Holger Thüs

Revisiting photobiont diversity in the lichen family Verrucariaceae (Ascomycota)

The Verrucariaceae (Ascomycota) is a family of mostly lichenized fungi with a unique diversity of algal symbionts, including some algae that are rarely or never associated with other lichens. The phylogenetic position of most of these algae has not yet been studied and, because morphology-based identifications can often be misleading, molecular data is necessary to revisit their identity and to explore patterns of association between fungal and algal partners. For this reason, the diversity of photobionts in this lichen family was investigated using molecular markers (rbcL and nuSSU) amplified from DNA extracts of lichen thalli and cultured isolates. Although a single algal genus, Diplosphaera (Trebouxiophyceae), was associated with 12 out of the 17 sampled genera of Verrucariaceae, representatives of eight other genera in five orders of the Chlorophyta and one genus in the Xanthophyceae also form lichen associations with members of the family. Fungal genera with simple crustose thalli (e.g. Hydropunctaria, Wahlenbergiella, Bagliettoa) use a high diversity and unusual selection of photobionts. In contrast, fungal genera with more complex thalli (e.g. Placidium, Dermatocarpon) tend to have lower photobiont diversity. Habitat requirements and phylogenetic histories are both partly reflected in the observed patterns of associations between lichenized fungi from the family Verrucariaceae and their photobionts.

Early colonization of stone by freshwater lichens of restored habitats: a case study in northern Italy.

This study evaluated the effectiveness and life-strategies of freshwater lichens in colonizing newly constructed stone structures in low-elevation streams in a small nature reserve in northern Italy. Species richness, size of thalli, morphological and ontogenetic traits of the species were related to the age of restored habitats. Lichen colonization was surprisingly rapid, indicating the high potential of these organisms in colonizing restored habitats. However, the species pool found in the restored habitats was different than that found in natural sites in the same study area. The age of newly constructed habitats influenced both species richness and thallus size of the two most frequent Verrucaria species. Verrucaria aquatilis was a rapid colonizer invading the substrate by several small-sized and thin thalli which soon supported a large number of small perithecia whose development began in the earlier phase of thallus formation. V. elaeomelaena, on the contrary, developed according to a different strategy, establishing a thick thallus on which relatively large perithecia were formed much later than in V. aquatilis. As these taxa are important photoautotrophic components of freshwater ecosystems more ecological knowledge is needed to evaluate the effectiveness of different measures of river restoration on lichen communities. The main practical implication of our study is related to the value of small stone structures, such as riffles and ramps, for enhancing the establishment of pioneer freshwater lichens to rapidly colonize newly available substrata.

Contributions toward a new taxonomy of Central European freshwater species of the lichen genus Thelidium ( Verrucariales , Ascomycota)

The morphological circumscription of selected Central European freshwater species in the lichen genus Thelidium was re-examined against the background of a molecular phylogeny based on ITS sequences. Molecular data reveal a close relationship between Thelidium methorium , T. pertusatii and Verrucaria latebrosa contradicting the traditional separation of Verrucaria and Thelidium by ascospore septation. Thelidium methorium and T. pertusatii are closely related species. The distinction of Thelidium methorium and T. submethorium was supported both by differences in ITS sequences and morphology. Thelidium minutulum , T. pluvium and T. zwackhii form a distinct clade with small perithecia and a thin or absent involucrellum. Thelidium rehmii and T. minutulum differ morphologically only in larger variability of ascospore length and the arrangement of photobiont cells, but are clearly separated by their ITS sequences as well their ecological requirements. An identification key for epilithic freshwater species of Thelidium in Central Europe is given, a lectotype for T. pertusatii is chosen, and detailed remarks for each species are provided.

Phylogenetic position of the brown algae-associated lichenized fungus Verrucaria tavaresiae (Verrucariaceae)

Abstract The lichen species Verrucaria tavaresiae is associated with Petroderma maculiforme, an unusual photobiont belonging to the brown algae. This marine ascomycete has so far been found only on the coast of Central California, although its photobiont has a much broader geographical distribution. Morphological and ecological characters have led a previous author to attribute this marine fungus to Verrucaria, a genus including other species colonizing the intertidal zone of rocky seashores. Phylogenetic inferences from two nuclear and one mitochondrial loci confirm the placement of Verrucaria tavaresiae within the lichen family Verrucariaceae and more specifically within the marine genus Wahlenbergiella. The new combination Wahlenbergiella tavaresiae (R.L. Moe) Gueidan, Thüs & Pérez-Ortega is therefore proposed here.

Three new species of Krogia (Ramalinaceae, lichenised Ascomycota) from the Paleotropics

Abstract Krogiaborneensis Kistenich & Timdal, K.isidiata Kistenich & Timdal and K.macrophylla Kistenich & Timdal are described as new species, the first from Borneo and the two latter from New Caledonia. The new species are supported by morphology, secondary chemistry and DNA sequence data. Krogiaborneensis and K.isidiata contain sekikaic and homosekikaic acid, both compounds reported here for the first time from the genus. Krogiamacrophylla contains an unknown compound apparently related to boninic acid as the major compound. DNA sequences (mtSSU and nrITS) are provided for the first time for Krogia and a phylogeny of the genus based on 15 accessions of five of the six accepted species is presented. Krogiaantillarum is reported as new to Brazil, Guatemala and Mexico.

First records of two freshwater lichens, Hydropunctaria scabra and Verrucaria alpicola, from Bulgaria

Two lichen-forming fungi, Hydropunctaria scabra and Verrucaria alpicola (Verrucariaceae, Ascomycota), are reported for the fi rst time from Bulgaria. Descriptions and ecological observations based on the Bulgarian populations are provided. For Verrucaria alpicola the ability to survive a continuous submersion over a period of at least four years is confi rmed.