title: Specialist enemies, generalist weapons and the potential spread of exotic pathogens: malaria parasites in a highly invasive bird.
abstract: Pathogens can influence the success of invaders. The Enemy Release Hypothesis predicts invaders encounter reduced pathogen abundance and diversity, while the Novel Weapons Hypothesis predicts invaders carry novel pathogens that spill over to competitors. We tested these hypotheses using avian malaria (haemosporidian) infections in the invasive myna (Acridotheres tristis), which was introduced to southeastern Australia from India and was secondarily expanded to the eastern Australian coast. Mynas and native Australian birds were screened in the secondary introduction range for haemosporidians (Plasmodium and Haemoproteus spp.) and results were combined with published data from the myna's primary introduction and native ranges. We compared malaria prevalence and diversity across myna populations to test for Enemy Release and used phylogeographic analyses to test for exotic strains acting as Novel Weapons. Introduced mynas carried significantly lower parasite diversity than native mynas and significantly lower Haemoproteus prevalence than native Australian birds. Despite commonly infecting native species that directly co-occur with mynas, Haemoproteus spp. were only recorded in introduced mynas in the primary introduction range and were apparently lost during secondary expansion. In contrast, Plasmodium infections were common in all ranges and prevalence was significantly higher in both introduced and native mynas than in native Australian birds. Introduced mynas carried several exotic Plasmodium lineages that were shared with native mynas, some of which also infected native Australian birds and two of which are highly invasive in other bioregions. Our results suggest that introduced mynas may benefit through escape from Haemoproteus spp. while acting as important reservoirs for Plasmodium spp., some of which are known exotic lineages.
authors.affiliation: Environmental Futures Research Institute, School of Environment, Griffith University, Gold Coast Campus, Queensland 4222, Australia; Natural Environments Program, Queensland Museum, PO Box 3300, South Brisbane, Queensland 4101, Australia. Electronic address: nicholas.j.clark1214@gmail.com.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Clark
authors.affiliation: Environmental Futures Research Institute, School of Environment, Griffith University, Gold Coast Campus, Queensland 4222, Australia.
authors.forename: Sophie
authors.initials: S
authors.lastname: Olsson-Pons
authors.affiliation: Centre for Ecological Sciences, Indian Institute of Science, India.
authors.forename: Farah
authors.initials: F
authors.lastname: Ishtiaq
authors.affiliation: Environmental Futures Research Institute, School of Environment, Griffith University, Gold Coast Campus, Queensland 4222, Australia; Edward Grey Institute, Department of Zoology, University of Oxford, Oxford OX1 3PS, UK.
authors.forename: Sonya M
authors.initials: SM
authors.lastname: Clegg
mesh_terms: D000818:Animals; D001315:Australia / Q000453:epidemiology; D001715:Bird Diseases / Q000453:epidemiology* / Q000469:parasitology*; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D016787:Haemosporida / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D008969:Molecular Sequence Data; D058974:Phylogeography; D010961:Plasmodium / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D015995:Prevalence; D011528:Protozoan Infections / Q000453:epidemiology* / Q000469:parasitology*; D017422:Sequence Analysis, DNA; D046749:Starlings / Q000254:growth & development / Q000469:parasitology*
chemical_list: D016054:DNA, Protozoan
keywords: Acridotheres tristis; Australia; Biological invasions; Enemy release; Haemoproteus; Host-specificity; Plasmodium; Wildlife diseases