title: Continental-scale patterns of pathogen prevalence: a case study on the corncrake.
abstract: Pathogen infections can represent a substantial threat to wild populations, especially those already limited in size. To determine how much variation in the pathogens observed among fragmented populations is caused by ecological factors, one needs to examine systems where host genetic diversity is consistent among the populations, thus controlling for any potentially confounding genetic effects. Here, we report geographic variation in haemosporidian infection among European populations of corncrake. This species now occurs in fragmented populations, but there is little genetic structure and equally high levels of genetic diversity among these populations. We observed a longitudinal gradient of prevalence from western to Eastern Europe negatively correlated with national agricultural yield, but positively correlated with corncrake census population sizes when only the most widespread lineage is considered. This likely reveals a possible impact of local agriculture intensity, which reduced host population densities in Western Europe and, potentially, insect vector abundance, thus reducing the transmission of pathogens. We conclude that in the corncrake system, where metapopulation dynamics resulted in variations in local census population sizes, but not in the genetic impoverishment of these populations, anthropogenic activity has led to a reduction in host populations and pathogen prevalence.
authors.affiliation: Université d'Angers, GECCO Angers, France ; Centre for Ecology, Evolution and Conservation, School of Biological Sciences, University of East Anglia Norwich, UK.
authors.forename: Yoan
authors.initials: Y
authors.lastname: Fourcade
authors.affiliation: Laboratory of Ornithology, Institute of Biology, University of Latvia Salaspils, Latvia.
authors.forename: Oskars
authors.initials: O
authors.lastname: Keišs
authors.affiliation: Centre for Ecology, Evolution and Conservation, School of Biological Sciences, University of East Anglia Norwich, UK.
authors.forename: David S
authors.initials: DS
authors.lastname: Richardson
authors.affiliation: Université d'Angers, GECCO Angers, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Secondi
keywords: Crex crex; agriculture intensity; approximate Bayesian computation; avian malaria; bird; corncrake; effective population size; haemosporidian parasites; parasite transmission