Darragh lab opening at Indiana University Bloomington in Jan 2024!

We investigate the evolution of chemical diversity across biological scales, from population level variation to genes and molecular mechanisms.

How are compounds produced?

Assays of enzymes in the lab (in vitro) can allow us to test their activity, which substrates they can accept and what products they produce. Assessing protein structure can help us understand why enzymes have different functions.

Understanding the genetic and molecular bases of adaptive traits is key in evolutionary biology. Chemical compounds are often produced via well-studied biosynthetic pathways, facilitating our ability to identify candidate genes. To functionally validate e.g. an enzyme that we think produces an insect pheromone, we express the gene in bacteria and assay the enzyme in the lab to test if it can produce the pheromone based off the likely substrates in the pathway is would use. We are also interested in studying how protein structure affects enzyme function and how enzymes evolve to produce different chemical compounds.

How does compound production evolve?

Understanding how novelty arises is a fundamental question in evolutionary biology. We can study how biosynthetic pathways and specific enzymes evolve by studying the evolutionary history of the genes across species. This can allow us to ask questions such as: Are these gene families evolving rapidly? What role does selection play in their evolution? What is the role for gene duplication in the evolution of new functions?

What is the behavioral function of chemical cues?

Chemical cues are used for a variety of functions, for example, they are used by flowers to attract pollinators, and for mate choice in insects

Chemical cues are used for many different biological functions: mate attraction, pollinator attraction, defense, aggregation, trail-finding. Behavioral experiments are the ideal approach to determine the function of a particular compound or set of compounds. We also use statistical techniques to assess which compounds are of likely biological importance.

What drives variation in chemical profiles?

Phylogeny of Heliconius butterflies illustrating their evolutionary relationships and a plot showing their chemical profile where points which are more closely together have a more similar chemical profile. Different species group together showing that species have different chemical profiles!

We are interested in what drives the variation between individuals of the same species or between species. For example, does diet affect the production of chemical compounds? How much variation is due to drift vs selection? Is there geographic or temporal variation within a species? We quantify chemical profiles, genotype individuals, and carry out controlled experiments to allow us to answer these types of question.

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