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Herbivorous fishes include a diverse assemblage of species that target primarily benthic autotrophs. This is perhaps one of the most well-studied groups of coral reef fishes, often reputed to be key components of coral reef communities, contributing to coral reef health in numerous ways. Through their feeding ecology and benthic interactions, they help mediate algae-coral interactions which can allow for improved coral survival and health. Despite the wealth of literature documenting the prominent roles of these fishes in coral reef ecosystems, studies from the Red Sea are surprisingly lacking. The Red Sea is a marginal reef environment, with a host of unique environmental and biological characteristics making it a unique environment where dynamics of herbivory may differ. This dissertation aims to fill key gaps in our knowledge of herbivorous fishes through the study of their distribution and trophic ecology. Herein, I describe habitat-specific partitioning of Red Sea herbivorous fish assemblages, discovering higher diversity and abundance found in reefs closer to shower, dissimilar to findings from other regions. Cross-shelf variation in assemblage structure seems to be quite robust through time, indicating short-term stability in herbivore assemblages. Through the use of stomach contents and stable isotope analyses, I then investigate the trophic ecology of browsing herbivores across the same shelf-gradient. I found higher trophic redundancy on nearshore reefs through time, with increased variation in diet and high levels of complementarity on offshore reefs where macroalgae are scarce. Stable isotope analyses of both liver and muscle revealed the stability of this resource partitioning through time, demonstrating for the first-time temporal stability of resource partitioning within this group. This dissertation broadens our knowledge of herbivorous fishes, filling important gaps. It offers new insight into the role of habitat in structuring trophic ecology and how flexible the diets of browsing species can be. Together, this information creates a foundation where improved knowledge of herbivorous fish ecology could be incorporated into future management plans of ongoing giga projects within the Kingdom. Incorporating herbivores into these plans could allow for increased resiliency for Red Sea coral reefs in the face of future development and shifting climatology.

Understanding factors limiting population growth is crucial to evaluating species persistence in changing environments. I used Integral Projection Models (IPMs) to elucidate the role of biotic interactions and disturbance on population growth rate in two plants: Helianthemum squamatum, a perennial endemic to gypsum habitats in central Spain, and Liatris ohlingerae, a long-lived perennial endemic to the Lake Wales Ridge of central Florida. In H. squamatum, there was a strong positive effect of trampling in the site with the highest plant density and moderate positive effects of seed addition in the site with the lowest plant density. Differences in treatment effectiveness between sites may represent a shift from seed to microsite limitation at increasing densities. Additionally, a distinct drop in population growth rate occurred in the hottest and driest year (2009-10). In Liatris ohlingerae, roadside populations had consistently higher population growth rates than scrub populations. A modest negative effect of time-since-fire was observed in plants that did not experience herbivory. Both habitat and time-since-fire showed distinct interactions with vertebrate herbivory, with herbivory increasing the difference in growth rate between habitats and decreasing the difference between time-since-fire classes. The direct effect of herbivory was negative in all environmental combinations except in long unburned populations. These results demonstrate the importance of considering environmental interactions when constructing population models, as well as the validity of using IPMs to assess interactions in species with differing life histories.

Eastern hemlock hosts the hemlock woolly adelgid, an introduced sap-feeding insect that causes rapid deterioration of the host. Like most conifers, eastern hemlock produces a variety of constitutive and induced defenses, primarily terpenoids. To explore the relationship of terpenoid defenses with adelgid infestations, we artificially infested hemlocks at a forest site and a plantation site, and compared their terpenoid concentrations to those in control trees. Infested trees showed lower terpenoid concentrations than control trees, suggesting that eastern hemlock not only fails to induce production of terpenoids in response to adelgid infestation, but becomes less able to produce carbon-based defenses due to loss of carbon resources to the adelgid. Greater light intensity may account for consistently higher terpenoid concentrations at the plantation site, supporting the explanation that carbon limitation restricts terpenoid production. Recent studies have identified a small number of individual eastern hemlock trees that demonstrate relative resistance to the hemlock woolly adelgid. We compared concentrations of terpenoids in susceptible and relatively resistant trees, both in the forest and in propagated cuttings in a common-garden setting. Terpenoid concentrations were higher in twig tissue of resistant versus susceptible trees, across six sampling dates and at both sites. Because the common-garden cuttings were free of herbivores, the higher terpenoid concentrations are interpreted as a constitutive defense. Increased levels of monoterpenes and sesquiterpenes imply an overall increase in the input of carbon precursors to both terpenoid synthesis pathways. This result suggests either an altered growth-defense balance favoring allocation of carbon resources towards production of defenses, or overall greater carbon availability in growing twig tissue of adelgid-resistant eastern hemlock individuals. We contribute detailed terpenoid data to the study of the eastern hemlock – hemlock woolly adelgid system. Our solvent extraction method permits us to examine needle and twig tissues separately, capture minor components at low concentrations, and focus on stored rather than volatilized terpenoids. By relating terpenoid concentrations to insect densities, we explore the relationships of tentatively defensive chemistry to insect population dynamics. The question remains which terpenoids, if any, directly affect hemlock woolly adelgid and what role phenols may play in the system.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19536号 / 理博第4196号 / 新制||理||1602(附属図書館) / 32572 / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 工藤 洋, 教授 田村 実, 教授 石田 厚 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Root-feeding insects can have top-down influence on vegetative composition and ecosystem processes; however, they may respond to bottom-up factors such as soil resources, site productivity, and disturbance.  My research addressed the following questions: (1) Do disturbance (fire), vegetative composition, soil resources, and fine root standing mass influence the structure of root-feeding insect assemblages? (2) What types of roots do root-feeding insects eat, and do they forage selectively?  (3) Do root-feeding insects influence fine root productivity?  To address these questions, I studied root-feeding insect assemblages in longleaf pine wiregrass (Pinus palustris-Aristida stricta) ecosystems of southwestern Georgia, U.S.A.  On a random basis, study sites were burned at least every other year (B), or left unburned (UB) for about 9 years.  Fine root productivity and root-feeding insect abundances were sampled repeatedly across 54 random plots in UB and B sites.  In Chapter 2, I characterized spatial and temporal patterns of root-feeding insect abundance, understory plant composition, soil resource availability, and fine root standing mass within each plot.  Insect population densities were low overall, but abundance, patchiness, and diversity were greater in UB sites.  Abundance patterns were significantly related to vegetative composition.  In Chapter 3, I quantified the diet of root-feeding insects by measuring the natural abundance of carbon (C) and nitrogen (N) stable isotopes in insects and fine roots.  Using 13C abundance, I examined the contribution of warm season grass roots to insect diet, relative to the proportion of warm season grass roots within adjacent root standing crop samples; 15N abundance was used to detect omnivory.  Overall, insects appeared to be non-selective herbivores and omnivores that may alter foraging behavior to maintain a mixed diet (i.e. reducing or increasing warm season grass consumption when its abundance was high or low, respectively).  The extent of omnivory varied within and among taxa.  In Chapter 4, I estimated the top-down influence of root-feeding insects on fine root productivity by comparison of ingrowth cores with or without an insecticide treatment.  I detected a weak positive effect of herbivores on the productivity of non-grass fine roots (< 10% of fine root productivity). / Ph. D.

Field and laboratory studies were used to elucidate the factors affecting temporal and spatial variations of species abundance and structure of macroalgal assemblage and environmental variables between fish farming (FFA) and non-fish farming (NFFA) areas in Hsiao-Lu-Chiao island, a coral island in southwestern Taiwan. Four experiments have been approached: 1. field surveys of macroalgal assemblage structure on 5-m and 10-m depth at 3 sampling sites at FFA (FFA1, FFA2 and FFA3) and 1 sampling site at NFFA from September 2004, January 2005 and April 2005; 2.the relationship between abiotic (monthly maximum air temperature, monthly minimum air temperature, monthly mean air temperature, monthly cumulative precipitation, monthly cumulative irradiance, seawater temperature, light extinction coefficient, water motion, and nutrient (NO3-, NO2-, NH4+, SRP, DON, and DOP) and biotic (seaurchin density) factors and spatio-temporal variations in macroalgal structures analyzed by non-parametric multivariate model; 3. Factors affecting macroalgal abundance and structure: (1). Comparison of growth temperature ranges in different species to field temperature fluctuation; (2).Comparison of growth irradiance ranges in different species to field irradiance fluctuation; 4.Herbivore pressure: (1). Spatio-temporal variations of sea urchin abundance and structure of assemblage; (2). Gut contents and food preference of sea urchin experiment; (3). Herbivore exclusion experiment. Macroalgal %cover, biomass, species richness, diversity (H¡¦) and evenness (J¡¦) showed temporal and spatial variations, low values in January 2005 and also low values in the 5 m- and 10 m-depth areas of FFA1 and the 10 m-depth areas of FFA2. The data of k-dominance curve, hierarchical cluster and ANOSIM tests indicate that macroalgal assemblage is different between 4 sampling sites, between 2 depths and between 3 seasons. Ceratodictyon spongiosum is the most important species that separates September and January assemblages from April assemblage and separates the FFA1 and FFA2 assemblages from the FFA3 and NFFA assemblages. BVSTEP analysis shows that nutrients (NO3-, DON, DOP), temperature, monthly cumulative precipitation, and sea urchin density are the factors corresponding to variations of macroalgal assemblages, this correlation is more significant for 5 m-depth assemblage. Fish farming area FFA1and FFA2 assemblage are affect by sea urchin density, temperature and DON. Sea urchin influnces macroalgal abundance and assemblage structure in FFA1 and FFA2. Macroalgal %cover in 5 m-depth area shows a reversal relationship with sea urchin density; however, this relationship is not observed for 10 m-depth area. FFA1 and FFA2 are belong to high grazing pressure sites as indicated by high sea urchin density and exclusion experiment. Sea urchin gut contents and feeding preference test show that sea urchin has strong food selectivity with Hypnea charoides and Gracilaria coronopifolia as the most preferred species. Herbivore exclusion experiment shows that Hypnea charoides and Gracilaria coronopifolia are the species recruited in the cages. Ceratodictyon spongiosum had high biomass in FFA1 and FFA2 in January, which was ¡¥low DOP/high DON¡¦. The coindicence of temporal variations in FFA3 assemblage structure with a change from ¡¦Halimeda opuntia and Boodlea compostia¡¦ ¡÷ ¡¦Amphiroa fragilissima, Corallina phhulifera and Galaxaura oblongata¡¦ ¡÷¡¦Halimeda opuntia and Boodlea compostia¡¦ with low nitrogen/ high phosphorous¡¦ ¡÷¡¦ high nitrogen/ low phosphorous¡¦ ¡÷ ¡¦low nitrogen/ high phosphorous¡¦ suggest a role of ¡¦low nitrogen (NO3-)/high phosphorous (DOP)¡¦ for FFA3 structure modification. NFFA assemblage is controlled by temperature and monthly cumulative precipitation. Monthly cumulative precipitation in September was higher than January and April, in which Boodlea compostia and Gracilaria coronopifolia were dominant algae in September. The temperature growth responses of algae using the continuous-flow outdoor laboratory tank culture system fit their seasonal growth, reflecting the temperature-dependent manner of seasonal variations in abundance. It could be concluded from the present investigation that the structure of benthic macroalgal assemblage in Hsiao-Lu-Chiao island in southwestern Taiwan is affected by predicted natural and pulse disturbances. Temperature fluctuations involve in overall temporal variations in structure. Sea urchin herbivory and nutrient as pulse nutrient modulate the structure in fish farming area while monthly cumulative precipitation is associated with algal structure in non-fish farming area.

Qui du phénomène de résistance (RA) ou de susceptibilité (SA) par association est prépondérant en milieu forestier ? En d’autres termes, la défoliation par les insectes herbivores est-elle moins (RA) ou plus (SA) importante sur des arbres hôtes situés en mélange comparés à des monocultures ? A cause des contraintes méthodologiques, les connaissances sur la relation diversité - résistance en forêts matures restent faibles. Pour répondre à cette question, nous avons utilisé le dispositif exploratoire du projet FunDivEUROPE. Sur un réseau de 209 parcelles forestières sélectionnées le long de deux gradients orthogonaux de richesse spécifique (d’une à cinq essences en mélange) et de latitude (de la forêt méditerranéenne à la boréale), nous avons évalué la défoliation des houppiers des arbres. A l’aide d’un échantillon constitué de onze essences différentes, nous avons démontré pour la première fois un patron global de diminution de l’herbivorie (RA) en forêts matures à travers l’Europe. Nous avons également comparé l’herbivorie des insectes dans des placettes constituées de chênes purs ou mélangés à d’autres espèces, placées en lisière ou à l’intérieur de petits bois présents dans les vallées et coteaux de Gascogne. Nous avons observé moins de dégâts foliaires sur les chênes entourés par des voisins hétérospécifiques, et nous avons montré que la magnitude de cette résistance (RA) était plus importante en lisière qu’à l’intérieur des bois. Enfin, nous avons testé cette hypothèse de RA sur une espèce d’herbivore invasif en Italie, le cynips du châtaignier. Basée sur la même approche méthodologique, notre étude a montré de plus faibles dégâts de galles sur les châtaigniers lorsque la richesse spécifique de la parcelle était élevée. Notre travail fournit donc de nouvelles preuves supportant l’hypothèse de RA à travers trois contributions originales : i) la RA existe en forêt mature, ii) quelle que soit l’espèce d’herbivore, iii) y compris sur des espèces exotiques. Ces résultats devraient avoir d’importantes implications pour la gestion des insectes herbivores en forêt puisque le maintien et l’amélioration de la diversité des essences représentent un outil prometteur pour prévenir les dégâts d’insectes. / Whether increasing forest diversity should result in less insect damage (Associational Resistance, AR) or more damage (Associational Susceptibility, AS) is still debated. Moreover little is known about the diversity - resistance relationships in mature forests due to methodological constraints. To answer this question we used the FundivEUROPE exploratory platform. In this network of 209 mature forest plots sampled along two orthogonal gradients of tree species richness (from one to five species mixtures) and latitude (from the Mediterranean to the boreal forest biomes), we assessed insect defoliation in tree crown. Focusing on eleven broadleaved species, we could for the first time demonstrate a global pattern of reduced defoliation (AR) in mature forests across Europe. We replicated the comparison of insect herbivory in pure vs. mixed plots of oak trees, at the edge or within forest patches of the valleys and hills of Gascony. Here we found significantly less damage on oaks surrounded by heterospecific neighbors, and showed that the magnitude of AR was larger at forest edge than in forest interiors. Last we tested the AR hypothesis with an invasive alien species, the Asian chestnut gall wasp, in Italy. Based on the same methodological approach, our study showed lower gall damage on chestnuts when tree species richness was higher in mixed mature stands. Our work therefore provide new evidences to support the AR hypothesis with three original contributions: i) AR does apply to mature forests, ii) irrespective of the identity of insect herbivores, iii) including exotic species. These findings may have important implications for pest management in forest since the maintenance or improvement of tree species diversity represent a promising tool to prevent insect damage.

Animals and plants in temperate regions must adapt their life cycle to pronounced seasonal variation. The research effort that has gone into studying these cyclical life history events, or phenological traits, has increased greatly in recent decades. As phenological traits are often correlated to temperature, they are relevant to study in terms of understanding the effect of short term environmental variation as well as long term climate change. Because of this, changes in phenology are the most obvious and among the most commonly reported responses to climate change. Moreover, phenological traits are important for fitness as they determine the biotic and abiotic environment an individual encounters. Fine-tuning of phenology allows for synchronisation at a local scale to mates, food resources and appropriate weather conditions. On a between-population scale, variation in phenology may reflect regional variation in climate. Such differences can not only give insights to life cycle adaptation, but also to how populations may respond to environmental change through time. This applies both on an ecological scale through phenotypic plasticity as well as an evolutionary scale through genetic adaptation. In this thesis I have used statistical and experimental methods to investigate both the larger geographical patterns as well as mechanisms of fine-tuning of phenology of several butterfly species. The main focus, however, is on the orange tip butterfly, Anthocharis cardamines, in Sweden and the United Kingdom. I show a contrasting effect of spring temperature and winter condition on spring phenology for three out of the five studied butterfly species. For A. cardamines there are population differences in traits responding to these environmental factors between and within Sweden and the UK that suggest adaptation to local environmental conditions. All populations show a strong negative plastic relationship between spring temperature and spring phenology, while the opposite is true for winter cold duration. Spring phenology is shifted earlier with increasing cold duration. The environmental variables show correlations, for example, during a warm year a short winter delays phenology while a warm spring speeds phenology up. Correlations between the environmental variables also occur through space, as the locations that have long winters also have cold springs. The combined effects of these two environmental variables cause a complex geographical pattern of phenology across the UK and Sweden. When predicting phenology with future climate change or interpreting larger geographical patterns one must therefore have a good enough understanding of how the phenology is controlled and take the relevant environmental factors in to account. In terms of the effect of phenological change, it should be discussed with regards to change in life cycle timing among interacting species. For example, the phenology of the host plants is important for A. cardamines fitness, and it is also the main determining factor for oviposition. In summary, this thesis shows that the broad geographical pattern of phenology of the butterflies is formed by counteracting environmental variables, but that there also are significant population differences that enable fine-tuning of phenology according to the seasonal progression and variation at the local scale. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>

<p>Tolerance to herbivory is the ability of plants to maintain fitness in spite of damage. The goal of this thesis is to investigate the genetic variation and expression of tolerance within species, determine whether and in what conditions tolerance has negative side-effects, and how tolerance is affected by different ecological factors. Tolerance is investigated with special focus on the effects of different damage types, competitive regimes, history of herbivory, and polyploidization in plants. Studies are conducted as a literature review and three experiments on two cruciferous species Raphanus raphanistrum and Cardamine pratensis.</p><p>In the tolerance experiments, plants are subjected to artificial damage solely, or in a combination with natural damage. A literature review was conducted in order to investigate the effects of damage method. We found that traits related to tolerance, such as growth and fitness were not as sensitive in regard to damage method as measures of induced chemical traits, or measures of secondary herbivory.</p><p>Genetic variation of tolerance was demonstrated within populations of R. raphanistrum and between subspecies of C. pratensis. In R. raphanistrum, traits involved in floral display and male fitness were positively associated with plant tolerance to herbivore damage. A potential cost of tolerance was demonstrated as a negative correlation between levels of tolerance in high and low competitive regimes. I found no evidence of other proposed costs of tolerance in terms of highly tolerant plants suffering of reduced fitness in the absence of herbivores or trade-offs in terms of a negative association between tolerance to apical and leaf damage, or between tolerance and competitive ability. In C. pratensis, higher ploidy level in plants involved higher levels of tolerance measured as clonal reproduction. Furthermore, populations exposed to higher levels of herbivory had better tolerance than populations exposed to lower levels of herbivory. In this thesis, I demonstrate evidence of different components for the evolution of tolerance in plants: genotypic variation, selective factors in terms of costs and ploidization, and selective agents in terms of changing environment or herbivore pressure.</p>