Genetic diversity of photobionts in Antarctic lecideoid lichens from an ecological view point

As part of a comprehensive study on lecideoid lichens in Antarctica, we investigated the photobiont diversity and abundance in 119 specimens of lecideoid lichens from 11 localities in the continental and maritime Antarctic. A phylogeny of these photobiont ITS sequences, including samples from arctic, alpine and temperate lowland regions, reveals the presence of five majorTrebouxiaclades in Antarctic lecideoid lichens. Two clades are formed by members of theT. jamesiiandT. impressaaggregates but for all other clades no close match to any knownTrebouxiaspecies could be found in sequence databases. One genetically uniform and well-supportedTrebouxiaclade was found only in the climatically unique cold desert regions of the Antarctic (preliminarily calledTrebouxiasp.URa1), where it is preferentially associated with the highly adapted Antarctic endemic lichenLecidea cancriformis. Levels of genetic photobiont diversity differ slightly, but insignificantly among ecological regions of the Antarctic and do not decrease towards regions with more unfavourable ecological conditions. The genetic diversity of photobionts varies among mycobiont species. Most pairwise comparisons reveal that these differences are insignificant, probably due to the small sample size for most species. The Antarctic lichens studied here are predominantly not specific for a single photobiont species or lineage, except forLecidella greeniiandL. siplei. These two species are preferably associated withTrebouxiasp. URa2, although in the sampling areas of both species, a pool of several other photobionts is available.Lecidea cancriformisassociates with the highest diversity of photobionts followed byL. andersonii.