Grant: Discovery Grants Program - Individual

Animals have close and longstanding relationships with the microbes (bacteria and other microscopic life forms) that live on them and inside them. Many microbes are parasites and harm the health of their host, but many others benefit their host, for example by generating odours that help to attract mates. My research asks how birds' harmful and helpful microbes affect the birds' evolution and behaviour. Because birds have dealt with harmful microbes for millions of generations, they have developed complex immune systems to protect against these parasites. One of my major lines of research asks how natural selection has shaped different types of immune genes over evolutionary time. Why have some immune genes changed very little in birds while others have changed quickly? Why do some genes have very different alleles in birds in different places, while others are the same throughout a species' whole range? We know that for one type of immune gene, birds prefer mates who are genetically different to themselves, but does this happen at other immune genes too? Are there any immune genes at which birds prefer mates who are genetically similar, not different? How can birds recognize genetically similar individuals, anyway? My students and I will study wild song sparrows (a common songbird that lives in wetlands all across Canada) and sequence the DNA of 14 different immune genes to answer these questions. We think that selection operates differently on immune genes that target different types of microbe (e.g. bacteria vs viruses) or that have different jobs (sensing microbes vs killing microbes). We also think that these differences in selection result in different mating preferences at different types of immune gene. My students and I will study which immune genes have lots of variation and why. Such information will help predict the ability of natural populations to evolve and withstand future parasite outbreaks. We will also study how birds interact with helpful microbes living in their preen gland. This gland produces a scented oil that protects birds' feathers but also affects their body odour. We were among the first to show that birds pay attention to individual differences in odour, prefer some odours to others, and that birds who are similar at one type of immune gene also have similar preen oil and odour. We think this occurs because immune genes affect which microbes can live in the preen gland, and these microbes affect odour. We will test this idea for different types of immune genes using DNA sequencing of the birds and their preen gland bacteria, and chemical analysis of preen oil and other sources of body odour. We will use antibiotics to kill off some of the preen gland bacteria, and ask whether this changes birds' odour and their ability to recognize genetically similar individuals by smell. This research will cast light on how birds identify suitable mates and recognize close relatives, and the role of microbes in these processes.