Rames, Kasey M. Welch, and Victoria Wyllie-Echeverria, 187-198

In the Northeast Pacific the nonnative seagrass Zostera japonica frequently exists at the same sites as the native seagrass Zostera marina. Although at some sites their vertical distributions overlap, at most sites in the Pacific Northwest there is a distinctive unvegetated zone between them. The objective of this study was to better understand why a gap between the lower limit of Z. japonica and the upper limit of Z. marina exists. To address this issue we carried out transplant experiments, conducted in situ monitoring of existing Z. japonica patches, and collected sediment samples at South Beach on Shaw Island, Washington, during the spring and summer of 2006. Transplant and in situ monitoring data indicate that survival and performance of Z. japonica are reduced lower in the intertidal zone. In addition, Z. japonica patches tended to be smaller and more spaced out at lower tidal heights. Although we found no Z. japonica seeds within or outside extant Z. japonica patches, high transplant mortality indicates that Z. japonica dispersal limitation is an unlikely cause of the unvegetated gap zone. Our field observations further suggest that herbivory, bioturbation, and epiphytes are unlikely causes of the gap pattern at our study site. Instead, we hypothesize that light limitation prevents Z. japonica from occurring lower in the intertidal. A review of published vertical distribution data for both Zostera species indicates that the lower limit of Z. japonica is relatively invariant among sites. In contrast, the upper limit of Z. marina is highly variable, ranging by more than 4 m within some subregions in Washington State. Consequently we hypothesize that intersite variability in the vertical distribution of Z. marina is the primary driver of spatial variability in the presence of the unvegetated gap.

Estimation of Fire Danger in Hawai‘i Using Limited Weather Data and Simulation
David R. Weise, Scott L. Stephens, Francis M. Fujioka, Tadashi J. Moody, and John Benoit, 199-220

The presence of fire in Hawai‘i has increased with introduction of nonnative grasses. Fire danger estimation using the National Fire Danger Rating System (NFDRS) typically requires 5 to 10 yr of data to determine percentile weather values and fire activity. The U.S. Army Pōhakuloa Training Area in Hawai‘i is located in the interface zone between windward and leeward weather conditions and needed to develop fire danger values but did not have sufficient weather or fire occurrence data. Use of simulation to estimate fire danger (expressed as fire risk) for areas with limited weather data was investigated. Influence of spatial resolution of weather information on fire risk was examined by comparing fire risk calculated using one or three weather stations and gridded weather predictions from the Mesoscale Spectral Model. Predicted gridded temperature was positively correlated with observed temperature; predicted and observed relative humidity were not significantly correlated. Simulated fire risk differed between weather data percentiles and between weather data resolutions. Predicted risk estimated from gridded weather data agreed more closely with observed risk estimated from weather data observed at all three remote automated weather stations. Correlation between simulated fire risk and the NFDRS Ignition Component was statistically significant for the single weather station simulations. Correlations between risk and the Ignition Component were not statistically significant for the three station and gridded weather data scenarios, which illustrates the difference between fire danger determined at broad spatial scales and fire risk resolved at finer spatial scales. Fire spread simulation modeling to estimate fire risk in areas with limited historical weather and fire occurrence data can provide finer-scale information than the NFDRS, which is better suited to larger, homogeneous areas with more complete fire and weather data. Values for the NFDRS Burning Index were determined and incorporated into the wildland fire management plan for Pōhakuloa Training Area.

New Species of Endemic Kleptoparasitic Spiders of the Genus Argyrodes (Araneae: Theridiidae) in the Hawaiian Islands
Malia Rivera and Rosemary G. Gillespie, 221-231

This study examined the endemic species of kleptoparasitic spiders in the genus Argyrodes from the Hawaiian Islands, a lineage previously known in the archipelago from only a single described species, Argyrodes hawaiiensis Simon. Here, two additional endemic species are described, A. ilipoepoe Rivera and Gillespie, n. sp., and A. laha Rivera and Gillespie, n. sp., with their biogeographical patterns, and the allotype female and paratypes of A. hawaiiensis are designated. As with A. hawaiiensis, both new species are commonly found as kleptoparasites on the sheet webs of large nocturnal spiders in the genus Orsonwelles (Linyphiidae). Hawaiian Argyrodes are characterized by small and rounded abdomens, unpronounced clypeal projections, and variably long fangs. Argyrodes hawaiiensis; A. ilipoepoe, n. sp.; and A. laha, n. sp., include all the known endemic representatives of the group in the Hawaiian Islands, which mostly occur in wet and mesic forests.

Ostracoda (Myodocopina) of the Hawaiian Islands
Louis S. Kornicker, Elizabeth Harrison-Nelson, and S. L. Coles, 233-283

Ostracoda (Myodocopina) from four of the Hawaiian Islands (Kaua‘i, Moloka‘i, Maui, and Hawai‘i) are identified, and a new species, Pterocypridina colesi Kornicker & Harrison-Nelson, that was present on all the Islands is described and illustrated, including all five instars and the adult male and female. The genus was not previously known from the area, and its ontogeny had not been described. The number of species collected on the Islands varied from two on Moloka‘i to six on Kaua‘i.

On Some Octocorallia (Alcyonacea) from Hong Kong, with Description of a New Species, Paraminabea rubeusa
Y. Benayahu and K. Fabricius, 285-296

Octocorals from Hong Kong were studied at 18 sites down to a depth of 25 m in 1999. The collection of ~90 specimens yielded nine species distributed in seven genera of the families Alcyoniidae, Nephtheidae, and Xeniidae (all are new zoogeographical records for Hong Kong), plus ca. 70 samples of azooxanthellate octocorals of the genera Dendronephthya (family Nephtheidae), Chironephthya, and Nephthyigorgia (family Nidaliidae), which were not identified to species level. The collection included Paraminabea rubeusa Benayahu & Fabricius, n. sp., which is described here. The impoverished nature of the zooxanthellate octocorals is reflected in the low number of species found in the families Alcyoniidae and Xeniidae (seven and one, respectively), families that typically contribute a high proportion of species in the Indo-Pacific region. It is crucial to implement effective conservation policies in Hong Kong to preserve its remaining zooxanthellate octocoral species and thereby prevent the local extinction of these species, including the newly described Sarcophyton tumulosum Benayahu & Ofwegen, 2009, and Lobophytum mortoni Benayahu & Ofwegen, 2009, which may be endemic to the region.

Breeding Avifauna of the Chesterfield Islands, Coral Sea: Current Population Sizes, Trends, and Threats
Philippe Borsa, Mireille Pandolfi, Serge Andréfouët, and Vincent Bretagnolle, 297-314

This paper reports on post-1991 census data and on the breeding phenology of seabirds of the Chesterfield-Bampton and Bellona groups of coral islets in the Coral Sea. In total, 13 resident bird species were observed [Wedge-tailed Shearwater (Puffinus pacificus), Masked Booby (S. dactylatra), Brown Booby (Sula leucogaster), Red-footed Booby (S. sula), Lesser Frigatebird (Fregata ariel), Great Frigatebird (F. minor), Black Noddy (Anous minutus), Brown Noddy (A. stolidus), Crested Tern (Sterna bergii), Sooty Tern (S. fuscata), Fairy Tern (S. nereis), Black-naped Tern (S. sumatrana), and Buff-banded Rail (Gallirallus philippensis)]. Segregation for nesting habitat was similar to that previously observed on other coral-reef islets of the Coral Sea. Breeding periods were either in the winter (Masked and Red-footed Boobies, Frigatebirds, Fairy Tern) or in the summer (Wedge-tailed Shearwater, Black and Brown Noddies, Crested and Black-naped Terns) or year-round (Brown Booby). Sooty Terns bred twice a year (summer and spring), but this was not consistent across years. Estimates of breeding population sizes for the whole Chesterfield-Bampton and Bellona groups are proposed for Wedge-tailed Shearwater (90,000 to 106,000 breeding pairs), Masked Booby (280–500 pairs), Brown Booby (3,800–5,800 pairs), Red-footed Booby (7,200–7,300 pairs), Lesser Frigatebird (1,600 pairs), Great Frigatebird (350–480 pairs), Black Noddy (29,000–45,000 pairs), Brown Noddy (15,000–23,000 pairs), Crested Tern (80–100 pairs), Sooty Tern (11,000–46,000 pairs), and Black-naped Tern (70–90 pairs). Interannual fluctuation in breeding population size was apparent in Wedge-tailed Shearwater. Over the last 30 yr, an increase in Brown Booby abundance was noted, whereas declines are suspected for the Fairy Tern and Buff-banded Rail. Among the threats to nesting seabirds are stress and other disturbances caused by human frequentation, including poaching of seabird chicks and introduced mice.

Prehistoric Birds from Rurutu, Austral Islands, East Polynesia
David W. Steadman and Robert Bollt, 315-325

We identify 70 bird bones from the Peva dune site, Rurutu, Austral Islands. These bones represent 10 species, dominated by the extant White-tailed Tropicbird, Phaethon lepturus; the nonnative chicken, Gallus gallus; and an undescribed species of extinct rail, Gallirallus sp. Two other species are extinct (the ground-doves Gallicolumba undescribed spp. 1 and 2). No species of Gallirallus or Gallicolumba has been recorded previously from the Austral Islands. All but three of the 70 bird bones are from the lowest cultural strata at Peva, which date from the thirteenth to early fifteenth century A.D. (the Archaic or Early East Polynesian cultural phase). The small set of bird bones from the Peva dune site increases the number of indigenous species of land birds known from Rurutu from three to six.

Body Size, Growth, and Feather Mass of the Endangered Hawaiian Moorhen (Gallinula chloropus sandvicensis)
David W. DesRochers, Michael D. Silbernagle, Aaron Nadig, and J. Michael Reed, 327-323

Body and feather mass data are important in avian studies and are required for determining things such as body condition and energetic carrying capacity. There are 12 subspecies of Common Moorhens (Gallinula chloropus), six continental and six island subspecies, of which two are endangered. Body mass data for multiple individuals are available for only three subspecies, and feather mass data have been reported for only one individual. Body mass (n = 82) and feather mass (n = 2) for adults and body mass for three subadult age classes (n = 27) are provided for the Hawaiian subspecies of Common Moorhen (G. c. sandvicensis). Other body size measurements, including tarsus length, shield-bill length, shield width, and wing cord length also are presented. Adult Hawaiian Moorhen body mass averaged 350.7 g (±50.0 SD; range, 232–522; 95% CI, 339.8–361.6), and young birds appear to develop like young of G. c. chloropus and other Rallidae. Based on published data, G. c. sandvicensis is heavier than G. c. guami, female G. c. chloropus, and G. c. meridionalis; lighter than G. c. garmani and males of G. c. cachinnans; and similar in mass to G. c. cachinnans females, males of G. c. chloropus, and G. c. orientalis. There do not appear to be systematic differences in body mass between mainland (data for four subspecies) and island subspecies (data for three subspecies). Total mass of all feathers for two males was 16.2 and 12.1 g, which made up 3.1% and 3.8%, respectively, of their total body mass.

Characteristics of Coral Cay Soils at Coringa-Herald Coral Sea Islands, Australia
George N. Batianoff, Gillian C. Naylor, Rod J. Fensham, and V. John Neldner, 335-347

Coral cay soil chemical and physical properties were described from Coringa-Herald National Nature Reserve, Australia. Soil A horizons under littoral herblands and Argusia argentea shrubs were shallow and coarse textured. Interior soil A horizons, particularly under Pisonia grandis closed forest, were deeper (1.2 m) with finer textures. Average surface soil pH values ranged from pH 8.76 at the seashores to pH 8.09 in the interior. Average surface soil organic carbon ranged from 2.4% to 4.8%; and phosphorus (Colwell-P) concentrations ranged from 467 mg/kg to 882 mg/kg within the interior areas. Chemical fertility of all A horizons increased from the seashore to the island interior. The higher fertility levels are attributed to high organic matter contributed by vegetation, combined with activities of seabirds, particularly the burrowing wedge-tailed shearwater, Puffinis pacificus. Leaching of nutrients from surface soils is reflected in the rapid decline in soil fertility with depth. Deeper interior A horizons are interrupted by formation of an abrupt white C profile. It is speculated that the formation of this layer is the product of periodic “washing” by a seasonally high fresh/brackish water table.

An Observation of Mating in Free-Ranging Blacktip Reef Sharks, Carcharhinus melanopterus
Douglas J. McCauley, Yannis P. Papastamatiou, and Hillary S. Young, 349-352

We describe the mating behavior of free-ranging Blacktip Reef Sharks, Carcharhinus melanopterus, at Palmyra Atoll. This is the first primary report of mating in C. melanopterus and the first direct observation of mating for an obligate swimming shark species. Similar to that in other nonobligate swimming shark species, mating in C. melanopterus was characterized by multiple males following a single female, a male grabbing the female near the pectoral fin and positioning her head down on the bottom, and the insertion of a single clasper. Copulation lasted 68 sec, which is shorter than the durations recorded for most other shark species.

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