Colletotrichum species and complexes: geographic distribution, host range and conservation status

The taxonomy of the genus Colletotrichum has undergone tremendous changes over the last decade, with over 200 species being currently recognised and species complexes being informally used to cluster those species. Many of these species are important plant pathogens, some rather polyphagous and others host-specific, but several occur seldomly and some may in fact be ecologically endangered. Based mainly on literature from the past decade, in this work we review the occurrence, geographic distribution and host spectrum of currently recognised Colletotrichum species under phylogenetic, pathological/agronomic and ecological perspectives, providing a list arranged by Colletotrichum species and species complexes. A total of 257 species are listed and grouped into 15 species complexes. In this work we have recorded 1353 unique host species-Colletotrichum species association records from 720 hosts, with the Fabaceae as the family with higher number of hosts (52 host species) but with the Rosaceae as the family with the highest number of host species-Colletotrichum species association records (118 association records). According to occurrence data, 88 species are common in nature, 128 were considered as data deficient and 41 are threatened, some of which are likely extinct from nature and preserved only in culture collections. Several species are relevant plant pathogens, in some cases geographically confined and thus of potential quarantine relevance. Based on the major changes that occurred on Colletotrichum taxonomy over the last decade, this work provides a comprehensive overview of occurrence data of Colletotrichum species, compiling host range and geographical distribution, with relevance for plant pathology and conservation mycology. The current taxonomic framework in Colletotrichum is revealing numerous species but poses challenges to the employment of standard criteria for the evaluation of biological conservation of these fungi. We advocate that conservation mycology and taxonomy should find common routes simultaneously enabling the correct delimitation of species of Colletotrichum and the implementation of feasible criteria for the evaluation of conservation. The employment of new technologies, such whole genome sequencing (WGS), will help and support the description of new species and to gain a better understanding of the genetic bases of speciation processes.