Pacific Science, vol. 61, no. 4 (2007)

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Biology and Impacts of Pacific Island Invasive Species. 3. The African Big-Headed Ant, Pheidole megacephala (Hymenoptera: Formicidae)
James K. Wetterer, 437

In the Pacific region, the African big-headed ant, Pheidole megacephala, is now widespread in tropical areas; populations are also found at higher latitudes in Australia, New Zealand, and Japan. On most inhabited tropical islands in the Pacific, P. megacephala is well known as a household and agricultural pest. Because P. megacephala does not attack humans, this species is often not recognized as an important threat. The negative ecological impact of P. megacephala, however, may be greater than that of any other invasive ant species. In areas where it occurs at high density, few native invertebrates persist. Loss of invertebrate species that serve key functions in the natural community (e.g., important prey species) may have cascading effects leading to the subsequent loss of additional species. Pheidole megacephala tends to thrive in open, disturbed habitats with weedy vegetation that can support high densities of plant-feeding Hemiptera, which these ants tend for honeydew. Before 1900, P. megacephala was known in the Pacific region only from Aru Island (Indonesia) and Hawai‘i. By the 1930s, it was found through much of Pacific Asia, Melanesia, and Polynesia, but it was not collected in Micronesia until 1950. Currently P. megacephala is known from virtually every tropical island group in the Pacific but not from many islands within the groups, particularly uninhabited islands. Quarantine efforts might be successful in keeping P. megacephala off these islands. Because P. megacephala does not commonly dominate areas with intact natural vegetation, setting aside relatively undisturbed habitat on inhabited islands may also be effective in protecting native invertebrates from attack by this ant.

Distribution of Parmarion cf. martensi (Pulmonata: Helicarionidae), a New Semi-Slug Pest on Hawai‘i Island, and Its Potential as a Vector for Human Angiostrongyliasis
Robert G. Hollingsworth, Rachel Kaneta, James J. Sullivan, Henry S. Bishop, Yvonne Qvarnstrom, Alexandre J. da Silva, and David G. Robinson, 457

The semi-slug Parmarion cf. martensi Simroth, 1893, was first discovered on O‘ahu, Hawai‘i, in 1996 and then on the island of Hawai‘i in 2004. This species, which is probably native to Southeast Asia, is abundant in eastern Hawai‘i Island, reportedly displacing the Cuban slug, Veronicella cubensis (Pfeiffer, 1840), in some areas. A survey in July–August 2005 found P. cf. martensi primarily in the lower Puna area of Hawai‘i Island, with an isolated population in Kailua-Kona (western Hawai‘i Island). It is now established in commercial papaya plantations, and survey participants reported it as a pest of lettuce and papaya in home gardens. Survey respondents considered P. cf. martensi a pest also because of its tendency to climb on structures where it deposits its feces and because of its potential to transmit disease. Individuals of this species were found to carry large numbers of infective third-stage larvae of the nematode Angiostrongylus cantonensis (Chen, 1935), the causative agent of human angiostrongyliasis and the most common cause of human eosinophilic meningoencephalitis. Using a newly developed polymerase chain reaction test, 77.5% of P. cf. martensi collected at survey sites were found infected with A. cantonensis, compared with 24.3% of V. cubensis sampled from the same areas. The transmission potential of this species may be higher than that for other slugs and snails in Hawai‘i because of the high prevalence of infection, worm burdens, and its greater association with human habitations, increasing the possibility of human-mollusk interactions.

Recent Records of Alien Anurans on the Pacific Island of Guam
Michelle T. Christy, Craig S. Clark, David E. Gee II, Diane Vice, Daniel S. Vice, Mitchell P. Warner, Claudine L. Tyrrell, Gordon H. Rodda, and Julie A. Savidge, 469

Eight anuran species were recorded for the first time in Guam in the period May 2003–December 2005, all apparently the result of arrivals to the island since 2000. Three of the eight species (Rana guentheri, Polypedates megacephalus, and Eleutherodactylus planirostris) had well-established breeding populations by 2005. A further three (Fejervarya cf. limnocharis, Fejervarya cancrivora, and Microhyla pulchra) were recorded from a number of individuals, but it is not known whether these species have established breeding opulations. Two species (Kaloula pulchra and Eleutherodactylus coqui) appear to be incidental transportations to the island that have not established. Before 2003, five anuran species, all introductions, had been recorded from Guam. Three of these, Polypedates leucomystax, Pseudacris regilla, and Kaloula picta, were detected on Guam in incoming cargo but destroyed. Two species established: Bufo marinus was deliberately introduced and the Australian hylid Litoria fallax was probably an accidental introduction. Successful establishment of anurans on Guam has increased the risk of frog introductions to nearby islands. By providing additional food sources for the brown tree snake (Boiga irregularis), anuran introductions have increased the chance that B. irregularis might substantially increase in numbers and in turn increase the risk of the snake being accidentally transported to other islands.

Arthropod Surveys on Palmyra Atoll, Line Islands, and Insights into the Decline of the Native Tree Pisonia grandis (Nyctaginaceae)
Alex T. Handler, Daniel S. Gruner, William P. Haines, Matthew W. Lange, and Kenneth Y. Kaneshiro, 485

Palmyra Atoll, in the Line Islands of the equatorial Pacific, supports one of the largest remaining native stands of Pisonia grandis forest in the tropical Pacific Ocean. In 2003, we surveyed terrestrial arthropods to document extant native and introduced species richness, compare these lists with historical records, and assess potential threats to native species and ecosystem integrity. In total, 115 arthropod taxa were collected, bringing the total number of taxa recorded since 1913 to 162. Few native species were collected; most taxa were accidental introductions also recorded from the Hawaiian Islands, the presumed main source of introductions to Palmyra. The overlap with previous historical surveys in 1913 and 1948 was low (<40%), and new species continue to establish, with one species of whitefly reaching pest status between 2003 and 2005. We observed numerous dead or dying large Pisonia grandis, and the green scale Pulvinaria urbicola (Coccidae) was particularly abundant on trees of poor health. Abundant introduced ants, particularly Pheidole megacephala, tended this and other hemipterans feeding on both native and introduced plants. We hypothesize that the Pheidole-Pulvinaria facultative mutualism is causing the decline of Pisonia grandis. Because of the unique properties of Pisonia grandis forest on oceanic atolls, its importance for nesting seabirds, and its alarming global decline, immediate conservation efforts should be directed at controlling introduced Hemiptera and disrupting their mutualisms with nonnative ants on Palmyra Atoll.

Scale and Benthic Composition Effects on Biomass and Trophic Group Distribution of Reef Fishes in American Samoa
Marlowe G. Sabater and Saolotoga P. Tofaeono, 503

We determined spatial patterns in distribution and biomass of 163 fish species in nearshore waters around Tutuila Island, American Samoa. Visual surveys of reef fishes along 30 by 5 m belt transects were conducted using a hierarchical nested design at five spatial scales from individual transects to tens of kilometers, allowing assessment of broad geographic patterns. Benthic cover data were derived from video transect surveys to test the relationship between habitat and distributions of reef fishes. We found that fish biomass, density, and numerical abundance in American Samoa are dominated by herbivores from relatively few species in the families Acanthuridae and Scaridae. Subsets of carnivore species covaried positively with live coral, algae, and coralline algae cover. Herbivores, in contrast, covaried positively with filamentous algae and coralline algae (i.e., their foods). Biomass of fishes at different trophic categories was associated with higher abundance of food material and habitat availability. Significantly higher biomass occurred along the south shore of Tutuila and at reefs with greater exposure to wave energy, such as topographic points, despite the occurrence of lower live coral cover. Significant variations in fish biomass occurred at large spatial scales, specifically at habitat and exposure levels. Variations at these scales were apparently driven by association of the most dominant trophic group with its food source and the extent but not the quality of habitat.

Life History and Courtship Behavior of Black Perch, Embiotoca jacksoni (Teleostomi: Embiotocidae), from Southern California
Bridgette Froeschke, Larry G. Allen, and Daniel J. Pondella II, 521

The black perch, Embiotoca jacksoni Agassiz, 1853, is a common reef fish associated with nearshore marine habitats of California, with the majority of the population occurring within the Southern California Bight. Black perch were collected throughout southern California from Santa Barbara to Carlsbad, including Santa Catalina Island, to determine their physical characteristics, growth, sex ratio, periodicity of reproduction, and length of gestation. Courtship observations were conducted using scuba along the King Harbor Breakwater in Redondo Beach, California, from January 2004 to December 2005 to verify periodicity of courting and associated reproductive behaviors. Specimens captured ranged from 75 to 220 mm standard length and from 18 to 487 g in total body weight. Seven age-classes were determined by otolith aging, with the growth rate tapering off after age-class one. Seventy percent of the individuals captured were from age-classes one to three. Growth rates did not differ between sexes. Mean monthly gonosomatic indexes for males peaked from July to November, with the highest mean occurring in October. Gestating females were found from December to May, with youngest gestating females being in age-class one. Courtship behaviors were observed within aggregations and in pairs from July to November, with males being the primary aggressors. Courtship postures occurred along the base of the reef, with pairs departing into caves for copulation. This study suggests that the black perch population within the Southern California Bight has different life history characteristics and reproductive timing than those in northern California.

Vertical Distribution of Fish Larvae and Its Relation to Water Column Structure in the Southwestern Gulf of California
L. Sánchez-Velasco, S. P. A. Jiménez-Rosenberg, and M. F. Lavín, 533

The seasonal evolution of vertical distribution of fish larvae and its relationship with seasonal stratification, as measured by a quantitative stability parameter, were analyzed for a region off Bahía de La Paz in the southwestern Gulf of California. Samples were obtained with an opening-closing net (505 μm) in 50-m depth strata from surface to 200-m depth in May, July, and October 2001 and February 2002. Significant differences in total larval abundance and in dominant species (mesopelagic and epipelagic) were found among strata from May to October. More larvae were found in maximum-stability strata (from 16 ± 5 to 48 ± 17 m depth) than below the pycnocline (from 100- to 150-m depth). In February, the 100-m-deep surface mixed layer had a weak pycnocline at its base, and no significant difference was found. Results show that vertical distribution of fish larvae in this area depends mainly on the seasonal evolution of the water column structure, with most fish larvae in the pycnocline, at the most stable stratum of the water column.

Shallow-Water Sea Anemones (Cnidaria: Anthozoa: Actiniaria) and Tube Anemones (Cnidaria: Anthozoa: Ceriantharia) of the Galápagos Islands
Daphne Gail Fautin, Cleveland P. Hickman Jr., Marymegan Daly, and Tina Molodtsova, 549

We provide the first inventory of members of orders Actiniaria (sea anemones sensu stricto) and Ceriantharia (tube anemones) from the Galápagos Islands. Based on observations and collections at 48 localities throughout the archipelago that span nearly a decade, we report on eight species of actiniarians (representing families Actiniidae, Actinostolidae, Aiptasiidae, Hormathiidae, and Isophelliidae) and two of cerianthids (in families Arachnactidae and Botrucnidiferidae). We include live photographs and diagnostic features of the animals, as well as a key and map of their occurrence in the Galápagos. Two actiniarians and one cerianthid are resolved only to genus level; of those identified to species, three of the actiniarians and one of the cerianthids have an eastern Pacific distribution, one actiniarian appears to be endemic to the Galápagos Islands, and two actiniarians are broadly distributed in the Indo-West Pacific.

Vegetative and Reproductive Variability of Dictyota crenulata (Phaeophyta: Dictyotales) along the Central and Southwestern Gulf of California, México
María del Carmen Altamirano-Cerecedo and Rafael Riosmena-Rodríguez, 575

Dictyota crenulata J. Agardh is widely distributed throughout the Gulf of California. Comparative analyses of morphology, anatomy, and reproductive features of this species were conducted along the central western and southwestern regions of the Gulf of California. Thalli showed geographical variations in length and apical width. No differences were observed in anatomy of vegetative thalli or relative abundance of reproductive structures. Dictyota crenulata had unilayered or multilayered medullas in the basal region and in proliferations. Most thalli presented unilayered medullas in the middle section. Our observations indicate that number of medullary layers is indeed a phenotypically plastic character, in agreement with previously published results. Variations in thallus morphology such as proliferations and length are likely the result of environmental differences, also reflected in the reproduction of D. crenulata. The southwestern region had the highest percentage of all life cycle stages (female gametophytes and sporophytes, both 22%, and vegetative thalli, 14%). Our results demonstrate morphological variability in Dictyota crenulata across its distribution in the Gulf of California.

Checklist of Pacific Operculina (Convolvulaceae), Including a New Species
G. W. Staples, 587

A new species of Operculina (Convolvulaceae), O. polynesica Staples, is described from the Pacific. This brings to five the number of species known from Micronesia, Melanesia, and Polynesia. A key for identification is provided, nomenclature and distributions are summarized, and a list of specimens examined is included to aid herbarium curators in naming Pacific material.

Index to Volume 61, 599