Top-Down Analysis of Forest Structure and Biogeochemistry across Hawaiian Landscapes
Peter M. Vitousek, Michael A. Tweiten, James Kellner, Sara C. Hotchkiss, Oliver A. Chadwick, and Gregory P. Asner, 359-366
Technical and analytical improvements in aircraft-based remote sensing allow synoptic measurements of structural and chemical properties of vegetation across whole landscapes. We used the Carnegie Airborne Observatory, which includes waveform light detection and ranging (LiDAR) and high-fidelity imaging spectroscopy, to evaluate the landscapes surrounding four well-studied sites on a substrate age gradient across the Hawaiian Islands. The airborne measurements yielded variations in ground topography, canopy height, and canopy nitrogen (N) concentration more accurately than they could have been obtained by any reasonable intensity of ground-based sampling. We detected spatial variation in ecosystem properties associated with the properties of different species, including differences in canopy N concentrations associated with the native species Metrosideros polymorpha and Acacia koa, and differences brought about by invasions of the biological N fixer Morella faya. Structural and chemical differences associated with exotic tree plantations and with dominance of forest patches by the native mat-forming fern Dicranopteris linearis also could be analyzed straightforwardly. This approach provides a powerful tool for ecologists seeking to expand from plot-based measurements to landscape-level analyses.
Potential Effects of an Invasive Nitrogen-Fixing Tree on a Hawaiian Stream Food Web
Trisha B. Atwood, Tracy N. Wiegner, Jason P. Turner, and Richard A. MacKenzie, 367-379
Falcataria moluccana (albizia) is an exotic nitrogen (N)-fixing tree currently invading riparian forests in Hawai‘i, U.S.A. This study examined how this invasion is impacting stream ecosystems by using naturally occurring stable isotopes of carbon (C) and N to compare food web structure between a noninvaded and an albizia-invaded stream reach on the island of Hawai‘i. Isotopic signatures of particulate organic matter (POM), macroalgae, invertebrates, and fishes were collected and compared between the two stream reaches. Stable C isotopic signatures of organic matter sources (POM and macroalgae) and consumers (amphipods, caddisflies, crayfish, and fishes) from the invaded site were depleted in ¹³C compared with the noninvaded site. In contrast, all samples from the invaded site were enriched in ¹⁵N compared with the noninvaded site. Results from IsoSource and two-source mixing models suggested that albizia was a major contributor to diets of lower-level consumers within the invaded site, displacing POM and macroalgae as their major food sources. Albizia was also an indirect C and N source for higher-level consumers within the invaded site because albizia was the major dietary constituent of their prey. In addition, ¹⁵N enrichment of the macroalgae at the invaded site suggests that albizia may be an important N source to benthic primary producers and could be further altering the food web from bottom up. Our study provides some of the first evidence that invasive riparian N-fixing trees can potentially alter the structure of stream food webs.
Survival of Feral Cats, Felis catus (Carnivora: Felidae), on Mauna Kea, Hawai‘i, Based on Tooth Cementum Lines
Raymond M. Danner, Chris Farmer, Steven C. Hess, Robert M. Stephens, and Paul C. Banko, 381-389
Feral cats (Felis catus) have spread throughout anthropogenic and insular environments of the world. They now threaten many species of native wildlife with chronic depredation. Knowledge of feral cat population dynamics is necessary to understand their ecological effects and to develop effective control strategies. However, there are few studies worldwide regarding annual or lifetime survival rates in remote systems, and none on Pacific islands. We constructed the age distribution and estimated survival of feral cats in a remote area of Hawai‘i Island using cementum lines present in lower canine teeth. Our data suggest annual cementum line formation. A log-linear model estimated annual survival ≥1 yr of age to be 0.647. Relatively high survival coupled with high reproductive output allows individual cats to affect native wildlife for many years and cat populations to rebound quickly after control efforts.
Changes in Benthic Macrofauna Associated with a Shallow-Water Hydrothermal Vent Gradient in Papua New Guinea
David J. Karlen, Roy E. Price, Thomas Pichler, and James R. Garey, 391-404
Infaunal macroinvertebrates were characterized along an environmental gradient from a shallow-water hydrothermal vent located at Tutum Bay, Ambitle Island, Papua New Guinea. Samples were collected at three sites located at 7.5, 60, and 150 m from the vent and from a nonhydrothermal reference site located to the north. Temperature and arsenic concentration were found to decrease and pH increased with distance away from the vent. At each site, five replicate core samples were taken randomly from a 1 m² sampling grid. All infaunal invertebrates >500 μm were sorted, identified to the lowest practical taxonomic level and counted. Results from the macrofauna data show a strong trend of increasing abundance, species richness and diversity relative to distance away from the vent, but even at 150 m the benthic macrofauna appeared to be depressed relative to the reference site. Mollusks were completely absent 7.5 m from the vent, rare at 60 m, and abundant at 150 m, suggesting that the low pH values associated with the hydrothermal activity play an important role in the benthic community structure.
Reproductive Synchrony in Acropora Assemblages on Reefs of New Caledonia
Andrew H. Baird, Marie C. Kospartov, and Steven Purcell, 405-412
Despite a recent expansion in the geographical focus of studies on coral reproduction, there remain many regions in the Indo-Pacific, such as Melanesia, where research is limited. For example, although New Caledonia in southern Melanesia is home to the world’s second largest barrier reef, which has recently been given UNESCO World Heritage listing, almost nothing is known of the reproductive biology of the coral fauna there, in particular the timing of spawning. In this study we sampled Acropora assemblages in November 2004 to test for reproductive synchrony at eight sites in New Caledonia separated by up to 200 km. In total, 80% of 1,055 Acropora colonies sampled contained mature oocytes, and 34 (92%) of 37 species sampled had at least one mature colony. These data demonstrate that reproduction in Acropora is highly synchronous over a large scale in New Caledonia and suggest a multispecies spawning event following the full moon in November coincident with the mass spawning period on the Great Barrier Reef, Australia. The high synchrony of reproductive effort implies that even a brief halt of activities that threaten fertilization and early development of coral propagules, such as discharge of liquid waste from ore processing, could have a major mitigating effect on the potential damage to these globally valued reefs.
Ten species of Hawaiian primnoids are described and/or discussed, completing the review of the 28 primnoids known from the Hawaiian Islands. This family constitutes 29% of the Hawaiian octocoral fauna. Callogorgia americana is synonymized with C. gilberti, resulting in a disjunct distribution in the Pacific and Northwest Atlantic. Two new species are described (Plumarella circumoperculum Cairns and Parastenella bayeri Cairns), and two (Callogorgia gilberti and C. robusta) are reported for the first time since their original descriptions over a century ago. Keys are provided for the Hawaiian primnoid genera and all species of the genus Parastenella; comparative tables are provided for the Hawaiian Callogorgia and Fanellia. A distinctive nematocyst pad is described for the genus Parastenella. Highly modified polyps caused by copepod parasites are described for two species: Callogorgia gilberti and Thouarella hilgendorfi.
Microhabitat Distribution of the Hermit Crabs Calcinus haigae and Calcinus hazletti (Decapoda: Anomura: Diogenidae)
Brian A. Hazlett and Catherine E. Bach, 441-447
Two sympatric species of hermit crabs, Calcinus haigae and Calcinus hazletti, appear to have different microhabitat distributions in the subtidal. Several biotic factors may be influencing this microhabitat difference. We documented the field distributions of these two species as a function of coral species and investigated whether aggregation behavior, avoidance behavior, and/or shell exchanges are influencing the distribution patterns. Individuals of C. hazletti occurred predominantly on the cauliflower coral Pocillipora meandrina. In addition, individuals of C. hazletti aggregated toward conspecifics in the laboratory. Individuals of C. haigae avoided individuals of C. hazletti in the field unless the C. haigae were in damaged shells. Individuals of C. haigae did not initiate interspecific shell exchange attempts in the laboratory, but individuals of C. hazletti did initiate interspecific shell exchanges. Thus, both intraspecific and interspecific interactions affect the distributions of these crabs.
Rare Sightings of a Bryde’s Whale (Balaenoptera edeni) and Sei Whales (B. borealis) (Cetacea: Balaenopteridae) Northeast of O‘ahu, Hawai‘i
Mari A. Smultea, Thomas A. Jefferson, and Ann M. Zoidis, 449-457
In the Hawaiian Islands small numbers of Bryde’s whales (Balaenoptera edeni) have been documented only in the Northwestern (leeward) Hawaiian Islands, and sei whales (B. borealis) have only recently been confirmed near the islands of Maui and Hawai‘i. In November 2007, one Bryde’s whale and two sei whale groups (including three subadults) were documented during a 7-day, systematic vessel-transect survey conducted east and northeast of O‘ahu. The Bryde’s whale sighting is the first in nearshore (<70 km) waters of the main Hawaiian Islands, and the two sei whale sightings are the first near O‘ahu, including the first documented subadult sei whales there. The latter information suggests that Hawai‘i may be a reproductive area for the endangered sei whale, whose breeding and calving ground locations remain unknown in the Pacific Ocean. Other than rare incidence, the lack of historical sightings of these two species despite many years of previous shipboard and aerial surveys off Hawai‘i may be due to misidentification and/or poor sea conditions prevalent in deep, offshore windward waters of the Hawaiian Islands. We recommend conducting more offshore vessel surveys for, and biopsy sampling of, these species to clarify habitat use and current stock boundaries and numbers, information important for management of Pacific populations.
Occurrence of the Phoronid Phoronopsis albomaculata in Cocos Island, Costa Rica
Harlan K. Dean, Jeffrey A. Sibaja-Cordero, and Jorge Cortés, 459-462
The phoronid Phoronopsis albomaculata was collected in subtidal (28-35 m) sandy sediments in Bahía Chatham during a benthic survey designed to describe the biota of Cocos Island (Isla del Coco), Costa Rica, a national park and Human Heritage Site. Occurrence of this widespread species in Cocos Island is the first report of a phoronid for Costa Rican waters and is the second locality recorded for the eastern Pacific. Taxonomically significant characters (presence of an epidermal collar, extent of coiling of lophophore and nephridia) are discussed. Comparisons are made between depth and abundance of this species from Cocos Island and results of previous studies.
Protodrilidae (Annelida: Polychaeta) from the Hawaiian Islands and Comparison with Specimens from French Polynesia
Julie H. Bailey-Brock, Claude Jouin-Toulmond, and Richard E. Brock, 463-472
Three species of Protodrilidae were collected from the islands of O‘ahu and Ni‘ihau in the Hawaiian chain, including specimens closely resembling Parenterodrilus taenioides (Jouin, 1979), described from Mo‘orea (French Polynesia). Others are probably an undescribed species of Parenterodrilus that was found in fine sand substrate collected off Wai‘anae, O‘ahu. A third species, Protodrilus albicans Jouin, 1970, described from Banyuls-sur-Mer (Mediterranean Sea) and recorded from Mo‘orea and Tahiti as well, was also collected from O‘ahu. Depths and habitat characteristics are given for these new records to the Hawaiian fauna. It is suggested that the wide geographical distribution of the different “cosmopolitan species” of Protodrilidae is related both to the dispersal by free-swimming larvae and to the ancient origin of this interstitial fauna.
Reptiles of Ngulu Atoll, Yap State, Federated States of Micronesia
Donald W. Buden, 473-480
Fourteen species of reptiles (two sea turtles, six geckos, six skinks) are recorded from Ngulu Atoll, Yap, Micronesia, all but the turtles for the first time. None is endemic and most occur widely in Oceania; the phylogenetic status of an undescribed species of Lepidodactylus is undetermined, and a phenotypically male Nactus cf. pelagicus is recorded from Micronesia for the first time. Lepidodactylus moestus is the most common gecko on Ngulu Island, and Emoia caeruleocauda, E. impar, and E. jakati are the most abundant skinks. The islands are an important nesting site for green turtles, Chelonia mydas. Isolation, a small resident human population, and traditional conservation practices contribute to sustaining turtle populations, although occasional poaching by outside visitors persists. The report of a small snake on Ylangchel Island, possibly a species of Ramphotyphlops, requires confirmation.
Association Affairs, 481-487