Diversity and Host Specificity in the Genus Sarea Fr. (Ascomycota)

Abstract:

First published by Fries in 1825, the genus Sarea today comprises two accepted species of resinicolous discomycetes. Both species have a very broad range, with S. difformis reported from North America, Europe, and northwestern Africa, and S. resinae reported from North America, Europe, northern and central Africa, and central and eastern Asia. Both species have also been reported in southern hemisphere locations, such as New Zealand, on non-native trees. Both species also have a broad range of hosts in the Pinaceae, with S. difformis reported on Cedrus atlantica and both Sarea species reported on species of Pinus, Picea, Larix, Pseudotsuga, Abies and Tsuga. In addition, S. resinae has been reported on species in the Cupressaceae, including members of the genera Cupressus, Chamaecyparis, Juniperus and Taxodium. With few exceptions, specimens of each Sarea species share a very similar macro- and micromorphology, with specimens from multiple hosts fitting the specific concepts published by Hawksworth and Sherwood in 1981. Some molecular work has been done on the genus, but in almost all cases sequences are not associated with a vouchered herbarium specimen including the sexual morph. The objective of this study is to determine the degree of relatedness of geographically distant specimens collected in North America, Europe, and Macaronesia on different native and non-native host species. With permission, collections have been made of both species of Sarea from California, Georgia and the New England states in the USA, Northern and Southern Europe and Macaronesia. In addition to detailed measurements of the micromorphological features of specimens, ITS and LSU sequences have been generated using Sanger sequencing for analysis and comparison with published sequences. In contrast to the generally only slight morphological differences noted among specimens, ITS sequences from Europe, Asia, and North America not only differ by about 4% from each other, but also when submitted to phylogenetic analyses form multiple well-supported clades for each continent. These patterns are supported by similar analyses using the LSU sequences and ITS+LSU sequences. These clades also point to host specificity at the host family or genus level. In conclusion, the composition of the genus Sarea seems much more complicated than previously reported, with the possibility of multiple cryptic species in both accepted taxa; additional work must be done to further expand geographical and host range sampling of specimens to include in these analyses in order to approach a full picture of the diversity in Sarea.