title: Host Jumps and Radiation, Not Co-Divergence Drives Diversification of Obligate Pathogens. A Case Study in Downy Mildews and Asteraceae.
abstract: Even though the microevolution of plant hosts and pathogens has been intensely studied, knowledge regarding macro-evolutionary patterns is limited. Having the highest species diversity and host-specificity among Oomycetes, downy mildews are a useful a model for investigating long-term host-pathogen coevolution. We show that phylogenies of Bremia and Asteraceae are significantly congruent. The accepted hypothesis is that pathogens have diverged contemporarily with their hosts. But maximum clade age estimation and sequence divergence comparison reveal that congruence is not due to long-term coevolution but rather due to host-shift driven speciation (pseudo-cospeciation). This pattern results from parasite radiation in related hosts, long after radiation and speciation of the hosts. As large host shifts free pathogens from hosts with effector triggered immunity subsequent radiation and diversification in related hosts with similar innate immunity may follow, resulting in a pattern mimicking true co-divergence, which is probably limited to the terminal nodes in many pathogen groups.
authors.affiliation: Faculty of Biosciences, Institute of Ecology, Evolution and Diversity, Goethe University Frankfurt am Main, D-60438, Frankfurt am Main, Germany; Biodiversity and Climate Research Centre (BiK-F), D-60325, Frankfurt am Main, Germany.
authors.forename: Young-Joon
authors.initials: YJ
authors.lastname: Choi
authors.affiliation: Faculty of Biosciences, Institute of Ecology, Evolution and Diversity, Goethe University Frankfurt am Main, D-60438, Frankfurt am Main, Germany; Biodiversity and Climate Research Centre (BiK-F), D-60325, Frankfurt am Main, Germany; Integrative Fungal Research Cluster (IPF), D-60325, Frankfurt am Main, Germany; Senckenberg Gesellschaft für Naturforschung, D-60325, Frankfurt am Main, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Thines
mesh_terms: D019659:Asteraceae / Q000235:genetics*; D019143:Evolution, Molecular; D049810:Genetic Speciation; D006790:Host-Parasite Interactions / Q000235:genetics*; D009868:Oomycetes / Q000235:genetics*; D044742:Peronospora / Q000235:genetics*; D010802:Phylogeny; D011827:Radiation