Belize has been identified as an important location for Antillean manatees (Trichechus manatus manatus), harboring the highest known population density of this subspecies. Information about their dietary habit is important in determining habitat requirements and aiding in conservation efforts. The main objective of this study was to identify the key plant species consumed by manatees in Belize and to establish differences in diet based on location, sex, size classification, and season. Samples were collected from two different locations within Belize where manatees are known to aggregate: Southern Lagoon and the Drowned Cayes off of Belize City. The contents of thirteen mouth, six digestive tract (stomach, duodenum and colon), and 124 fecal samples were analyzed. Five species of seagrasses (Halodule wrightii, Thalassia testudinum, Ruppia maritima, Syringodium filiforme, and Halophila sp.) made up the highest percentage of plants consumed; undigested rhizome was most prevalent. A vascular plant, the red mangrove (Rhizophora mangle), was identified as an important food item of manatees in Belize. Algae (Chara sp., Lyngbia sp., and Ulvasp.) and invertebrates (diatoms and sponges) were represented as well. These items are comparable to other reports of manatee diets in areas near Belize and areas with similar habitat. Variation in the percentage of seagrass, mangrove, and algae consumption was analyzed as a 4-factor factorial Analysis of Variance (ANOVA) with main effects and interactions for locality (Southern Lagoon and the Drowned Cayes), sex, size classification (>245 cm & ˂245 cm), and season (December – May and June – November). Sex and season did not influence diet composition; differences for locality and size classification were observed. Seagrass was more often consumed in Southern Lagoon (P = 0.03), whereas mangroves and algae were more prevalent in the Drowned Cayes (P = 0.03). No differences among size classifications in consumption of seagrasses or mangroves were observed. A significantly higher number of samples from adults (>245 cm) than juveniles (˂245 cm) contained algae (P = 0.04). This is most likely attributed to inexperience in foraging. Findings from these results suggest that diet composition analysis can be used to interpret Antillean manatee habitat and resource utilization and can aid in the conservation of this endangered species.

Abstract In this thesis I studied responses of three biennial, monocarpic plants Erysimum strictum, Gentianella amarella, and G. campestris, to various aspects in resource availability (i.e. competition, mineral nutrition, neighbor removal) and environmental stress (early frost) at adult or rosette stages and how these effects are related to grazing tolerance. I also studied how manipulations in resource availability affected arbuscular mycorrhizal colonization of the roots. All three species were relatively tolerant to simulated grazing and in most cases plants were able to compensate quite well for minor biomass losses. According to the compensatory continuum hypothesis, tolerance is most pronounced in resource-rich conditions, but this was not always the case in the present experiments. Erysimum strictum compensated for defoliation at the rosette stage but the reproductive output of adult plants was reduced markedly in the next year. This reduction was strongest among fertilized plants. Moreover, apex removal at the adult stage resulted in overcompensation (i.e. clipped plants were more productive) but only in the absence of fertilization and in the presence of competition, which is against the compensatory continuum hypothesis. In E. strictum a potential cost of compensation appeared as delayed flowering and fruit maturation among clipped plants. However, in spite of early frost treatment clipped plants were still able to overcompensate. In Gentianella amarella and G. campestris, apex removal reduced growth and reproductive performance in most cases. Effects on root fungal parameters were positive or neutral. This pattern suggests that simulated above-ground herbivory tends to increase carbon limitation, and therefore regrowing shoots and the fungal symbionts may appear as alternative, competing sinks for the limited carbon reserves of the host plant. Both shoot architecture and resource availability modify the responses of the study plants to apical damage at both rosette and adult stages. In addition, different environmental stress factors affect success in compensatory growth.

Shallow seagrass ecosystems frequently experience physical disturbance from vessel groundings. Specific restoration methods that modify physical, chemical, and biological aspects of disturbances are used to accelerate recovery. This study evaluated loss and recovery of ecosystem structure in disturbed seagrass meadows through plant and soil properties used as proxies for primary and secondary production, habitat quality, benthic metabolism, remineralization, and nutrient storage and exchange. The efficacy of common seagrass restoration techniques in accelerating recovery was also assessed. Beyond removal of macrophyte biomass, disturbance to seagrass sediments resulted in loss of organic matter and stored nutrients, and altered microbial and infaunal communities. Evidence of the effectiveness of restoration actions was variable. Fill placement prevented additional erosion, but the resulting sediment matrix had different physical properties, low organic matter content and nutrient pools, reduced benthic metabolism, and less primary and secondary production relative to the undisturbed ecosystem. Fertilization was effective in increasing nitrogen and phosphorus availability in the sediments, but concurrent enhancement of seagrass production was not detected. Seagrass herbivores removed substantial seagrass biomass via direct grazing, suggesting that leaf loss to seagrass herbivores is a spatially variable but critically important determinant of seagrass transplanting success. Convergence of plant and sediment response variables with levels in undisturbed seagrass meadows was not detected via natural recovery of disturbed sites, or through filling and fertilizing restoration sites. However, several indicators of ecosystem development related to primary production and nutrient accumulation suggest that early stages of ecosystem development have begun at these sites. This research suggests that vessel grounding disturbances in seagrass ecosystems create more complex and persistent resource losses than previously understood by resource managers. While the mechanics of implementing common seagrass restoration actions have been successfully developed by the restoration community, expectations of consistent or rapid recovery trajectories following restoration remain elusive.

Human domination of global nutrient cycles is profoundly altering our planet. Yet on coral reefs, the effects of changing nutrient regimes have likely been over-simplified. This dissertation investigates the complexity of animal-nutrient interactions at the organismal level and explores how the outcomes of these interactions cascade through levels of biological organization. To do so, I examined the effects of nitrogen (N) and phosphorus (P) on corals and macroalgae, and how these effects in turn influenced reef communities and entire ecosystems. I show that P consistently increases coral growth rates while N has variable, often negative, effects on coral growth. The majority of this variability was explained by the contrasting responses of corals to ammonium, which had negligible effects on coral growth, versus nitrate, which consistently had negative effects on corals. Experimental manipulations of nutrient regimes revealed that these effects could be attributed, in part, to increased damage to the photosynthetic components of the corals’ endosymbionts. Nitrogen and P-enrichment also impacted macroalgae, increasing the nutrient content of algal tissue and in turn, consumption patterns of herbivorous fishes. Initial phase parrotfishes and juvenile surgeonfishes increased their feeding rates on algae rich in N and P respectively. However, adults from both species were irresponsive to algal nutrient content. At the community level, the effects of N and P on corals, algae and herbivory were linked to the development of distinct benthic communities. Algae cover was lower and coral growth rates higher around reef structures that were consistently enriched with N and P excreted by sheltering fishes. At the ecosystem level, I found that the responses of corals to N and P enrichment were similar to those of other nutrient-sharing mutualists. Across terrestrial and marine environments, I show that N and P enrichment consistently decouples mutualism performance, benefiting one partner at the expense of the other. Thus, collectively this dissertation demonstrates that the impacts of global nutrient loading resonate from single organisms through whole ecosystems.

Angadenia berteroi is a tropical perennial subshrub of the pine rocklands with large yellow flowers that set very few fruits. My dissertation seeks to elucidate the factors that affect the reproductive fitness of Angadenia berteroi a native species of the south Florida pine rocklands. I provide novel information on the pollination biology of this native species. I also assess the effects of herbivory on growth and the reproductive success of A. berteroi. Finally, I elucidate how habitat fragmentation and quality are correlated with reproductive fitness of this native perennial plant. Using a novel experimental approach, I determined the most effective pollinator group. I used nylon fishing line of widths corresponding to proboscis diameter of the major groups of visitors to examine pollen removal and deposition. In the field, I estimated visitation frequency and efficacy of each pollinator type. Using potted plants, I exposed flowers to single visit from different types of pollinators to measure fruit set. I performed artificial defoliation with scissors on plants growing in the greenhouse to assess the effects of defoliation before flowering as well as during flowering. Additionally, I used structural equation modelling (SEM) to elucidate how A. berteroi reproductive fitness was affected by habitat fragmentation and quality. My experiments provide evidence that Angadenia berteroi is specialized for bee pollination; though butterflies, skippers and others also visit its flowers, A. berteroi is exclusively pollinated by two native bees of the South Florida pine rocklands . This research also demonstrated that herbivory by the oleander moth may have direct and indirect effects on Angadenia berteroi growth and reproductive success. The SEM results suggested that habitat quality (litter depth and subcanopy cover) may favor reproduction in native species of the South Florida pine rocklands that are properly maintained by periodic fires and exotic control. Insights from this threatened and charismatic species may provide impetus to properly manage remaining pine rocklands in South Florida for this and other endemic understory species.

Herbivory can have many effects on plant fitness, including altering plant-pollinator interactions and sexual reproduction in angiosperms. Pollinator-mediated interactions may be impacted when herbivores alter plant traits, such as floral display size, that can influence pollinator visitation rates, and, ultimately, the reproductive component of plant fitness. Here I describe an investigation into the indirect effects of feeding by beetles released as a biological control agent, Galerucella calmariensis and G. pusilla, on plant-pollinator interactions and reproductive output in the invasive plant Lythrum salicaria L. (purple loosestrife). During the summer of 2011, three treatments (low, ambient and mechanical herbivory) were applied to 105 plants during the pre-flowering period of growth. At the onset of flowering, a series of pollinator observations were conducted over the course of approximately 1.5 weeks. Several aspects of floral display were affected by the herbivory treatments, including increased inflorescence and flower production in the ambient and mechanical herbivory treatments, relative to the low herbivory treatment. Treatment type did not have a significant effect on the number of pollinator foraging bouts, but had marginally significant effects on the number of flowers probed per pollinator foraging bout and per 30-minutes. Moreover, treatment had a significant effect on the number of switches among the inflorescences on a single plant. I discuss the possibility that the differences in pollinator visitation were mediated by differences in the architecture and the size of floral display. There were no detectable differences in fruit or seed production (i.e., female fitness) among treatments. However, as I discuss, differences in pollinator visitation may affect other unmeasured aspects of fitness, such as the level of inbreeding or the number of seeds sired through male function.

Studies assessing the evolution of plant traits frequently focus on pollinators as the primary drivers of floral trait evolution. However, herbivores can also play a role, and, under some circumstances, may even impose stronger selection on floral display than pollinators. This is especially true when the traits under selection are linked to anti-herbivore defense. Here I describe a study in which I quantified the relative role of herbivores and pollinators in selection for floral traits in the North American invasive plant, purple loosestrife (Lythrum salicaria). Because L. salicaria responds to leaf-chewing herbivores by producing compensatory tissue growth, and this in turn alters the architecture of the floral display, I further tested whether herbivores can indirectly modify pollinator-mediated selection through this pathway. Using a split-plot design, I measured pollen limitation and reproductive output in experimentally manipulated plants in the presence and absence of simulated herbivore damage in order to quantify the effects of damage and pollination on natural selection for floral display. My results showed that damage significantly increased direct selection (beta-i) for earlier flowering time and decreased selection on the number of inflorescences, even more than pollinators did. Because damage did not modify pollinator-mediated selection for floral display traits, the selection imposed by herbivores is likely only having direct effects. My findings demonstrate the importance of considering multiple agents of selection and their potential interactions when quantifying natural selection in a study system. In particular, it is important to consider that the agent most frequently studied may not be imposing the brunt of selection.

This research investigated the impact of invertebrates to four species of native aquatic macrophytes: V. americana, P. nodosus, P. illinoensis, and N. mexicana. Two treatments were utilized on each plant species, an insecticide treatment to remove most invertebrates and a non-treated control. Ten herbivore taxa were collected during the duration of the study including; Synclita, Paraponyx, Donacia, Rhopalosiphum, and Hydrellia. Macrophyte biomass differences between treatments were not measured for V. americana or N. mexicana. The biomasses of P. nodosus and P. illinoensis in non-treated areas were reduced by 40% and 63% respectively. This indicated that herbivory, once thought to be insignificant to aquatic macrophytes, can cause substantial reductions in biomass.

The loss of large-bodied herbivores and/or top predators has been associated with large-scale changes in terrestrial, freshwater, and marine ecosystems around the world. Understanding the consequences of these declines has been hampered by a lack of studies in relatively pristine systems. To fill this gap, I investigated the dynamics of the relatively pristine seagrass ecosystem of Shark Bay, Australia. I began by examining the seagrass species distributions, stoichiometry, and patterns of nutrient limitation across the whole of Shark Bay. Large areas were N-limited, P-limited, or limited by factors other than nutrients. Phosphorus-limitation was centered in areas of restricted water exchange with the ocean. Nutrient content of seagrasses varied seasonally, but the strength of seasonal responses were species-specific. Using a cafeteria-style experiment, I found that fast-growing seagrass species, which had higher nutrient content experienced higher rates of herbivory than slow-growing species that are dominant in the bay but have low nutrient content. Although removal rates correlated well with nutrient content at a broad scale, within fast-growing species removal rates were not closely tied to N or P content. Using a combination of stable isotope analysis and animal borne video, I found that green turtles (Chelonia mydas) – one of the most abundant large-bodied herbivores in Shark Bay – appear to assimilate little energy from seagrasses at the population level. There was, however, evidence of individual specialization in turtle diets with some individuals foraging largely on seagrasses and others feeding primarily on macroalgae and gelatinous macroplankton. Finally, I used exclusion cages, to examine whether predation-sensitive habitat shifts by megagrazers (green turtles, dugongs) transmitted a behavior-mediated trophic cascade (BMTC) between sharks and seagrasses. In general, data were consistent with predictions of a behavior-mediated trophic cascade. Megaherbivore impacts on seagrasses were large only in the microhabitat where megaherbivores congregate to reduce predation risk. My study highlights the importance of large herbivores in structuring seagrass communities and, more generally, suggests that roving top predators likely are important in structuring communities - and possibly ecosystems - through non-consumptive pathways.

The increasing global demand for renewable energy to replace fossil fuels has given great emphasis on sugar cane (Saccharum spp) As this has been considered as the most efficient crop for energy production. Brazil is the largest producer of sugar cane with a production of 652.02 million tonnes in the 2013/2014 season, in an area of 8.1 million hectares. One major barrier to the production of sugar cane is still the attack of pests and diseases. It is estimated that about 10 % of the crop losses to be caused by insects, and the bit of sugar cane (Diatraea saccharalis) the most important. Plants, during evolution, to reduce the damage caused by the attack of insects, have developed a number of defense mechanisms, among them physical, toxic metabolites and volatile metabolites. Many studies have been developed to decipher the mechanisms of defense sugar cane to attack by herbivorous insects in an attempt to support breeding and biotechnology information programs for the development of more resistant plants, but many of these mechanisms still remain to be clarified. This project aimed to evaluate the response of sugar cane in herbivory by Diatraea saccharalis identifying volatile organic compounds, secondary metabolites and proteins produced during the response to the attack. We investigated the possible sequence of a terpene synthase, and Benzoxazinoides (Bx) sugar cane genes and the expression of these genes in the infected plants. Our results show that sugar cane has a systemic response when attacked by the larva Diatraea saccharalis producing β - caryophyllene volatile compound with increased expression of TPs cane putative gene, hydroxamic acid DIMBOA in roots increased with the expression of genes involved in the biosynthesis and defense-related proteins in attempts to inhibit the attack of the larvae and preserve the plant. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A crescente demanda mundial para a produção de energias renováveis em substituição aos combustíveis fósseis tem dado grande destaque à cana-de-açúcar (Saccharum sp.), pois esta tem sido considerada como a cultura mais eficiente para a produção de energia. O Brasil é o maior produtor mundial de cana-de-açúcar com uma produção de 652,02 milhões de toneladas na safra 2013/2014, em uma área de 8,1 milhões de hectares. Um dos grandes entraves à produção de cana-de-açúcar ainda é o ataque de pragas e doenças. Estima-se que cerca de 10% das perdas para esta cultura sejam ocasionadas por insetos, sendo a broca da cana-de-açúcar (Diatraea saccharalis) a mais importante. As plantas, durante a evolução, para reduzir os danos causados pelo ataque dos insetos, têm desenvolvido uma série de mecanismos de defesa, dentre eles, barreiras físicas, metabólitos tóxicos e metabólitos voláteis sinalizadores. Muitos trabalhos têm sido desenvolvidos para decifrar os mecanismos de defesa da cana-de-açúcar ao ataque de insetos herbívoros, na tentativa de subsidiar programas de melhoramento genético e a biotecnologia de informação para o desenvolvimento de plantas mais resistentes, mas, muito destes mecanismos ainda permanecem a ser esclarecidos. Este projeto se propôs a avaliar a resposta da cana-de-açúcar na herbivoria por Diatraea sccharalis através da identificação de importantes compostos orgânicos voláteis, metabólitos secundários e proteínas produzidas durante o processo de resposta ao ataque. Investigamos a sequência de uma possível terpeno sintase, bem como genes Benzoxazinoides (Bx) de cana de açúcar e a expressão destes genes nas plantas infestadas. Nossos resultados mostram que a cana-de-açúcar apresenta uma resposta sistêmica quando atacada pela larva de Diatraea saccharalis produzindo o composto volátil β-cariofileno, com aumento da expressão do gene putativo TPs de cana, o aumento ácido hidroxâmico DIMBOA nas raízes junto com o aumento da expressão dos genes envolvidos na sua biossíntese e proteínas relacionadas a defesa na tentativas de inibir o ataque da larva e preservar a planta.