No selection on immunological markers in response to a highly virulent pathogen in an Arctic breeding bird / Pierre Legagneux, Lisha L. Berzins, Mark Forbes, Naomi Jane Harms, Holly L. Hennin, Sophie Bourgeon, H.G. Gilchrist, Joel Bety, Catherine Soos, Oliver P. Love, Jeffrey T. Foster, Sebastien Descamps, and Gary Burness.

Includes bibliographical references (pages 771-773).

In natural populations, epidemics provide opportunities to look for intense natural
selection on genes coding for life history and immune or other physiological
traits. If the populations being considered are of management or conservation
concern, then identifying the traits under selection (or ‘markers’) might provide
insights into possible intervention strategies during epidemics. We assessed
potential for selection on multiple immune and life history traits of Arctic breeding
common eiders (Somateria mollissima) during annual avian cholera outbreaks
(summers of 2006, 2007 & 2008). We measured prelaying body condition,
immune traits, and subsequent reproductive investment (i.e., clutch size) and
survival of female common eiders and whether they were infected with Pasteurella
multocida, the causative agent of avian cholera. We found no clear and consistent
evidence of directional selection on immune traits; however, infected birds
had higher levels of haptoglobin than uninfected birds. Also, females that laid larger
clutches had slightly lower immune responses during the prelaying period
reflecting possible downregulation of the immune system to support higher costs
of reproduction. This supports a recent study indicating that birds investing in
larger clutches were more likely to die from avian cholera and points to a possible
management option to maximize female survival during outbreaks.