京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第18660号 / 農博第2089号 / 新制||農||1028(附属図書館) / 学位論文||H26||N4883(農学部図書室) / 31574 / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 井鷺 裕司, 教授 北島 薫, 教授 北山 兼弘 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Prey availability, directly or indirectly, affects all aspects of a predator’s life history and is a primary factor influencing habitat selection and movements. This is especially true for delphinid species where it has been documented that the behaviors and movements of dolphins are strongly influenced by food availability. Unfortunately, the feeding ecology and habitat use patterns of many of these species are poorly understood. Many methodologies that have been employed to explore these facets of dolphin ecology have limitations and constraints or are logistically infeasible. Stable isotope and fatty acid signature analyses have been used extensively on a wide variety of species and have been shown to be methodologies that overcome some of these limitations. These approaches can provide information on feeding habits and the geographic origin of the prey thereby giving tremendous insight into habitat usage patterns. The present study applied stable isotope and fatty acid signature methodologies to gain insight into the feeding ecology and habitat usage of various dolphin species to improve upon our understanding of these important facets of their life histories. The application of stable isotope analysis in ecological studies relies on both species and tissue specific measurements of parameters such as diet-tissue discrimination factors, the difference in stable isotope ratio between a consumer and its prey, and turnover rates, the change in tissue isotopic composition attributable to growth and tissue replacement. Initially, controlled studies were conducted and animals were switched from one isotopically distinct diet to another which allowed for the calculation of these values in bottlenose dolphin skin. Diet-tissue discrimination factors for dolphin skin averaged 2.20‰ for nitrogen and 0.82‰ for carbon. Average turnover rates (expressed in half-lives) in dolphin skin were 17 days for nitrogen and iv 16.5 days for carbon. The present study represents the first reported diet-tissue discrimination factors and turnover rates for carbon and nitrogen in the skin of any cetacean. Next, skin samples were collected from net-entangled and free-ranging dolphin species off the coast of South Africa and analyzed for stable carbon (δ13C) and nitrogen (δ15N) isotope ratios. The Indo-Pacific bottlenose dolphin (Tursiops aduncus), the common dolphin (Delphinus capensis), the striped dolphin (Stenella coeruleoalba), and the humpback dolphin (Sousa chinensis) all occur off the southeastern coast of South Africa with overlapping distributions. Isotopic signatures revealed resource partitioning among these four species of dolphins with differences in diets, as well as differences in the use of habitat. Mean values for δ 15N ranged from 11.92 ± 0.11‰ (n=3) for striped dolphins to 14.95 ± 0.19‰ (n=27) for humpback dolphins, indicating that these species are feeding at different trophic levels. Striped dolphin carbon isotope signatures were consistent with evidence that they typically forage further offshore (- 17.94 ± 0.14‰) and the carbon isotope values of the humpback dolphins reflected their use of inshore habitats by comparison (-15.16 ± 0.12‰). Common and bottlenose dolphins for nitrogen (13.66 ± 0.08‰, 14.35 ± 0.07‰ respectively) and carbon (-15.48 ± 0.07‰, -15.76 ± 0.06‰ respectively) fell in between these two extremes. Analyses also revealed that males and females have differences in their diets. On average, males were enriched in δ 15N by 0.74‰ compared to females suggesting some dietary differences in prey composition. Isotopic niche width has been compared to traditional measures of niches used by ecologists and was measured for these South African dolphins. Humpback and bottlenose dolphins had the largest standard elliptical area (SEA), striped dolphins had the smallest SEA, and the SEA for common dolphins was intermediate. Larger SEA values reflect a broader trophic diversity, while smaller SEA values reflect a narrower trophic diversity or a more specialized niche. v Finally, a resident group of bottlenose dolphins (Tursiops truncatus) in the Indian River Lagoon (IRL) in east central Florida were sampled and explored for differences in isotopic signatures based on sex, age category, season, and location within the IRL. In addition to stable isotope analysis, fatty acid analysis was also used to compare and contrast the findings between the two techniques. Comparison of stable isotopic signatures revealed differences among age categories and among locations. Fatty acid analysis was able to discern further and found differences in the signatures between male and female dolphins. The combination of both techniques allowed for an extensive examination into the feeding ecology and habitat utilization of these resident dolphins. The Bayesian mixing model (Stable Isotope Analysis in R- SIAR) was validated using controlled study data and was found to be accurate when inputting isotopically distinct prey items (sources). The mixing model was then used to estimate the proportions of prey items that make up the diet of Indian River Lagoon bottlenose dolphins. Two models were run in which dolphins were grouped together (model 1) and dolphins were separated by year (model 2). Results of the model reaffirm stomach content analysis results previously obtained. Stable isotope techniques were applied to various dolphin species to gain better understanding of their feeding ecology and habitat utilization. Resource partitioning was suggested for four South African dolphin species which gives crucial insight into the ecology of both at-risk and data-deficient species. These discernments will provide much needed data to conservationists and managers and contributes to our general understanding of these species. This is the first study of its kind to undertake controlled diet studies with bottlenose dolphins which determined diet-tissue discrimination values and turnover rates for carbon and nitrogen isotopes in the skin of any cetacean. The current study is also the first of its kind to attempt to vi model bottlenose dolphin diet in the Indian River using stable isotopes. Food, being a primary driver for many species, can lend explanation of things like movement patterns, habitat usage, competition, reproductive success, survival, and the spread of diseases, which has been an issue in Indian River dolphins in recent years. Dietary information modeled in this study provided new data for the relative contribution of a suite of potential prey to an apex predator in the Indian River. Data produced through the current study contributes towards a large, unprecedented step forward in understanding dolphin ecology and the roll of cetacean stable isotope ecology.

The West Indian manatee (Trichechus manatus) is an herbivorous marine mammal that occupies freshwater, estuarine, and marine habitats. Despite being considered endangered, relatively little is known about the feeding ecology of either of the two recognized subspecies, the Florida manatee (T.m. latirostris) and Caribbean or Antillean manatee (T.m. manatus). A better understanding of their respective feeding preferences and habitat use is essential to establish criteria on which conservation plans can be based. The present study expands on previous work on manatee feeding ecology by both assessing the application of stable isotope analysis to manatee tissue and providing critical baseline parameters for accurate isotopic data interpretation. The present study was the first to calculate stable isotope turnover rate in the skin of any marine mammal. Stable carbon and nitrogen isotope ratios were examined over a period of more than one year in the epidermis of rescued Florida manatees that were transitioning from a diet of aquatic forage to terrestrial forage (lettuce) in captivity. Mean half-life for 13C turnover in manatee epidermis was 55 days and mean half-life for 15N turnover was 42 days. Due to these slow turnover rates, carbon and nitrogen stable isotope analysis in manatee epidermis is useful in summarizing average dietary intake over a long period of time rather than assessing recent diet. In addition to turnover rate, a diet-tissue discrimination value of 2.8‰ for 13C was calculated for long-term captive manatees on a lettuce diet. Turnover and diet-tissue discrimination results were subsequently used to interpret carbon and nitrogen stable isotope data in epidermis samples collected from free-ranging manatees in Florida, Belize, and Puerto Rico. This study was the first application of stable isotope analysis to Antillean manatees. Regional differences in stable isotope ratios in manatee skin were consistent with ratios in plant samples collected in those regions. Signatures in the skin of manatees sampled in Belize and Puerto Rico indicated a diet composed mainly of seagrasses, whereas those of Florida manatees exhibited greater variation. Mixing model results indicated manatees sampled from Crystal River and Homosassa Springs had an overall average intake of primarily freshwater vegetation whereas manatees sampled from Big Bend Power Plant, Ten Thousand Islands, and Warm Mineral Springs fed primarily on seagrasses. Possible diet tissue discrimination values for 15N ranged from 1.0 to 1.5‰. Stable isotope analysis can be successfully applied to interpret manatee feeding behavior over a long period of time, specifically the use of freshwater vegetation vs. seagrasses, and can aid in improving conservation efforts.

Coleoptera is currently the most diverse lineage of life on Earth with more than 400,000 described species. The group also contains unbelievable ecological and morphological variation that has been evolving since the early Carboniferous (>350 MYA). The group provides the perfect playground to test evolutionary hypotheses with large-scale phylogenies. First, a newly developed bioinformatics tool is presented that allows for the critical assessment of the stability of phylogenetic nodes with even minor changes in taxon sampling (i.e. a single taxon jackknifed). The tool, TANOS, is capable of performing tests on large genomics-scale datasets. The case study included is a widely used phylogenomics effort to resolve the higher level relationships of all Insecta. The specific beetle group chosen for the remaining products is the superfamily Cucujoidea, and more specifically the family Nitidulidae, or sap beetles. Several taxonomic and nomenclatural projects were necessary to provide a more stable classification and begin the process of establishing the group as a model system for questions concerning feeding behavior evolution. Several new species of the genus Carpophilus were described from both the West Indies and the New World tropics and subtropics. Several type designations were also needed for many species in the subfamily Carpophilinae. In addition, the fossil diversity of Nitidulidae was reviewed with the addition of the oldest known member of the Cillaeinae from amber (Dominican). With the reviewed fossil fauna, as well as many more from across the Cucujoidea more broadly, a divergence-time estimated phylogeny was generated for >250 species of the superfamily. The phylogeny, based on the combination of multiple published Sanger datasets and supplemented with newly generated data for a further 50 species, was used to date multiple feeding shifts in the group. Specifically, the clade ages were used to compare with published clade ages for the corresponding food resource each clade is known to exploit. A significant relationship was recovered between age of the beetle clade and the corresponding food resource clade. Interestingly, it was found that clades that shifted to a food resource first, in the absence of existing beetle competitors, were significantly more diverse over subsequent lineages that shifted to the same resource. A feeding ecology of specific importance, at least to many groups of nitidulid, is anthophily, or flower-visiting. An extreme variation in eye size is observable across the family and so multiple factors including; sex, day-night activity, and feeding behavior were tested in a phylogenetic context. No sexual dimorphism nor variation consistent with activity period was found. Relative eye size of flower visiting species was significantly larger than that of all other feeding behaviors in sap beetles. This correlation was also tested in a phylogenetic context, with the increase in morphological investment in vision repeatedly shown to correspond to shifts in flower associated behavior. In an attempt to investigate the interplay between behavior, morphology, and genetics in the same process, opsin data was captured as part of a large targeted enrichment sequencing effort (AHE) across Nitidulidae and their relatives. The first phylogenomic estimate was generated for the group, with a taxon sampling of 192, and data sampling depth of 703 loci. A newly updated pipeline was developed for AHE data and is presented herein. Topological results support the recent idea of a non-monophyletic Cucujoidea. Results also demonstrate multiple classification issues within the Nitidulidae with several new subfamilies/tribes necessary to maintain diagnosable monophyletic groups in the family. The vast majority of sampled genera were supported, with the exception of Brachypeplus and Pallodes. Preliminary opsin diversity across the group is much greater than previously estimated. Opsin copy number is potentially plastic even within individual genera, although consistently duplications are associated with taxa that visit flowers. It is clear that the complexity of cucujoid visual systems increases with anthophilous behavior.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20217号 / 理博第4302号 / 新制||理||1618(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)准教授 半谷 吾郎, 教授 湯本 貴和, 教授 平井 啓久 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

The Indian River Lagoon, Florida, is a unique closed “bar built” estuary system that has little interchange with the Atlantic Ocean and which is home to many resident species. Three fish species were investigated to see if their isotopic and fatty acid signatures differed based on geographic location. The goal was to assess the degree of resolution of spatial variation that is possible when using stable isotope and fatty acid signature analysis to interpret feeding habits and potential linkages between feeding habits and health status. Spotted seatrout (n=40), pinfish (n=60) and white mullet (n=60) were collected over a 4 week period at sites 30 km apart in two distinct biogeographic regions of the IRL. Fish were analyzed for stable isotope (δ13C and δ15N) and fatty acid composition. All three species were significantly different from each other in both isotopic and fatty acid signatures. In the North Indian River segment, spotted seatrout, white mullet and pinfish had mean values (± SE) for δ13C of -18.00 ± 0.08, -14.59 ± 0.07 and -16.88 ± 0.04 respectively and for δ15N, mean values were 14.43 ± 0.05, 8.30 ± 0.04 and 10.43 ± 0.03 respectively. For the North-Central Indian River segment, spotted seatrout, white mullet and pinfish had mean values for δ13C of -18.98 ± 0.02, -16.25 ±0.06 and -16.94 ± 0.04 respectively and for δ15N, mean values were 14.21 ± 0.02, 8.07 ± 0.03 and 10.64 ±0.03 respectively. When species and location interactions were examined using ANCOVA, a post-hoc Tukey’s HSD test showed that δ13C was significantly affected by sampling segment only for spotted seatrout and that there was no significant effect of location on δ15N values. Spotted seatrout was the only species that differed between segments for δ13C. Classification and Regression Tree (CART) analysis was then performed on the “extended dietary fatty acids” for each individual species and collection location. In this analysis, all three species were correctly identified to segment (white mullet - MR 2/53 p~ 0.03; spotted seatrout (MR 0/40), and pinfish (MR 0/56) indicating that individual species were exhibiting significant differences in their fatty acid signature over distances of 30 km. The ability to discern fine-scale differences in potential prey allows for the possibility of better resolution of dolphin feeding habits and hence a better understanding of both habitat utilization and health impacts. Due to limited exchange of clean salt water, contaminants can theoretically become a problem and there are indications that the health of the resident population of bottlenose dolphins (Tursiops truncatus) has been declining over recent years.

No description available.

No description available.

No description available.

No description available.