Roman Türk

SEQUESTRATION OF LICHEN COMPOUNDS BY LICHEN-FEEDING MEMBERS OF THE ARCTIIDAE (LEPIDOPTERA)

A survey for the presence of sequestered lichen compounds in 103 wild-caught imagines representing eight different genera and 16 different species of the Arctiidae was conducted. Known lichen compounds were detected for the first time in 24 of the analyzed specimens (representing five different genera and 11 different species) based on their HPLC retention times and on their UV-absorption spectra. The anthraquinone parietin, the depside atranorin, as well as a hydrolytic cleavage product of the latter were among the lichen compounds most frequently detected in wild-caught imagines. The observed variation of sequestered lichen compounds in wild-caught imagines with unknown feeding history may be due to several reasons. Lack of lichen compounds in imagines may have been caused, for example, by larvae feeding on lichens with no or only minute amounts of phenolic products. The age of the specimens analyzed may also influence the results obtained. Avoidance of lichen compounds by selective feeding on those parts of lichen thalli that have no or little lichen products may be another reason for the lack of lichen compounds in imagines. Preliminary feeding experiments conducted with larvae ofEilema complana, for example, indicated that the larvae fed exclusively on the algal layer and cortex of the lichenCladonia pyxidata, whereas the medulla, which is rich in fumarprotocetrarie acid, was avoided. As expected, imagines hatching from the larvae were free of this lichen compound. Any ecological role of the sequestered lichen compounds for the herbivores is unknown. It is possible, however, that sequestered lichen compounds may be utilized for the chemical defense of arctiid moths or against microbial pathogens.

At limits of life: multidisciplinary insights reveal environmental constraints on biotic diversity in continental Antarctica.

Multitrophic communities that maintain the functionality of the extreme Antarctic terrestrial ecosystems, while the simplest of any natural community, are still challenging our knowledge about the limits to life on earth. In this study, we describe and interpret the linkage between the diversity of different trophic level communities to the geological morphology and soil geochemistry in the remote Transantarctic Mountains (Darwin Mountains, 80°S). We examined the distribution and diversity of biota (bacteria, cyanobacteria, lichens, algae, invertebrates) with respect to elevation, age of glacial drift sheets, and soil physicochemistry. Results showed an abiotic spatial gradient with respect to the diversity of the organisms across different trophic levels. More complex communities, in terms of trophic level diversity, were related to the weakly developed younger drifts (Hatherton and Britannia) with higher soil C/N ratio and lower total soluble salts content (thus lower conductivity). Our results indicate that an increase of ion concentration from younger to older drift regions drives a succession of complex to more simple communities, in terms of number of trophic levels and diversity within each group of organisms analysed. This study revealed that integrating diversity across multi-trophic levels of biotic communities with abiotic spatial heterogeneity and geological history is fundamental to understand environmental constraints influencing biological distribution in Antarctic soil ecosystems.

Photoprotection of reaction centres in photosynthetic organisms: mechanisms of thermal energy dissipation in desiccated thalli of the lichen Lobaria pulmonaria

*The photobionts of lichens have previously been shown to reversibly inactivate their photosystem II (PSII) upon desiccation, presumably as a photoprotective mechanism. The mechanism and the consequences of this process have been investigated in the green algal lichen Lobaria pulmonaria. *Lichen thalli were collected from a shaded and a sun-exposed site. The activation of PSII was followed by chlorophyll fluorescence measurements. *Inactivation of PSII, as indicated by the total loss of variable fluorescence, was accompanied by a strong decrease of basal fluorescence (F(0)). Sun-grown thalli, as well as thalli exposed to low irradiance during drying, showed a larger reduction of F(0) than shade-grown thalli or thalli desiccated in the dark. Desiccation increased phototolerance, which was positively correlated to enhanced quenching of F(0). Quenching of F(0) could be reversed by heating, and could be inhibited by glutaraldehyde but not by the uncoupler nigericin. *Activation of energy dissipation, apparent as F(0) quenching, is proposed to be based on an alteration in the conformation of a pigment protein complex. This permits thermal energy dissipation and gives considerable flexibility to photoprotection. Zeaxanthin formation apparently did not contribute to the enhancement of photoprotection by desiccation in the light. Light-induced absorbance changes indicated the involvement of chlorophyll and carotenoid cation radicals.

Photosynthetic responses of three common mosses from continental Antarctica

Predicting the effects of climate change on Antarctic terrestrial vegetation requires a better knowledge of the ecophysiology of common moss species. In this paper we provide a comprehensive matrix for photosynthesis and major environmental parameters for three dominant Antarctic moss species (Bryum subrotundifolium, B. pseudotriquetrum and Ceratodon purpureus). Using locations in southern Victoria Land, (Granite Harbour, 77°S) and northern Victoria Land (Cape Hallett, 72°S) we determined the responses of net photosynthesis and dark respiration to thallus water content, thallus temperature, photosynthetic photon flux densities and CO2 concentration over several summer seasons. The studies also included microclimate recordings at all sites where the research was carried out in field laboratories. Plant temperature was influenced predominantly by the water regime at the site with dry mosses being warmer. Optimal temperatures for net photosynthesis were 13.7°C, 12.0°C and 6.6°C for B. subrotundifolium, B. pseudotriquetrum and C. purpureus, respectively and fall within the known range for Antarctic mosses. Maximal net photosynthesis at 10°C ranked as B. subrotundifolium > B. pseudotriquetrum > C. purpureus. Net photosynthesis was strongly depressed at subzero temperatures but was substantial at 0°C. Net photosynthesis of the mosses was not saturated by light at optimal water content and thallus temperature. Response of net photosynthesis to increase in water content was as expected for mosses although B. subrotundifolium showed a large depression (60%) at the highest hydrations. Net photosynthesis of both B. subrotundifolium and B. pseudotriquetrum showed a large response to increase in CO2 concentration and this rose with increase in temperature; saturation was not reached for B. pseudotriquetrum at 20°C. There was a high level of variability for species at the same sites in different years and between different locations. This was substantial enough to make prediction of the effects of climate change very difficult at the moment.

Diversity of Lecidea (Lecideaceae, Ascomycota) species revealed by molecular data and morphological characters

Abstract The diversity of lichens, especially crustose species, in continental Antarctica is still poorly known. To overcome difficulties with the morphology based species delimitations in these groups, we employed molecular data (nuclear ITS and mitochondrial SSU rDNA sequences) to test species boundaries within the genus Lecidea. Sampling was done along a north–south transect at five different areas in the Ross Sea region (Cape Hallett, Botany Bay to Mount Suess, Taylor Valley, Darwin Area and Mount Kyffin). A total of 153 specimens were collected from 13 localities. Phylogenetic analyses also include specimens from other regions in Antarctica and non-Antarctic areas. Maximum parsimony, maximum likelihood and Bayesian analyses agreed in placing the samples from continental Antarctica into four major groups. Based on this phylogenetic estimate, we restudied the micromorphology and secondary chemistry of these four clades to evaluate the use of these characters as phylogenetic discriminators. These clades are identified as the following species Lecidea cancriformis, L. andersonii as well as the new species L. polypycnidophora Ruprecht & Türk sp. nov. and another previously unnamed clade of uncertain status, referred to as Lecidea sp. (L. UCR1).

Lichen and moss communities of Botany Bay, Granite Harbour, Ross Sea, Antarctica.

Abstract Botany Bay is one of the richest sites for lichen and bryophyte biodiversity in continental Antarctica. A total of 29 lichen, nine moss and one liverwort species have been identified. The most extensive vegetation occurs on a sheltered raised beach terrace. Vegetation associations are described and compared to other continental Antarctic localities that also possess a rich vegetation cover. Ordination analysis clearly indicates the importance of the type of water supply, its regularity, the substrate type, and particularly in Botany Bay, the influence of nutrients derived from the local bird population in governing plant distribution and associations. A vegetation map has been produced and can be used as a baseline to assess vegetation changes over time.

Artificial resynthesis of thalli of the cyanobacterial lichen Peltigera praetextata under laboratory conditions

The resynthesis of foliose thalli of the cyanobacterial lichen Peltigera praetextata was achieved on a soil substratum under laboratory conditions. On agar plates mycelia formation by this lichen fungus only occurred when a sufficient number of photobiont cells was present. Resynthesis on agar was restricted to the formation of loose algal-fungal associations, which showed no lichen-like structures. Early resynthesis stages were formed on soil only after a very long lag phase of 2–3 months. First soredia-like stages (resynthesis products of fungal hyphae and cyanobacteria) appeared, later tissue clumps and thallus primordia differentiated. Welldeveloped lichen thalli with rhizines that resembled young thalli from the natural environment were formed after an incubation time of 2–3 years.

High photobiont diversity in the common European soil crust lichen Psora decipiens

The genetic diversity of green algal photobionts (chlorobionts) in soil crust forming lichens was studied as part of the SCIN-project (Soil Crust InterNational). A total of 64 lichen samples were collected from four different sites along latitudinal and altitudinal gradients in Europe (Tabernas/Spain; Hochtor-Großglockner/Austria; Gynge Alvar/Sweden; Ruine Homburg/Germany). The dominant lichen species at all four sites was Psora decipiens, often occurring with Buellia elegans, Fulgensia bracteata, F. fulgens and Peltigera rufescens. Genetic identification of chlorobionts was carried out using the nuclear marker (nrITS) and a chloroplast marker (psbL-J). We found P. decipiens to be associated with several different species of Trebouxia and Asterochloris, although previously described to only have Asterochloris sp. The phylogenetic analyses revealed a high chlorobiont diversity with 12 well supported clades, including Trebouxia asymmetrica, T. jamesii, T. impressa and other, as yet taxonomically unidentified clades (Trebouxia sp. URa1-4, T. sp. URa6, T. sp. URa7-13). Additionally, five clades of Asterochloris were identified (A. magna, A. sp. URa14 -17). Most of the chlorobiont species appeared to be cosmopolitan, but five clades were unevenly distributed between the sampling sites with only Trebouxia being found in the warm and dry Spanish habitats and combinations of Trebouxia and Asterochloris in the cooler and more humid habitats. The wide range of chlorobiont species might contribute to the observed domination of P. decipiens at all four research sites of the SCIN project which range from a desert in Spain to an alpine site in the Alps of Austria.

Terrestrial biodiversity along the Ross Sea coastline, Antarctica: lack of a latitudinal gradient and potential limits of bioclimatic modeling

AbstractAntarctica has several apparent advantages for the study of biodiversity change along latitudinal gradients including a relatively pristine environment and simple community structures. Published analyses for lichens and mosses show no apparent gradient in biodiversity along the western Ross Sea coast line, the longest ice-free area in Antarctica spanning 14° latitude. One suggestion is that the area remains poorly surveyed. Here, we combine available species lists from four sites along the coast with new own data from two additional sites [Taylor Valley (77°30′S) and Diamond Hill (79°S)]. We show a decline in total terrestrial biodiversity with latitude from Cape Hallett (72°S) to Diamond Hill. However, the southernmost site, the Queen Maud Mountains (84°S), is exceptional with almost the same diversity as Cape Hallett. A categorization of lichens according to their proposed ecology shows the proportion of tolerant species remains relatively constant. However, the absolute number of conformant species declines with latitude, again with a minimum at Diamond Hill. Similarity indices are low and not very different between sites with Diamond Hill being the exception with very few species. We suggest that terrestrial biodiversity best reflects microhabitat water availability rather than macroclimatic temperature changes and use climate data from Taylor Valley and Diamond Hill to support this suggestion. We propose that the importance of microhabitats and landscape location is one of several possible limitations to the application of bioclimatic modeling along the Ross sea coastline. In the absence of a definitive link between macroclimate and the biota, predicting the effects of climate changes will be more challenging.

Quantified vegetation change over 42 years at Cape Hallett, East Antarctica

This paper reports on the remapping of a carefully documented vegetation plot at Cape Hallett (72°19′S 170°16′E) to provide an assessment of the rates of vegetation change over decadal time scales. E.D. Rudolph, in 1962, mapped in detail the vegetation of a site approximately 28 m by 120 m at Cape Hallett, Victoria Land, Antarctica. This site was relocated and remapped in January 2004 and changes were assessed using GIS techniques. This appears to be the longest available time period for assessing vegetation change in Antarctica. The analysis indicated that considerable change had occurred in moss and algae distribution patterns and this seems to have been caused by increased water supply, particularly in wetter areas. There was also evidence of some change in lichen distribution. The extent of the change indicates that vegetation cover can be used for monitoring change in areas as extreme as the Ross Sea region. For this analysis to be successful it was important that the mapping techniques used were totally explicit and could easily be replicated. Fortunately, Rudolph had defined his cover classes and the site was also clearly marked. The application of GIS mapping techniques allows the mapping to be more explicitly defined and easily replicated.