The risk to Myrtaceae of Austropuccinia psidii, myrtle rust, in Mexico

Austropuccinia psidii is a biotrophic rust fungus that affects species from the Myrtaceae family. In Mexico, Myrtaceae is widely distributed in temperate, tropical and semi-arid ecosystems, and includes 20 genera and 192 endemic and exotic species. Austropuccinia psidii has been present in Mexico for the last four decades; however, little is known about the distribution of this rust or the vulnerability of native and exotic Myrtaceae to infection. In this study, we used global occurrence records for the pandemic biotype of myrtle rust to model its current and future suitable habitat using a species distribution model, Maxent. We identified regions that are highly suitable for myrtle rust establishment, now and in the future (2050). Additionally, we identified the Myrtaceae species known to be susceptible to rust infection and that are currently distributed in areas with high rust habitat suitability. Thirty-six susceptible plant species and 142 untested species are distributed within areas of suitable rust habitat and are considered potentially at risk of rust infection. Current suitable habitat is mainly restricted to the east coast of Mexico, with Veracruz, Puebla, Chiapas, Tabasco and Oaxaca being the most vulnerable regions to the rust under current and future climates. We encourage monitoring within these regions by surveying locations where the rust occurs and within areas with high suitable habitat to determine the threat to native ecosystems and industries reliant on Myrtaceae. We also recommend screening to test the susceptibility of Myrtaceae species with no known susceptibility rating.