Immune Gene Variation in Resident vs. Migratory Ducks
Abstract Birds, in particular poultry and ducks, are a source of many infectious diseases such as avian influenza. These viruses are a threat not only to these birds themselves but also to poultry farming and human health, as forms that can infect humans have evolved. Migratory birds, water birds in particular, play an important role in the global spread of avian influenza. The mallard (Anas platyrhynchos) is the most numerous and well-known waterfowl species with a Holarctic distribution. Most mallards are migratory and spring and fall flights can exceed thousands of kilometres. Northern breeding birds are mostly migratory, wintering much further south, while birds breeding in temperate regions (much of Western Europe) are resident or dispersive. The foraging habitat of the mallard in shallow waters brings it into contact with a wide variety of pathogens and it may act as a reservoir and disperser for many of them.
Migratory lifestyle challenges the immune system because migration is an intense form of exercise and therefore impacts the energy budget of the whole organism – incl. energetic costs of immune defence. Additionally, encountering diverse locations during migration brings the organism into contact with a sundry of pathogens. Each pathogen community at one site (wintering, staging, breeding) is potentially different from the one visited before. We therefore expect differences in immunogenetic constitution of mallards (or other ducks) between migratory populations and those that do not migrate: the residents.
The innate immune system is a first line of defence of an organism against infection. An important component in the innate immune reaction of birds are beta-defensins. These are small anti-microbial peptides capable of inhibiting growth or killing of pathogens. Beta-defensins have been proposed to play a key role in the immune defence of ducks against avian influenza. Recently, a suite of genetic makers targeting multiple genes of the beta-defensin gene family has been developed.
The successful PhD candidate will study genetic variation at beta-defensin genes in several migratory and resident mallard populations. The project is carried out within the greater framework of migration ecology and disease ecology incl. the use of GPS and heart-rate loggers to follow fine-scale movements of ducks, plus monitoring their immune status by veterinary techniques. Technologies for studying these genes may include traditional sequencing of target loci (Sanger sequencing locus by locus), assessing general genetic variation at neutral loci (microsatellites or single nucleotide polymorphisms) and/or use next generation sequencing (454, Illumina) for amplicon sequencing of the whole gene family.
Keywords population genetics, phylogeography, disease ecology, avian influenza, migration ecology
Main advisor Martin Wikelski, Inge Müller, Wolfgang Fiedler & Robert Kraus, MPIO Radolfzell