An annotated checklist of rust fungi (Pucciniales) occurring in Portugal.
In this work we have retrieved and analysed data for 2319 occurrences of rust fungi from 246 Pucciniales taxa in Portugal based on 115 publications and our own surveys, totalizing 683 rust taxon-host taxon unique combinations. This list was updated according to current taxonomic framework and georeferenced using the GBIF's recommended methods. The present checklist includes host names, seasonality, life cycle stage, geographical distribution and comments. A list of rust fungi sorted according to their host plants was also prepared. Altogether, this provides a tool for diagnosis of rust fungi occurring in Portugal (and elsewhere in Europe), enabling to understand their spatio-temporal dynamics and to point out recent introduction of exotic species, along with situations of potential conservation value. Eleven species (Puccinia addita, P. arnoseridis, P. avenae-barbatae, P. campanulae-herminii, P. ficalhoana, P. silenicola, Uromyces hippomarathricola, U. seselis, U. vulpiae, Aecidium umbilici and Uredo pallens) were recorded only in Portugal and are not reported for decades, raising great concern about their true existence. Five species (Puccinia jasmini, P. saniculae, P. tanaceti, Chrysomixa rhododendri and Naohidemyces vaccinii) occur on endemic hosts whose populations are physically isolated from other hosts of the same rust species, mostly at the archipelagos of Azores and Madeira, illustrating scenarios where a speciation process may be occurring and thus urging the clarification of their taxonomic and ecological status, following the example of the Madeiran endemic Dicheirinia maderensis. The geographical position of Azores and Madeira highlight these territories as entry/detection points for new rusts in Europe, as exemplified by Coleosporium asterum, Puccinia hemerocallidis, P. oxalidis, P. stenotaphricola and P. thaliae. Additionally, the vast majority of quarantine rusts currently absent from Europe are present in the American continent and several of them (Austropuccinia psidii, Cronartium spp., Gymnosporangium spp., Puccinia pittieriana and Thekopsora minima) have suitable hosts in the Azores and Madeira. With a rust species:vascular flora ratio of 1:12.2, the Portuguese rust mycobiota can be considered well characterized. The proportion of number of species per genus/family in Portugal is similar to that found in other temperate countries, while tropical areas, and specially the neotropics, present the widest diversity.