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Chemical Ecology

Course Description

Course investigates the ecology of the unseen chemistry underlying species interactions. Students do not need to be chemists, only to have a curiosity about how nature works. We will cover diverse topics using Darwinian natural selection as a framework: e.g., communication, defenses, pheromones, toxins, mutualism, deception, mimicry, social interactions.

Athena Title

Chemical Ecology

Prerequisite

(BIOL 1107 or BIOL 1107E or BIOL 2107H) and (BIOL 1108 or BIOL 2108H)

Semester Course Offered

Offered spring

Grading System

A - F (Traditional)

Student Learning Outcomes

  • Students will be able to understand experimental design and the scientific method as it applies to species interactions.
  • Students will be able to categorize ecological interactions and potential mechanism by which they are mediated.
  • Students will be able to discuss these mechanisms in the context of evolutionary theory and draw conclusions about potential applications to agriculture and health.
  • Students will be familiar with a number of analytical, behavioral, and experimental techniques used to analyze chemical compounds that mediate ecological interactions.
  • Students will be familiar with the general chemical structures of organic molecules and their relationship to function.
  • Students will be able to read and synthesize findings from original scientific research in chemical ecology by studying and discussing the literature.

Topical Outline

  • 1. Course Introduction, What is chemical ecology and how can we use it to learn about interactions between insects, plants, and microbes? 2. A chemical ecology case study: Chilies, capsaicin, seed dispersal, and human use • Plant interactions with animals and microbes • Directed Deterrence Hypothesis 3. A ecological primer on species interactions and the roles chemicals play • Chemical signals: Hormones, pheromones, allelochemicals (allomone, kairomone, synomone) • Types of ecological interactions • Competitive exclusion principle 4. An evolutionary primer on species interactions and the roles chemicals play • Coevolution: phenotype matching and allele matching • Mimicry: Batesian and Mullerian 5. Ecological chemistry and biological activity, Pheromones • Classes of organic compounds and functional groups • How chemical structure and ecological context determine mode of action • Biosynthetic pathways and secondary metabolism • Types of pheromones: sex, trail, aggregation, alarm • Pheromone actions: primers and releasers • Pheromone detection: receptors, coding and signal perception 6. Methods in Chemical Ecology • Chemical analytical techniques to identify natural products: Extraction, volatile headspace, chromatography, Fractionation • Experimental assays to measure biological activity: Bioassay design and controls, attraction assays of scale and choice, relative response assays, induction assays 7. Lab demonstration of Gas Chromotography – Mass Spectrometry 8. Pollinator networks and floral markets • Pollination strategies: hypergeneralist, specialist guild, obligate mutualist, deception • Chemical floral rewards - Nectar sugars, amino acids, and salts; Pollen starches, lipids, and proteins, floral oils • Floral strategies for increasing gene flow and dispersal • Floral advertisement • Insect learned preference 9. Toxic nectar • Food webs • Costs and Benefits of specialization vs generalization pollination • Nicotine case study: alter pollinator behavior, repel herbivores 10. Pollination by sexual deception • Behavioral differences in insect sex and the impact on floral outcrossing • Ecological context of insect pheromones and floral mimics • Orchid bee pheromone collection from flowers 11. Nursery pollination and obligate mutualism • How does obligate mutualism evolove • Conflicts of interest between plants and pollinators that feed on floral parts • Obligate pollination in dioecious plants • Mechanisms of stabilizing mutualisms (partner choice and sanctions) • Cheaters and parasites 12. Chemistry of fruit dispersal • Directed dispersal through fruit chemistry • Chemistry of dispersal dynamics • Chemistry of ant seed dispersal 13. Discussion 1 – Pollination syndromes 14. Project 1: ‘Design a Flower’ breakout group work 15. Animal defense and toxicity • Sequestration • Convergent evolution 16. Tri-tropic interactions • Ecological niche • Chemical mediated interactions: functional redundance, multi-functionality, synergistic functionality, specificity, signal cross-talk, complexity, context-dependent • Plant tannins context dependent impact on herbivory 17. Plant defense and herbivore counter-defense • Mechanisms of plant resistance (deterrence, toxicity, reduce digestibility) and herbivore counter-defense • Herbivore physiology of plant defense traits • Herbivore counter-defense 18. Discussion 2 ¬– Plant-plant communication 19. Community ecology of plant defense, why are there so many secondary compounds • Plant hormonal response to herbivory and pathogens • Direct defense and indirect defense • Cross talk between plant hormonal pathways and the impact on plant visitors (herbivores and pollinators) • Hypothesis for multiple secondary compounds: specificity, synergism, environmental impact of effectiveness • Population variation in defense 20. Induced defenses • Induced responses, induced resistance and induced defenses • Induced resistance vs constitutive resistance • Transgenerational induced resistance
  • 21. Social insect chemical communication • Genetic relatedness of social insects • Chemistry of altruistic behavior in genetically related insects • Ant trail pheromones • Bumblebee volatile signaling for food availability • Honeybee odor communication 22. Host-microbe and microbe-microbe interactions • Chemical communication of microbes: quorum sensing, siderophores, biofluorescence • Microbial cooperation: biofilms • Multi-cellular microbial behaviors: nutrient acquisition, competition • Symbiosis: mutualistic, communalistic, parasitic; obligate, facultative • Vertical and horizontal transmission 23. Lab demonstration 2: Bioassay techniques and olfactometers 24. Peer review of perspectives paper in small groups 25. Pheromones revisited: mating disruption and pest management • Methods of trap development • Pheromone traps for monitoring pests • Push-pull strategies for pest control 26. Bioprospecting; Chemical ecology of insect vectored diseases • Natural products • Mosquito attraction 27. Discussion 3 – Push-pull agriculture in Africa 28. Invasive Pest Project breakout group work 29. Human Chemical Ecology • Animal pheromones to reduce inbreeding • Human pheromones 30. Present final project
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