From leaf to continent: The multi-scale distribution of an invasive cryptic pathogen complex on oak

Abstract

The spatial distribution and niche differentiation of three closely related species (Erysiphe alphitoides, Erysiphe quercicola and Erysiphe hypophylla) causing oak powdery mildew was studied at scales ranging from the European continent, where they are invasive, to a single leaf. While E. alphitoides was dominant at all scales, E. quercicola and E. hypophylla had restricted geographic, stand and leaf distributions. The large-scale distributions were likely explained by climatic factors and species environmental tolerances, with E. quercicola being more frequent in warmer climates and E. hypophylla in colder climates. The extensive sampling and molecular analyses revealed the cryptic invasion of E. quercicola in nine countries from which it had not previously been recorded. The presence of the three species was also strongly affected by host factors, such as oak species and developmental stage. Segregation patterns between Erysiphe species were observed at the leaf scale, between and within leaf surfaces, suggesting competitive effects.

Part of the analyses were performed at the Genome Transcriptome Facility of Bordeaux (grants from the Conseil Régional d’Aquitaine n°20030304002FA and 20040305003FA, from the European Union FEDER n°2003227 and from Investissements d'Avenir ANR-10-EQPX-16-01). Funding was obtained through the European BiodivERsA project "RESIPATH: Responses of European Forests and Society to Invasive Pathogens" co-financed by national funds (ANR-13-EBID-0005-01 for France, Portuguese Science and Technology Foundation Ref. BIODIVERSA/0002/2012). Other grants came from the ANR (France) Funfit project (ANR-13-BSV7-0011), the Japan Society for the Promotion of Science Grant-in-Aid for Scientific Research (Nos. 16K07613 and16F16097), and the Slovak Research and Development Agency under the contract No. APVV-15-0210.