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Fruit doves of the genus Ptilinopus (Columbidae) form a large group of more than 50 species that have been successful in colonizing most of the Pacific Ocean, with sympatric species on several small oceanic islands. A recent new phylogeny of this genus and allies by Cibois and coworkers showed that all these cases of sympatry derived from multiple independent colonizations, with the exception of the Marquesas Islands (eastern Polynesia), where the two fruit doves that occurred sympatrically are sister species: the Red-moustached Fruit Dove, Ptilinopus mercierii, and the White-capped Fruit Dove, Ptilinopus dupetithouarsii. Both Marquesas fruit doves coexisted on several Marquesas islands until the recent extinction of the Red-moustached Fruit Dove. Here, we analyze their morphology, review their life history, and discuss the two most likely scenarios for the divergence of the two species, in light of the geological history of the Marquesas hot-spot volcanoes (5.5–1.1 Ma). The microallopatry scenario takes into account the large initial size of the islands and involves partitioning of the fruit doves' distributions within the same island, whereas in the intra-archipelago scenario, the birds' speciation occurred on different islands, in conjunction with their sequential emergence. We discuss both hypotheses and conclude that estimated time of divergence of the two species and known ecology of the birds favor the intra-archipelago scenario.
Skinks are successful colonizers and are commonly found throughout the Pacific islands, but introduced predators such as mongoose are known to threaten their survival. The two most abundant skinks found within the Fiji Islands are Emoia cyanura and E. impar. Abundance of these species encountered during visual transect counts on 16 islands within four habitats formed the basis of this study. Half of these islands had mongoose present, and the other half were known to be mongoose free. Our results showed that skink abundance under mongoose-free conditions was approximately five times higher than when mongoose were present. We conclude that it is very likely that mongoose severely supress even commonly found skink species across all the habitat types on these small islands, and it is likely that they impact even more severely on rarer species. Conservation actions that could protect these native species include biosecurity mechanisms to prevent secondary invasion of introduced predators, habitat protection and management, and captive rearing programs. Failure to implement such actions is likely to result in even common species being at risk of extirpation.
This study assembles and analyzes published and unpublished data on inorganic nutrient concentrations in the waters of Kāne‘ohe Bay, O‘ahu, Hawai‘i, over the past 48 yr, but particularly over the 34-yr period since elimination of the major point-source of input of nutrients in 1977. As reported in a previous study, in the 1.5-yr period immediately following termination of the point-source input of nutrients (1978–1979), concentrations of PO42- NO3- NO2-, and NH4- in the water column declined in all three basins of the bay, followed by improvement in the state of the benthos and planktonic communities. Since 1979, nutrient concentrations have remained low (PO42- < 0.15 µM, NO3- NO2- < 0.30 µm, NH4- < 0.15 µM) despite continued growth of the human population in the bay's watershed. Increase in nutrient levels in the bay in the 1960s probably contributed to a phase shift from corals to the macroalga Dictyosphaeria cavernosa in the 1960s. Decline in nutrient concentrations beginning in 1977 may ultimately have contributed to the drastic decline in this alga that occurred in 2006. A protracted rainfall that occurred in spring 2006 produced elevated average nutrient concentrations for the year, but nutrient concentrations fell back to pre-2006 concentrations within 1 to 2 months. The record also contains evidence of a decrease of nutrient concentrations in the bay in response to a 4-yr period (1998–2001) of lower than normal rainfall. The response to elimination of the point-source input of nutrients and the responses to a season of exceptional rainfall and years of drought indicate that conditions in the bay's water column are dependent on both natural events in the bay's watershed and human activity. Kāne‘ohe Bay is one of a number of marine and aquatic systems whose degradation has been reversed by terminating nutrient addition caused by sewage disposal.
Around intertidal coral reefs, viscous layers, flocs, and bubbles can form on the water surface, and these are collectively referred to as mucus aggregates. To assess effects of substances contained in mucus aggregates on population growth rates of autotrophic and heterotrophic organisms, aqueous materials extracted from mucus aggregates and polysaccharides collected from cultured microalgae were added to rocky intertidal reef sediments in a controlled laboratory experiment. Temporal changes in autofluorescence cell density and nonautoflorescence cell density in reef sediments were examined. Results suggested that microorganism population growth in subtropical rocky intertidal reefs is limited by low concentrations of organic carbon and nutrients in the environment, and that components of mucus aggregates can supplement these materials, leading to increased microbial population growth rates. In particular, aqueous extracts of mucus aggregates contained nutrients that likely promoted growth of autotrophic bacteria, whereas extracellular polymeric substances (EPS) contained polysaccharides that likely promoted growth of heterotrophic bacteria.
Microsatellite markers are valuable tools for determining amount and distribution of genetic diversity and differentiation within and between populations. In this study we examined the level of microsatellite variability within and among five populations of Lobelia villosa, a rare Hawaiian endemic lobeliad on the island of Kaua‘i. Populations of L. villosa were sampled from two regions on Kaua‘i: two populations at the Kilohana Lookout area and three populations from Alaka‘i Swamp. Nineteen microsatellite DNA primers were developed for L. villosa, 12 of which demonstrated polymorphism and were subsequently multiplexed and labeled for genotyping. An overall moderate degree of genetic differentiation was found within and between populations. Pairwise FST data showed population structure, and analysis with Structure software indicated two genetic clusters (K = 2) corresponding to the two sampled geographic regions. Although L. villosa exhibits moderate diversity, which exceeds that of other Hawaiian endemics with restricted distributions, measurements of FIS were positive across 10 out of 12 loci, suggesting that inbreeding is occurring at the population level.
In this study we examined historic drought frequency and hydrologic effects of removing invasive plants from one of the few remaining Hawaiian wet lowland forests, near Hilo, Hawai‘i. We developed a conceptual and statistical model of Hilo droughts using historic rainfall and pan evaporation data and discovered that episodes of low soil moisture were most likely from January to March but also occurred in June or July. Field measurements were taken in four pairs of plots. Nonnative woody and herbaceous species were removed from four plots; control plots were undisturbed. Soil water potential measurements documented partial soil drying in control plots, but not removal plots, during droughts with recurrence intervals of 2–3 yr. Drier soils exhibited strong small-scale heterogeneity in soil water potential that presumably reflects macroporosity in the young ‘a‘ā lava flow substrate. Transpiration from and rainfall interception by the dense canopy of nonnative species were most likely responsible for drier conditions in control plots. Removal plots experienced changes to shading, midday vapor pressure deficit, albedo, and aerodynamic resistance, but it appears that hydrologic impact of these variables was minor. We suggest that efforts to restore Hawaiian tropical rain forests should consider drought resilience as one objective, among many, of a restoration program. Germinating seeds, shallowrooted saplings and deeper-rooted mature trees may respond differently to hydrologic effects of removing invasive plants.
Lantana camara L. is known to be one of the world's worst invasive species, yet in Hawai‘i, where it has been present for decades, little is known about factors influencing its establishment. This study examines influence of tree composition and disturbance, including fire and disturbance corridors, on its spread at the edge of its current distribution. We assessed whether lantana spreads in association with particular plants, disturbances, or environmental features within protected areas. Using 100 m2 plots, we measured vegetation cover, soil depth, evidence of pig disturbance, and presence of fallen trees in 105 plots (84 randomly generated and 21 selected for presence of lantana) across submontane woodland in Hawai‘i Volcanoes National Park on Hawai‘i Island. We found that lantana was more common than expected in association with the native nitrogen-fixing tree Sophora chrysophylla, and less common than expected near the exotic nitrogen-fixing tree Morella faya. Fire also strongly predicted its occurrence, as did proximity to roads: it was absent from all unburned plots, and in burned areas it was more common within 200 m of roads. Thus, three factors facilitated invasion by lantana: fire, roads, and presence of a native nitrogen-fixing tree.
Spodosols, one of the major orders of soils in the U.S. Department of Agriculture Soil Taxonomy, are believed to be formed by down-profile movement of colloidal humic materials complexed with aluminum and iron. Conditions favoring formation of these soils are normally cool and humid climates, but some tropical Spodosols have been observed in continental and island situations, mainly at higher elevations. Here we report on observation of two Spodosols at low elevations in Fiji, the first such report for the South Pacific islands. Soil field descriptions and associated laboratory data are presented, along with interpretation of data in terms of soil genesis, classification, and land use. Soils are classified as an Aquic Haplorthod, coarse-loamy, siliceous, isohyperthermic (from Drekeiwaila, Viti Levu) and an Oxyaquic Ultic Haplorthod, sandy over clayey, siliceous, isohyperthermic (from Lovonivia, Vanua Levu).
Karst forest represents a distinct landscape with highly alkaline soil and limestone rocks. This specialized topography supports many unique species of plants and animals. Thus, documenting species in this area is important for any biodiversity research. In this study, a field survey was conducted to assess abundance, diversity, and distribution of myxomycetes in a karst forest within Quezon National Park, Philippines. Fruiting bodies were collected in addition to decaying substrates (e.g., aerial leaves and ground leaf litter) and twigs for culture in moist chambers. A total of 35 species from 16 genera was identified. The majority of these species occurred only rarely. Myxomycete communities between aerial and ground litter had the highest level of similarity based on their species composition and corresponding relative abundance. This study documented diversity of myxomycetes from the lowland karst landscape in the Philippines and now serves as baseline information for investigating plasmodial slime molds in Quezon National Park.