Pseudocyphellaria dissimilis: a desiccation-sensitive,highly shade-adapted lichen from New Zealand

Summary Pseudocyphellaria dissimilis, a foliose, cyanobacterial lichen, is shown not to fit into the normal ecological concept of lichens. This species is both extremely shade-tolerant and also more intolerant to drying than aquatic lichens previously thought to be the most desiccation-sensitive of lichens. Samples of P. dissimilis from a humid rain-forest site in New Zealand were transported in a moist state to Germany. Photosynthesis response curves were generated. The effect of desiccation was measured by comparing CO₂ exchange before and after a standard 20-h drying routine. Lichen thalli could be equilibrated at 15° C to relative humidities (RH) from 5% to almost 100%. Photosynthesis was saturated at a photosynthetically active radiation (PAR) level of 20 mol m^-2 s^-1 (350 bar CO₂) and PAR compensation was a very low 1 mol m^-2 s^-1. Photosynthesis did not saturate until 1500 bar CO₂. Net photosynthesis was relatively unaffected by temperature between 10° C and 30° C with upper compensation at over 40° C. Temporary depression of photosynthesis occurred after a drying period of 20 h with equilibration at 45–65% relative humidity (RH). Sustained damage occurred at 15–25% RH and many samples died after equilibration at 5–16% RH. Microclimate studies of the lichen habitat below the evergreen, broadleaf forest canopy revealed consistently low PAR (normally below 10–20 mol m^-2 s^-1) and high humidities (over 80% RH even during the day time). The species shows many features of an extremely deep shade-adapted plant including low PAR saturation and compensation, low photosynthetic and respiratory rates and low dry weight per unit area.     

Herbivory on calcicolous lichens: different food preferences and growth rates in two co-existing land snails

A total of 32 calcicolous lichen species, one alga and one bryophyte were recorded on a limestone wall in the grassland Great Alvar on the Baltic island of Öland, Sweden. Fourteen (41%) of these 34 species and free-living cyanobacteria showed herbivore damage, most probably due to grazing by the land snails Chondrina clienta and Balea perversa which inhabited the limestone wall. Three laboratory experiments were conducted to examine the food preferences of individuals of C. clienta and B. perversa collected at this site and to evaluate any association between their preference and the net food quality of the lichens to the snails. Chondrina clienta and B. perversa exhibited food preferences, which differed significantly between species. Within species, variation in food choice was similar among individuals. This indicates that snail populations may be composed of polyphagous individuals with similar food preferences. Different lichen species were of different net food quality to the snails as indicated by growth rate differences. In both snail species the most preferred lichen species of the choice experiment caused the largest weight increase in juveniles, viz. Caloplaca flavovirescens for C. clienta and Aspicilia calcarea for B. perversa. This suggest that the snail species studied differ in their abilities to deal with secondary compounds and physical characteristics of certain lichens or that they can utilize the energy and nutrients of these lichens to a different extent. It is suggested that differential food preferences might reduce the intensity of interspecific competition for resources (lichens) between C. clienta and B. perversa.     

Temperate rainforest lichens in New Zealand: high thallus water content can severely limit photosynthetic CO2 exchange

CO₂ exchange rate in relation to thallus water content (WC, % of dry weight) was determined for 22 species of lichens, mainly members of the genera Pseudocyphellaria and Sticta, from a temperate rainforest, Urewere National Park, New Zealand. All data were obtained in the field, either using a standard technique in which the lichens were initially wetted (soaked or sprayed, then shaken) and allowed to slowly dry, or from periodic measurements on samples that were continuously exposed in their natural habitat. A wide range of WC was found, with species varying from 357 to 3360% for maximal WC in the field, and from 86 to 1300% for optimal WC for photosynthesis. Maximal WC for lichens, wetted by the standard technique, were almost always much less than the field maxima, due to the presence of water on the thalli. The relationships between CO₂ exchange rate and WC could be divided into four response types based on the presence, and degree, of depression of photosynthesis at high WC. Type A lichens showed no depression, and Type B only a little at maximal WC. Type C had a very large depression and, at the highest WC, CO₂ release could occur even in the light. Photosynthetic depression commenced soon after optimal WC was reached. Type D lichens showed a similar depression but the response curve had an inflection so that net photosynthesis was low but almost constant, and never negative, at higher WC. There was little apparent relationship between lichen genus or photobiont type and the response type. It was shown that high WC does limit photosynthetic CO₂ uptake under natural conditions. Lichens, taken directly from the field and allowed to dry under controlled conditions, had net photosynthesis rates that were initially strongly inhibited but rose to an optimum, before declining at low WC. The limiting effects of high WC were clearly shown when, under similar light conditions, severe photosynthetic depression followed a brief, midday, rain storm. Over the whole measuring period the lichens were rarely at their optimal WC for photosynthesis, being mostly too wet or, occasionally, too dry. Photosynthetic performance by the lichens exposed in the field was similar to that expected from the relationship between the photosynthetic rate and WC established by the standard procedure.     

The response of lichens inhabiting exposed wood of spruce logs to post-hurricane disturbances in Western Carpathian forests

We investigated which of the following environmental factors: the number of years since the windthrow of the tree (the age of dead wood), the phytocenosis (the type of forest community), altitude, exposure, wood hardness and the spatial scale of forest disturbances (small gaps with a few fallen spruces vs large-area windthrows) contributed to the diversity and abundance of lichens inhabiting the exposed wood of windthrown spruce trees in Polish Western Carpathian forests. Both Shannon H index and sum of coverage coefficients rose with increasing age of the wood, levelling off after 11–14 y (diversity) and 14–17 y (abundance). This factor appeared to be the most important for this group of lichens, but the significant positive impact of large-area windthrows on the lichen abundance was also demonstrated by using a GLM model. The age of the wood we precisely determined on the basis of data on Norway spruce mortality collected annually in permanent plots of the Gorce National Park since 2000. Using the Shore durometer we linked the course of the wood-inhabiting lichen succession with wood decay more precisely than before. The largest number of species was associated with medium hard wood, i.e., 51 < x ≤ 80 on the Shore scale. Based on the NMDS analysis, we distinguished four age groups of logs, differing in lichen abundance and defined by the dominance of distinctive species. A large number of usually corticolous lichen species used the wood of windthrown spruce logs as an optional habitat to survive large-scale, post-hurricane forest disturbances.     

Effect of low-humidity treatment on growth of the lichenParmotrema tinctorum in a growth cabinet

Low-humidity treatment triggered an increase of the thallus area and the chlorophyll content in the following high-humidity condition. When low-humidity treatment for 4 days was intercalated in high-humidity conditions every 16 days, the thallus area increased 40% in 76 days.     

Studies on epiphytic flora of a tropical rain forest in Southwestern Nigeria

Bark microflora of 12 rainforest trees were examined. Crustose, foliose, and fruticose forms of lichens were observed. Bacillus sp., Erwinia sp., Micrococcus sp., Proteus sp., and Pseudomonas sp. were the five genera of bacteria recorded while three genera of Cyanobacteria; Entophysalis, Gleocapsa and Stigonema were observed. In the algal division, three genera of Chlorophyta found are Chlorococcum, Pleurococcus and Physolinum. Only one diatom, Cocconeis sp. was present on just one tree. Most of the epiphytic microflora found are mainly terrestrial and their spores might have been deposited on the barks by air, or dust-currents. While moisture is regarded as the most critical factor in growth of bark microflora, other factors like texture of the bark, insolation and especially chemical characteristics of the barks may play a key role in occurrence and distribution of micro-organisms on them.     

A new depsidone of Lobaria pulmonaria with acetylcholinesterase inhibition activity

The phytochemical investigation conducted on a foliose lichen, Lobaria pulmonaria(L.) Hoffm. (Lobariaceae), led to the isolation of a new depsidone in the form of its diacetate derivative which showed a moderate acetylcholinesterase inhibition activity (1 µg) in vitro. This is the first record of identified depsidone structure in searching for these inhibitors.     

PTP1B inhibitory effects of tridepside and related metabolites isolated from the Antarctic lichen Umbilicaria antarctica

The selective inhibition of PTP1B has been widely recognized as a potential drug target for the treatment of type 2 diabetes and obesity. In the course of screening for PTP1B inhibitory natural products, the MeOH extract of the dried sample of the Antarctic lichen Umbilicaria antarctica was found to exhibit significant inhibitory effect, and the bioassay-guided fractionation and purification afforded three related lichen metabolites 1-3. Compounds 1-3 were identified as gyrophoric acid (1), lecanoric acid (2), and methyl orsellinate (3) mainly by analysis of NMR and MS data. These compounds inhibited PTP1B activity with 50% inhibitory concentration values of 3.6 ± 0.04 μM, 31 ± 2.7 μM, and 277 ± 8.6 μM, respectively. Furthermore, the kinetic analysis of PTP1B inhibition by compound 1 suggested that the compound inhibited PTP1B activity in a non-competitive manner.