Article

Beta diversity and similarity of lichen communities as a sign of the times

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Abstract

Currently, change in lichen community structure depends on a combination of several pollutants instead of just one. Consequently, alpha lichen diversity no longer represents an effective response variable for assessing trends in atmospheric pollutants over time. Here we investigated the value of the relationship between alpha diversity and different aspects of gamma diversity (similarity, replacement and differences in richness of species) together with that of beta diversity (calculated as the sum of replacement and difference in richness of species), for assessing complex variations in epiphytic lichen communities in response to a changing pollution scenario. We considered an area subjected to extreme variation in atmospheric pollution in recent decades and explored temporal and spatial aspects of lichen community succession over short-, intermediate- and long-term reference periods. We found that variation in lichen communities for long- and intermediate-term reference periods was strongly dependent on the alpha diversity of single trees at the beginning of the observation period. The occurrence of nitrophytic species, which responded to the decrease in SO 2 concentrations, contribute to this trend. The effect of land use was observed only over long observation periods, with trees in urban areas showing less variation than those located in rural areas. In particular, the analysis of similarity, species replacement and differences in richness of tree pairs demonstrated that trends and patterns within lichen communities are neither always nor to the same extent associated with alpha diversity. Our results show that a thorough study of gamma diversity, including beta diversity and similarity, is required to detect changes in air quality in long-term biomonitoring surveys.

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... Diversity 2019, 11, 43 2 of 17 variations can also be described by components of the gamma diversity, such as species replacement, richness difference, and similarity [24,25]. ...
... Probabilistic sampling based on the location of plots and sub-plots within a survey area can provide reliable estimates of the overall diversity, even though a given number of rare species are often unrecorded [44]. Among several descriptors of lichen diversity, Giordani et al. [25] showed that the components of gamma diversity are important to highlight temporal and spatial variation in epiphytic lichen communities and to follow their progress over time. In the present work, we compared pairs of subsequent surveys carried out at time intervals ranging from 1 to 8 years. ...
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... Although we did not detect differences in the mean number of species per tree (alpha diversity) when comparing forest habitat types, MFC forests were characterized by higher beta-and gamma diversity compared to FC forests. Giordani et al. (2018) conducted biomonitoring surveys. e authors recommended using beta diversity and similarity to analyze temporal and spatial variation in lichen diversity to evaluate anthropogenic impacts. ...
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... В основном работы по применению лишайников в качестве биоиндикаторов сосредоточены на эпифитных лишайниках, т.е. растущих на коре деревьев [2][3][4]. Значительно меньше работ посвящено использованию лишайников других эколого-субстратных групп для выявления наличия и уровня антропогенного воздействия. Например, рассмотрено влияние пожаров на видовое разнообразие и функциональные характеристики эпилитного лишайникового покрова в травяных сообществах [5], эпилитные лишайники использованы для оценки воздушного загрязнения [6; 7]. ...
... As a consequence, limited studies comprehensively describe the diversity of lichens associated with rural roadside trees (Zarabska-Bożejewicz 2016). Detailed lichenological data may serve as basis for further research to reveal local or global trends and directions of changes in the structure of epiphytic lichen communities (Wolseley et al. 2006, Giordani et al. 2018). ...
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... Temporal and spatial variation in lichen diversity could be evaluated using beta diversity and similarity. This information could then be used to quantify anthropogenic impacts in a given region (Giordani et al., 2018). ...
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Chapter
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Epiphytic lichens were recorded on wayside trees in the Netherlands. Four statistical methods were used to detect the relationship between presence and abundance of lichen species and measured atmospheric concentrations of SO2, NO2 and NH3. The observed relationships were compared to published indicator scales of lichen sensitivity to atmospheric pollution. For SO2, a good agreement was found between all scales and calculated sensitivities based on presence or absence of species. For NO2 and NH3 the correspondence was less obvious. The sensitivity to NH3 was inversely related to Wirth's;s acidity indicator positively to NH3 tend to be sensitive to SO2 and NO2.
Article
A conceptual framework is proposed to evaluate the relative importance of beta diversity, nestedness and agreement in species richness in presence – absence data matrices via partitioning pairwise gamma diversity into additive components. This is achieved by calculating three complementary indices that measure similarity, relative species replacement, and relative richness difference for all pairs of sites, and by displaying the results in a two-dimensional simplex diagram, or ternary plot. By summing two terms at a time, three one-dimensional simplices are derived correspondig to different contrasts: beta diversity versus similarity, species replacement versus nestedness and, finally, richness difference versus richness agreement. The simplex diagrams can be used to interpret underlying data structures by showing departure from randomness towards well-interpretable directions, as demonstrated by artificial and actual examples. In particular, one may appreciate how far data structure deviates from three extreme model situations: perfect nestedness, anti-nestedness and perfect gradient. Throughout the paper, we pay special attention to the measurement and interpetation of beta diversity and nestedness for pairs of sites, because these concepts have been in focus of ecological reseach for decades. The novel method can be used in community ecology, conservation biology, and biogeography, whenever the objective is to recover explanatory ecological processes behind patterns conveyed by presence–absence data.
Article
The development of the epiphytic lichen vegetation on tree trunks inside and nearby twelve towns and industrial areas in south-west Sweden was investigated 1986/88 and 1997 using a photographic technique. The lichen vegetation studied in terms of area cover as well as the air pollution sensitivity and preference for nitrogen of the individual lichens. During both surveys the lichen flora was strongly impoverished in urban areas compared to suburban areas and especially to the countryside (reference) areas nearby. The air pollution situation has improved in the area both before and during the study period. This holds especially for SO2, to a lesser extent also for NO2. Following the improvement of the air quality, an increased lichen area cover on the tree trunks was observed. Also the cumulative pollution sensitivity of the lichens present was higher in 1997 compared to 1986/88 in suburban and countryside areas. For the nitrogen impact, the increase from 1986/88 to 1997 was smaller than for pollution sensitivity, but still statistically significant. The trends are interpreted as signs of a normalisation of the lichen flora. It is concluded that the observed pattern of lichen recovery reflects the fact that the reduction of the air pollution level in the central parts of the towns is still not large enough to permit a large-scale recovery of the lichen flora, while in the suburban areas and the countryside next to the towns, the air quality has now improved to an extent, which permits the reinvasion of a number of lichens.
Article
The evaluation of air quality is an important topic. It is well known that lichens have a set of characteristics that make them well suited for biomonitoring purposes. Sampling lichen diversity is not as expensive as chemical analysis, allowing a dense sampling grid and reducing the costs. Lichen diversity can be used to identify more disturbed areas, resulting from pollution, land use or ecological variables. In recent years, in order to enable extended use of lichens and to reduce ambiguities, i.e., variations due to unwanted environmental variables, efforts have been made to develop a feasible protocol for lichen sampling for biomonitoring purposes. This work aims at providing the information needed a priori for an air quality assessment study, in the form of a map showing areas where lichen diversity and abundance is lower. This study was done by sampling foliose and fruticulose lichen diversity and frequency, in a region in southwest Portugal (Sines) with large industrial facilities. A long-term study has been underway in the same area since the 1970s using lichens as bioindicators to evaluate air quality. In this work, we used a standard protocol to determine a lichen diversity value (LDV), to be used as an indicator of environmental quality. In order to reduce uncertainty concerning the type of disturbance affecting lichens, sampling sites were restricted using well-defined criteria. Whenever possible, sampling site variables were quantified. This method allowed us to reduce the many sources of variability affecting lichen diversity.
Article
ABSTRACT Aim Beta diversity (variation of the species composition of assemblages) may reflect two different phenomena, spatial species turnover and nestedness of assemblages, which result from two antithetic processes, namely species replacement and species loss, respectively. The aim of this paper is to provide a unified framework for the assessment of beta diversity, disentangling the contribution of spatial turnover and nestedness to beta-diversity patterns. Innovation I derive an additive partitioning of beta diversity that provides the two separate components of spatial turnover and nestedness underlying the total amount of beta diversity. I propose two families of measures of beta diversity for pairwise and multiple-site situations. Each family comprises one measure accounting for all aspects of beta diversity, which is additively decomposed into two measures accounting for the pure spatial turnover and nestedness components, respectively. Finally, I provide a case study using European longhorn beetles to exemplify the relevance of disentangling spatial turnover and nestedness patterns. Main conclusion Assigning the different beta-diversity patterns to their respective biological phenomena is essential for analysing the causality of the processes underlying biodiversity. Thus, the differentiation of the spatial turnover and nestedness components of beta diversity is crucial for our understanding of central biogeographic, ecological and conservation issues.
Article
What are the most relevant environmental variables influencing the distribution and the species richness of epiphytic lichens in heterogeneous areas of the Mediterranean region? What is the relative importance of substrate- vs. environmental-related variables? How do climatic and disturbance factors interact? The study was carried out in the Liguria region (northwestern Italy). This is a complex region where steep environmental gradients occur over a few kilometres of longitude and latitude. Data on lichen species frequencies, collected on the basis of stratified random sampling, were analyzed using non-metric multidimensional scaling (NMS) and DCA. Indicator Value Analysis (IVA) analysis was used to find indicator species for the environmental predictors. In the survey area, epiphytic lichen distribution depends on both substrate- and environment-related factors. Climatic variables (in particular average yearly temperature and rainfall), anthropogenic pressures (particularly harvesting and atmospheric pollution), bark pH and texture were associated with the main axes of variability in the dataset. Mean annual rainfall is the best predictor for epiphytic lichen richness in the survey area. The particular effects of the Mediterranean region (e.g. the influence of forest fires) and of heterogeneous areas (the variability of diversity in relation to habitat) were pointed out. Several indicator species, closely linked to particular ecological conditions, were found for both substrate-and environment-related variables. The main variables involved seemed to be the same reported for other areas, but their relative importance and their spatial scale of action were in some cases different, probably due to the geomorphological and climatic heterogeneity of the survey area. The significant influence of climatic predictors and disturbance factors on epiphytic lichens was confirmed, suggesting that these organisms may be used successfully to describe ecological trends in natural environments, also providing practical information at ecosystem level.
Article
The effects of air pollution on lichen biodiversity (LB) were monitored in Liguria (northwest Italy). A systematic sampling strategy was adopted in order to avoid the influence of spatial autocorrelation on the results. An eight LB class scale permitted to point out the levels of naturality/alteration in the region. The comparison of these results with the ones obtained by mean of physico-chemical methodologies shows a good accordance. The results of this study suggest the possibility of designing an integrated monitoring network, in which biological monitoring will allow to estimate the level of alteration in remote areas, which account for most of this region and which are currently not covered by measurements with automatic systems.
Article
The results of a biomonitoring survey carried out in the town of Montecatini Terme (central Italy) in the period 1993-2000 using the biodiversity of epiphytic lichens and the accumulation of heavy metals in thalli of Flavoparmelia caperata as indicators of air pollution are reported. From 1993 to 2000, the mean ILD value for the whole study area increased from 18+/-18 to 42+/-22, the lowest ILD value increased from 0 to 11 and the highest ILD value increased from 67 to 84. A 'lichen desert' was found only in 1993 and stations classified as 'natural' were lacking only in 1993 and 1996. Concentrations of all heavy metals decreased from 1993 to 1999. It is concluded that vehicular traffic is the main source of atmospheric pollution in the study area. The most likely changes that may have caused lichen communities to improve and heavy metals to drop is conversion of heating systems to methane (abatement of SO2) and the use of unleaded gasoline (reduction of Pb). The present results showed that despite their slow growth rate, lichens respond rapidly to decreasing concentrations of air pollutants, allowing annual changes to be detected.
Article
This work provided additional information for a better interpretation of lichen diversity values in biomonitoring studies of air pollution. The effects of 12 predictive variables were estimated for the Genova province (NW Italy) by means of a non-parametric model. The diversity of epiphytic lichens was strictly correlated with mean annual rainfall and mean annual temperature. Different variables were found to affect the lichen diversity in urban vs. forested areas. In urban areas, air pollutants, mainly SO2, are still the main limiting factor, even if under ameliorating conditions this relationship becomes less significant. In forested areas, harvesting and forest fires showed a predominant effect, suggesting the need to develop a more defined sampling protocol to estimate atmospheric pollution in such ecosystems.
Article
Epiphytic lichen and bryophyte distribution and frequency were investigated on the trunks of 145 young oak trees throughout London and surrounding counties, and compared with pollution levels and bark pH. Sixty-four lichen and four bryophyte species were recorded. Three major zones were identified: (i) two central regions with a few lichens, bryophytes absent; (ii) a surrounding region with a more diverse flora including a high cover of nitrophyte lichens; and (iii) an outer region, characterised by species absent from central London, including acidophytes. Nineteen species were correlated with nitrogen oxides and 16 with bark pH, suggesting that transport-related pollution and bark acidity influence lichen and bryophyte distribution in London today. Lichens and bryophytes are responding to factors that influence human and environmental health in London. Biomonitoring therefore has a practical role to assess the effects of measures to improve London's air quality.