Tropical Conservation Biology and Environmental Science Program

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Investigating the growth dynamics of mamane (Sophora chrysophylla) on Maunakea, Hawai`i using radiocarbon dating and classical dendrochronology methods
(ProQuest LLC, 2012) Francisco, Kainana S.
When trees form annual growth rings, the patterns can be used to provide information on tree age and growth dynamics that is essential to developing appropriate forest management strategies. Annual rings are not commonly produced in tropical trees because they grow in a relatively aseasonal environment, however, in the subalpine zones of Hawai'i's highest volcanoes, there is often strong seasonal variability in temperature and rainfall. Using a combination of classical dendrochronology methods and radiocarbon dating I determined that annual growth rings occur in mamane ( Sophora chrysophylla ), a native hardwood tree species, on Maunakea, Hawai'i. I developed a baseline chronology for mamane, and used this to explore the relationship between local precipitation and the growth dynamics of this native tree. I also used tree-rings to estimate the age and growth rates of these trees. This study is the first in the eastern tropical Pacific region to utilize dendrochronology methods to gain a better understanding of the stand history, growth dynamics, and life history strategies of any of a native forest tree. The results from this research will greatly benefit efforts to protect, conserve, and effectively manage the subalpine forest ecosystem on Maunakea.
Vegetation Patterns in Lowland Wet Forests of Hawai'i
(2012) Dupuis, Cindy J.
The easternmost part of the Big Island contains some of Hawai'i's last remaining native lowland wet forests. My goals in this study were to examine how substrate age and elevation influence the degree of invasion present in this lower elevation (< 300 m) region by assessing native and non-native canopy cover of trees, to evaluate native-dominated communities for the influence of substrate age and elevation on diversity and species composition, to examine canopy conditions surrounding rare plant occurrences, and to identify priority areas for restoration. I focused on East Hawai'i's five forest reserves using Braun-Blanquet cover estimate methods to assess vegetation patterns. Plots were stratified to represent combinations of variables including three categories of substrate age (< 200 yrs, 200-750 yrs, >750 yrs), and three elevation zones (< 100 m, 101-200 m, 201-300 m). I analyzed 291 plots, of which 125 had a native-dominated canopy. On intermediate flows, absolute cover of native tree species was higher when compared to young flows; relative cover of native tree species was higher, and absolute cover of non-native species was lower, when compared to older substrates. On young flows, absolute cover of native trees equaled that of non-native trees. The oldest substrate proved to be most degraded, with the relative cover of native trees being lower than on other substrates. At native-dominated sites, there was higher native species richness on intermediate substrates relative to the young, and higher non-native species richness on the older substrate when compared to the young. Young and old substrates had higher numbers of non-native species than they did native species. There was a greater relative canopy cover of native trees where rare plants occur compared to plots where they do not occur. All 34 individuals from rare species were entirely on the 200-750 year old substrate. Together, these trends point to intermediate age substrates as holding the most intact native assemblages and highest potential for restoration.
Endemic grazer (Halocaridina rubra) forces and obscured nutrient effects on benthic autotrophy in Hawaiian anchialine pools
(ProQuest LLC, 2013-08) Sakihara, Troy S.
Anthropogenic impacts on aquatic ecosystems alter the controls of epilithon structure and biomass by altering top-down and bottom-up forces, and their interactions. In Hawai'i, these impacts include increased nutrient loading from development and invasive nitrogen-fixing plants, as well as the continual spread of other alien invasive species. This study examined the effects of nutrient availability and the grazing effects of an endemic aytid shrimp, Halocaridina rubra , on epilithon structure and biomass in Hawaiian anchialine pools. Epilithon was sampled by deploying terra-cotta plates with a combination of nutrient enrichment and grazer exclusion treatments in anchialine pools across a background NO2- +NO3 - concentration gradient. Autotrophy and epilithon biomass significantly decreased across this background NO2- +NO 3- gradient and with grazing by H. rubra , whereas the effect of grazing treatments on relative autotrophy (ash-free dry mass chlorophyll a-1 ) was more pronounced in pools with higher background NO2 - +NO3- concentrations. However, minimal effects of nutrient enrichment treatment were found and no algal communities from pools sampled appeared to be nutrient limited over the range of background NO2- +NO3- concentrations investigated. Relatively high background NO2 - +NO3- concentrations in the pools may be responsible for the lack of nutrient treatment effects. Instead, potential effects of salinity and nutrient toxicity on epilithon may be important factors. My results suggest that grazing by H. rubra is a primary driver of epilithon structure and biomass and that this endemic grazer is a key species in maintaining the natural conditions of Hawaiian anchialine pools across a range of nutrient concentrations and abiotic conditions.
Documenting acoustic variability among windward Hawai'i 'Amakihi (Hemignathus virens virens) populations on Hawai'i Island
(ProQuest LLC, 2014) Pang-Ching, Joshua
Vocalizations play a fundamental role in many aspects of a bird's life, including territoriality, mate choice, individual recognition, and predator avoidance. This is the first study to investigate how vocalizations differ across populations of a Hawaiian honeycreeper. I recorded song from 329 adult male Hawaii 'Amakihi (Hemignathus virens virens) in five populations across an elevational gradient on the windward side of Hawaii Island during the 2011-2013 breeding season and used sound analysis software to examine how eight song components vary within and among populations. Our results demonstrated that song varies greatly among populations with greatest divergence and lowest song variability in the low elevation population, where 'Amakihi have recently recovered from a disease-induced bottleneck. I also tested predictions of the Acoustic Adaptation Hypothesis (AAH) by examining how song characteristics vary between open and closed understory vegetation. 'Amakihi in open understory sang at higher frequencies relative to neighboring 'Amakihi in dense understory, thus providing moderate support for the AAH. This study demonstrates that both isolation and habitat heterogeneity has led to localized structuring of song over relatively short geographic distances.
Home range ecology of Naso unicornis (Bluespine Unicornfish): Use of acoustic telemetry to define foraging interactions with an invasive alga, Gracilaria salicornia, in a marine reserve
(Thesis (M.S.)--University of Hawaiʻi at Hilo, 2014., 2014) Bierwagen, Stacy Lynn
Blooms of non-indigenous marine macroalgae have been reported throughout the Hawaiian Islands over the past 30 years. Successful invaders have dominated regions on both the Eastern and Western shores of Oahu. In Kaneohe Bay, a particular species of rhodophyte, Gracilaria salicornia , has successfully monopolized macroalgal communites throughout the Southern portion and is currently distributed to the most Northern regions of the bay. In a healthy reef community, herbivorous grazers play a large role in maintaining coral dominance by containing overgrowth of indigenous algae by grazing. Because of this known association, other studies have suggested that marine protected areas may carry the capacity to suppress overgrowth of successful invaders via promoting increased biomass of herbivorous reef fish. The interactions of Naso unicornis , bluespine unicornfish, with G. salicornia have never been addressed in a field capacity. By determining whether these fish select for habitats covered with G. salicornia and actively graze on the invasive macroalgae, we can determine whether or not this species-specific interaction exists. Recent studies also suggest that herbivorous reef fish contribute to the dispersal of some macroalgal species via gut passage. We used a combination of active tracking with underwater visual census to determine habitat selectivity and residence of N. unicornis in a marine protected area in Kaneohe Bay. After confirming that N. unicornis selects for and grazes G. salicornia , we collected the fecal fragments to determine regenerative capacity once passed through the gut. Using a pulse amplitude modulation fluorometer along with observation, we were able to determine fluorescence at different stages of growth post-egestion.
Investigating the efficacy of commercial baits for the control of yellow crazy ants (Anoplolepis gracilipes) and their impacts on Red-tailed Tropicbirds (Phaethon rubricauda)
(ProQuest LLC, 2014) Kropidlowski, Stefan Jozef
Invasive ants are one of the largest threats to Pacific island ecosystem conservation. I investigated effective ant control options by examining the relative attractiveness of five commercial ant baits to yellow crazy ants (Anoplolepis gracilipes ). The results were used to select three baits whose efficacy at reducing A. gracilipes abundance was then tested in experimental treatment plots. The trials failed to identify an obvious preference for any of the baits and none of experimental treatments resulted in decreases in A. gracilipes abundance that differed from untreated plots. Additionally, the impact of A. gracilipes on nest initiation rates of Red-tailed Tropicbirds (Phaethon rubricauda ) was explored. The survey found 90% fewer nest occurred in plots containing A. gracilipes. These results demonstrate the negative impacts invasive ants can have on ground-nesting seabirds and suggest that commercial ant baits may be ineffective against controlling A. gracilipes supercolonies.
Phylogeny, Bioactivity, and Physiology of Unique Bacterial Isolates from Hawaiian Marine Sponges from Hawaii Island: Insights into the Bacteria-Sponge Relationship
(ProQuest LLC, 2015) Nguyen, Hoang-Yen Xuan
The goals of this study were to 1) investigate the diversity of cultured bacterial isolates from Hawaiian marine sponges Haliclona sp., Petrosia sp., and Iotrochota protea from Coconut Island and Puhi Bay on the East side of Hawaii Island, 2) identify any unique and/or strong candidates for carrying out further bioactivity and gene screening such as nonribosomal peptide synthetase and polyketide peptide synthase assays and 3) begin to assess their significance to their sponge host. The bacterial isolates contained unique and diverse bacterial isolates according to phylogenetic analysis, nonribosomal peptide synthetase and polyketide peptide synthase screening, Violacein synthetic gene screening, bioactivity assay, and physiological assessments. One isolate, designated PB004-2 (A1), contrasts with its most similar BLAST neighbor, Brevibacterium frigoritolerans, in color, form, and media and temperature growth conditions. Another isolate, designated S0022 B001, whose BLAST neighbor is a Pseudomonas sp., shows nonmotility, absence of flagella in SEM images, and may possess Violacein-like synthesis genes, indicating S0022 B001 may be a new Pseudomonas species. The crystal formation, inconclusively precipitated calcium carbonate, may serve a purpose in the sponge. Findings from this research may indicate that 1) bacteria isolated from the Hawaiian sponges have their unique role in their respective sponge host, 2) may be important to each other's health, and 3) may be important to sponge health.
Local adaptation of the Hawaiian endemic tree (Metrosideros polymorpha) across a long elevation gradient
(2015) Sakishima, Tomoko; Stacy, Elizabeth; Tropical Conservation Biology & Environmental Science
Elevation gradients are important drivers of divergence in trees, yet little is known about the spatial scales over which divergence occurs, nor the abiotic factors that drive divergence. The endemic Hawaiian tree, ‘ōhi‘a lehua (Metrosideros polymorpha) spans a striking elevation gradient on Hawai‘i Island, from near sea level to 2,470 m, and comprises two pubescent varieties; M. polymorpha var. incana tends to be found at lower elevations, M. polymorpha var. polymorpha is limited to higher elevations, and purported hybrids occur at middle elevations. To better understand the scale and drivers of divergence in tree populations along elevation gradients, I conducted field, greenhouse, and growth-chamber experiments on open-pollinated seedlings from six populations of pubescent M. polymorpha spanning the full elevation range of this species on Hawai‘i Island. The reciprocal outplanting experiment revealed universally low survivorship at the extreme ends of the elevation gradient, suggesting these environments are the most challenging. Results of the 12-month UV-light experiment in the greenhouse revealed relatively lower survivorship under high-UV light of seedlings from the three highest-elevation populations (counter to expectations), contrasting relationships between anthocyanin concentration and survivorship between the two varieties, and possible heat sensitivity of high-elevation seedlings. Lastly, short-term stress response tests were done under extreme environmental conditions (i.e., high UV radiation and low temperature) in a growth chamber. No seedlings from the highest-elevation population died after exposure to -5°C for four nights, while seedlings from all other populations had lower survivorship. These results indicate local adaptation at both the variety level and suggest that both UV radiation and temperature are important drivers of local adaptation of trees across long elevation gradients.
Food Web Analysis of Hawai‘i Island’s Blackburnia hawaiiensis (Coleoptera: Carabidae) Using Next-generation Sequencing and Stable Isotope Techniques
(2015) Roy, Kylle; Price, Donald K.; Tropical Conservation Biology & Environmental Science
Tropical montane forests are valuable ecosystems in Hawai‘i, providing fresh water to the people of the islands as well as acting as reservoirs of biodiversity. These forests are experiencing rapid alterations due to anthropogenic effects such as climate change, habitat degradation, invasive species, and industrialization. Some of the detrimental effects caused by these ecosystem alterations can be mitigated through understanding the genetics and ecology of the organisms within it. Despite the importance of these arthropod-dominated ecosystems, knowledge of food webs and predator-prey interactions is sparse. In order to supplement the understanding of Hawai‘i’s montane forest ecosystems, we have implemented two different methods of diet analysis on the endemic Hawaiian carabid beetle, Blackburnia hawaiiensis. This understudied carabid may provide important ecosystem functions, being a numerically dominant predatory insect and widely distributed throughout Hawai‘i Island. B. hawaiiensis populations and potential prey in similar, highly isolated geographic locations were used to employ two different yet complimentary laboratory techniques: natural abundance stable isotope analysis (SIA) and metagenomics of gut contents using next-generation sequencing (NGS). Both NGS and SIA have revealed B. hawaiiensis to be a high trophic consumer with evidence of intraguild predation in three study sites: Ka‘iholena, Thurston, and Pu‘u Maka‘ala. In a broader context, the combined SIA and NGS techniques have great potential to further our understanding of the arthropod food webs of the montane forests of Hawai‘i Island, ultimately improving conservation efforts for the entire arthropod community. These two methods in combination could potentially be implemented in any ecosystem globally to better determine the diets of species within complex food webs, enhancing ecosystem management strategies.
Assessment of light quality, variability, and seedling presence in Hawaiian lowland wet forests
(2015) Rosam, Jodie Ray; Ostertag, Rebecca; Tropical Conservation Biology & Environmental Science
Hawaiian lowland wet forest (HLWF) plant species are light-limited, yet no information exists on how the understory light varies in relation to species invasion, or if patterns of seedling regeneration and light are linked. I measured the red-to-far-red ratio (R:FR) of light to assess light quality and quantified diurnal variability in three forest types: native-dominated, partially-invaded, and fully invaded by strawberry guava (Psidium cattleianum). I asked: (1) how does understory light quality vary relative to invasion? (2) Are there differences in light quality moving vertically among forest types? (3) Are patterns of seedling regeneration and understory light related? Native-dominated forests had the greatest light quality (highest R:FR), and Psidium cattleianum-dominated forests had the lowest. While I predicted that native seedlings would prefer high-quality light sites, all seedlings preferred medium quality environments. In invaded HLWF, native seedling regeneration is hindered, and restoration efforts should focus on non-native understory removal.
Islands within islands: The effects of habitat fragmentation, novel community interactions, and climate on Hawaiian Drosophila populations.
(2015-12) Mueller, Matthew C.; Price, Donald K.; Tropical Conservation Biology & Environmental Science
Habitat fragmentation, invasive species, and shifting climate regimes are major threats to island ecosystems. Hawaii's ecosystems have been largely transformed since human colonization, with fragmented upland forests remaining important refugia for native organisms. Hawaiian Drosophila represent a large radiation of nearly 1000 endemic species, including a number of endangered and declining species. These endemic flies are important indicator species for ecosystem change, tending to be sensitive niche specialists. I examined a network of 28 lava-fragmented forests ("kipuka") on Mauna Loa to determine the effect of fragment size, presence of invasive rats, and seasonal changes in microclimate on the abundances of native Drosophila tanythrix, D. silvestris, D. sproati, and D. murphyi, and the exotic D. suzukii. All flies responded positively to increasing kipuka area. Rat exclusion had a significant and mostly positive impact on both native and exotic Drosophila abundances, but the effect varied with individual species, suggesting that rats may amplify the impact of predators on Drosophila or predate them directly, but also affect other nodes in the community. Increasing kipuka isolation from surrounding forest tended to benefit Drosophila, perhaps due to release from competitors. Exotic flies represent the vast majority of Drosophilids observed in small kipuka, and significantly outnumbered natives in all kipuka before crashing in the winter. In contrast, native flies were more abundant in winter, and rare picture-wing species were found almost exclusively in kipuka larger than 2.5 hectares. Overall, it appears that habitat fragmentation and invasive species disrupt Hawaiian Drosophila communities; the rarest species require large kipuka and the absence of rats. D. suzukii may be replacing native Drosophila in smaller kipuka, but appear maladapted to Hawaii's cold winters at higher elevations. This dynamic could tip in favor of D. suzukii as temperature isoclines climb upslope with global climate change.
Indigenous Microorganism 4 (IMO 4) as a Soil Inoculant
(2015-12) Rushing, James; Arancon, Norman Q.; Tropical Conservation Biology & Environmental Science
Since 1997, many farmers across the world have adopted techniques of an agricultural system called Natural Farming, which utilizes indigenous microorganisms and naturally derived soil amendments to improve soil dynamics and plant production. However, due to a dearth of peer reviewed reports that exist on the subject, many stakeholders and researchers have been hesitant to use these agricultural techniques. The most widely discussed and utilized Natural Farming amendment is Indigenous Microorganism 4 (IMO 4), which is a form of indigenous microorganism inoculated compost made from agriculture by-products, high in carbohydrates, and a moderate concentration of plant available nutrients. Because of this lack of scientific data discussing IMO 4 as a soil bio-stimulant, a series of experiments were designed and implemented to analyze the physical, chemical, and biological properties of IMO 4, as well as examine the effect of IMO 4 on soil dynamics and growth of corn (Zea mays) in Andisol soil, when compared to other organic amendments. It was determined that IMO 4 was rich in indigenous microorganisms and possesses an appreciable concentration of plant available nutrients. The physical, chemical, and biological analyses of IMO 4 indicated a potential as a soil bio-stimulant if the indigenous microorganisms survive inoculation. A greenhouse experiment comparing IMO 4 to organic matter applications showed IMO 4 had a similar effect on soil dynamics and growth of corn as the application of organic matter. A further experiment examining the effect of IMO 4 in conjunction with organic fertilizers showed that IMO 4 had similar impact on soil dynamics as organic matter amendments, due to the substrate effect of IMO 4 applications. Organic matter amendment applications also showed a significantly greater effect to plant height, dry weight, and total leaf area than the IMO 4 samples. There was no evidence the indigenous microorganisms on the IMO 4 substrate survived inoculation into the soil environment. It was concluded that IMO 4 was effective in adding organic matter and plant available nutrients to the soil via a substrate effect. Due to the lack of effect IMO 4 applications have on plant growth and the absence of significant improvement to plant production, organic matter amendment applications in the form of composts and mulch are recommended.
Evaluating techniques of quantifying lipid yield and cell density of Chlorella protothecoides (Kruger) grown on waste glycerol
(2015-12) Collins, Topaz Palakika; Adolf, Jason E.; Tropical Conservation Biology & Environmental Science
Chlorella protothecoides (Krüger) is ubiquitous as a research organism for biofuels. The genus consists of species that are photosynthetic, heterotrophic, and mixotrophic, and cellular lipid yield can be relatively high compared to other algal species. The research presented here addressed the differences between conventional and novel methods of quantifying lipid yield and cell density of C. protothecoides produced on various glycerol media. Conventional methods of light microscopy, gravimetric lipid analysis, and colony forming units, were compared with BODIPY 505/515 lipid-stained cells and NucRed Live 647 nucleic acid stained cells analyzed by flow cytometer. This is the first report of using a dual stain technique to simultaneously quantify cell density and lipid yield of an algal species for biofuel production. Results indicated that there is no significant difference (p > 0.05) between BODIPY 505/515 and NucRed Live 647 for cell density. There is no significance between the dyes and hemocytometer counts (p>0.05). Lipid analysis indicated no significant difference between flow cytometer lipid per cell and %oil/vol (p>0.05), especially for UTEX B25. This indicates that the novel method of utilizing BODIPY 505/515 or NucRed Live 647, singularly or in concert, is comparable to conventional methods of lipid and cell density analyses. Because all three strains of C. protothecoides obtained cell densities of between 107 and 109 cells/mL and highest oil yield was about 45% per cell, waste glycerol has the potential to become a viable feedstock for Hawaii’s growing biofuel industry.
Comparative genomics and host plant adaptation in Hawaiian Picture-wing Drosophila
(2016-05) Armstrong, Ellie; Price, Donald K.; Tropical Conservation Biology & Environmental Science
For arthropod lineages, host-switching and differential host adaptations are commonly suggested as important ecological drivers behind diversification and co-evolution. The Hawaiian picture-wing Drosophila are an ideal lineage for investigations of the genomics of speciation because of their close relationship to D. melanogaster, their well-known phylogeny, thoroughly documented ecology, and incredible diversity. I investigated the genomic landscape changes and genome evolution in relation to host-plant adaptation in four species of Hawaiian picture-wing Drosophila. Three of these species, Drosophila sproati, Drosophila murphyi, and Drosophila ochracea were sequenced for this study using de-novo whole-genome sequencing and assembly. All of these species are endemic to Hawaii Island and considered specialist species and oviposit on the plants Cheirodendron trigynum (D. sproati and D. murphyi) and Freycinetia arborea (D. ochracea). The last species, D. grimshawi from the Maui Nui complex, was originally sequenced by the Drosophila 12 Genomes Consortia and is considered a generalist species. I also used the outgroup, Scaptomyza flava, a continental species of the Scaptomyza genera, which originated in Hawaii. In the picture-wing lineage, there were 264 genes found to be under positive selection, notably those with chemosensory gene functions, plant detoxification functions, and inter-male aggression functions. Using all paralogs and orthologs of chemosensory genes, three genes in the odorant receptor and odorant binding protein gene families were detected to be under positive selection. It was also shown that specialists lost more chemosensory genes over time compared to the generalist species. Using 1:1 orthologs across species, I detected 12 genes under positive selection in individual picture-wing species that had a variety of functions in protein signaling, cell metabolism and division, and plant detoxification. These results highlight the genomic changes associated with host plant adaptation and sexual selection in the Hawaiian Drosophila. In addition, the results show that repeat content is strongly correlated with genome size across the Drosophila genus. Drosophila grimshawi has a repeat content 3x higher than the other picture-wings, but this does not correspond to increases in repeat diversity. There was no notable codon bias between picture-wing species, but there was codon bias between D. grimshawi and S. flava. Picture-wings tended to favor a single codon over other codons, whereas S. flava has evenly represented codon choice for any given amino acid. Genomic synteny across picture-wing species and D. melanogaster was highly conserved at the chromosome level.
Dietary behavior of the mangrove monitor lizard (Varanus indicus) on Cocos Island, Guam, and strategies for varanus indicus eradication
(2016-05) Ehrhard, Seamus Patrick; Mautz, William; Tropical Conservation Biology & Environmental Science
The mangrove monitor lizard (Varanus indicus), a large invasive predator, can be found on all areas of the 38.6 ha Cocos Island at an estimated density, in October 2011, of 6 V. Indicus per hectare on the island. Plans for the release of the endangered Guam rail (Gallirallus owstoni) on Cocos Island required the culling of V. Indicus, because the lizards are known to consume birds and bird eggs. Cocos Island has 7 different habitats; resort/horticulture, Casuarina forest, mixed strand forest, Pemphis scrub, Scaevola scrub, sand/open area, and wetlands. I removed as many V. Indicus as possible from the three principal habitats; Casuarina forest, mixed scrub forest, and a garbage dump (resort/horticulture) using six different trapping methods. Cage traps and garbage barrels were highly effective in capturing medium to large adults, while snake traps were the only trapping method that effectively captured neonate monitor lizards. An air rifle with pellet shot removed the most individual V. Indicus and was effective in capturing all sizes of the lizards. Polyvinyl chloride pipe retreats and monofilament live snares were much less effective. After 11 months of trapping and shooting on Cocos Island, V. Indicus density was reduced to an estimated one V. Indicus per ha. Live captured V. Indicus were euthanized then weighed, measured, and dissected to analyze diet. Combined with earlier dietary data, I compared the diet of V. Indicus before and after an earlier rodent eradication using a prior diet analysis when rodents were present. In contrast to data published on V. Indicus from mainland Guam, rodents did not constitute a large percentage of the V. Indicus diet on Cocos Island prior to rodent eradication. However, 20 months post-rodent eradication, there were increased numbers of reptile eggs, earthworms, and insect larvae in the stomach contents of V. Indicus. Comparison of the percent occurrence of ingested items from the three different habitats showed that garbage dump greatly differed from the Casuarina forest and the mixed scrub forest. Comparison of diet between the mixed scrub forest and Casuarina forest revealed that while both populations of V. Indicus were consuming high percentages of crabs, the species of crab consumed differed between the two areas. Dietary differences were quantified using the Importance Index, which analyzes prey importance in relation to predator body size. Combined prey Importance Index with the prey frequency Index, showed that birds are the most important prey item followed by crabs. Although birds are found in only 4% of V. indicus with identifiable stomach contents, birds are the most important component in terms of dietary energy acquisition.
Phylogenetics, biology, and ecology of two unclassified species of near-shore octopuses in Hawai‘i
(2016-05) Daw, Adam; Haws, Maria; Tropical Conservation Biology & Environmental Science
The current understanding of the biology and ecology of octopuses has focused on a limited number of species compared to the high diversity of species currently described. Within the tropical – subtropical Pacific there have been multiple studies describing the phylogenetic relationships among the near-shore octopus species, in particular within the southern and eastern regions. As we start to better understand species diversity through phylogenetic analysis, there is still limited information describing the biology and ecology of these species. In this study the phylogenetic relationships of two unclassified species of octopuses (Abdopus sp. 1 “Crescent octopus” and Octopus cf. vitiensis) inhabiting the near-shore coral reef ecosystem of Hawai‘i were compared to the octopus diversity of the tropical – subtropical Pacific. In order to better understand the physiology and biology of these two species, the growth rates of wild caught specimens and the effect of temperature on the onset of hatching were observed. Finally δ15N and δ13C stable isotope analyses were used to compare the trophic niche of four octopus species (Octopus cyanea, Callistoctopus ornatus, Abdopus sp. 1, and Octopus cf. vitiensis) that utilize the near-shore coral reef habitat in order to determine if there is a difference between species utilizing the same habitat. The results of the phylogenetic analysis indicate that Abdopus sp. 1 is a distinct species and is closely related to Octopus laqueus. Octopus cf. vitiensis is closely related to but distinct from Octopus oliveri, there were no genetic sequences of the type specimen or other non-Hawaiian Octopus cf. vitiensis available to conduct comparisons to determine if the Hawaiian population is the same or a distinct species. Growth observations of the two species indicate that Octopus. cf. vitiensis is sexual dimorphic with males obtaining a smaller maximum mass and mantle length (observed max 74.2g, 47.9mm) compared to females (observed max 133.0g, 60.0mm). There was no observed difference in size and mass between males and females of Abdopus sp. 1 in this study, possibly due to small sample size. The timing of the onset of hatching of the two species was negatively correlated with temperature, ranging from 27 days at 28°C to 57 days at 20°C for Octopus cf. vitiensis. There was no difference in egg developmental time between species at corresponding temperatures. Results from stable isotope analysis indicate that habitat/location has a greater effect on trophic niche than octopus size for the species and sizes analyzed. Differences in δ15N between species were variable between habitats/locations. This indicates that these species are opportunistic feeders, with prey selection based on what prey are more prevalent or easy to capture in a specific location.
High resolution habitat suitability modeling for a narrow-range endemic alpine Hawaiian species
(2016-05) Stephenson, Nathan Michael; Perroy, Ryan L.; Tropical Conservation Biology & Environmental Science
Mapping potentially suitable habitat is critical for effective species conservation and management but can be challenging in remote areas exhibiting complex substrate heterogeneity. An approach that combines a diverse set of nonintrusive spatial data collection techniques with field validation can lead to a better understanding of landscapes and species distributions. Nysius wekiuicola, commonly known as the wēkiu bug, is the most studied arthropod species endemic to the Maunakea summit in Hawai‘i, yet details of its life history and geographic distribution remain poorly understood. The wēkiu bug, a species of concern, provides an excellent opportunity to employ nonintrusive spatial data collection techniques to answer previously elusive questions about habitat quality and composition. To predict the geographic distribution of N. wekiuicola, MaxEnt habitat suitability models were generated from fifteen years of species occurrence data and a variety of spatial datasets, including high resolution digital elevation models, surface mineralogy based on hyperspectral remote sensing, and climate variables. MaxEnt model results indicate that the variables with the highest influence (in terms of percent contribution) were elevation (78.2%), presence of nanocrystalline hematite surface minerals (13.7%), and minor contributions from aspect, slope, and other surface minerals. A limitation of this study is that many historic trapping sites were placed near roads and other accessible pre-determined locations instead of being systematically or randomly placed, meaning final model results may be biased and not entirely indicative of true wēkiu bug distribution. Although climate data is available, these climatic variables were auto-correlated and at too coarse of a spatial resolution to include in the final analysis. A trapping experiment based on surface mineralogy and geomorphic position affirmed that both elevation and surface mineralogy play significant roles in the spatial patterns of wēkiu bugs, but observed presence upslope on a cinder cone and absence downslope, even within the same predominant surface mineral, suggests that other habitat variables may be at play such as competition/predation. The models of wēkiu bug range and predicted suitable locations will be incorporated into management efforts and restoration goals for land managers of Maunakea. In addition, environmental data layers created in this initiative have now unlocked the ability to create suitability models for other species of interest on Maunakea.
Investigating the growth periodicity, stable carbon isotope trend and climate reconstruction potential of 'Akoko (Euphorbia olowaluana), A native Hawaiian C4 tree on Mauna Kea, Hawaii, using tree ring analysis
(2016-05) Ben, Tishanna; Hart, Patrick; Tropical Conservation Biology & Environmental Science
Tree ring patterns provide one of the best records of historical climate variability. I evaluated growth increment periodicity and the stable isotope ratios of carbon in two woody plant species using the C3- and C4-photosynthetic pathway. The investigated species, Māmane (Sophora chrysophylla, C3) and ʻAkoko (Euphorbia olowaluana, C4), are small endemic Hawaiʻian trees sampled from a rather dry, high elevation habitat on the ridge between Mauna Loa and Mauna Kea on the island of Hawaiʻi, USA. A relatively strong correlation in ring patterns was found within the ʻAkoko and the Māmane individuals as well as with ring-width patterns from a nearby population of introduced Deodar Cedar (Cedrus odorata) trees that serve as a reference. This is evidence that the C4-plant ʻAkoko may form annual growth rings. In addition to being the first demonstration of annual growth rings in a C4 plant, our findings have important implications for future climate change research in Hawaiʻi. Unlike plants with a C3-photosynthetic pathway, C4 plants do not show strong bias against 13C during the photosynthetic fixation of CO2. Thus, ʻAkoko may provide a record of past atmospheric CO2 concentration that can be compared with, and possibly supplement, the well-known Keeling curve produced by the nearby Mauna Loa Atmospheric Observatory. Regression analysis indicates a significant relationship between ʻAkoko δ13C averages and atmospheric δ13C values. Furthermore, time series of tree ring data from both species provide long-term information on the response of C3 and C4-plants to increasing atmospheric CO2 concentrations and climate change. Trends in 13C (intrinsic water-use efficiency) of the two species show similar responses in that both demonstrate an increase in iWUE over time and with increased CO2atm. ‘Akoko and Māmane iWUE curves are different however, in that the ‘Akoko (C4) curve is non-linear and a significant increase could only be observed post 1975, while the Māmane curve shows a distinct linearly increasing trend throughout the observation period.
Microbial Diversity of Two Hawaiian picture wings and their Host Plants; Microbes, Mortality and Epicuticular Hydrocarbons
(2016-05) Yakym, Christopher-James A.V.; Price, Donald K.; Tropical Conservation Biology & Environmental Science
Although the microbiome influences numerous aspects of organismal biology and fitness, the community characterization and role in animal evolution is largely unknown. Microbial communities in insects can have a wide range of interactions from mutualistic to parasitic and can be important in host-plant adaptation. In Drosophila, microbial associations and interactions have been studied for over a century and recently have been shown to influence the fitness and evolution of their host. This study utilizes both traditional culturing methods and high-throughput next generation DNA sequencing to evaluate the bacterial and fungal communities associated with two Hawaiian Drosophila, D. sproati and D. ochracea and their host plants, Cheirodendron trigynum and Freycinetia arborea. The culture-based and high-throughput DNA sequencing approaches provided different but complementary results. Interestingly, we found some overlap between microbiomes of the Hawaiian Drosophila and their host plants. The bacterial family Enterobacteriaceae, as well as a variety of yeasts, consisted of the majority of these shared microbes. This suggests that these microbes may play a role in the fly-host plant interaction. To evaluate the effect of these microbes on Hawaiian Drosophila, we exposed a laboratory population of D. sproati to antibacterial and antifungal treatments to determine the effect on D. sproati survivorship and epicuticular hydrocarbons. Epicuticular hydrocarbons in Drosophila serve a dual function, aiding in desiccation resistance and pheromonal communication. Flies exposed to an antifungal treatment had dramatically reduced survivorship when compared to control flies, while antibacterial treated flies were not affected. This suggests that fungi are essential to Drosophila survival while bacteria are not. However, male flies that were exposed to the antibacterial treatment showed significant changes in two major epicuticular hydrocarbons. One of which, 2MeC28, has been shown to act as a contact pheromone in other insect species. This study shows that changes in microbial communities, specifically bacteria, influence epicuticular hydrocarbon production of D. sproati which can impact multiple levels of fitness.
Development of Decision Support Systems for Ecosystem Management: A case study on Hawai`i Island
(2016-05) Kimball, Heather; Price, Jonathan; Tropical Conservation Biology & Environmental Science
Ecosystem management decisions are inherently complex, requiring the integration of ecological science, economics, policy, cultural values, and stakeholder needs. Decision support systems (DSS) are tools intended to facilitate communication between researchers, land managers and policy makers, with the goal of more informed and holistic decision making at the ecosystem scale. The objective of this thesis was to assess the process of DSS development and generate components of a DSS for an individual land owner to assist in planning ecosystem management. The study area selected to demonstrate this process is 23,000 hectares in the Humu`ula tract on Hawai`i Island administered by the Department of Hawaiian Home Lands. This site was selected because it has an existing land management plan, the `Āina Mauna Legacy Plan, and it represents two main threats to ecosystems in Hawai`i, habitat degradation and non-native plant and animal species invasions. Based on nearly three years of discussions with the stakeholders, the following management goals were identified for the study area: restoration and protection of native plant and bird habitat, gorse (Ulex europaeus) removal, watershed restoration, fire reduction, and most importantly, increased and more consistent funding to support the aforementioned goals. This study is divided into three sections. The first section describes establishing Gross Primary Productivity and Net Primary Productivity parameter estimates for the different land cover classes in the study area in order to project the capacity of the ecosystem to capture carbon under the alternative scenarios. The second section evaluates the use of high resolution imagery to model the current land cover of the study area, particularly the spatial distribution of the invasive shrub gorse. The final section covers a summary, conclusion and the next steps for this project including the parameterization of a state and transition model, used in the Carbon Assessment of Hawai`i, to generate projections and data layers to develop a decision support system for the study area as an appendix.

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