Host Invasion Type Is a Phylogenetically Conserved Characteristic of Cephaleuros

Cephaleuros 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 Cephaleuros 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 Cephaleuros. 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 Cephaleuros phylogeny. The results also indicated that more than one Cephaleuros 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 Cephaleuros isolates were separated into two species complexes by host invasion types: the C. virescens species complex (CVSC) with subcuticular host invasion type and the C. parasiticus species complex (CPSC) with intercellular host invasion type. Molecular phylogenetic analysis indicated that Cephaleuros 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.

New insights into diversity and selectivity of trentepohlialean lichen photobionts from the extratropics

Aerial green algae of Trentepohliaceae can form conspicuous free-living colonies, be parasites of plants or photobionts of lichen-forming ascomycetes. So far, their diversity in temperate regions is still poorly known as it has been mostly studied by phenotypic approaches only. We present new insights in the phylogenetic relationships of lichenized representatives from temperate and Mediterranean parts of Europe by analysis of 18S rRNA and rbcL gene fragments, and nuclear ITS sequence data. For this purpose we isolated the trentepohlialean photobionts from lichens representing different genera. Algal cultures from lichenized and free-living Trentepohliaceae were used to design new primers for amplification of the marker loci. We constructed a phylogenetic hypothesis to reveal the phylogenetic placements of lichenized lineages with 18S rRNA and rbcL sequences. ITS variation among the clades was substantial and did not allow including them in the general phylogenetic assessment, yet ITS appears to be a promising marker for DNA-barcoding approaches. Specific algae were found in particular lichen but the overall diversity of photobionts was limited. The multilocus tree does not support the current morphological classification of genera in Trentepohliaceae, suggesting that morphology is more variable than previously thought in this group of algae.