Plants are under selection to simultaneously attract pollinators while deterring herbivores. This dilemma can lead to tradeoffs in floral traits, which are traditionally thought to be optimized for pollinators. My dissertation addresses the ecological costs and putative functional significance of nectar secondary metabolites, a paradoxical but widespread phenomenon in the angiosperms. I investigate this issue from the pollinator’s perspective using a series of controlled laboratory investigations focused primarily on the bumble bee Bombus impatiens and the nectar alkaloid gelsemine, from Gelsemium sempervirens. I begin by demonstrating that nectar enriched with the alkaloid gelsemine significantly deters visits from bumble bees at a range of natural alkaloid concentrations. However, this aversion can be mitigated by increasing the sucrose concentration such that the alkaloid-rich nectar is more rewarding than its alkaloid-free counterpart. I then demonstrate that the consumption of gelsemine-rich nectar can inhibit oocyte development and protein utilization in bees, but that this effect is limited to bees of suboptimal condition. Continuous consumption of the nectar alkaloid gelsemine also leads to a reduction in the pathogen load of bumble bees infected with Crithidia bombi, but direct interactions between the pathogen and the alkaloid have no impact on infection intensity. Gelsemine also fails to inhibit floral yeast growth, suggesting that nectar alkaloids may not be universally antimicrobial. Finally, I demonstrate that gross nectar cardenolides from the genus Asclepias are strongly correlated with gross leaf cardenolides and that the majority of individual cardenolides found in nectar are a subset of those identified in leaves. This pattern suggests that nectar cardenolides are a consequence of defense for Asclepias; however, they may not be a costly corollary because bumble bees show an overall preference for nectar cardenolides at mean concentrations. Altogether, my dissertation provides a new perspective on the role of chemical defenses against herbivores in plant-pollinator interactions.

Plants are under selection to simultaneously attract pollinators while deterring herbivores. This dilemma can lead to tradeoffs in floral traits, which are traditionally thought to be optimized for pollinators. My dissertation addresses the ecological costs and putative functional significance of nectar secondary metabolites, a paradoxical but widespread phenomenon in the angiosperms. I investigate this issue from the pollinator’s perspective using a series of controlled laboratory investigations focused primarily on the bumble bee Bombus impatiens and the nectar alkaloid gelsemine, from Gelsemium sempervirens. I begin by demonstrating that nectar enriched with the alkaloid gelsemine significantly deters visits from bumble bees at a range of natural alkaloid concentrations. However, this aversion can be mitigated by increasing the sucrose concentration such that the alkaloid-rich nectar is more rewarding than its alkaloid-free counterpart. I then demonstrate that the consumption of gelsemine-rich nectar can inhibit oocyte development and protein utilization in bees, but that this effect is limited to bees of suboptimal condition. Continuous consumption of the nectar alkaloid gelsemine also leads to a reduction in the pathogen load of bumble bees infected with Crithidia bombi, but direct interactions between the pathogen and the alkaloid have no impact on infection intensity. Gelsemine also fails to inhibit floral yeast growth, suggesting that nectar alkaloids may not be universally antimicrobial. Finally, I demonstrate that gross nectar cardenolides from the genus Asclepias are strongly correlated with gross leaf cardenolides and that the majority of individual cardenolides found in nectar are a subset of those identified in leaves. This pattern suggests that nectar cardenolides are a consequence of defense for Asclepias; however, they may not be a costly corollary because bumble bees show an overall preference for nectar cardenolides at mean concentrations. Altogether, my dissertation provides a new perspective on the role of chemical defenses against herbivores in plant-pollinator interactions.

The species composition of planktonic communities is determined not only by abiotic factors, such as nutrient availability, temperature, and water column stratification but also by biotic interactions between hosts and parasites, predators and prey, and among competitors. Blooms of the red tide dinoflagellate, Karenia brevis, can dramatically alter the planktonic community, reaching densities of millions of cells per liter and occurring nearly monospecifically. I investigated whether K. brevis uses chemical compounds to defend against grazing or to inhibit the growth of competitors. Because K. brevis is known to produce brevetoxins which act as potent neurotoxins in mammals, I also investigated whether brevetoxins played a role in competition or predator resistance. Experiments revealed that copepods fed diets rich in Karenia brevis experienced lowered fitness, however, nutritional inadequacy, rather than toxicity, was responsible for the decrease in grazer fitness. Compounds exuded from natural samples of K. brevis blooms did, however, inhibit the growth of four of five model competitors. Compounds exuded from K. brevis cultures were similarly allelopathic to competitors. Exposure to these allelopathic compounds resulted in lowered photosynthetic efficiency of all competitors, and decreased cell membrane integrity of three competitors. The allelopathic potency of K. brevis blooms was variable between collections and years, but allelopathy did not correlate with bloom density or concentration of brevetoxins. However, the variability of allelopathy could partially be explained by the presence of specific competitors. The diatom Skeletonema costatum reduced the growth-inhibiting effects of K. brevis bloom exudates, suggesting that S. costatum has a mechanism for undermining K. brevis allelopathy. Allelopathic compounds exuded by K. brevis that inhibited the growth of the diatom Asterionellopsis glacialis were partially characterized. K. brevis produced multiple, polar, organic compounds that inhibited A. glacialis growth. Exuded brevetoxins, on the other hand, had no effect on A.glacialis growth. Taken together, these results indicate that K. brevis is not chemically defended against grazing, but does produce yet-unidentified allelopathic compounds that inhibit the growth of competing phytoplankton. Blooms of K. brevis may be facilitated by the exudation of potent allelopathic compounds, but the specific phytoplankton assemblage has the potential to alter bloom dynamics.

Chemoreception plays an important role in predator-prey interactions and feeding dynamics. While the chemoreception of attractant or pleasant tasting compounds has been well studied, aversive chemoreceptive signaling has been difficult to investigate behaviorally in an ecological context because these interactions are species- and context- specific and deterrent compounds vary among prey. Using the coral reef system, this thesis explores on a molecular level the deterrent mechanism underlying detection by fish predators of an aversive compound, in order to gain a greater understanding of predator-prey interactions in this community. Like other organisms that are sessile or slow-moving, marine sponges have special mechanisms for defense from predation, commonly containing aversive-tasting compounds that defend these organisms from predation. To this end, we sought to identify and characterize a fish chemoreceptor that detects one or more of these compounds. We isolated a single cDNA clone encoding RAMP-like triterpene glycoside receptor (RL-TGR), a novel co-receptor involved in the signaling of triterpene glycosides. This co-receptor appears to be structurally and functionally related to receptor activity-modifying proteins (RAMPs), a family of co-receptors that physically associate with and modify the activity of G protein-coupled receptors (GPCRs). Expression in Xenopus oocytes showed that it responds to triterpene glycosides in a receptor-mediated manner and requires co-expression of a GPCR to enable signaling in oocytes; both of these receptors may be components of a larger signaling complex. A 40 bp portion of the gene is conserved across multiple fish species, but is not found in any other organism with a sequenced genome, suggesting that the expression of this receptor is limited to fish species. RL-TGR is the first identified gene encoding a co-receptor that responds to a chemical defense. This finding may lead the way for the identification of many other receptors that mediate chemical defense signaling in both marine and terrestrial environments, as this protein has the potential to represent the first of an entire family of co-receptors that respond to aversive compounds.

Delisea pulchra is a red macroalga that produces furanones, a class of secondary metabolites that inhibit the growth and colonization of a range of micro- and macroorganisms. In bacteria, furanones specifically inhibit acyl homoserine lactone (AHL)- driven quorum sensing, which is known to regulate a variety of colonization and virulence traits. This thesis aims to unveil multiple aspects of the chemically mediated interactions between an alga and its bacterial flora. It was demonstrated that the quorum sensing genetic machinery of bacteria is laterally transferred, making traditional 16S rRNA gene based-diversity techniques poorly suited to identify quorum sensing species. Previous studies had shown that AHL-producing bacteria belonging to the roseobacter clade can be readily isolated from D. pulchra. Because of this, it was decided to use a roseobacter epiphytic isolate from this alga, Ruegeria strain R11, to conduct a series of colonization experiments on furanone free and furanone producing D. pulchra. Furanones were shown to inhibit Ruegeria strain R11's colonization and infection of D. pulchra. In addition, it was demonstrated that Ruegeria strain R11 has temperature-regulated virulence, similar to what is seen for the coral pathogen Vibrio shiloi. Rising ocean temperatures may explain bleached D. pulchra specimens recently observed at Bare Island, Australia. To assess whether quorum sensing is common within the roseobacter clade, cultured isolates from the Roseobacter, Ruegeria and Roseovarius genera were screened for AHL production. Half of the bacteria screened produced the quorum sensing signal molecules, AHLs. These AHLs were identified using an overlay of an AHL reporter strain in conjunction with thin layer chromatography (TLC). The prevalence of quorum sensing within the roseobacter clade, suggests that these species may occupy marine niches where cellular density is high (such as surface associated communities on substratum and marine eukaryotes). Diversity studies in marine microbial communities require appropriate molecular markers. The 16S rRNA gene is the most commonly used marker for molecular microbial ecology studies. However, it has several limitations and shortcomings, to which attention has been drawn here. The rpoB gene is an alternate ???housekeeping??? gene used in molecular microbial ecology. Therefore, the phylogenetic properties of these two genes were compared. At most taxonomic levels the 16S rRNA and rpoB genes offer similar phylogenetic resolution. However, the 16S rRNA gene is unable to resolve relationships between strains at the subspecies level. This lack of resolving power is shown here to be a consequence of intragenomic heterogeneity.

Neste trabalho objetivou-se estudar o comportamento de acasalamento de Cyrtomon luridus Boheman (Coleoptera: Curculionidae), bem como a presença de semioquímicos mediando o acasalamento e a interação com a planta hospedeira Duboisia sp. (Solanaceae). Machos e fêmeas adultos recém-emergidos foram coletados no campo e levados para o laboratório. Incialmente foi determinado o melhor parâmetro morfológico para diferenciação de machos e fêmeas. Verificou-se que machos deste curculionídeo possuem a abertura genital oclusa pelo último tergito. O comportamento de acasalamento foi observado em casais virgens durante nove dias. Verificou-se que machos e fêmeas de C. luridus atingiram a maturidade sexual dois dias após a emergência. Machos e fêmeas realizaram acasalamentos repetidos com o mesmo parceiro em qualquer horário do dia. O comportamento de acasalamento deste curculionídeo foi dividido nas fases pré-copulatória, copulatória e pós-copulatória. Além disso, estudos de olfatometria revelaram que machos e fêmeas de C. luridus foram fortemente atraídos por voláteis de machos se alimentando sobre a planta hospedeira. A coleta e análise destes voláteis revelaram a presença dos compostos (Z)-3-hexenal, hexanal, (E)-2-hexenal, (E)-2-hexen-1-ol, fenilacetaldeido, linalol e geraniol, como eletrofisiologicamente ativos. O presente trabalho traz importantes informações sobre o comportamento de acasalamento e ecologia química de Entiminae e servirão de base para estudos com outras espécies desta importante subfamília de Curculionidae. / This work aimed to study the mating behavior of Cyrtomon luridus Boheman (Coleoptera: Curculionidae), as well as the presence of semiochemicals mediating the mating and the interaction of the insects with the host plant, Duboisia sp. (Solanaceae). Newly emerged males and females adults were collected in the field and taken to the laboratory. Initially it determined the best morphological parameter to differentiate males and females. It was found that males possess the genital opening occluded by the last tergite. The mating behavior was observed in virgin couples for nine days. It was found that males and females C. luridus reached sexual maturity two days after emergence. Males and females made repeated matings with the same partner at any time of day. The mating behavior was clearly divided into the pre-copulatory, copulatory, and post-copulatory phases. In addition, olfatometrics studies revealed that males and females C. luridus were strongly attracted to volatile males feeding on the host plant. The collection and analysis of these volatiles revealed the compounds (Z)-3-hexenal, hexanal, (E)-2-hexenal, (E)-2-hexen-1-ol, phenylacetaldehyde, linalool and geraniol as being eletrophysiologically. The present work brings important information about the mating behavior and chemical ecology of Entiminae, which will serve as support for studies with other species of this important subfamily of Curculionidae.

The pheromones are elegant and safe tool for controlling insects and it is possible to control their populations through the manipulation of communication between them, without adversely affecting other beneficial organisms. Pheromones may be involved in various behavioral activities such as food foraging, reproduction, the warning signal in the presence of predators and as chemical defense substances. Hundreds of pheromones and semiochemicals are known and useful for monitoring the presence and abundance of insects and to protect plants against insects and animals. In Brazil, almost all of the products used for this purpose are not produced here. Progress in agriculture is not being accompanied by the provision of inputs to the farmer. With this finding work in the development of pheromones for pest control, new ways of synthesis, formulation, immobilization and controlled release. The work on the synthesis and formulation of pheromones oviposition Culex quinquefasciatus: (5RS, 6S, R)-6-acetoxy-5 hexadecanolídeo via a semi-biotechnological towards a natural source of the acid (Z)-5-hexadecenoic in "scale up" reactions for the synthesis of the pheromone, sordidina, 2,8-dioxy-1-ethyl-3 ,5,7-Trimethylbicyclo [3.2.1] octane, the pheromone of Cosmopolites sordidus in banana boy, synthesis and formulation for the components of the pheromone Metamasius hemipterus alcohols (±)-2-methyl-4-octanol, (±)-2-methyl-4-heptanol, (±)-4-methyl-5-nonanol, (±) - 5-nonanol with the use of a Grignard reaction, synthesis of the main component of the sex pheromone of the moth Tuta absoluta ethyl (3E, 8Z, 11Z) -3,8,11-tetradecatrienila. Was explored alternative semi-biotechnological to obtain materials for the synthesis of (3E, 8Z, 11Z)-6-acetoxy-5 hexadecanolídeo and sordidina, 2,8-dioxy-1-ethyl-3, 5,7 Trimethylbicyclo-[3.2.1] octane. For the controlled release of pheromone work the development and application of microporous biomaterial chitosan and crosslinked chitosan. The pheromone oviposition Culex quinquefasciatus: (5RS, 6S, R)-6-acetoxy-5 hexadecanolídeo was obtained in low yield, the sordidina, 2,8-dioxy-1-ethyl-3 ,5,7-Trimethylbicyclo [3.2 .1] octane was obtained in good yield with a change in route of obtaining an intermediary facilitating and reducing the product cost. The components of the pheromone Metamasius hemipterus, alcohols (±)-2-methyl-4-octanol, (±)-2-methyl-4-heptanol, (±)-4-methyl-5-nonanol, (±) - 5-nonanol were obtained using a Grignard reaction in high yield. Synthesis of ethyl (3E, 8Z, 11Z) -3,8,11 tetradecatrienila was performed by a conventional synthetic route. The releasing chitosan was obtained with the crosslinked chitosan was effective in the release of pheromones. / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / Os feromônios são ferramentas elegantes e seguras para o controle de insetos e é possível controlar suas populações através da manipulação da comunicação entre eles sem afetar adversamente outros organismos benéficos. Os feromônios podem estar envolvidos em atividades comportamentais diversas como a procura por alimento, a reprodução, o sinal de alerta na presença de predadores e como substâncias de defesa química. Centenas de feromônios e semioquímicos são conhecidos e úteis para monitorar a presença e abundância de insetos e para proteger as plantas e animais contra os insetos. No Brasil a quase totalidade dos produtos utilizados para este fim não são produzidos aqui. O avanço na agricultura não está sendo acompanhado pela oferta de insumos para o produtor agrícola. Com esta constatação trabalhamos no desenvolvimento de feromônios para controle de pragas, novos caminhos de síntese, formulação, imobilização e liberação controlada. O trabalho realizado na síntese e formulação dos feromônios de oviposição do Culex quinquefasciatus: (5RS,6S,R)-6-acetoxi-5 hexadecanolídeo por uma via semi-biotecnológica visando uma fonte natural do ácido (z)-5-hexadecenóico, no “scale up” de reações para a síntese do feromônio, sordidina, 2,8-dioxi-1-etil-3,5,7-trimetilbiciclo[3.2.1]octano, o feromônio do moleque da bananeira Cosmopolites sordidus, síntese e formulação para os componentes do feromônio do Metamasius hemipterus os álcoois (±)-2-metil-4-octanol, (±)-2-metil-4-heptanol, (±)-4-metil-5-nonanol, (±)-5-nonanol com o uso de reação de Grignard, sintese do principal componente do feromônio sexual da mariposa Tuta absoluta o acetato de (3E,8Z,11Z)-3,8,11-tetradecatrienila com a tentativa de obtenção de intermediário importante de fonte natural e na preparação de liberadores eficientes para os feromônios. Foi explorada a alternativa semi-biotecnologica para a obtenção de materiais para a síntese do : (3E,8Z,11Z)-6-acetoxi-5 hexadecanolídeo e da sordidina, 2,8-dioxi-1-etil-3,5,7-trimetilbiciclo[3.2.1]octano. Para a liberação controlada de feromônio trabalhamos o desenvolvimento e aplicação de biomaterial microporoso a quitosana e quitosana reticulada. O feromônio de oviposição do Culex quinquefasciatus: (5RS,6S,R)-6-acetoxi-5 hexadecanolídeo foi obtido com rendimento baixo, a sordidina, 2,8-dioxi-1-etil-3,5,7-trimetilbiciclo[3.2.1]octano foi obtida em um bom rendimento com alteração na rota de obtenção de um intermediário facilitando e reduzindo o custo do produto. Os componentes do feromônio do Metamasius hemipterus, os álcoois (±)-2-metil-4-octanol, (±)-2-metil-4-heptanol, (±)-4-metil-5-nonanol, (±)-5-nonanol foram obtidos com o uso de reação de Grignard em alto rendimento. A síntese do acetato de (3E,8Z,11Z)-3,8,11 tetradecatrienila foi realizada por uma rota sintética convencional. O liberador obtido foi a quitosana sendo que a quitosana reticulada mostrou ser efetiva na liberação dos feromônios.

A capacidade de discriminação entre indivíduos geneticamente relacionados é de fundamental importância na teoria de Hamilton da Seleção Parental. Insetos sociais utilizam-se do olfato no reconhecimento, sendo os compostos presentes na cutícula dos indivíduos os responsáveis por esta mediação. Nesses insetos as pistas utilizadas no sistema de reconhecimento podem provir de diversas fontes distintas, tanto endógenas quanto exógenas. As pistas exógenas podem ser absorvidas a partir de materiais de construção do ninho, alimentos ou da rainha. Apesar de existir uma grande literatura a respeito dessa aquisição em formigas, cupins, abelhas melíferas e abelhas solitárias, pouco se sabe a respeito de abelhas sem ferrão. Dessa forma, o presente estudo teve como principais objetivos a análise da composição química cuticular da abelha sem ferrão Frieseomelitta varia (Lepeletier, 1836) e a verificação da influência da alimentação e dos materiais de construção do ninho na formação dos sinais utilizados nos sistemas de reconhecimento e defesa. Foram identificados um total de 48 compostos presentes na cutícula de F. varia. Dentre esses compostos os mais comuns foram hidrocarbonetos, divididos em alcanos, alcenos e alcadienos. Os hidrocarbonetos variaram de 21 a 31 átomos de carbono e os encontrados em maiores concentrações foram o heptacosano e o nonacosano. Os compostos variaram de acordo com a casta, o gênero e a idade dos indivíduos. Os testes comportamentais, juntamente com as análises químicas indicaram que os indivíduos absorvem compostos químicos a partir dos materiais do ninho. No entanto, foi mostrado que a convergência alimentar não resulta em uma maior aceitação dos indivíduos nem em uma convergência de compostos cuticulares. / The ability to discriminate among genetic related individuals has a main importance in the Kin selection Hamiltons theory. Social insects use odor cues in recognition systems, and the main used cues are compounds present in their cuticle. These cues may originate from endogenous and exogenous sources. The exogenous cues may be absorbed from nest materials, food or even from the queen. There are numerous reports concerning the origin of these cues in ants, termites, honeybees and solitary bees, although, little is known about stingless bees. Therefore, the present work had as main objectives the study of the chemical composition of Frieseomelitta varias cuticle and the verification of food and nest materials influence in the constitution of the cues used in recognition systems. A total of 48 compounds were identified in the cuticle of F. varia. The main compounds were hydrocarbons, divided into alkanes, alkenes and alkadienes. The hydrocarbons varied from 21 to 31 carbon atoms and those found in highest concentrations were heptacosane and nonacosane. The compounds varied between castes, gender and age. The behavioral tests, in agreement with the chemical analyses, showed that the individuals absorb chemical compounds from nest material. However, the results showed that food convergence imply neither in a higher acceptance of the individuals nor in a chemical convergence.

Plant–animal interaction systems are complex food webs where the members—plants, pollinators, herbivores, parasites and predators of the pollinators/herbivores—interact with each other in ways which maximize their own fitness. Based on the net outcome, such interactions could be mutually beneficial to the interacting members (mutualism) or beneficial to only one of the interacting members at the cost of the other interacting members (herbivory, predation, parasitism). It is possible that such outcomes are actually a continuum and could swing in either direction from beneficial to detrimental and vice versa. Such transitions happen not only over long time scales, but could also happen within shorter time scales based on conditionalities. Conditional outcomes are those in which the outcome of an interaction between two partners is conditional on the involvement of a third partner. Thus, studying such outcomes necessitates taking into account systems beyond the classical two-partner interactions. In such complex multitrophic plant–animal interaction systems in which there are direct and indirect interactions between species, comprehending the dynamics of these multiple partners is very important for an understanding of how the system is structured. In Chapter 2 we investigate Ficus racemosa and its community of obligatory mutualistic and parasitic fig wasps that develop within the fig inflorescence or syconium, as well as their interaction with opportunistic ants. We focus on temporal resource partitioning among members of the fig wasp community over the development cycle of the fig syconia during which wasp oviposition and development occur and we study the activity rhythm of the ants associated with this community. We found that the members of the wasp community partitioned their oviposition across fig syconium development phenology and showed interspecific variation in activity across the diel cycle. The wasps presented a distinct sequence in their arrival at fig syconia for oviposition. We documented night oviposition in several fig wasp species for the first time. Ant activity on the fig syconia was correlated with wasp activity and was dependent on whether the ants were predatory or trophobiont-tending species; only numbers of predatory ants increased during peak arrivals of the wasps. In Chapter 3, we found that predatory ants (Oecophylla smaragdina) patrolling F. racemosa trees were attracted to the odour from fig syconia at different developmental phases, as well as to the odours of fig wasps, whereas other predatory ants (Technomyrmex albipes) responded only to odours of syconia from which fig wasps were dispersing and to fig wasp odour. However, trophobiont-tending ants (Myrmicaria brunnea) patrolling the same trees and exposed to the same volatiles were unresponsive to fig or fig wasp odours. The predatory ants demonstrated a concentration-dependent response towards volatiles from figs receptive to pollinators and those from which wasps were dispersing while the trophobiont-tending ants were unresponsive to such odours at all concentrations. Naıve predatory ants failed to respond to the volatiles to which the experienced predatory ants responded, indicating that the response to fig-related odours is learned. In Chapter 4 we characterise the dynamics of the volatile bouquet of the fig syconium from the initiation through pre-receptive, receptive, and late inter-floral stages which act as signals/ cues for different fig wasp species. We were also interested in diel patterns of volatile emission as some fig wasp species were strictly diurnal (the pollinator, Ceratosolen fusciceps) whereas other fig wasps such as Apocryptophagus fusca were observed ovipositing even during the nocturnal hours. We identified volatiles that were specific to syconium development phase as well as to the time of day in this bouquet. α-muurolene was identified as the sesquiterpene specific to receptive-phase as well as being present only during the day thus coinciding with the diurnal pollinator arrival pattern. Volatiles such as (E)-β-ocimene were present in increasing levels across the developmental stages of the fig and thus could act as background volatiles providing suitable information to fig wasps about host plants and their phases. Chapter 5 examines the responses of predatory and trophobiont-tending ant species to the cuticular hydrocarbon (CHC) extracts of four galler and two parasitoid fig wasp species associated with F. racemosa. Interestingly, the antennation response of both experienced and na¨ıve ants to these wasp extracts was identical indicating that prior exposure to such compounds is not necessary for eliciting such response. We also characterised these cuticular hydrocarbon extracts to find potential compounds which could as short-range cues for predatory ants. Ants were more responsive to the cuticular extracts of parasitoids rather than to those of galler wasps, implying that the CHC profile of carnivorous prey may contain more elicitors of aggressive behaviour in ants compared to herbivorous prey whose profiles may be more similar to those of their plant resources. We also find congruency between the cuticular profiles of parasitoids and their hosts suggesting that parasitoids could sequester compounds from their diet. Important findings and conclusions of the thesis are presented in Chapter 6. The first two parts of the appendices section discuss work carried out on alternative ways of analysing multivariate data sets such as plant volatiles and insect cuticular hydrocarbons. Appendix A details the use of Random Forests, an algorithm-based method of analysing complex data sets where there are more variables than samples, a situation akin to microarray data sets. This work illustrates the use of such techniques in chemical ecology, highlighting the potential pitfalls of classical multivariate tests and the advantages of newer more robust methods. Appendix B, an invited article following the publication of the earlier work, compares different data transformation procedures currently employed in such multivariate analysis. Appendix C details sex-specific differences in cuticular hydrocarbons of fig wasps, using the pollinator C. fusciceps as a case study.

Natural products chemistry is the pursuit of bioactive small molecules from living organisms. These can be classified as primary metabolites if they are essential to survival, and secondary metabolites if they are accessory, playing a role in communication, defense, recruitment, etc.. Natural products have made a significant contribution to society – of 1,881 FDA-approved drugs from 1981 to 2019, 4% were pure natural products, 19% were natural products derived, and 3% were synthetic drugs with a natural products pharmacophore targeting a wide range of diseases and infections (Newman & Cragg, 2020). Pharmacophores are structural components of drugs that are responsible for the observed biological activity. Natural products often contain unique pharmacophores that exhibit potent bioactivity, thereby serving as inspiration for synthetic chemists to manufacture exciting new drug leads. Bacteria are ubiquitous in the environment. Marine bacteria are a prolific source of chemically diverse natural products due to the high biodiversity and competition in the marine environment. In 2018, 240 new marine natural products were reported in the literature from bacteria (Carroll et al., 2020). It is hypothesized that secondary metabolites offer an advantage to the producer, however, the roles that natural products play in their environment are not as well characterized. These pursuits are classified as chemical ecology. Throughout my thesis, I aim to identify the bacteria present from these environments and begin to understand the ecological role small molecules play in their environment. Staphylococcus aureus is notorious for causing chronic infections and resisting therapeutic treatment by forming biofilms. Biofilms are extracellular polymeric substance (EPS) matrices containing bacteria that attach to biotic and abiotic surfaces. The EPS matrix provides a refuge and anchorage to a surface, allowing biofilm inhabitants to be shielded from full strength of therapeutic treatments leading to resistance. Variovorax paradoxus is a gram-negative bacteria that also produces biofilms. It has been previously reported that V. paradoxus inhibits S. aureus biofilm formation. Preliminary data suggests V. paradoxus produces a small molecule that has biofilm inhibition activity. My work focuses on characterizing a GLP and another secondary metabolite produced by V. paradoxus that inhibits S. aureus biofilms through both molecular biology and natural products chemistry. Caulerpa spp. is a macroalgae native to tropical and subtropical oceans. Due to global warming, the temperature of oceans continues to rise, allowing Caulerpa spp. to inhabit higher latitudes. It has been hypothesized that successful invasion occurs by outcompeting native organisms via exerting adverse effects on the surrounding environment. The secondary metabolites of this algae are well characterized however their ecological role is hardly characterized. We hypothesize that Caulerpa spp. could be chemically mediating its surface microbiome by recruiting a higher percentage of Vibrio spp.. Vibrio spp. are known pathogens to humans and marine organisms by causing infections and forming biofilms. My goal was to identify a panel of culturable Caulerpa spp. surface-associated bacteria through molecular and microbiology methods. Microalgae are an exciting alternative source of biofuels. However, microalgae are grown in open algal ponds which are susceptible to crashing causing the total loss of an algal crop. Pond crashes are caused by a number of factors, one of which is contamination by unwanted pests such as protozoans and fungi. Previous studies focused on the use of bacterial communities as a built-in biocontrol to inhibit pests from causing algal pond crashes. Preliminary data demonstrated the addition of a bacterial community protected the microalgae Microchloropsis salina from grazing by the marine rotifer Brachionus plicatilis (Fisher et al., 2019). My work focuses on analyzing the composition of the protective bacterial community added to the microalgae that have been size filtered to observe bacterial association with algae, rotifers, or free-floating. M. salina cultures in the presence and absence of B. plicatilis were analyzed for the identification of protective bacterial species that were algae-, rotifer-associated, or free-floating. This work has been submitted to the journal Algal Research and is under review (Fisher et al., 2022). Bacteria play a significant role in their environment. The identification of bacterial species and the role their suite of small molecules play is crucial to fully characterizing the observed interactions. My thesis surveys several means of bacterial community analysis through identification and small molecule characterization.