Enrica Matteucci

Spores of lichen-forming fungi in the mycoaerosol and their relationships with climate factors

Fungal particulates are a dominant component of the bioaerosol, but aerobiological studies traditionally focused on a limited set of fungi having relevance as allergens or plant pathogens. This study first analyzes the occurrence of lichen meiospores in the mycoaerosol, quantitatively evaluating in the atmosphere of an alpine environment the occurrence of polar diblastic spores, unequivocally attributable to the lichen family Teloschistaceae. The analysis of air-samples collected one week per month for one year with a Hirst-type sampler displayed a low percentage occurrence of polar-diblastic spores (<0.1%) with respect to the whole mycoaerosol, dominated by Cladosporium. Spearmans correlation tests on aerobiological and climatic data highlighted a strong relationship between the detection of Teloschistaceae spores and rainfall events, excluding seasonal patterns or daily rhythms of dispersion. The fact that all the air-sampled spores were attributable to the species of Teloschistaceae occurring in the site, together with laboratory observations of predominant short range dispersal patterns for polar diblastic and other lichen spores, indicated that sexual reproduction is mostly involved in the local expansion of colonization, dispersal from a long distance appearing a less probable phenomenon. These findings indicated that responses of lichen communities to climate factors, usually related to physiological processes, also depend on their influence on meiospore dispersal dynamics. Spatial limitations in dispersal, however, have to be taken into account in evaluating lichen distributional shifts as indicators of environmental changes.

Image analysis for measuring lichen colonization on and within stonework

The suitability of image analysis by colour-based pixel classification to quantify lichen colonization on the surface of and within marble, travertine and mortar stonework has been investigated. High resolution images of lichenized stonework surfaces were acquired at different field sites using a scanner, thus avoiding invasive surveys, and the percentage cover of lichen species was subsequently measured in the laboratory using dedicated software. Furthermore, microphotographs of polished cross-sections of lichenized marble, travertine and mortar, stained using the periodic acid-Schiff (PAS) method to visualize hyphae, were produced by the same software to quantify hyphal spread within the substratum, a parameter which can be used more successfully than the commonly used depth of hyphal penetration to quantify how much the lichen has affected the conservation of a stone substratum. Significant statistical differences in hue, saturation and intensity (HSI) of the lichen thalli and PAS-stained hyphae, with respect to the lithic substrata, allowed the software to discriminate and quantify the lichen species cover on, and hyphal spread within, the three investigated lithotypes. Since such a quantitative approach highlights the volume of influence of lichens on stonework, where bioweathering processes are likely to develop, it could be used to support decisions on the preservation of our stone cultural heritage.

Epiphytic lichen communities in chestnut stands in Central-North Italy

Chestnut forest ecosystems represent an important component of the European Mediterranean basin and the Southern Alps landscape. Despite the good knowledge acquired in the phytosanitary and cultural aspects of chestnut, there is still a lack of data on the relationships between chestnut and epiphytes. We have investigated the changes in frequency of occurrence and species composition of lichen assemblages against the main site characteristics and environmental variables in chestnut woods along a bioclimatic and geographical gradient in Central-North Italy.The study has highlighted a geographic gradient from the Western Alps to the Northern Apennines. We recorded a total of 152 taxa, only 49 of which occurring in all the bioclimatic zones. The distribution of lichen communities in chestnut stands is mainly associated with increasing precipitation and decreasing temperature, thus confirming the prevailing influence of macroclimatic factors on epiphytic lichens. The species composition statistically differs also in stands differently managed (orchards vs. coppices).Chestnut woods host interesting communities, with rare species related to Lobarion, and can represent a good habitat for threatened epiphytic species.

Plant Colonization Limits Dispersion in the Air of Asbestos Fibers in an Abandoned Asbestos Mine

Abstract Asbestos exposure has been linked to adverse human health effects including asbestosis and mesothelioma. As such, mining and utilization of asbestos is restricted or has been banned in about 50 countries since 1990. Nevertheless, abandoned asbestos mines, mostly in serpentine areas, persist as sources of hazardous airborne fibers. Revegetation of asbestos mine spoils has been proposed as a way by which to stabilize asbestos-bearing substrate, thereby reducing fiber dispersion into the air. No study to date, however, has evaluated the revegetations effectiveness of reducing airborne asbestos pollution. In this study, we evaluated the effect of natural revegetation on the air dispersion of asbestos fibers from asbestos-rich serpentine lithosoils at an abandoned chrysotile mine. Air sampling of vegetated and barren plots within the mine demonstrated that vegetative cover significantly reduced asbestos dispersion into the air (50% reduction with 15–40% vegetative cover). Additionally, the effectiveness of several native, locally collected serpentine-tolerant species to revegetate the asbestos mine spoil, including Minuartia and Thymus species, was evaluated. Mat-forming, serpentine endemic Thymus sp. proved to be particularly effective at revegetating the mine spoil, having high transplantation survival, growth rates, and reproductive output.

Metals and secondary metabolites in saxicolous lichen communities on ultramafic and non-ultramafic rocks of the Western Italian Alps

There is a long history of studies on lichens found in ultramafic habitats, but comparisons between lichen communities on different ultramafic lithologies are scant, and potential metabolic adaptations to the multiple edaphic stresses of ultramafic substrates have been widely neglected. The present work is the first to characterise differences in the abundance and structure of saxicolous lichen communities on different ultramafic lithologies (dunite, lherzolite, and serpentinite), analysed in two areas of the Western Alps (NW Italy). Differences between communities on various ultramafic lithologies were observed, including differences between a mafic control (Mg-Al metagabbro); however, factors other than the substrate were observed to drive more remarkable differences between lichen communities on ultramafics of alpine and pre-alpine areas. XRF analyses demonstrated that the mineral composition of different lithologies is reflected by metal contents in crustose lichens, with weathering processes accounting for relative shifts in elemental abundances between rocks and thalli. A thin layer cromatography screening of lichen secondary metabolites (LSMs), which are thought to regulate metal and pH homeostasis in thalli, revealed lithological vicariance among dominant lichen species with different LSM patterns and intraspecific variability in LSM production associated with differences in lithology and location. In particular, the presence or absence of norstictic acid in species or lineages/individuals on the different lithologies, in relationship to concentrations of Fe, Mg, and Ni in lichen thalli, was recognised as a metabolic adaptation to metal stress. Pull-up tests revealed that physical factors such as a differential surface disaggregation may contribute more towards differences observed in lichen abundance on the different lithologies investigated.

Dispersal patterns of meiospores shape population spatial structure of saxicolous lichens

Relationships between reproductive strategies and population spatial structure have often been suggested for lichens, but there is a lack of supporting aerobiological data. For the first time, this study couples aerobiological investigations on meiospore dispersal by Caloplaca crenulatella (Nyl.) H. Olivier and Rhizocarpon geographicum (L.) DC. with analysis of local spatial patterns of thalli of both species. During a two-year monitoring period carried out on the walls of a medieval castle in NW Italy, a total of 169 polar diblastic spores, 20% of which were morphologically attributable to C. crenulatella, was detected in the mycoareosol, while muriform spores of R. geographicum were never found. Laboratory experiments confirmed that different dispersal patterns characterize the two species, the meiospores of R. geographicum being poorly discharged and only recovered at a short distance from thalli, whereas those of C. crenulatella were more abundantly discharged, suspended and better dispersed by a moderate air flow. This difference was reflected on the castle walls by the random spatial pattern of C. crenulatella, while R. geographicum showed a clustered distribution. Different discharge rates and take-off limitations, possibly related to size differences between the spores, are not sufficient to explain the different colonization patterns and dynamics of the two species. Additional intrinsic and extrinsic factors are likely to drive their dispersal and establishment success. Nevertheless, information on the relationships between different dispersal patterns of the species and the local spatial structure of their populations might help to predict the recovery potential of lichen species exposed to habitat loss or disturbance, or encrusting monument surfaces.

Morphological, secondary metabolite and ITS (rDNA) variability within usnic acid containing lichen thalli of the genus Xanthoparmelia explored at the local scale of rock outcrop in Western Italian Alps

Lichen secondary metabolites (LSMs) are regarded with interest for valuable biological properties, but chemical variability among/within lichen taxa has been only fragmentarily characterized by advanced analytical techniques. Knowledge of variability at a local geographic scale has been particularly neglected, while it should address the collection of chemically homogeneous materials to test and exploit LSMs. Here we evaluated the chemical variability of 48 Xanthoparmelia specimens from two rock outcrops in Western Italian Alps, representative of nine morphotypes and sixteen rDNA ITS haplotypes. Qualitative and quantitative analyses were performed by HPLC‐DAD‐ESI‐MS2 and UPLC‐HDR‐DAD, respectively, and revealed the occurrence of 18 LSMs. Chemical partition allowed distinguishing six chemical groups, only partially overlapping with distinct morphotypes and three divergent haplotype groups, which, overall, accounted for the co‐occurrence of different taxa only in part identifiable with species described for Europe. Some morphotypes were variable in presence and concentration of LSMs, and chemical divergences also characterized single ITS haplotypes. Accordingly, the collection of chemically homogeneous materials, even at a local scale, may be not properly addressed by morphological features and ITS barcoding, and should be confirmed by a specimen‐level chemical characterization.

Diversity and functional traits of lichens in ultramafic areas: a literature-based worldwide analysis integrated by field data at the regional scale

While higher plant communities found on ultramafics are known to display peculiar characteristics, the distinguishability of any peculiarity in lichen communities is still a matter of contention. Other biotic or abiotic factors, rather than substrate chemistry, may contribute to differences in species composition reported for lichens on adjacent ultramafic and non-ultramafic areas. This work examines the lichen biota of ultramafics, at global and regional scales, with reference to species-specific functional traits. An updated world list of lichens on ultramafic substrates was analyzed to verify potential relationships between diversity and functional traits of lichens in different Köppen–Geiger climate zones. Moreover, a survey of diversity and functional traits in saxicolous communities on ultramafic and non-ultramafic substrates was conducted in Valle d’Aosta (North-West Italy) to verify whether a relationship can be detected between substrate and functional traits that cannot be explained by other environmental factors related to altitude. Analyses (unweighted pair group mean average clustering, canonical correspondence analysis, similarity-difference-replacement simplex approach) of global lichen diversity on ultramafic substrates (2314 reports of 881 taxa from 43 areas) displayed a zonal species distribution in different climate zones rather than an azonal distribution driven by the shared substrate. Accordingly, variations in the frequency of functional attributes reflected reported adaptations to the climate conditions of the different geographic areas. At the regional scale, higher similarity and lower species replacement were detected at each altitude, independent from the substrate, suggesting that altitude-related climate factors prevail over putative substrate–factors in driving community assemblages. In conclusion, data do not reveal peculiarities in lichen diversity or the frequency of functional traits in ultramafic areas.

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

Hyphal 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 been also 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 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. This article is protected by copyright. All rights reserved.

New and noteworthy lichens from the Western Italian Alps

Abstract Western Italian Alps (namely Piedmont and the Aosta Valley) are among the lichenologically best known regions of Italy with c.1200 species listed. However, despite the long temporal continuity of lichen studies, information is still geographically uneven and data on the occurrence and distribution of many species are missing. An opportunity to fill this gap is currently provided by ecological and applied studies that assess the response of lichen communities to environmental factors in terms of species richness and composition. This study reports species that are new or interesting records for the western Italian Alps or noteworthy mainly because of their conservation status provided by ecological and applied studies in Aosta Valley and Piedmont and by some recent floristic surveys. A list of 51 records referring to 47 species is reported and discussed; 20 species are new to the Aosta Valley, 17 are new to Piedmont and 11 species are reported for the first time in the Western Italian Alps, being new for both regions. More than 25% of the records derive from stonework biodeterioration studies providing noteworthy data due to substrata analysed. About 35% of records derive from both air pollution monitoring studies and research on lichen conservation in relation to forest management. Biomonitoring studies are based on robust sampling design that allows data to be compared across regions and time series, improving the information associated with floristic data. Research on epiphytic lichens in Italian forests, rapidly increasing in Italy in the last years, has contributed significant advances in lichen floristics in Italy and in modelling environmental factors that are relevant for lichen ecology and conservation.