Host Invasion Type Is a Phylogenetically Conserved Characteristic of .

species cause algal spot diseases, also known as red rust diseases, on many plants, including fruit crops. Most algal species are defined based on their morphological characteristics. Recent phylogenetic studies of species showed that morphological determination was not congruent with phylogeny. Our study examined the phylogenetic congruence of the host invasion types (or growth habits), which are the most critical characteristics in the taxonomy of . To ensure that host invasion types and phylogenetic characteristics could be inferred from the same isolate, host invasion types were assessed using microanatomical observation, and rRNA sequences from the same algal spot and/or the derived algal cultures were compared. Host invasion types were found to be conserved classification traits and were congruent with phylogeny. The results also indicated that more than one species commonly grew on the same leaf or, in a few cases, the same algal spot, suggesting that identification using different algal spots could result in misidentification. The isolates were separated into two species complexes by host invasion types: the species complex (CVSC) with subcuticular host invasion type and the species complex (CPSC) with intercellular host invasion type. Molecular phylogenetic analysis indicated that isolates clustered into 14 clades of CVSC and three clades of CPSC. This study also identified 16 and eight new hosts of CVSC and CPSC in Taiwan, respectively.