Myoporum Sandwicense Research Articles

Volatile Constituents and Antimicrobial Activity of Naio (Myoporum Sandwicense A. Gray), a Native Hawaiian Tree

Myoporum sandwicense A. Gray (naio) is one of the characteristic trees of Hawaiian montane–subalpine mesic forests. In this study, lab-distilled oils of M. sandwicense leaves, wood, and twigs growing on the island of Hawaii, as well as industrially produced wood oils, were characterized by gas chromatography–mass spectrometry (GC-MS). The lab-distilled oils were screened for antimicrobial activity. M. sandwicense leaf essential oil was rich in β-caryophyllene (15.1%), α-humulene (12.8%), germacrene D (7.9%), bicyclogermacrene (12.5%), brigalow ketol (9.6%), and myoporone (16.8%), while the wood essential oils were dominated by α-bisabolol and trans-α-bisabolol oxide B. The sapwood oil was dominated by palmitic acid (35.5%), linoleic acid (19.7%), oleic acid (31.9%), and stearic acid (5.7%), whereas the oil from twigs was rich in tricosane (77.3%) and pentacosane (13.1%). M. sandwicense essential oils were screened for antimicrobial activity against a panel of potentially pathogenic bacteria and fungi. The leaf essential oil of M. sandwicense showed excellent antibacterial activity against S. pyogenes and antifungal activity against A. fumigatus. The wood essential oil showed notable activity against S. pyogenes, A. fumigatus, A. niger, and M. gypseum. The twig oil was remarkably active against mold species. This work is the first report we are aware of on the composition and antimicrobial properties of naio essential oils.

Shifting Limitations to Restoration across Dryland Ecosystems in Hawaiʻi

Hawaiian dryland ecosystems are important for global biodiversity conservation and contain numerous species threatened with extinction. Over the past century, wildfire frequency and size have increased dramatically because of invasion by fire-promoting non-native invasive species, greatly threatening these ecosystems. Native species restoration is a tool that can disrupt the cycle of increased fire and invasion in lowland dry forest communities, but restoration prescriptions have not been studied systematically in other dryland plant communities. We examined the restoration of three Hawaiian dryland plant communities (a high-productivity Diospyros sandwicensis and Metrosideros polymorpha lowland dry forest (HP), a moderate-productivity Myoporum sandwicense and Sophora chrysophylla dry forest/woodland (MP), and a low-productivity Dodonaea viscosa shrubland (LP)), using a community-assembly framework to understand the abiotic and biotic constraints to species establishment and growth in each community. Because active restoration methods are often needed, at both high and low levels of productivity, we also examined restoration treatments and outcomes across the three sites, which spanned a gradient of rainfall and substrate age. At each site, we used the same factorial field experiment with three factors: habitat quality (high or low), weed control (yes or no), and species addition (none, seeding, or outplanting). Outplants (cohort 1) and seeds were added in the winter of 2009–2010, and outplants were added again in March 2011 (cohort 2). Dispersal limitation was apparent at the LP and HP sites, but was not observed in the MP site, which had, overall, greater native diversity and abundance. Outplant survival was greater in high-quality habitats at the HP site, likely due to reduced abiotic stress. Invasive species were found in greater abundance in certain types of microsites at the LP and MP sites, suggesting that shade or topography can be used to plan restoration and weed-control activities. Overall, active restoration methods improved restoration outcomes at the high- and low-productivity sites, and less so at the moderately productive site. Weed removal and outplanting were effective restoration prescriptions at the LP and HP sites, and habitat quality could also be used to increase survival at the HP site. Active restoration could be a lower priority for moderately invaded, moderate-productivity communities, which have the capability to maintain a native ecosystem state.

Evidence of Competition between Honey Bees and Hylaeus anthracinus (Hymenoptera: Colletidae), an Endangered Hawaiian Yellow-Faced Bee

European honey bees (Apis mellifera) were first introduced to the Hawaiian Islands in the late 1800s, and are now ubiquitous across the state in both managed and feral colonies. Though they play an important role in pollination services for native plants and agricultural crops, the competitive impacts they may have on native bees are not well understood. We assessed bee interactions on the preferred floral resources of Hylaeus anthracinus at the Ka Iwi State Scenic Shoreline on O‘ahu, including Heliotropium foertherianum, Scaevola taccada, and Myoporum sandwicense. Bee visitation frequency and duration were documented and analyzed in one-hour increments from 08:00–13:00 totaling 90 hours of video recordings of the focal plants. Honey bee visitation frequency to H. foertherianum peaked at 11:00, and corresponded with a significant reduction in H. anthracinus visitation that resulted in a bimodal activity distribution for H. anthracinus. Feeding duration of H. anthracinus was significantly reduced when visiting H. foertherianum flowers following a honey bee, but unchanged when visiting after conspecifics. Honey bee feeding duration was unaltered by the species of the previous visitor, indicating that deterrence of H. anthracinus to flowers may not be the result of nectar exploitation. S. taccada and M. sandwicense received low overall bee visitation, prohibiting further analyses. We conclude that the presence of honey bees on a preferred foraging resource results in a temporal niche partitioning of H. anthracinus indicative of interference competition, possibly the result of interspecific chemical cues. Future honey bee management considerations are discussed.

A hard nut to crack: rapid evolution in the Kona Grosbeak of Hawaii for a locally abundant food source (Drepanidini:Chloridops kona)

Abstract The Kona Grosbeak (Chloridops kona), last seen in 1892, was restricted to a small mid-elevation area on the leeward (Kona) side of the island of Hawaii. It was reported to feed almost exclusively on the fruits of the naio tree (Myoporum sandwicense), which are extremely hard, requiring a force of perhaps 400 newtons or more to open. The morphology of the skull and mandible of the Kona Grosbeak was accordingly much more modified for the hypertrophied adductor musculature needed to crack naio fruits than its closest relative, the Wahi Grosbeak (Chloridops wahi), which has been found as fossils on most of the other main Hawaiian islands. The Wahi Grosbeak is here hypothesized to have fed on less resistant seeds, such as those of the Hawaiian prickly-ash (Zanthoxylum spp.). Naio is widely distributed in diverse habitats in the Hawaiian Islands but its fruits were apparently an energetically viable food source only on relatively young (ca. 1200 year old) aa lava flows on the dry side of Hawaii, where ...

Habitat and food preferences of the endangered Palila (Loxioides bailleui) on Mauna Kea, Hawai‘i

Seeds and flowers of the leguminous māmane (Sophora chrysophylla) tree are the primary food resource of the federally endangered Palila (Loxioides bailleui; Fringillidae: Drepanidinae), which is now restricted to dry subalpine woodland on Mauna Kea Volcano on the island of Hawai‘i because of centuries of habitat degradation by non-native ungulates. Palila are morphologically and behaviorally adapted to consume māmane seeds by grasping seed pods with their feet and opening pods with stout bills and demonstrate limited ability to exploit alternative food resources. This degree of single species dependency is rare among birds and illustrates unique adaptations that also occurred in other Hawaiian species that are now extinct. In mixed-woodland with co-dominant naio (Myoporum sandwicense), Palila spent 1.7–3.9 times longer in māmane than in naio during foraging observations where naio was 1.3–4.6 times as dense as māmane. Naio fruit was readily available, but it comprised proportionally <11% of food items taken by Palila. Although māmane flowers were more abundant than māmane pods throughout this study except at one lower-elevation mixed-woodland site, Palila spent more time foraging on pods than flowers in both māmane woodland and mixed-woodland, but consumed more flowers than pods in mixed-woodland. Insects, which have been reported as an important component of the diet of Palila, were apparently taken rarely in this study. Protecting and restoring māmane in woodlands adjacent to the current range of Palila will benefit their recovery, allowing them to exploit increased food availability in areas of their former range.

Inadvertent biological control: an Australian thrips killing an invasive New Zealand tree in California

Transport hubs of international trade and tourism are sites of unprecedented long-distance dispersal of species and novel ecological interactions. In cases of invasive plants released from their specialist natural enemies, novel interactions with both resident enemies and new arrivals can accumulate and potentially reduce weed competitiveness. I present here one dramatic example of this, where an invasive woody weed in southern California is being rapidly controlled by an accidentally introduced genus-specialist herbivorous insect. The New Zealand native shrub/small tree, Myoporum laetum, is a long-time popular ornamental plant in California and has become an invasive woody weed. In 2005, a Myoporum-specific thrips, Klambothrips myopori, was discovered (and described) in California feeding on M. laetum leaves. Several searches have failed to find K. myopori in New Zealand and a population has recently been discovered in Tasmania, Australia, feeding on Myoporum insulare. In 5 years, K. myopori has killed off about half of southern Californian M. laetum with almost all surviving individuals being gradually defoliated. Inadequate border biosecurity has resulted in inadvertent biological control, in a rapid timeframe, caused by a novel enemy. Unfortunately, K. myopori has subsequently been accidentally transported from California to Hawaii where it is now killing off Hawaiian native Myoporum sandwicense. Transport hubs can both connect weeds with natural enemies and disperse those enemies more widely.

Citeromyces hawaiiensis sp. nov., an ascosporic yeast associated with Myoporum sandwicense

Citeromyces hawaiiensis sp. nov. (NRRL Y-11581(T) = CBS 12303(T), type strain) is described from 12 strains isolated from flux of the sandalwood (Myoporum sandwicense) and adjacent soil in Hawaii, USA. Analyses of gene sequences from the D1/D2 domains of nuclear large subunit rRNA, internal transcribed spacer (ITS), mitochondrial small-subunit rRNA and translation elongation factor-1α each separated the proposed novel species from Citeromyces matritensis and Citeromyces siamensis, the other known species of the genus Citeromyces. The three species are morphologically similar but they can be separated by growth reactions in standard assimilation tests. An additional strain of Citeromyces siamensis (NRRL Y-11788), a species previously known only from Thailand, was obtained from spoiled condensed milk in Ohio, USA.

Competition between Native Hawaiian Plants and the Invasive Grass Megathyrsus maximus: Implications of Functional Diversity for Ecological Restoration

Biodiversity loss is a global crisis, due primarily to habitat destruction and widespread nonnative invasions. Invasive grasses are particularly problematic in many tropical ecosystems, where they possess traits that promote their persistence and can drastically alter native plant communities. We explored the ecophysiological basis for restoring native Hawaiian dryland ecosystems currently dominated by the nonnative invasive grass Megathyrsus maximus (guinea grass) in a garden experiment. Three native species—Myoporum sandwicense (naio; canopy tree), Dodonaea viscosa (aalii; shrub), and Plumbago zeylanica (iliee; groundcover)—were grown with M. maximus at three levels of native functional diversity (one, two, or three species) while holding overall plant density constant. We tested which individual and functional combinations of native species were more productive and best suppressed M. maximus growth and reproduction. Megathyrsus maximus had 39–94% higher maximum photosynthetic rates (Amax) than native species and increasing native functional diversity did not affect M. maximus Amax. Aboveground, belowground, and total biomass of M. maximus varied with functional diversity, although intraspecific competition reduced growth as much as interspecific competition. Reproductive tiller production by M. maximus decreased significantly when planted with any of the native species and with increasing native functional diversity. These results indicate that high native functional diversity in an ecological restoration setting may aid in the control of a dominant invasive grass and the reintroduction of diverse native species. Recommendations for restoring degraded nonnative grasslands in Hawaii and throughout the tropics include selection of native species that are ecophysiologically competitive and have high functional diversity.

Understory structure in a 23-year-old Acacia koa forest and 2-year growth responses to silvicultural treatments

Restoration of degraded Acacia koa forests in Hawaii often involves mechanical scarification to stimulate germination of seed buried in the soil and to suppress vegetation that competes with shade intolerant A. koa. Resulting even-age stands are gradually colonized by other plant species, but understory structure is poorly quantified, and the effects of management on understory vegetation are unknown. We examined the structure of the dominant understory species 23 years after stand initiation and determined their subsequent 2-year growth responses to silvicultural treatments prescribed to improve growth of koa. Release thinning, chemical control of introduced grasses, and phosphorus fertilization were applied in a split-plot experimental design. Results for DBH and height class distributions indicated that recruitment for most tree species began within a few years of stand initiation. By 23 years understory trees made up only 14% of total stand basal area, but they added greatly to native plant biodiversity. Alien grasses covered 92% of the forest floor and averaged 1.35 Mg ha −1. Of the four most abundant native understory tree species, only shade intolerant Myoporum sandwicense grew faster in response to the treatments. P-fertilizer combined with grass control significantly increased production of the native shrub, Rubus hawaiiensis. Notably, alien grass biomass did not increase in response to thinning, and actually declined in P-fertilized plots. Only, where P-fertilizer was applied were P concentrations of understory leaves elevated. Foliar concentrations of other nutrients were generally unaffected by treatments. Our findings suggest that the conservative silvicultural treatments we used can be applied without adversely impacting the capacity of aggrading A. koa forests to support a diversity of native understory plants. Lack of an increase in alien grass biomass, and in the case of P fertilization, a reduction in grass biomass, indicates that treatments should not increase competition with native species.

Phytoremediation of petroleum hydrocarbons in tropical coastal soils II. microbial response to plant roots and contaminant

The goal of this study was to understand the interaction between plants and microorganisms during petroleum-hydrocarbon bioremediation in Pacific Islands coastal soils. Total bacteria and hydrocarbon-degrading microorganisms population dyanamics were examined in the rhizospheres of tropical trees and shrubs, which were evaluated for their phytoremediation potential in a greenhouse experiment. The respective and combined effects of plant roots and diesel contaminant on the microbial populations were determined in relation to diesel fuel depletion. An increase in the grading populations size of the hydrocarbon-degrading populations of microbes, elicited by rhizodeposition, is generally regarded as conducive to an enhanced degradation of petroleum hydrocarbon pollutants in vegetated soil. The soil was a coastal sandy loam (pH 7.8) which was artificially contaminated with 10 g of No. 2 diesel fuel/kg soil or left uncontaminated. The pots were irrigated with fertilizer and 1% NaCl. The enumerations were carried out in the contaminated and uncontaminated rhizospheres of three trees, kiawe (Prosopis pallida), milo (Thespesia populnea), and kou (Cordia subcordata) and three shrubs, beach naupaka (Scaevola sericea), false sandalwood (Myoporum sandwicense), and oleander (Nerium oleander). Unplanted control soils were included in the experiment. Total bacteria and phenanthrene-degrading bacteria were enumerated on plates. Diesel- and pristane-degrading microorganisms were enumerated by the most-probable-number technique in tissue-culture plates. All four types of microorganisms responded to the rhizosphere of the 6 plants in uncontaminated soil and to the diesel contaminant in unplanted soil. In contaminated rhizospheres, no effect of the plant on the hydrocarbon-degrader numbers was visible. Total bacteria responded more to the plant roots than to the contaminant. The phenanthrene-degrading bacteria and pristane-degrading microorganisms were more influenced by the contaminant than by the plants. The diesel-degrading microorganisms were equally stimulated by the plants and the contaminant. The numbers of hydrocarbon degraders were similar in the contaminated rhizospheres of the three effective plants (kiawe, kou, and milo) and in those of the three ineffective shrubs. The results suggest the quality of the rhizodeposition is plant-dependent and governs the type of diesel-degrader populations that will be enhanced by a given plant. In the proposed phytoremediation-benefit model plant roots maintain high levels of hydrocaron degraders in uncontaminated soil. When the root enters a contaminated zone of soil, those hydrocarbon degraders that prefer the contaminant would switch to the contaminant as a carbon source, effectively removing the hydrocarbons. If the root exudates and the contaminant are equally attractive to the hydrocarbon degraders, the contaminant degradaton would be less effective.

Phytoremediation of petroleum hydrocarbons in tropical coastal soils. I. Selection of promising woody plants.

This glasshouse study is aimed at evaluating tropical plants for phytoremediation of petroleum hydrocarbon-contaminated saline sandy subsurface soils. Tropical plants were selected for their ability to tolerate high salinity and remove No. 2 diesel fuel in coastal topsoil prior to further investigation of the phytoremediation feasibility in deep contaminated soils. The residual petroleum-hydrocarbon contaminant at the John Rogers Tank Farm site, a former petroleum storage facility, at Hickam Air Force Base, Honolulu, Hawaii, is located in a coastal area. It lies below a layer of silt in the subsurface, in loamy sand characterized by moderate salinity and high pH. Little is known regarding the ability of tropical plants to remediate petroleum hydrocarbon-contaminated subsurface soil in Hawaiian and other Pacific Island ecosystems although suitable plants have been identified and utilized for bioremediation in surface soil or marine sediments. The experiments were conducted in long narrow pots under glasshouse conditions in two phases. A preliminary experiment was done with nine tropical plants: kiawe (Prosopis pallida), milo (Thespesia populnea), common ironwood (Casuarina equisetifolia), kou (Cordia subcordata), tropical coral tree (Erythrina variegata), false sandalwood (Myoporum sandwicense), beach naupaka (Scaevola sericea), oleander (Nerium oleander), and buffelgrass (Cenchrus ciliaris). These plants were screened for resistance to high salinity treatment (2% NaCl) and two diesel fuel levels (5 and 10 g No. 2 diesel fuel/kg soil) in separate treatments. Plants that showed good tolerance of both factors were further evaluated in a second phase for their efficacy in the phytoremediation of diesel-fuel petroleum hydrocarbons under moderate salinity treatment (1% NaCl). Tropical coral tree and buffelgrass were susceptible to either 2% NaCl or diesel fuel at 10 g/kg soil, but tolerant of diesel fuel at 5 g/kg soil. Kiawe, milo, kou, common ironwood, N. oleander, beach naupaka and false sandalwood were tolerant of high salinity (2% NaCl) or high diesel fuel level (10 g/kg soil). These seven plants were also tolerant of the combined adverse effects of a moderate salinity (1% NaCl) and 10 g diesel fuel/kg soil. Three trees, kiawe, milo and kou significantly accelerated the degradation of petroleum hydrocarbons in the soil spiked with 10 g diesel fuel/kg soil under a moderate salinity treatment (1% NaCl). Thus the tropical woody plants, kiawe, milo and kou showed potential for use in phytoremediation of petroleum hydrocarbons in coastal tropical soils. Two fast growing trees, milo and kou, appeared promising for further phytoremediation evaluation in experiments that simulate the soil profile at the field site.

Evaluation of Agriculture-Based Phytoremediation in Pacific Island Ecosystems Using Trisector Planters

ABSTRACT It is difficult to directly evaluate the efficacy of phytoremediation of petroleum hydrocarbon contaminants embedded in deep soil layers, especially if the contaminants are of relatively low concentration and are unevenly distributed. This report describes the greenhouse and laboratory experiments carried out to evaluate a field demonstration project. A trisector planter was designed to simulate field conditions, including soil profiles and field management of the trees selected. The third or bottom section of the planter was spiked with known quantities of 6 diesel-fuel components and the reduction of their concentrations was monitored after 200 days under the influence of the plant root systems. Results are statistically compared; among the three tree species used, milo (Thespesia populnea) and kou (Cordia subcordata) are more effective than false sandalwood (Myoporum sandwicense) in reducing the concentration of the spiked contaminant. Enumerations of populations of hydrocarbon-degrading microoorganisms in the bottom section suggest that biodegradation may be affected by the response of microorganisms to both the “close rhizosphere” (soil within 1 mm of the root) and the “expanded rhizosphere” (soil in the bottom section after root removal). Root exudates leached from the upper sections could be responsible for the expanded rhizosphere effect in the bottom section.

Temporal and spatial partitioning of water resources among eight woody species in a Hawaiian dry forest.

Lowland dry forests are unique in Hawaii for their high diversity of tree species compared with wet forests. We characterized spatial and temporal partitioning of soil water resources among seven indigenous and one invasive dry forest species to determine whether the degree of partitioning was consistent with the relatively high species richness in these forests. Patterns of water utilization were inferred from stable hydrogen isotope ratios (δD) of soil and xylem water, zones of soil water depletion, plant water status, leaf phenology, and spatial patterns of species distribution. Soil water δD values ranged from -20‰ near the surface to -48‰ at 130 cm depth. Metrosideros polymorpha, an evergreen species, and Reynoldsia sandwicensis, a drought-deciduous species, had xylem sap δD values of about -52‰, and appeared to obtain their water largely from deeper soil layers. The remaining six species had xylem δD values ranging from -33 to -42‰, and apparently obtained water from shallower soil layers. Xylem water δD values were negatively correlated with minimum annual leaf water potential and positively correlated with leaf solute content, an integrated measure of leaf water deficit. Seasonal patterns of leaf production ranged from dry season deciduous at one extreme to evergreen with near constant leaf expansion rates at the other. Species tapping water more actively from deeper soil layers tended to exhibit larger seasonality of leaf production than species relying on shallower soil water sources. Individuals of Myoporum sandwicense were more spatially isolated than would be expected by chance. Even though this species apparently extracted water primarily from shallow soil layers, as indicated by its xylem δD values, its nearly constant growth rates across all seasons may have been the result of a larger volume of soil water available per individual. The two dominant species, Diospyros sandwicensis and Nestegis sandwicensis, exhibited low leaf water potentials during the dry season and apparently drew water mostly from the upper portion of the soil profile, which may have allowed them to exploit light precipitation events more effectively than the more deeply rooted species. Character displacement in spatial and temporal patterns of soil water uptake was consistent with the relatively high diversity of woody species in Hawaiian dry forests.

Factors Related to the Recovery of Subalpine Woodland on Mauna Kea, Hawaii1

ABSTRACTWe measured mature tree and sapling density, tree associations, crown size, age structure, recovery from ungulate browsing, and grass cover at four study sites in two types of subalpine woodland on Mauna Kea volcano, island of Hawaii. Beginning in 1981, introduced ungulates were reduced in number to allow regeneration of Sophora chrysophylla (mamane) in habitat supporting the endangered Hawaiian finch, Loxioides bailleui (palila). We found Sophora regeneration at all four study sites, but regeneration was higher in mixed species woodland with codominant Myoporum sandwicense (naio) than in areas where Sophora dominated. Regeneration of Myoporum was uniformly very low in comparison. Invasive grass cover, which suppresses Sophora germination, was highest in mid‐elevation woodland where Sophora dominated. The distribution of mature and sapling Sophora were both related to study site, reflecting previous ungulate browsing and uneven recovery due to grasses. Densities of Sophora snags were not different among any of the sites, suggesting a more even distribution in the past. Selective browsing before ungulate reduction may have favored Myoporum over Sophora, leading to high densities of mature Myoporum in codominant woodland. After ungulate reduction, however, we found no pattern of competitive inhibition by Myoporum on regeneration of Sophora. Reduction of Myoporum is not likely to enhance habitat for Loxioides as much as supplemental plantings of Sophora, glass control, and continued ungulate eradication. Mid‐elevation Sophora woodland areas, where Loxioides forage and nest in high densities, would benefit the most from these management actions.

Feral Herbivores Suppress Mamane and Other Browse Species on Mauna Kea, Hawaii

Abundance, survival, and growth of ma paneSh cysophyfla) regeneration were determined inside and outside sheep exclosures located in heavily browsed portions of the mamane forest of Mauna Kea, Hawaii. Vegetational cover of other species was estimated. Mamane grew abundantly inside 16-year-old exclosures but was sparse outside. Height class distributions indicated that feral sheep prevented establshment of regeneration. Survival of seedlings and sprouts at 2-year-old exclosures was greater inside than outside. The largest difference between survival inside and outside was found where browsing pressure was greatest. Mamane reproduction exposed to browsing tended to be shorter than protected reproduction. Rate of height growth for protected mamane reproduction was significantly affected by exclosure location. Cover data for preferred browse species other than mamane indicated that 3 endemic grasses-Hawaiian bent (Agrostis sandwicense), he'u-pueo (Trisetum glomeratum), and Deschampsia australis, an endemic shrub-aheahea (Chenopodium oahuense), and an introduced forb-gosmore (Hypochoeris radicata)-were susceptible to browsing. On the basis of these findings, vegetation recovery should be rapid in most areas where feral sheep are eliminated or reduced. The mamane (Sophora chrysophylla) forest of Mauna Kea, island of Hawaii, occupies about 22,000 ha between 1,800to 2,900-m elevation. The forest is open woodland of pure mamane, except along the southern flank where mamane and naio (Myoporum sandwicense) form dense stands to about 2,500-m elevation. The xeric, high elevation forest is critical habitat for the Palila (Psittirostra bailleui), an endangered Hawaiian bird (Berger et al. 1977). Fifteen Hawaiian plant species growing within the forest have been recommended for inclusion in the list of threatened and endangered species of the United States (Ripley 1975). These species are endangered partly because of the damage done by feral sheep (Ovis aries) during the last 150 years. Feral sheep became established on Mauna Kea in the 1820's. Lacking natural predators, except for the wild dog, the sheep population reached about 40,000 animals by the early 1930's, one for every 2 ha of habitat (Bryan 1937). They extensively suppressed mamane and other tree reproduction, stripped bark from tree stems, and consumed herbaceous vegetation, thereby leaving the soil exposed to accelerated erosion (Warner 1960). Because damage to the forest was severe, Hawaii Territorial foresters reduced the population through sheep drives and hunter-guide programs. Under sustained yield management for public hunting, which started in 1955, the population was kept below 5,000. During the 1970's, the population averaged 1,500 animals. Even at this relatively low level, mamane regenerated little or not at all in areas where sheep tended to concentrate, especially at tree line. Cattle (Bos taurus), Mouflon sheep (Ovis musimon), and feral Authors are research forester, Pacific Southwest Forest and Range Experiment Station, Forest Service, USDA, Honolulu, Hawaii, and wildlife biologist, Hawaii Department of Land and Natural Resources, Divsion of Forestry and Wildlife, Hilo, Hawaii. The authors thank Howard Sakaii for collectingdata from the 1972 exclosures; C.J. Ralph, C.W. Smith, R.A. Merriam, J.D. Jacobi, and R. L. Walker for the critical review of earlier drafts of this manuscript; and J. Baldwin for his invaluable statistical guidance. Manuscript received February 2, 1982. goats (Capra hircus) also have contributed to destruction of native vegetation in this ecosystem. Cattle have done the most damage on the forest below 1,800-m elevation. Mouflon and goats are found primarily above 1,800 m, but damage has been limited because of their recent establishment in the forest and small populations (200 to 300 mouflon and 150 to 200 goats). Because of continued forest degradation and the attendant threat to the Palila, the United States District Court for the District of Hawaii ordered the State of Hawaii to remove feral goats and sheep completely and permanently from those portions of the amane forest designated as critical Palila habitat. Included were the Mauna Kea Forest Reserve up to an elevation of 3,000 m, the Kaohe Game Management area, and the upper Waikii parcel (U.S. Government Printing Office 1977). Eradication was completed in August 1981. But influx of feral sheep from areas adjacent to the critical habitat will require periodic hunts to comply with the court

The Phenology of the Dryland Forest of Mauna Kea, Hawaii, and the Impact of Recent Environmental Perturbations

The forest of Mauna Kea, Hawaii, was studied from 1973 through 1975 in order to define composition and phenology patterns of the two dominant tree species, and to determine the influence of man and feral mammals upon the ecosystem. There was a significant change in tree species composition across a 150 m elevational gradient; soil characteristics, drainage conditions, past disturbances by man, and browsing pressure by feral mammals are suggested as possible reasons. Although species composition varied with elevation, the tree density did not change. The phenological patterns of Sophora chrysophylla were found more closely tied to the weather pattern than were those of Myoporum sandwicense. Methods of pollination and seed dispersal were different between Sophora and Myoporum, and the spread of the latter is thought to be related to increased seed dispersal by recently introduced avian species, in conjunction with the limitation of Sophora reproduction due to browsing pressure by feral sheep. Because of the changes that are affecting the ecological organization of this community, the forest and its associated fauna need to be carefully examined in terms of present management policies. ONE OF THE LAST REMAINING NATIVE DRYFOREST ECOSYSTEMS in Hawaii is composed of 12,000 hectares of high mountain savanna on the southwestern slope of Mauna Kea. Sophora chrysophylla (Leguminosae) and Myoporum sandwicense (Myoporaceae) are the most abundant trees, with scattered stands of Euphorbia olowaluana (Euphorbiaceae), Santalum ellipticum (Santalaceae), Dubautia arborea (Compositae), and two small plantings of introduced pine, eucalyptus, and cedar. Shrub and ground-cover species are considered elsewhere. No one has described the phenology of this forest although Hartt and Neal (1940) gave a species account of the vegetation on the eastern slope of Mauna Kea. This ecosystem has been greatly influenced by the activities of man and introduced animals for the last 100 years (Warner 1960). Until the 1950's Parker Ranch grazed horses and cut Sophora for fence posts. Since the 1820's herds of feral sheep have roamed these volcanic slopes eliminating much of the Sophora reproduction by destroying the younger trees (Giffin 1976). Because of these perturbations, information was desperately needed on the present condition of the forest. This study was undertaken from April 1973 through August 1975 to compare forest composition and reproductive strategies of the two primary tree species (Sophora and Myoporum) in an effort to understand ecological interactions and influences on the forest as it exists today. METHODS Study sites were selected on the southwestern slope of Mauna Kea at elevations of 1980, 2130, and 2290 m along the jeep road from Kilohana to Puu Laau (fig. 1). The 1980 and 2130 m sites were open to grazing by feral sheep, while the 2290 m study site was fenced on all sides. Five contiguous 30 x 30 m releves, arranged in the shape of a T, were arbitrarily established near the center of each study site. All trees taller than 2 m (the height when Sophora and Myoporum first flower) were numbered, tagged, and, with the aid of a grid system, recorded on a map. Circumference at breast height (CBH) measured 1.4 m above the ground, was determined with a tape measure, and total tree height was measured with a clinometer. Canopy density, flowering, and fruiting were measured monthly (see Lamoureux 1973, Frankie et al. 1974). Canopy density was determined by standing under each tree and recording the percentage of open sky observed. Flowering and fruiting were measured by estimating the number of available terminal branches on each tree, and recording the percentage of those that possessed fully opened flowers or mature ripe fruit. To offset the phenomenon of trees in one area being in heavy flower while 500 m away others lacked blossoms, every month I systematically walked across each study area outside the releve's, measuring the nearest tree each 30 m until 50 trees had been considered. These data were then added to those obtained from the releves. With the density of trees and intensity of flowering known, it was possible to extrapolate the yearly lPresent address: Department of Zoology and C.P.S.U., University of California, Davis, California 95616, U.S.A. 282 BIOTROPICA 12(4): 282-291 1980 This content downloaded from 207.46.13.127 on Fri, 14 Oct 2016 04:07:05 UTC All use subject to http://about.jstor.org/terms Mauna Kea Game Management Area

Aspects of House Finch Breeding Biology in Hawaii

Bent (1968) summarized information available on the breeding biology of the House Finch (Carpodacus mexicanus). Although this species has been studied quite extensively in its North American home range, little attention has been paid to it in Hawaii. Grinnell (1911) reported on different color patterns of the House Finch in Hawaii, and Richardson and Bowles (1964) mentioned that on 23 June 1960 they found a nestling that had fallen from its nest on Kauai. On Mauna Kea, Berger (1972) found House Finch nests with eggs as early as 6 April (1968) and as late as 17 July (1967). Eleven nests were built on horizontal branches of mamane (Sophora chrysophylla) and two in naio (Myoporum sandwicense) trees. Complete clutches of three eggs were found in two nests, four eggs in five nests, and five eggs in one nest. only other reference I have found to the breeding aspects of the House Finch in Hawaii is that of Hirai (1974) who studied an urban House Finch population in Honolulu from 1972 through 1974. According to Caum (1933), the House Finch was introduced to Hawaii prior to 1870, probably having escaped from captivity. It is now established on all of the main Hawaiian islands. Berger (1972) wrote that The Linnet is common in cities and towns, in both wet and dry rural areas, and in the high ranch and forest lands on Maui and Hawaii. It is uncommon in the depths of the near-virgin rain forests, but it is abundant in the mamaninaio forests on Mauna Kea, as well as in partly cutover mixed ohia-koa forests.

Niche Separation in a Pair of Homosequential Drosophila Species from the Island of Hawaii

Two exceedingly closely related species of Drosophila coexist in a sparsely vegetated xeric area on the island of Hawaii. Of the two major trees in the area, Myoporum sandwicense alone appears to support the existence of both species. Whereas both feed as adults on Myoporum flux, D. silvarentis oviposits only on fluxes which wet the trunk well above the ground surface. Drosophila heedi larvae are found exclusively in caked soil moistened by flux dripping from above. Implications of this type of niche separation for the evolution of sibling or near-sibling species are discussed.