Endolithic Research Articles

The enigmatic enrichment of potassium and magnesium in runoff and floodwater in the Negev: Do biocrusts hold the key?

Regardless of lithology and plant cover, chemical composition of floodwater in the Negev show a consistent enrichment in K+ and Mg2+ ions, which could not have been explained by the rock or clay minerals or (due to the scarcity of plants) by plant decomposition. Hypothesizing that rock-dwelling (lithobionts) or soil (loess)-dwelling biocrusts may shed light on the phenomena, we conducted sprinkling experiments in the Negev Highlands. Sprinkling was conducted on 4 types of lithobionts: cyanobacteria which inhabit the south-facing bedrock (ENC), epilithic lichens, inhabiting the inclined (EPIi) and the flat (EPIf) north-facing bedrocks, and endolithic lichens (ENL) inhabiting south-facing boulders. Additional sprinkling took place on two types of soil biocrusts, a mixed crust composed of cyanobacteria, lichens and mosses at the north-facing footslope and a cyanobacterial crust at the more xeric south-facing footslope. The runoff water (of 5 and for 4 plots for each lithobiont and soil biocrust type, respectively) was analyzed for the ionic composition of Na+, K+, Mg2+, Ca2+, NH4+, Cl−, SO42−, and NO3−, whereas HCO3− was calculated. In comparison to rainwater, all habitats (except for K+ in ENL) showed high enrichment ratios (ERs) in K+ and Mg2+, which, unlike the high ERs of the other ions (such as SO42− that may stem from gypsum dissolution), could not have been explained by the rock lithology, clay or dust composition. It is suggested that following wetting, K+, serving for osmoregulation of cells, is released by the crust organisms, being thus responsible for K+ enrichment, while chlorophyll degradation is responsible for Mg2+ enrichment. It is suggested that rock- and soil-dwelling microorganisms may explain K+ and Mg2+ enrichment in runoff and floodwater and subsequently in groundwater of the Negev, and possibly in other arid zones worldwide, affecting in turn the quality of irrigation and drinking water.

Gypsum endolithic phototrophs under moderate climate (Southern Sicily): their diversity and pigment composition.

In this study, we used microscopic, spectroscopic, and molecular analysis to characterize endolithic colonization in gypsum (selenites and white crystalline gypsum) from several sites in Sicily. Our results showed that the dominant microorganisms in these environments are cyanobacteria, including: Chroococcidiopsis sp., Gloeocapsopsis pleurocapsoides, Gloeocapsa compacta, and Nostoc sp., as well as orange pigmented green microalgae from the Stephanospherinia clade. Single cell and filament sequencing coupled with 16S rRNA amplicon metagenomic profiling provided new insights into the phylogenetic and taxonomic diversity of the endolithic cyanobacteria. These organisms form differently pigmented zones within the gypsum. Our metagenomic profiling also showed differences in the taxonomic composition of endoliths in different gypsum varieties. Raman spectroscopy revealed that carotenoids were the most common pigments present in the samples. Other pigments such as gloeocapsin and scytonemin were also detected in the near-surface areas, suggesting that they play a significant role in the biology of endoliths in this environment. These pigments can be used as biomarkers for basic taxonomic identification, especially in case of cyanobacteria. The findings of this study provide new insights into the diversity and distribution of phototrophic microorganisms and their pigments in gypsum in Southern Sicily. Furthemore, this study highlights the complex nature of endolithic ecosystems and the effects of gypsum varieties on these communities, providing additional information on the general bioreceptivity of these environments.

Neoichnology of endolithic lichens: an update on the traces produced in fossil bones and teeth

ABSTRACT The present contribution is motivated by the frequent occurrence of traces generated by lichens on the fossil record, the usual and erroneous attribution of them to plant roots, and the scarce information published about bioerosive damage caused by lichens. As a result, two different patterns were identified on the surface and inside the fossil bones and teeth. The first one is characterised by the presence of lines clearer than the rest of the surface, produced by the hyphae and interrupted by small pits corresponding to the apothecia. These traces are often confused with Corrossichnia and Sphenoichnia, a situation that leads to taphonomic and palaeoecological misinterpretation. The second pattern, more unnoticed among other visible traces, consists of isolated pits without any other surficial trace distributed in the fossil surface. These pits can be confused with perforations made by many organisms. However, the presence of apothecia and, in some cases, also hyphae on the fossil remains, allows the accurate identification of the causal agent and the mechanism of action by which it occurs.

Biodeterioration of Antarctic fossil penguin bones caused by lichens from the Eocene La Meseta Formation

A large part of the Antarctic surface is covered by lichens since they can withstand extreme environmental conditions. Lichens are primary colonizers and contribute to soil formation by deteriorating rocks through a combination of chemical and physical mechanisms. Therefore, fossil remains found exposed on the surface are usually colonized by epilithic and endolithic lichens. The objective of this work is to determine the biodeterioration generated by lichens on fossil remains and its taphonomic implications. We identified the presence of the euendolithic lichens Lecidea andersonii and Athallia holocarpa growing into fossil penguin bones from Antarctica. The bioerosive damage was evaluated using light and electron microscopic techniques. Pits corresponding to apothecium and sinuous thin fissures remodeled, or in some cases produced, by hyphae were distinguished from the cracks originating from physical weathering. The maximum depth that hyphae extend inside the bone, probably constrained by the light supply, was established to be 2.5 mm. We provided a tool for the reconstruction of the chronology of the taphonomic events, describing the type and magnitude of the damage into the bones.

Tafoni weathering is an azonal process: Examples from Antarctica, Sardinia and Australia

Cavernous weathering (tafoni) is described from coarse-grained granitic bedrock in Northern Victoria Land (Antarctica), northern Sardinia (Italy) and southwestern Australia. It also occurs elsewhere in the world and on other coarse-grained lithologies. The cause of this unusual in-situ flaking and granular disintegration is problematic. Azonal conditions appear to be: (1) the presence of salt, (2) aridity and (3) high evaporation and sublimation rates. Zonal (site-specific) considerations are: (1) snow may transport salts far inland in Antarctica and (2) epilithic and endolithic lichen growth may assist biological weathering in Sardinia and Antarctica. In stable landscapes of great antiquity, such as southwestern Australia, tafoni-like forms appear to have developed over millions of years; they suggest that salts in solution move slowly and continuously towards the surface where they evaporate. Combinations of these conditions result in tafoni in these different environments.

Lithobiont-dependent ionic composition in runoff water

Abstract Rock dwelling organisms (lithobionts) such as cyanobacteria (prokaryotes) and chlorolichens (eukaryotes) abound in the Negev Desert, where they cover almost all calcareous bedrocks and rock particles (cobbles, boulders). In a small limestone watershed in the Negev Highlands, cyanobacteria inhabit the south-facing (SF) bedrocks, epilithic lichens (accompanied by endolithic lichens) inhabit the north-facing (NF) bedrocks, while endolithic lichens cover most of the cobbles and boulders in both aspects. In order to study their contribution to runoff water, a pair of runoff plots was established on habitats with cyanobacteria, endolithic lichens, and epilithic lichens. Rain and runoff were collected during the hydrological year 2006/07, and the chemical composition (Ca, Mg, Na, K, Cl, SO4, HCO3, Si) of the rain and runoff water was analyzed. Several patterns were observed: (a) as indicated by Si, more dust accumulated on the bedrocks; (b) all substrates exhibited high amounts of Ca, and HCO3; (c) while SF-bedrocks showed enrichment in K, both bedrocks (and especially the NF bedrocks), as well as the NF boulders showed an enrichment in Mg. While the enrichment in Ca and HCO3 can be explained by the contribution of the limestone parent material, the enrichment in K and Mg can be explained by the contribution of the living lithobionts, with K being mainly contributed by the cyanobacteria and Mg mainly by the epilithic lichens. Ion enrichment may therefore be aspect-dependent, reflecting the lithobiont distribution within the drainage basin, partially explaining the enrichment in K and Mg previously recorded in runoff water from the Negev.

Acarospora scottii and Sarcogyne paradoxa spp. nov. from North America

Acarospora scottii, a facultative lichenicolous lichen on crustose lichens, is described and typified from Minnesota. Sarcogyne paradoxa, which is described and typified from California, grows as an endolithic lichen or as a lichenicolous fungus endokapylic in crustose lichens.

Sun exposure drives Antarctic cryptoendolithic community structure and composition

The harsh environmental conditions of the ice-free regions of Continental Antarctica are considered one of the closest Martian analogues on Earth. There, rocks play a pivotal role as substratum for life and endolithism represents a primary habitat for microorganisms when external environmental conditions become incompatible with active life on rock surfaces, allowing life to spread throughout these regions with extreme temperatures and low water availability. Previous research concluded that altitude and distance from sea do not play as driving factors in shaping microbial abundance and diversity, while sun exposure was hypothesized as significant parameter influencing endolithic settlement and development. With this in mind, eight localities were visited in the Victoria Land along an altitudinal transect from 834 to 3100 m a.s.l. and 48 differently sun-exposed rocks were collected. We explored our hypothesis that changes in sun exposure translate to shifts in community composition and abundances of main biological compartments (fungi, algae and bacteria) using Denaturing Gel Gradient Electrophoresis and quantitative PCR techniques. Major changes in community composition and abundance occurred between north and south sun-exposed samples. As Antarctic endolithic ecosystems are extremely adapted and specialized but scarcely resilient to external perturbation, any shifts in community structure may serve as early-alarm systems of climate change; our findings will be of wide interest for microbial ecologists of extreme environments such as arid and hyper-arid area.

Lichens and other lithobionts on the carbonate rock surfaces of the heritage site of the tomb of Lazarus (Palestinian territories): diversity, biodeterioration, and control issues in a semi-arid environment

Investigations on the lithobiontic colonization of the stone cultural heritage in (semi-)arid regions are needed to address conservation strategies. In this work, lithobiontic communities were examined on the carbonate rock surfaces of the heritage site of the Tomb of Lazarus. We aimed to evaluate their distribution and interaction with the lithic substrate, together with the efficacy of biocidal treatments for their control. Diversity and abundance of lithobionts were surveyed on the Jerusalem stone blocks of three architectural elements. Observations at the lichen-rock interface were carried out by reflected light and scanning electron microscopy. The efficacy against lichens of the widely used biocide benzalkonium chloride (BZC) was compared for different concentrations and application methods, and evaluated by epifluorescence microscopy. Chlorolichens were the dominant component of lithobiontic communities, more thoroughly adapted to the semi-arid conditions of the site than mosses and black biofilms of cyanobacteria and dematiaceous fungi. A different structural organization, in terms of thallus thickness and depth of the hyphal penetration component, characterized epilithic and endolithic lichen species, responsible for different deteriogenic activities. Biocidal assays showed that even the methodologies that are usually effective in temperate conditions (as the application of BZC 1.5% by poultice) may not completely devitalize lichens adapted to the stress conditions of semi-arid climates, unless a pervasive biocide diffusion through metabolically active thalli is carefully guaranteed. Lithobionts act as biodeteriogens on the semi-arid surfaces of the investigated heritage site. Their removal is thus recommendable, but it needs to be adequately supported with a careful calibration of devitalization strategies.

Inter planetary hemispheric endolithic drifters

inter planetary hemispheric endolithic drifters

Brasilonema lichenoides sp. nov. and Chroococcidiopsis lichenoides sp. nov. (Cyanobacteria): two novel cyanobacterial constituents isolated from a tripartite lichen of headstones.

Cyanolichens are an assemblage of fungi and cyanobacteria from diverse, cosmopolitan habitats. Typically composed of a single species of cyanobacterium, with or without another eukaryotic alga, here we present two novel cyanobionts isolated from an undescribed tripartite lichen. This endolithic lichen was isolated from a granite cemetery tombstone from Jacksonville, FL, and contains two potentially nitrogen-fixing cyanobionts. Employing a total evidence approach, we characterized the cyanobionts using molecular (the 16S rDNA and ITS gene region), morphological, and ecological data. Phylogenetic analyses revealed two novel taxa: Brasilonema lichenoides and Chroococcidiopsis lichenoides, both of which fell within well-supported clades. To our knowledge, this represents the first instance of a tripartite lichen with two cyanobacterial and no eukaryotic members. These types of lichens may well represent an unexplored reservoir of cyanobacterial diversity. The specific epithets are proposed under the provisions of the International Code of Nomenclature for algae, fungi, and plants.

The influence of structural organization of epilithic and endolithic lichens on limestone weathering

AbstractHyphal penetration, mineral dissolution and neoformation at the lichen–rock interface have been widely characterized by microscopic and spectroscopic studies, and considered as proxies of lichen deterioration of stone substrates. However, these phenomena have not been clearly related to experimental data on physical properties related to stone durability, and the physical consequences of lichen removal from stone surfaces have also been overlooked. In this study, we combine microscopic and spectroscopic characterization of the structural organization of epi‐ and endolithic lichens (Caloplaca marina (Wedd.) Du Rietz, Caloplaca ochracea (Schaer.) Flagey, Bagliettoa baldensis (A.Massal.) Vězda, Porina linearis (Leight.) Zahlbr., Verrucaria nigrescens Pers.) at the interface with limestones of interest for Cultural Heritage (Portland Limestone, Botticino Limestone), with analysis of rock properties (water absorption, surface hardness) relevant for durability, before and after the removal or scraping of lichen thalli. Observations using reflected‐light and electron microscopy, and Raman analyses, showed lichen–limestone stratified interfaces, differing in the presence/absence and depth of lichen anatomical layers (lithocortex, photobiont layer, pervasive and sparse hyphal penetration component) depending on species and lithology. Specific structural organizations of lichen–rock interface were found to be associated with differential patterns of water absorption increase, evaluated by Karsten tube, in comparison with surfaces with microbial biofilms only, even more pronounced after the removal or scraping of the upper structural layers. Equotip measurements on surfaces bearing intact thalli showed lower hardness in comparison with control surfaces. By contrast, after the removal or scraping procedures, Equotip values were similar to or higher than those of controls, suggesting that the increasing open porosity may be related to a biogenic hardening process. Such counterposed patterns of porosity increase and hardening need to be considered when models relating lichen occurrence on limestones and biogeomorphological surface evolution are proposed, and to evaluate the consequences of lichen removal from stone‐built cultural heritage. Copyright © 2017 John Wiley & Sons, Ltd.

Ecology of Endolithic Bivalve Mollusks from Ko Chang, Thailand.

Cheewarat Printrakoon, Thamasak Yeemin, and Paul Valentich-Scott (2016) The objective of this study was to examine the ecology of coral boring bivalves from four islands southeast of Ko Chang, Trat Province, Thailand. A total of 11 bivalve families containing 18 species were recorded in the survey, including six reported for this first time in the region. Members of the Mytilidae comprised the highest bivalve diversity with five species recorded. The five most abundant species were Leiosolenus lima (Jousseaume in Lamy), Lithophaga teres (Philippi), Botula cinnamomea (Gmelin), Coralliophaga coralliophaga (Gmelin), and Gastrochaena cuneiformis Spengler. Ecological analysis showed that Ko Bai Dung had the highest density of boring bivalves, with 196.29 ± 118.24 individual/ m2. Density of coral boring bivalves was variable; the highest density was recorded for Coralliophaga coralliophaga (85.18 ± 74.35 individual/m2) at Ko Bai Dung. The highest diversity of boring bivalves was found on Ko Phrao Nok, and in dead coral. Multivariate analyses did not reveal a clear differences in the boring bivalve community composition between sites, or with coral age, or with coral species, however dead coral was well-grouped at 50% similarity. The number of species and number of specimens of boring bivalves in this study was significantly positively correlated with coral age. The maximum number of boring bivalve specimens was found in the oldest coral (11 years old) and in dead Porites host corals. Following the same trend of all dominant boring bivalves, corals more than nine years old showed the highest frequency distribution and the largest shell length. The distribution of shell height frequency showed Leiosolenus lima and Lithophaga teres had more variation in shell height than the other five dominant boring bivalve species. Endolithic bivalves are one of the main bioeroders in the coral biome. The ecologic data presented in this study can be used as one indicator of coral reef status, including bioerosion and nutrient recycling in coral ecosystems.

Wind as a cooling agent: substrate temperatures are responsible for variable lithobiont‐induced weathering patterns on west‐ and east‐facing limestone bedrock of the Negev

AbstractSpatial variability in lithobiont‐induced weathering patterns on desert rocks is aspect‐dependent. While differences between the northern and southern aspects have been extensively studied, little is known concerning the differences between east‐facing (EF) and west‐facing (WF) aspects in deserts, including the Negev Desert. Whereas cobbles on both slopes are inhabited by endolithic lichens, epilithic lichens, which render the bedrock a smooth appearance, and free‐living cyanobacteria, which give the bedrock a rugged microrelief, predominate on WF and EF bedrock, respectively. Following previous research that regarded dew as the principal factor that determines lithobiont distribution, measurements of radiation, temperature, wind and dew were carried out during 2008–2009 in the Negev Desert. The data indicated that albeit slightly higher midday surface temperatures that characterize WF surfaces (cobbles and bedrock), nocturnal temperatures on these surfaces were significantly lower, therefore facilitating higher dew condensation. High amounts of dew result from the relatively rapid drop in temperatures (14:00–20:00) due to the afternoon northwesterly sea‐breeze wind (with a cooling rate of the WF bedrock being 52.9% higher than on EF bedrock, 2.6 °C h−1 in comparison to only 1.7 °C h−1), and facilitate the growth of high‐chlorophyll dew‐fed (and rain‐fed) epilithic lichens, which may act as bio‐protectors on WF bedrock. Lack of condensation on EF bedrock results in turn in the growth of rain‐fed free‐living cyanobacteria, responsible for high rock dissolution and subsequently for a rugged microrelief. By affecting the nocturnal bedrock temperatures, wind acts as a cooling agent, impacting in turn the amount of dew, and subsequently lithobiont composition and weathering patterns in the Negev Desert. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

The Role of Fungi and Lichens in the Biodeterioration of Stone Monuments

This review elucidates current knowledge on the significant role of fungi and lichens in the biodeterioration of stone monuments. The effect caused by many epilithic lichen species in the deterioration of different types of stone has been extensively investigated and demonstrated. Nonetheless, many aspects of the deterioration mechanisms of microcolonial fungi (MFC) and endolithic lichens are still to be proved. An interesting hypothesis has recently been put forward involving the secretion of siderophores like compounds. Lichens can provide bioprotection for stone surfaces, acting as a barrier against weathering, retaining moisture, increasing waterproofing, reducing thermal stress and erosion, and absorbing pollutants. Nevertheless, the evaluation of biodeterioration vs. bioprotection cannot be generalised, since it can vary according to the behaviour of different species, as well as being affected by both the lithotype and the environment. In addition to the laboratory studies, more field studies of biological communities are required, to analyse their establishment and succession in natural conditions and after conservation treatments. In order to guarantee the best decision for stone conservation, cleaning operations should not be based on a generalised approach, but should rather be based on a careful evaluation of different aspects concerning biodeterioration and bioprotection.

Suitability of hyperspectral imaging technique to evaluate the effectiveness of the cleaning of a crustose lichen developed on granite

The aim of this paper was to evaluate the effectiveness of the laser cleaning of a complex biogenic patina, a crustose lichen, by means of hyperspectral imaging techniques. Samples of a Hercynian granite from NW Spain colonised by an endolithic crustose lichen (Pertusaria amara) were collected and cleaned following three procedures: a scalpel, the third harmonic of a Nd:YVO4 ns laser and the scalpel followed by the laser. The suitability of the hyperspectral camera as a non-destructive, online, fast and in situ monitoring technique to assess the effectiveness of the cleaning was evaluated using optical microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and colour measurements in CIELAB space. The hyperspectral imaging technique allowed us to measure the reflectivity variations of the cleaned surfaces in a non-invasive way, allowing the identification of the cleaning effectiveness of each procedure. Nevertheless, the results of the hyperspectral imaging technique must be validated by conventional techniques.

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.

Supratidal Extremophiles--Cyanobacterial Diversity in the Rock Pools of the Croatian Adria.

Hardly any molecular studies have been done on euendoliths of marine coastal environments, especially along the supratidal ranges of carbonate coasts. In our study, we provide a comparative sequence analysis using 454 pyrosequencing of the 16S ribosomal RNA (rRNA) gene combined with extensive microscopy of the endolithic community from rock pools of the Croatian Adria. Molecular diversity indices and richness estimates showed high level of diversity, particularly in high-salinity samples. The most common cyanobacteria belong to the order Pleurocapsales, similar to observations on limestone coasts in other parts of the world. Using single-cell amplification sequences of Hormathonema spp., Hyella caespitosa, and Kyrtuthrix dalmatica was for the first time introduced to the public GenBank.Microscopic investigations did not show qualitative variances in diversity among sites with different salinity but clear differences in prevalent organisms from similar environments suggesting that most of them are adapted to inhabit extreme, marine endolithic habitats and that similar species inhabit geographically separated but ecologically similar environments. This is a remarkable concordance rather seldom seen in molecular community studies in support of the hypothesis that endolithic ecosystems are seeded from a global meta-community.The relative diversity of the community is greater than those described from harsh endolithic habitats of cold and hot deserts. The maximum likelihood phylogenetic tree consisting of 166 operational taxonomic units (OTUs) at 96 % sequence similarity revealed 11 distinct clusters. Three clusters contained only epilithic or endolithic taxa, and five clusters contained mixed epilithic and endolithic taxa. Organisms clustered according to their taxonomic affiliations and not to their preferences to salt concentrations.

The effect of dew on flint and limestone lichen communities in the Negev Desert

Although lichens are important components of arid ecosystems, the influence of microclimatic factors (particularly dew) conducive to their distribution on rock habitats in the Negev Desert are still not sufficiently investigated. Here, we present a study on adjacent lichen communities inhabiting slightly acidic flint (chert) and slightly alkaline limestone cobbles in the north-facing slopes of two sites in the Negev Desert, Nizzana, NIZ (with long-term mean precipitation of 95mm and average daily dew amount of 0.1mm) and Sede Boqer, SB (with long-term mean precipitation of 95mm and average daily dew amount of 0.2mm). The communities on flint consisted of either scarce or lush cover of exclusively epilithic species, while endolithic lichens predominated on limestone. Following previous measurements that indicated that similar dew amounts characterize limestone and flint cobbles, we hypothesized that differences in the flint- and limestone-lichen communities may stem from differences in dew duration. Our results pointed indeed to the fact that while non-significant differences characterized the amounts of dew condensed on both substrates, dew duration on some of the flint cobbles (such as flat cobbles that readily permits long-lasting condensation) was by ∼1.2 longer. With longer dew duration, the cover of the epilithic lichens Aspicilia contorta subsp. hoffmanniana and Buellia sorediosa on flint increased along with the cover of the fruticose lichen Ramalina maciformis. Some of the species (Caloplaca circumalbata var. circumalbata, Caloplaca flavocitrina, Caloplaca oasis, Candelariella minuta, Diplotomma epipolium) inhabited both substrates pointing to the possibility that dew duration rather than alkalinity determines their distribution. While not explaining the higher lichen cover on limestone, dew duration explains the significantly higher cover of epilithic lichens and chlorophyll content (per inhabited surface) on flint in comparison to limestone.

Molecular phylogeny and taxonomy of the endolithic lichen genus Bagliettoa (Ascomycota: Verrucariaceae)

AbstractDespite their importance in bio‐deterioration, the taxonomy of the calcicolous endolithic lichen genus Bagliettoa is still problematic, mostly because of difficult identifications and unsettled species concepts. In this study, the traditional morphology‐based species and genus delimitations were tested using the phylogenetic markers ITS, mcm7 and mtSSU. Bayesian and maximum likelihood approaches were used on a dataset of 82 specimens to reconstruct phylogenetic relationships between the eight most common species of Bagliettoa. Molecular data confirmed the placement of B. limborioides, the type of the generic name, within the clade including species usually considered as part of Bagliettoa. Five other species were monophyletic and well supported (B. baldensis, B. calciseda, B. cazzae, B. marmorea, B. parmigerella). Relationships within a clade including B. parmigera, B. steineri and specimens with intermediate characters (here referred to as B. cf. suzaeana) were not resolved and weakly supported. This species complex (also called B. parmigera s.l.) is in need of a further revision. After revision of the type material, a lectotype is chosen for Bagliettoa parmigerella. Additionally, the new combinations Bagliettoa rubrocincta and Bagliettoa suzaeana are proposed based on their morphological similarity to other species of Bagliettoa. A key to the 12 currently recognized species is provided, which will hopefully help ecologists and biogeologists to identify species from this difficult genus of endolithic lichens.