Pioneer Lichens Research Articles

Heavy-metal pollution induces changes in the genetic composition and anatomical properties of photobionts in pioneer lichens colonising post-industrial habitats

Certain lichens are effective colonisers of polluted sites. However, little is known about the tolerance of photobionts and the degree of mycobiont selectivity to photobionts relative to metal pollution. The present study recognises the genetic and anatomical diversity of Asterochloris photobionts in epigeic lichens, i.e. Cladonia cariosa, C. rei, and Diploschistes muscorum, in relation to a wide spectrum of soil pollution. In accordance with phylogenetic analysis, photobionts were clustered in 7 moderately- to well-supported clades, including 19 haplotypes. The mycobionts of all studied lichens demonstrated a low level of selectivity and were capable of associating with various Asterochloris lineages. This tendency was also expressed by the frequent (~25%) occurrence of multiple algal genotypes in a single thallus. This indicates that identified Asterochloris lineages are generally tolerant to heavy-metal pollution, and the low level of selectivity of mycobionts enables them to select the most suitable and/or available partner. The trend of increasing incidence of certain Asterochloris lineages and decreasing frequency of others along with increasing soil pollution was observed. This proves the superior adaptation of some photobionts to polluted sites. Such symbiotic plasticity constitute an adaptive feature necessary for the successful colonisation. High number of haplotypes at polluted sites could be the result of multiple introduction events from different areas during the initial stages of spontaneous succession. Regardless of the genetic pattern, Asterochloris cells were considerably smaller, and the density and compaction of cells in the algal layer were higher, in lichen specimens from polluted sites, indicating that photobiont characteristics may be closely dependent on heavy-metal pollution.

Insight into the pattern of heavy-metal accumulation in lichen thalli

BackgroundHeavy metals that pass through the plasmalemma are expected to influence on lichen metabolic processes; however, lichens may tolerate high concentrations of metals by sequestrating them extracellularly. Heavy metal accumulation level fundamentally determine the success of lichens in the colonisation of polluted sites; however, the proportions between extra- and intracellular metal concentrations in lichen thalli are still poorly recognized. In this study metal accumulation patterns of selected toxic trace elements, i.e. Pb, Cd, and micronutrients, i.e. Zn, Cu and Ni, in Cladonia cariosa thalli were recognised in relation to extra- and intracellular fractions. MethodsThe intracellular and total concentrations of Zn, Pb, Cd, Cu and Ni in lichen thalli collected from eleven variously polluted sites were determined by means of atomic absorption spectrometry. Additionally, organic carbon and total nitrogen contents as well as pH of soil substrate were measured. ResultsThe accumulation patterns differed between studied metal elements; the major part of Zn, Pb and Cd loads was accumulated extracellularly, whereas Cu and Ni accumulation was mostly intracellular. Like toxic trace elements, Zn was accumulated mainly extracellularly at high polluted sites. The non-linear models most reliably reflect relationships between intracellular and extracellular metal contents in C. cariosa thalli. The intracellular contents of Zn, Pb, Cd and Cu increased slower at higher than at lower extracellular concentrations. Moreover, at higher total concentrations of elements in the thalli, their extracellular proportions were markedly increased. ConclusionThe results suggest that in the face of extreme Zn-enrichment, lichens demonstrate the ability to accumulate the excess of Zn outside the cells. Therefore, it can be concluded that metal accumulation depend not only on the element but also on its abundance in the environment and direct availability for lichens. The studied species showed a defence against excessive intracellular accumulation when a given element is in excess. Such capability may facilitate the colonization of extremely polluted sites by certain pioneer lichens.

The pioneer lichen Placopsis in maritime Antarctica: Genetic diversity of their mycobionts and green algal symbionts, and their correlation with deglaciation time

Since ice-free areas in Antarctica are predicted to increase by up to 25% before the end of this century, lichens such as the genus Placopsis will be important colonizers of these newly available grounds and will still be present in later successional stages of the lichen community. The main symbionts of Placopsis species are examined for 56 specimens collected from the South Shetland Islands, Antarctica using molecular (fungal and algal nrITS, fungal RPB1, algal rbcL sequences) and morphological methods. The specimens were collected from soils with different deglaciation times. Eight uni-algal photobiont cultures were obtained and analysed from two specimens. Placopsis antarctica and P. contortuplicata proved to be monophyletic and are sister species, only the former producing vegetative diaspores (soredia). Both share the same photobiont pool and are lichenized with two closely related species, Stichococcus antarcticus and S. allas. Two haplotypes of S. antarcticus are restricted to areas deglaciated for more than 5000 years and the volcanic Deception Island indicating a shift in the photobionts of Placopsis in the course of the soil and lichen community development. These photobiont haplotypes exhibit different ecological preferences, possibly leading to adaptation of the symbiotic entity to changing environmental conditions.

Heavy-metal tolerance of photobiont in pioneer lichens inhabiting heavily polluted sites

Heavy metals are known for their negative impact on the physiological processes of lichen photobiont. In spite of this, certain lichens are known to be effective pioneers of polluted sites. Cladonia cariosa, C. rei, and Diploschistes muscorum are prominent examples of lichens that spontaneously colonise post-industrial wastes. We examined the effect of total and intracellular Zn, Pb, Cd, As, Cu, and Ni accumulation in the thalli of these species on the physiological parameters of photobiont. Increased accumulation of Zn, Cd, Cu, and Ni in D. muscorum and of Zn and Ni in C. rei negatively affected contents of photosynthetic pigments, whereas concentrations of Pb had a positive effect in all lichen species. Moreover, pigment contents were positively associated with the concentrations of most examined elements in C. cariosa. The results indicate that even if chlorophyll contents reduced, its degradation does not progress. This suggests that metal stress may exert a negative effect on the synthesis rather than on the integrity of chlorophyll. Most importantly, lichen samples of each of the species from polluted sites proved to possess significantly higher FV/FM ratios than those from a reference site; moreover, the contents of elements of lichen thalli positively influenced this parameter. The efficient functioning of the algal component under heavy-metal stress conditions indicates that the examined lichens are well adapted to extremely contaminated substrates.

Pioneer lichen communities of the Teteriv River Basin (Ukraine)

The results of phytosociological studies of pioneer lichen communities of siliceous outcrops carried out in 2014–2016 in Teteriv River basin (Ukraine) are provided. The dataset of 302 relevés was analysed, 6 associations and 1 subassociation from 3 classes were distinguished as a result of the phytosociological survey in the Teteriv River basin. Four associations, i.e.: Aspicilietum contortae Kaiser ex Klement 1955, Cladonietum mitis Krieger 1937, Parmelietum conspersae Hilitzer 1925, Parmelietum somloensis Wirth 1995 and the alliance Aspicilion calcareae Albertson ex Roux 1978 are new for Ukraine, and one new association Aspicilio cinerei-Ramalinetum pollinariae Kapets et Khomyak, ass. nova is described here.

Weakening of gneiss surfaces colonized by endolithic lichens in the temperate climate area of northwest Italy

AbstractA role of lithobionts in geomorphological processes is increasingly argued, but the spatio‐temporal scale of their impact is largely unexplored in many ecosystems. This study first characterizes in the temperate zone (northwest Italy) the relationships between lithobiontic communities including endolithic lichens and the hardness of their siliceous rock substrate (Villarfocchiardo Gneiss). The communities are characterized, on humid and xeric quarry surfaces exposed for decades and natural outcrops exposed for centuries, in terms of lichen and microbial constituents, using a combined morphological and molecular approach, and with regard to their development on and within the gneiss.A lichen species belonging to Acarosporaceae (Polysporina‐Sarcogyne‐Acarospora group, needing taxonomic revision) chasmoendolithically colonizes both the humid and xeric quarry surfaces, on which epilithic cyanobacterial biofilms and epilithic pioneer lichens respectively occur. Light and electron microscopic observations show the development of the endolithic thalli within rock microcracks and the hyphal penetration along crystal boundaries down to depths of 1 to 3 mm, more pronounced within the humid surfaces. Such colonization patterns are likely related to biogeophysical deterioration, while no chemical alteration characterizes minerals contacted by the endolithic lichen. By contrast, on natural outcrops, where the endolithic colonization is negligible, a reddish rind below epilithic lichens indicates chemical weathering processes.Schmidt Hammer measurements highlight that the endolithic lichens deeply affect the hardness of the gneiss (down to −60% with respect to fresh controls and surfaces only colonized by cyanobacteria), exerting a significantly higher weakening effect with respect to the associated epilithic lithobionts. The phenomenon is more remarkable on humid than on xeric quarry surfaces and natural outcrops, where epilithic lichens are likely involved in long‐term hardening processes supporting surface stabilization.Endolithic lichens are thus active biogeomorphological agents at the upper millimetric layer of siliceous rocks in temperate areas, exerting their weakening action during the early decade‐scaled stages of surface exposure. Copyright © 2015 John Wiley & Sons, Ltd.

Comparative ecophysiology of three Placopsis species, pioneer lichens in recently exposed Chilean glacial forelands

Lichen species belonging to the genus Placopsis are early colonisers on snow free moraines of exposed land surfaces in the subantarctic region of Tierra de Fuego, South Chile. The physiological performance of three co-occurring species, P. pycnotheca, (terricolous), and P. perrugosa, and P. stenophylla (both saxicolous) was studied. All, possess green algal photobionts but have cyanobacteria in cephalodia. It was found that there was (i) a strong positive correlation between the acetylene reduction rate (AR) and the maximum photosynthetic rate (Amax), between the N content and the AR rate, and between the N and P contents, and (ii) the relationship between the CO2-exchange rates and the responses obtained in the laboratory reflected the ecology of these three lichens in the field. The results provide new information about the dynamics of some of the fastest growing crustose lichens. We hypothesize that the performance of these three species may have developed as a response to growing in an unstable environment that resulted from frequent glacial fluctuations.

Does UV-B influence biomass growth in lichens deficient in sun-screening pigments?

This study aimed to assess biomass growth as a response variable in lichens during short-term laboratory experiments. To do this, we studied the influence of UV-B and temperature on lichen performance including the synthesis of solar radiation screening cortical compounds. The pioneer lichen Xanthoria aureola from exposed sea cliffs and the old forest lichen Lobaria pulmonaria were cultivated for 15 days in the laboratory in a factorial experiments with temperature (12 and 21 °C) and UV-B (0, 0.1, 0.3 and 1.0 W m −2) as treatments. Prior to the experiment, the cortical pigment parietin was non-destructively extracted from X. aureola, whereas the sampled shade-adapted thalli of L. pulmonaria lacked cortical melanic compounds. Therefore both lichens were deficient in cortical sun-screening compounds when the UV-B exposure started. At 12 °C, the relative growth rate was 7.2 ± 0.6 and 3.0 ± 0.8 mg g −1 day −1 in L. pulmonaria and X. aureola, respectively, reduced to 1.8 ± 0.5 and −2.6 ± 0.9 mg g −1 day −1, at 21 °C. These figures showed that lichen growth is a useful response variable in short-term laboratory experiments. Growth was not influenced by UV-B alone in these pigment-deficient transplants, suggesting that UV-B had little adverse effects on either of the lichen bionts. The cortical sun screens (parietin and melanic compounds) were synthesized in the presence of UV-B, and increased statistically significantly with increasing UV-B at both cultivation temperatures. However, in X. aureola the synthesis was highest at the lowest temperature (12 °C). At 12 °C, changes in chlorophylls, F v/ F m and NPQ during cultivation were consistent with a substantial level of acclimation to the growth chamber conditions for both species, whereas strong reductions in photosynthetic pigments, F v/ F m and Ф II at 21 °C indicated serious damage and chlorophyll degradation at high temperature. In conclusion, lichen growth and the synthesis of protective compounds are highly responsive lichen processes in short-term experiments.

Vegetation change in a lichen-rich inland drift sand area in the Netherlands

In this paper we compare the cryptogam vegetation in the Spergulo-Corynephoretum and Genisto-Callunetum in an inland drift-sand area in three periods (1968, 1993 and 2004). In the early period the lichen diversity in these plant communities appeared to be very high. The aspect was formed by Corynephorus canescens and Polytrichum piliferum. The highest numbers of lichen species are found in the S.-C. cladonietosum, irrespective of the period. In all years, variants of this subassociation are found, with many lichen species. In time pH decreases and organic matter, % total N and % total P increase by humus production. Cover sands having relatively high content of cations form a suitable substrate for lichens. Since the 1970s the neophytic moss Campylopus introflexus, a species adapted to acidic, nutrient-poor sand, has invaded the sand dunes. These changes have been attributed to the high aerial deposition of N in this central part of the Netherlands. In the more recent periods the actual lichen diversity did not really diminish, but the cover of lichen-rich plant communities was clearly reduced when encroaching mosses outgrew the lichens in all succession stages. However, when C. introflexus is less vital because of ageing, desiccation or burial under wind-blown sand, common humicole, aero-hygrophytic and even pioneer lichen species may locally establish on or between the moss cushions. The former succession series starting with P. piliferum and ending with lichen-rich Calluna heath (1968) has been partly replaced by one including C. introflexus (1993 and 2004). Process management is necessary to keep the sand blowing and hereby reduce the colonization by C. introflexus. Habitat restoration by small-scale management consisting of cutting down self-sown trees and removing the top soil has positively influenced lichen diversity and needs to be continued.

Gregorella, a new genus to accommodate Moelleropsis humida and a molecular phylogeny of Arctomiaceae

The phylogenetic position of the European crustose pioneer lichen Moelleropsis (Biatora) humida (Kullhem) Coppins & P. M. Jørg. is studied using partial sequences of the mitochondrial SSU and nuclear LSU rDNA of 64 ascomycetes, including sequences of all known species of Arctomiaceae. The analysis places M. humida in the Arctomiaceae with strong support as sister to the Tasmanian genus Wawea. The genus Arctomia is monophyletic and sister-group to the Wawea+Moelleropsis humida clade. The new genus Gregorella is described to accommodate Moelleropsis humida and the new combination Gregorella humida (Kullhem) Lumbsch is proposed. The ontogeny of the ascomata of Gregorella humida is similar to that of other Arctomiaceae, in that the generative tissue is formed on a thallus outgrowth. The Arctomiaceae did not cluster with the bulk of cyanobacterial lichens in the Lecanorales suborder Peltigerineae (or Peltigerales), but is part of Ostropomycetidae. The closest relative of Arctomiaceae could not be identified, since the relationships of major clades within Ostropomycetidae lacked support.

Ecology of soil lichens from Pliocene clay badlands of central Italy in relation to geomorphology and vascular vegetation

The terricolous lichen communities occurring under a temperate sub-arid to sub-humid climate (mean annual rainfall about 750 mm) on Pliocene clay soils of southern Tuscany (central Italy) are similar to those reported for arid or sub-arid areas, with mean annual rainfall around 200 mm. The distribution of these communities is influenced by the availability of bare soil and percentage cover of vascular plants. Where vascular communities are more important and pedogenetic processes lead to the development of more structured and evolved soils, pioneer lichen communities of the Toninio-Psoretum decipientis are replaced by communities such as that of Cladonietum convolutae, which are more capable of competing for light and nutrients with dense communities of tall grasses such as Bromus erectus. The distribution patterns of Artemisia cretacea and B. erectus among vascular plants, and Fulgensia fulgens and Cladonia rangiformis among lichens, account for most of the variability in vascular and lichen communities, respectively.

Selectivity of photobiont choice in a defined lichen community: inferences from cultural and molecular studies

Axenic cultures of lichen photobionts isolated from bark‐inhabiting lichen thalli of the Physcietum adscendentis Ochsner were identified by light microscopy and sequence comparisons of internal transcribed spacer rDNAs to investigate principles of lichenization within a defined lichen sociological unit. The photobiont identity of eight lichen species is reported for the first time (photobiont species in square brackets): Lecania cyrtella (Ach.) Th. Fr. [Trebouxia arboricola Puym.], Lecania naegelii (Hepp) Diederich & v. d. Boom [Dictyochloropsis symbiontica Tscherm.‐Woess], Candelaria concolor (Dicks) B. Stein [Trebouxia jamesii (Hildreth & Ahmadjian) Gärtner], Candelariella cf. reflexa (Nyl.) Lettau [T. jamesii], Lecanora spec. [T. arboricola], Phaeophyscia orbicularis (Neck.) Moberg [T. impressa Ahmadjian], Physcia adscendens (Fr.) H. Olivier [T. impressa] and Lecidella elaeochroma (Ach.) M. Choisy [T. arboricola] and could be confirmed for another two species, Physcia stellaris (L.) Nyl. [Trebouxia impressa] and Xanthoria parietina (L.) Th. Fr. [Trebouxia arboricola]. The observation that pioneer lichens without vegetative propagules, growing on smooth bark, had Trebouxia arboricola as photobiont can be explained by the assumption of a free‐living population of Trebouxia arboricola. Species of photobionts from Xanthoria parietina were morphologically and genetically different from those of Physcia adscendens and Phaeophyscia orbicularis, respectively; a finding that does not support the previous assumption that Xanthoria parietina takes over its algal partner from a Physcia species, at least at the sites investigated.

Vegetation sequence on three boreal Manitoban rock outcrops and seral position of Opuntia fragilis

The vegetation sequence on granitic outcrops containing Opuntia fragilis (Nutt.) Haw. was examined at three sites in southeastern Manitoba. The experimentally determined species sequence supported those in the literature: (0) bare rock – pioneer lichens, (1) primary moss mat, (2) secondary moss and lichen mat, (3) tertiary moss and lichen mat, (4) stress-tolerant ruderals, (5) stress-tolerant perennials, (6) perennial grasses, and (7) chamaephytes and phanerophytes. The primary factor determining the sequence was substrate depth, presumably because of its effect on moisture retention. The species composition of the earliest seral stages (0–3) was consistent at all three sites, presumably as a result of propagule availability and the extremely xeric nature of the sere. Variations in the species of subsequent stages may be attributed to the more restrictive dispersal mechanisms of mesic species. Local variations in vegetation scale and pattern were caused by slope, disturbance, crevices or depressions, and encroachment of forest at the forest–outcrop ecotone. Opuntia fragilis, a stress-tolerant perennial, was the first vascular plant in the sequence and colonized mats in stage 2 (occasionally 3). It did not persist in stage 5.

NITROGEN FIXATION BY LICHENS ON GLACIAL DRIFT IN ICELAND

SummarySpecies of Peltigera Willd. and Stereocaulon Schreb. are among the most abundant macrolichens in the developing and older Rhacomitrium heaths on glacial drift at Sólheimajökull. The crustaceous Placopsisgelida (L.) Linds. is also a common pioneer lichen on rocks. These species contain a blue‐green alga either as the primary or secondary phycobiont. Five species of these genera were studied and showed appreciable rates of acetylene reduction. The total N content was greater in species with high nitrogenase activity. The biomass of Peltigera and Stereocaulon and surface area of Placopsis were determined at four sites of different ages and estimates of N2‐fixation m−2 day−1 are computed.