Growth analysis of circular lichen thalli

A new model which describes the growth pattern of circular lichen thalli (foliose and placodioid) is developed. It is tested with published data and fits better than any previous models. A method is described for the calculation of the values of two constants, α and β which may be determined by the extent of lateral movement of carbohydrate and the rate of carbohydrate production respectively. It is believed that the model is sufficiently simple to be of general application in lichen ecology and physiology and in lichenometry.     

Parasitism of an insect Manduca sexta L. alters feeding behaviour and nutrient utilization to influence developmental success of a parasitoid

The effects of macronutrient balance on nutrient intake and utilization were examined in Manduca sexta larvae parasitized by Cotesia congregata. Insects fed an artificial diet having constant total macronutrient, but with varied ratios of protein and carbohydrate, with altered diet consumption in response to excesses and deficiencies of the individual macronutrients. Bivariate plots of protein and carbohydrate consumption for non-parasitized larvae demonstrated a curvilinear relationship between points of nutrient intake for the various diets, and the larvae grew best on carbohydrate-biased diets. The relationship was linear for parasitized larvae with the growth uniform across diets. On protein-biased diets, the larvae regulated the nitrogen content, containing similar amounts of nitrogen regardless of consumption. Efficiency of nitrogen conversion in non-parasitized larvae was greatest on carbohydrate-biased diets, while nitrogen conversion by parasitized larvae was greatest with intermediate nutrient ratios. Accounting for carbohydrate consumption, the lipid content decreased as dietary carbohydrate increased, but parasitized larvae contained significantly less lipid. The total biomass of parasites developing in individual host larvae was positively correlated with host protein consumption, but the individual parasites were similar in size. Parasitism influences host nutrient consumption in a manner that achieves uniform host growth under diverse nutritional regimes, thereby constraining blood nutrient concentrations within limits suitable for parasite growth and development.     

A simple theory regarding ambimobility of xenobiotics with special reference to the nematicide, oxamyl

A theory is presented to explain the phloem mobility of certain systemic xenobiotics that are not weak acids. It is shown that there is a theoretically optimum permeability that permits optimum circulation through the symplasm and apoplast (including the phloem and xylem) of Solanum tuberosum plants. The optimum permeability is large enough to permit substantial passive permeation into sieve cells in the source leaf and yet is small enough to permit phloem transport with some retention. The optimum permeability is a function of the velocity of sap flow in sieve tubes, the radius of the sieve tube, the over-all length of the plant, and the length of the carbohydrate and xenobiotic sources. It is argued that the nematicide, oxamyl, is near the optimum permeability under some experimental conditions. It is shown that depending on the strength of the carbohydrate sink in roots or growth points and depending on the permeability of the xenobiotic, there can be passive accumulation of xenobiotics in the sieve tubes in the carbohydrate sink regions.     

Contrasting changes in palatability following senescence of the lichenized fungi Lobaria pulmonaria and L. scrobiculata

Epiphytic lichens can contribute significantly to ecosystem nutrient input because they efficiently accumulate atmospheric mineral nutrients and, in the case of cyanolichens, also fix nitrogen. The rate at which carbon and other nutrients gained by lichens enters the ecosystem is determined by lichen litter decomposability and by invertebrate consumption of lichen litter. In turn, these processes are driven by the secondary compounds present in senesced lichens. Therefore, we explored how lichen palatability and concentrations of secondary compounds change with tissue senescence for Lobaria pulmonaria, a green-algal lichen with cyanobacterial cephalodia, and Lobaria scrobiculata, a cyanobacterial lichen. During senescence both lichens lost 38–48 % of their stictic acid chemosyndrome, while m-scrobiculin and usnic acid in L. scrobiculata remained unchanged. Snails preferred senesced rather than fresh L. pulmonaria, while senesced L. scrobiculata were avoided. This provides evidence that species with labile secondary compounds will have higher turnover rates, through consumption and decomposition, than those producing more stable secondary compounds.     

FACTORS AFFECTING THE TOXICITY OF SEVERAL LICHEN ACIDS: EFFECT OF PH AND LICHEN ACID CONCENTRATION

The effect of pH 5–8 and lichen acid concentration gradients (2.7 times 10⁻² - 2.7 times 10⁻⁶ m ) on the toxicity of the following lichen acids: usnic, lecanoric, evernic, vulpinic, stictic, fumarpro-tocetraric, psoromic, and atranorin, on spores of Funaria hygrometrica was tested. Percent germination and sporeling growth were used as indicators of toxicity. None of the lichen acids were significantly toxic, for either percent germination or sporeling growth at concentrations equal to or below 2.7 times 10⁻⁵ m at pH 7.0, but many of the lichen acids which increased in toxicity at values different from pH 7 may have been toxic at lower concentrations if a different pH was used for the assay. Lichen acid toxicity showed a good correlation with pH for the parameter of spore germination, or sporeling growth, or both. Some lichen acids did not inhibit germination but were effective in retarding sporeling growth, or vice versa. This observation is discussed in relation to changing fatty acids and other lipid composition as germination occurs. Two of the three O-methylated lichen acids (evernic and psoromic) were among the most effective in inhibiting growth over all, but at lower pH values these were less effective than non-O-methylated lichen acids. Stictic, which is also an O-methylated lichen acid, was the least effective inhibitor over all the pH values for both parameters, while vulpinic was the most toxic over all the pH values. The order of relative toxicity for the lichen acids is different, depending on the pH and concentration at which they are tested and depending on the parameter measured. Thus, in an ecological sense, it is difficult to evaluate the adaptive significance of a particular compound or group of compounds without knowing what factors influence the toxicity of those compounds and how these factors vary in the organism's habitat.     

Cultivation of the lichenParmotrema tinctorum in growth cabinets

The growth of lichens in the field is slow and their cultivation is generally thought to be difficult. We studied the effects of environmental conditions and culture solutions on the growth of a lichen, and found that growth ofParmotrema tinctorum (Nyl.) Hale in growth cabinets was possible. The thallus area increased by about 20% monthly when the lichen was soaked in a culture solution for 90 min every four days and then grown at 100% relative humidity when the temperature in the growth cabinet was 20C and illumination was at 12 W/m² for 16 hr daily.     

The weight of the crust: Biomass of crustose lichens in tropical dry forest represents more than half of foliar biomass

In recent years, our ecological knowledge of tropical dry forests has increased dramatically. However, the functional contributions of whole ecosystem components, such as lichens, remain mostly unknown. In these forests, the abundance of epiphyte crustose lichens is responsible for the characteristic white bark on most woody plants, conspicuous during the dry season, but the amount of resources that the lichen component represents remains unexplored. We estimated lichen biomass in a Mexican tropical dry forest using the bark area of trees, the dry mass of lichens per unit area and the percentage of bark covered by lichens, together with previously known tree densities. The lowest 2.5 m of the forests main trunks contained 188 kg/ha of lichen biomass, with lichens covering 85% of the available bark for trees <12 cm DBH and 38% for trees >12 cm. Total epiphytic lichen biomass was 1.34–1.99 Mg/ha. Lichen biomass represented 61% of the foliar biomass in the forest. To our knowledge, this is the first time that a lichen biomass estimate is provided for an ecosystem in which crustose lichens are the dominant lichen growth form. Crustose lichens are typically considered to contribute little to the total lichen biomass and to be difficult to include in ecological analyses. The high lichen biomass in this ecosystem implies a significant ecological role which so far is unexplored. We suggest the crustose lichen component should not be underestimated a priori in ecological studies, especially in ecosystems with abundant lichen cover.     

DISPERSAL PATTERNS OF TERRICOLOUS LICHENS BY THALLUS FRAGMENTS

Dispersal patterns from seven terricolous lichen species, with a high capacity for asexual reproduction by fragmentation (Cetraria muricata, Cladonia species), were studied in differing vegetation types in north-eastern Germany. Marked lichen thalli were fragmented by trampling. After 15 days the spread of thallus fragments was monitored. Whereas most of the fragments that were dispersed by wind remained within a 20-cm radius from the source, the maximal dispersal distance was 57 cm in a dry sand grassland and 68 cm in an open pioneer pine forest. Dispersal was negligible in a closed old-growth pine forest. Several fragmented lichen cushions were disturbed and removed by animals, and led to a maximal dispersal distance of 9·70 m. These results suggest that: (a) thallus fragments provide good short-distance dispersal in open vegetation, but are inefficient for long-distance dispersal, and (b) wind and animals are important factors for the dispersal of thallus fragments. For restoration management of man-made substrata, artificial introduction of lichen thalli is proposed.     

Asymmetric Co-evolution in the Lichen Symbiosis Caused by a Limited Capacity for Adaptation in the Photobiont

It is proposed that lichen photobionts, compared to mycobionts, have very limited capacity to evolve adaptations to lichenization, so that the symbionts in lichens do not co-evolve. This is because lichens have (a) no sequential selection of photobiont cells from one lichen into another needed for Darwinian natural selection and (b) no photobiont sexual reproduction in the thallus. Molecular studies of lichen photobionts indicate no predictable patterns of photobiont lineages that occur in lichens so supporting this proposal. Any adaptation by photobionts accumulating beneficial mutations for lichenization is probably insignificant compared to the rate of mycobiont adaptation. This proposal poses questions for research relating the photobiont sexual cycle (genetic and cellular), the fate of photobiont lineages after lichenization, whether lineages of photobionts in thalli change with time, thallus formation by from spores as well as carbohydrate movement from photobionts to mycobionts and regulation of co-development of the symbionts in the thallus.     

The lichen rock tripe (Lasallia pustulata) as survival food: effects on growth, metabolism and immune function in Balb/c mice

The present study was performed to investigate whether the lichen rock tripe (Lasallia pustulata) can be used as food during survival situations. The effects of 30% lichen supplementation given to female Balb/c mice were studied on growth rate, metabolism and immune functions. After 3 weeks on this diet, it was found that the lichen supplementation did not affect the growth rate or the well-being of the animals. The growth rate tended to be higher in the lichen group when compared to control mice. Food consumption was similar in both groups, but with a trend towards slightly higher intake (12%) in the lichen group. The heart, liver, kidney and lymphoid organ (spleen and thymus) weights were not affected by the lichen. Histological hematoxylin eosin staining showed that all these organs were normal. Plasma glucose levels were unchanged, but plasma urea levels decreased by 24% (p < 0.05) with the lichen diet. Red and white blood cells and the number of lymphoid cells in the thymus and spleen were normal. The activity of thymocytes and spleen T-lymphocytes were not affected by the lichen diet, but spontaneous cell-mediated cytotoxicity (NK cells) tended (n.s.) to increase and spleen B-lymphocyte activity increased by 40% (p < 0.05). This study shows that the lichen rock tripe has immune stimulating effects important for host defence reactions and can be used as food in survival situations without any adverse effects on the metabolism.     

Carbohydrate dynamics and growth rate of natural phytoplankton populations

Diurnal changes in carbohydrate content of natural phytoplankton populations differed from those found for cyanobacteria grown in continuous cultures. The carbohydrate accumulation rate was not constant during the light period. Also in contrast to results obtained using continuous cultures the photosynthetic characteristics changed during the light period. A close correlation was observed between changes in carbohydrate accumulation rate and the efficiency of photosynthesis over 24 hours. Seasonal changes in carbohydrate consumption rate over the dark period were proportional to changes in growth rate.     

Colonization,growth, and survival strategies of lichens on leaves in a subtropical rainforest

Rainforest leaves are a relatively short-lived habitat which is well defined in both time and space, and which is occupied by a range of specialized lichens which might be expected to show survival strategies contrasting with those of other lichens. Changes in the lichen populations of individual leaves in subtropical rainforest at Ml Glorious, Queensland, Australia were observed for 1662 days. Over 1100 days elapsed before 50% of surviving leaves showed visible lichen thalli and the probability of colonization estimated from life tables did not exceed 0.42 ± 0.20 at any time. Porina epiphylla had a relative growth rate of 3.01 × 10^?2 mm² mm^?2 week^?1, a high value for a lichen. The relative growth rate of Strigula subtilissima, however, was 6.86 × 10^?2 mm² mm^?2 week^?1, the highest rate known for any lichen. Small size and high relative growth rates indicate that lichens on leaves have the most extreme ruderal strategy yet demonstrated amongst the lichens.     

Separation and Purification of Molecular Species of Galactolipids by High Performance Liquid Chromatography

The NaCl concentration of the growth medium affected hydrogen production by Lyngbya sp. (No. 108) strain. Cells grown in medium containing 3% NaCl produced the most hydrogen. The carbohydrate content of this strain also increased with increasing NaCl concentration of the growth medium up to 720 fig/mg cells at 5 % NaCl. In the presence of 20 finlol/ml MFA (monofluoroacetic acid), inhibition of hydrogen production was observed. We extracted the glycogen from this nonheterocystous filamentous cyanobacterium, Lyngbya sp. (No. 108), and observed that glycogen and carbohydrate consumption of this strain is coincident with hydrogen production.

These results led us to the conclusion that the reserve glycogen or other carbohydrate were used as sources of electron donors for hydrogen production, and that the NaCl concentration of the medium affected the hydrogen production by this strain.     

Protein-leverage in mice: the geometry of macronutrient balancing and consequences for fat deposition

Objective: The Protein‐Leverage Hypothesis proposes that humans regulate their intake of macronutrients and that protein intake is prioritized over fat and carbohydrate intake, causing excess energy ingestion when diets contain low %protein. Here we test in a model animal, the mouse: (i) the extent to which intakes of protein and carbohydrate are regulated; (ii) if protein intake has priority over carbohydrates so that unbalanced foods low in %protein leads to increased energy intake; and (iii) how such variations in energy intake are converted into growth and storage. Methods and Procedures: We fed mice one of five isocaloric foods having different protein to carbohydrate composition, or a combination of two of these foods (N = 15). Nutrient intake and corresponding growth in lean body mass and lipid mass were measured. Data were analyzed using a geometric approach for analyzing intake of multiple nutrients. Results: (i) Mice fed different combinations of complementary foods regulated their intake of protein and carbohydrate toward a relatively well‐defined intake target. (ii) When mice were offered diets with fixed protein to carbohydrate ratio, they regulated the intake of protein more strongly than carbohydrate. This protein‐leverage resulted in higher energy consumption when diets had lower %protein and led to increased lipid storage in mice fed the diet containing the lowest %protein. Discussion: Although the protein‐leverage in mice was less than what has been proposed for humans, energy intakes were clearly higher on diets containing low %protein. This result indicates that tight protein regulation can be responsible for excess energy ingestion and higher fat deposition when the diet contains low %protein.     

Induction of a complete secondary-product pathway in a cultured lichen fungus

Experimental studies on the secondary metabolism characteristic of lichens have been impeded by the slow growth of the fungi and by the inconsistent results of many attempts to induce the pathways in the fungi isolated from their photosynthetic partners. In the present study, a lichen-specific secondary pathway was consistently induced in a lichen fungus (Cladonia grayi) grown in the absence of the alga. The depside (4-O-demethylsphaerophorin) and two depsidones (grayanic and 4-O-demethylgrayanic acids) found in the natural lichen began to accumulate a few days after the transfer of lightly fragmented mycelia from liquid to solid medium. Induction was enhanced on drier substrates and was correlated with the proliferation of aerial hyphae, where the major product (grayanic acid) accumulated in extracellular patches visible by fluorescence microscopy. The time course was analyzed by quantitative high-performance liquid chromatography of extracts from small cultures grown on nylon filters. Induction was rapid in view of the slow growth of the fungus, and secondary productivity was comparable to that of some nonlichen fungi. These results confirm that the alga is not needed for catalysis in lichen depside and depsidone biosynthesis and suggest instead that the characteristic secondary metabolism of natural lichen is linked to their aerial habit of growth.     

Destruction of lichen chemical defenses by a fungal

Lichen secondary metabolites are known to inhibit various animal consumers and pathogenic microorganisms. Nevertheless, many obligate fungal pathogens have evolved a tolerance to these inhibitory lichen compounds. We recently discovered a new lichen pathogen in the fungal genus Fusarium that is not only tolerant of lichen compounds but also able to degrade many of these compounds. This organism was discovered in field investigations of a different lichenicolous fungus, Marchandiomyces corallinus, which was found growing on lichens (Lasallia papulosa and L. pensylvanica) that normally inhibit its growth. Subsequent experiments established that M. corallinus is found on Lasallia species only when Fusarium is also present. We hypothesized that Fusarium altered the inhibitory chemistry of Lasallia spp. and permitted colonization by M. corallinus. A laboratory experiment to test this hypothesis demonstrated that sterilized tissues of Lasallia papulosa exposed to Fusarium for 30 d are readily degraded by M. corallinus; control tissues left in sterile water for 30 d continue to inhibit growth of M. corallinus. High performance liquid chromatography (HPLC) established that the lichen compound lecanoric acid, one of several lichen compounds that inhibit growth of M. corallinus, is degraded by extracellular enzymes produced by this newly discovered Fusarium. Taken together, our results demonstrate that enzymatic degradation of lichen compounds permits colonization of lichens by fungi that would otherwise be chemically excluded.     

Lichen planus and liver diseases: a multicentre case-control study. Gruppo Italiano Studi Epidemiologici in Dermatologia (GISED).

OBJECTIVE--To assess the association of lichen planus with liver complaints and with known aetiological factors of liver diseases. DESIGN--Multicentre case-control study. Interviews were conducted by trained medical investigators on the basis of a structured questionnaire. At the interview patients and controls were asked for consent to blood samples being taken to determine transaminase activities and the presence of hepatitis B virus surface antigen. SETTING--Outpatient departments of 27 Italian general and teaching hospitals that were collaborating in the Gruppo Italiano Studi Epidemiologici in Dermatologia (GISED). SUBJECTS--Incident cases and controls were eligible. A total of 577 patients with lichen planus and 1031 controls with dermatological diseases other than lichen planus were interviewed. Less than 1% of the people contacted refused to participate. Patients and controls were matched for sex and age in five year intervals. RESULTS--The risk of lichen planus was higher in patients with a history of liver diseases requiring hospital admission or specialist consultation (relative risk = 1.6; 95% confidence interval = 1.2 to 2.2), those who had had liver biopsy (5.5; 1.9 to 15.6), and those with a history of viral hepatitis (1.9; 1.1 to 3.1). High activities of liver enzymes and positive results of tests for hepatitis B virus surface antigen were also associated with lichen planus. The association with alcohol consumption was not clearly confirmed by a dose-risk relation. CONCLUSION--This study adds quantitative epidemiological evidence to the clinical observation that liver disease is a risk factor for lichen planus although not a specific marker of it.     

Growth of foliose lichens: a review

This review considers various aspects of the growth of foliose lichens including early growth and development, variation in radial growth rate (RaGR) of different species, growth to maturity, lobe growth variation, senescence and fragmentation, growth models, the influence of environmental variables, and the maintenance of thallus symmetry. The data suggest that a foliose lichen thallus is essentially a ‘colony’ in which the individual lobes exhibit a considerable degree of autonomy in their growth processes. During development, recognisable juvenile thalli are usually formed by 15 months to 4 years while most mature thalli exhibit RaGR between 1 and 5 mm yr⁻¹. RaGR within a species is highly variable. The growth rate-size curve of a foliose lichen thallus may result from growth processes that take place at the tips of individual lobes together with size-related changes in the intensity of competition for space between the marginal lobes. Radial growth and growth in mass is influenced by climatic and microclimatic factors and also by substratum factors such as rock and bark texture, chemistry, and nutrient enrichment. Possible future research topics include: (1) measuring fast growing foliose species through life, (2) the three dimensional changes that occur during lobe growth, (3) the cellular changes that occur during regeneration, growth, and division of lobes, and (4) the distribution and allocation of the major lichen carbohydrates within lobes.     

Growth of reindeer lichens and effects of reindeer grazing on ground cover vegetation in a Scots pine forest and a subarctic heathland in Finnish Lapland

Reindeer lichens are an important component of northern ecosystems. The aim of this study was to measure the growth rate of terricolous lichens as it is a key parameter involved in productivity of these ecosystems and an important part of lichen tolerance to reindeer grazing. Furthermore, the natural succession and the long-term effects of reindeer grazing on lichen community characteristics in two contrasting habitats were investigated as well as the interactions between lichen cover and mosses and vascular plants. Biomass and coverage measurements were conducted in a lichen woodland and in a subarctic heath with grazed and ungrazed areas in northern Finland. Measurements spanning over 13 yr of undisturbed development show that the growth rate of Cladina stellaris can be as high as >0.17 g g⁻¹ produced annually, although in average growth rates were much lower. During the succession of ground vegetation, C. stellaris , C. rangiferina , C. mitis and Cetraria nivalis increased in biomass in fenced areas and were reduced most in biomass by reindeer in unprotected areas. Reindeer grazing and trampling seem to change the vegetation towards a type that is dominated by small dwarf shrubs, bare soil and minute-cup lichens ( Cladonia spp.). Removing the lichen layer by reindeer may reduce natural regeneration of pine trees as implied by increasing numbers of pine seedlings with increasing lichen cover.     

The importance of host tree age, size and growth rate as determinants of epiphytic lichen diversity in boreal spruce forests

The amount of large and old trees has decreased in the boreal forests during the last centuries of forestry. Such trees are important habitats for epiphytic lichens and there is a growing concern for lichen species that are associated with large and old trees. However, only little is known about the relative importance of tree size versus age as determinants of lichen diversity. Here we have determined the size, age and growth rate of 157 Norway spruce trees and recorded the occurrence of epiphytic lichen species on their branches and lower stems. The study includes crustose lichens and was done in two old-growth forests in SE Norway. Tree age and tree size were the parameters that explained the largest part of epiphytic lichen diversity. Only the growth rate of the most recent time period, i.e. 1984–2004, showed a statistically significant relationship to diversity. There was no indication of a stabilising species number with increasing tree age. Slow-growing and old trees were, however, mainly of importance to the lichen species growing on stems, and this set of species were in general adversely affected by a large amount of branches. The opposite was the case for the species that were confined to branches as their diversity increased when the amount of branches increased. Our study adds empirical data to support the importance of large and old trees as bearers of biodiversity in boreal forests. Site preservation and patch retention of groups of old and large trees is recommended as measures to maintain epiphytic lichen diversity.