A challenge for nature conservation is to know why many species are absent from suitable habitats and whether they might be able to disperse and to establish. Here, we used 272 dry grassland patches within a fragmented landscape to investigate the role of local abiotic conditions and dispersal filtering in determining the likelihood of vascular plants to belong to the dark diversity (i.e. absent portion of the species pool). First, we quantified the species (SD), functional (FD) and phylogenetic (PD) diversity of both observed and dark communities. Second, we determined the roles of abiotic, present‐day and historical landscape configuration variables in shaping their patterns. Third, we evaluated the importance of each variable in determining their species. Environmental filtering was assessed as effects of local abiotic conditions and dispersal filtering as the effects of present‐day and historical landscape configuration. Dispersal filtering was also estimated by comparing dispersal traits of observed and dark diversity. Finally, we assessed community completeness to determine how much of the species pool was realized within a local community. We found higher SD in the observed compared to the dark communities, but PD did not differ. Contrary to expectations, dark communities resembled higher FD compared to the observed communities. Species with low dispersal capacity, low competitive abilities and high stress‐tolerance were more often absent. Observed and dark diversities were mostly affected by local abiotic variables. In the observed communities, present‐day landscape configuration variables affected SD while historical landscape configuration variables explained FD and PD. In the dark communities, we found the opposite pattern. Completeness was affected by present‐day and historical patch size. Our results explain why dry grassland species may belong to the dark diversity and highlight the importance of local abiotic and dispersal traits of the species to conserve dry grasslands in changing landscapes.

Many grasslands have disappeared over the last century as a result of anthropogenic land use intensification, while new patches are emerging through abandonment of arable fields. Here, we compared species (SD), functional (FD) and phylogenetic (PD) (alpha) diversity among 272 dry grassland patches of two age-classes: old and new, with the new patches being dry grasslands established on previous intensively managed fields during the last 30 years. We first compared SD, FD and PD, between patches of different age. Then, we performed generalized linear models to determine the influence of abiotic, present-day and historical landscape configuration variables on SD, FD and PD. By measuring abiotic variables, we explained the effect of environmental filtering on species diversity, whereas the present-day and historical landscape configuration variables were included to describe how the spatial and temporal configuration of the patches influence patterns of species. Finally, we applied partial regressions to explore the relative importance of abiotic, present-day and historical variables in explaining the diversity metrics and how this varies between patches of different ages. We found higher SD in the old compared to the new patches, but no changes in FD and PD. SD was mostly affected by abiotic and present-day landscape configuration variables in the new and the old patches, respectively. In the new patches, historical variables explained variation in the FD, while present-day variables explained the PD. In the old patches, historical variables accounted for most of the variation in both FD and PD. Our evidence suggests that the relative importance of assembly processes has changed over time, showing that environmental filtering and changes in the landscape configuration prevented the establishment of species in the new patches. However, the loss of species (i.e. SD) is not necessarily linked to a loss of functions and evolutionary potential.

Genetic variation is expected to be influenced by the interaction between reproductive mode and dispersal traits on the one hand and environmental and habitat setting affecting establishment success on the other. We evaluated how environmental/habitat setting affects population genetic variation (i.e. variation in genetic diversity and structure) when regulated by contrasting dispersal traits. We used fungus-specific microsatellite markers to examine genetic diversity and structure of two closely related epiphytic lichen fungi that differ in their primary reproductive mode: Nephroma laevigatum (sexually reproducing, n = 191, 10 microsatellites) and N. parile (asexually reproducing, n = 182, 12 microsatellites), along a steep climatic gradient in Scotland. Despite their reproductive differences, we found a high proportion of clones in both species and a background pattern of genetic structure related to climatic gradients. We also demonstrated that woodland connectivity, rather than geographic distance, explained genetic diversity in both species. Environmental/habitat setting, modulated by the reproductive mode of the species, affects genetic diversity and structure, but the putative dissimilarity in their reproductive mode is less important than has been previously assumed. We reinforce the importance of protecting highly connected populations, positioned along a gradient capturing the segregation of gene pool differences in response to climatic variation.

Understanding the relative importance of different ecological processes on the metapopulation dynamics of species is the basis for accurately forecasting metapopulation size in fragmented landscapes. Successful local colonization depends on both species dispersal range and how local habitat conditions affect establishment success. Moreover, there is limited understanding of the effects of different spatiotemporal landscape properties on future metapopulation size. We investigate which factors drive the future metapopulation size of the epiphytic model lichen species Lobaria pulmonaria in a managed forest landscape. First, we test the importance of dispersal and local conditions on the colonization-extinction dynamics of the species using Bayesian state-space modelling of a large-scale data set collected over a 10-yr period. Second, we test the importance of dispersal and establishment limitation in explaining establishment probability and subsequent local population growth, based on a 10-yr propagule sowing experiment. Third, we test how future metapopulation size is affected by different metapopulation and spatiotemporal landscape dynamics, using simulations with the metapopulation models fitted to the empirical data. The colonization probability increased with tree inclination and connectivity, with a mean dispersal distance of 97 m (95% credible intervals, 5-530 m). Local extinctions were mainly deterministic set by tree mortality, but also by tree cutting by forestry. No experimental establishments took place on clearcuts, and in closed forest the establishment probability was higher on trees growing on moist than on dry-mesic soils. The subsequent local population growth rate increased with increasing bark roughness. The simulations showed that the restricted dispersal range estimated (compared to non-restricted dispersal range), and short tree rotation length (65 yr instead of 120) had approximately the same negative effects on future metapopulation size, while regeneration of trees creating a random tree pattern instead of an aggregated one had only some negative effect. However, using the colonization rate obtained with the experimentally added diaspores led to a considerable increase in metapopulation size, making the dispersal limitation of the species clear. The future metapopulation size is thus set by the number of host trees located in shady conditions, not isolated from occupied trees, and by the rotation length of these host trees.

Background: Oceanic hazelwoods in western Scotland are hypothesised to be unmanaged post-glacial relicts, representing an unusual type of old-growth forest habitat in Europe. They are characterised by an exceptionally high epiphytic diversity, including their status as hotspots' for indicators of woodland ecological continuity.Aims: The aim of this study was to evaluate the effects of climate, pollution and management on the occurrence of epiphytic lichens and bryophytes on Corylus avellana.Methods: Thirteen hazelwood study sites were systematically sampled along a climate, pollution and management gradient in Britain. Epiphyte composition and richness were examined in a strict hierarchical framework, and compared against site-, stool- and stem-scale environmental predictors.Results: The study showed that along the gradient from clean-air' relict sites to polluted' coppiced sites: (i) epiphytic local stem-scale diversity declined, (ii) there was a loss of late-successional species including foliose cyano- and tripartite lichens and bryophytes and (iii) stem sizes were reduced, providing a further limit to the accumulation of species richness within a site.Conclusions: Relict hazelwoods in western Scotland are confirmed as an example of the most intact epiphyte communities. In particular, we show that the transition to coppicing can be clearly linked to ecological processes causing species loss.

Edge effect involves microclimatic variations (light, temperature and humidity) in the forest edge that become unsuitable for organisms adapted to forest interior conditions. We speculate that under similar edge types (shrubland matrix), the pattern in the response to forest edge might be different and more hostile for epiphytes in south-oriented edges. Because different matrix types have different effects on microclimate, we hypothesized that the magnitude of the edge effects will depend on the contrast between the physiognomy of the matrix and the forest fragment. The study was carried out in central Spain and consisted of a beech fragment surrounded by different types of vegetation matrices: pine plantation (south orientation), semi-deciduous oak forest (south orientation) and shrubland (north and south orientations). For each type of edge, we established ten transects perpendicular to the edge, running 100 m into the forest patch. Data were collected from three plots placed at 5, 50 and 100 m from the beginning of each transect. The results revealed that variations in the epiphytic composition mainly showed a replacement of forest interior species with generalist light-demanding species at forest edge. Shrubs-bordered edges showed the strongest influence on epiphytic composition, with high species dissimilarity between edge and forest interior, whereas the edge effects were mitigated when the patch was surrounded by other forests. Besides, in the case of shrub-bordered edge, the dissimilarity of species composition between edge interior was higher in the south than in the north-facing edge. We conclude that the magnitude of the edge effect on epiphytic communities is modulated by the physiognomy of the surrounding matrix and the orientation of the forest edge. In the case of a hard contrast matrix, at least 100 m of an edge buffer are required for the conservation of the species with high humidity requirements. Therefore, one of the main problems affecting the loss and even disappearance of shaded species is the decreasing of the amount of core conditions under the increasing forest fragmentation scenarios. This potentially exacerbates forest fragmentation effects linked to livestock use, due to the physiognomically different surrounding matrix compared to forest patches.

The species richness of epiphytic lichens is continuously decreasing by degradation and loss of habitat. Considering that taxonomic identification of all species is time and resource consuming, rapid assessment methods to extrapolate the total number of species are needed for practical conservation. This paper describes an alternative method using the correlation between lichens growth forms and species richness. The study was conducted in 406 forest stands located in Central Spain, covering a wide range of mediterranean-climate ecosystem regions, management intensity levels, canopy cover conditions, and tree sizes. The presence/absence of epiphytic lichens was determined in 6090 trees, which were dominated by oak species (Quercus ilex, Q, faginea, and Q. pyrenaica). In all type of forests, the diversity of growth forms was positively correlated with the total epiphytic lichen richness. In all cases, species richness increased in non-managed forest stands with dense canopies. Thus, we propose the use of lichen growth forms as a helpful surrogate of species richness to detect potentially conservation priority areas in the Mediterranean region. (C) 2015 Elsevier Ltd. All rights reserved.

Understanding how the biodiversity response to climate change will be modified at ecological scales, e.g. by species interactions, is a major challenge. Lichen epiphytes – the close interdependent relationship between a heterotrophic fungus and photosynthetic partner (photobiont) – are used here to explore how interaction regimes (between lichen species, and between lichens and their photobionts) explain distribution patterns along spatial climatic gradients. To do this we tested field evidence for the ‘core‐fringe hypothesis’, which proposes a facilitative interaction; sexually‐reproducing and spore‐dispersed lichens with a requirement for resynthesis with a compatible photobiont (Nostoc) are facilitated by the prior establishment of asexual lichens which disperse both the fungus and photobiont together. We used two closely related Nephroma species which differ in their reproductive mode – N. laevigatum (sexual spore‐dispersed) and N. parile (asexual) – and compared their occurrence along a bioclimatic gradient to local habitat factors, including the co‐occurrence of asexual lichens which have shared specificity for compatible Nostoc genotypes. The results showed that: 1) N. laevigatum is significantly more likely to occur on trees that have already been colonised by asexual lichens with shared specificity for Nostoc, supporting the core‐fringe hypothesis, while 2) N. parile is independent of this association (strengthening the core‐fringe hypothesis), with its response to a precipitation gradient modified by microhabitat factors. This positive test for the core‐fringe hypothesis demonstrates how interaction regimes can fundamentally alter expectations under climate change. There is an assumption that spore‐dispersed lichen species could more easily track their suitable bioclimatic space through fragmented habitat, compared to asexual species with larger and heavier propagules. However, the establishment of spore‐dispersed lichen epiphytes into new habitat may be limited by the dispersal rates of asexual species, which act as key facilitators.

The biodiversity response to climate change is a major focus in conservation research and policy. Predictive models that are used to project the impact of climate change scenarios - such as bioclimatic envelope models - are widely applied and have come under severe scrutiny. Criticisms of such models have focussed on at least two problems. First, there is an assumption that climate is the primary driver of observed species distributions ('climatic equilibrium'), when other biogeographical controls are often reliably established. Second, a species' sensitivity to macroclimate may become less relevant when impacts are down-scaled to a local level, incorporating a modifying effect of species interactions structuring communities. This article examines the role of different drivers (climate, pollution and landscape habitat structure) in explaining spatial community variation for a widely applied bioindicator group: lichen epiphytes. To provide an analysis free of 'legacy effects' (e. g. formerly higher pollution loads), the study focused on hazel stems as a relatively short-lived and recently colonized substratum. For communities during the present day, climate is shown to interact with stem size/age as the most likely explanation of community composition, thus coupling a macroclimatic and community-scale effect. The position of present-day communities was projected into ordination space for eight sites in England and compared to the position of historical epiphyte communities from the same sites, reconstructed using preserved hazel wattles dating mainly to the 16th Century. This comparison of community structure for the late-to post-Mediaeval period, with the post-Industrial period, demonstrated a consistent shift among independent sites towards warmer and drier conditions, concurrent with the end of the Little Ice Age. Long-term temporal sensitivity of epiphyte communities to climate variation thus complements spatial community patterns. If more widely applied, preserved lichen epiphytes have potential to generate new baseline conditions of environment and biodiversity for preindustrial lowland Europe.

Premise of the study: Microsatellite markers were characterized for two epiphytic cyanolichens, Nephroma laevigatum and N. parile (Nephromataceae), and will be used to investigate population structure and estimate gene flow among populations of these two closely related species with contrasting dispersal modes. Methods and Results: Twelve and 14 microsatellite loci were characterized for N. laevigatum and N. parile, respectively. Allele number in N. laevigatum ranged from three to 13 per locus, while in N. parile there were from two to six alleles per locus. As expected, the sexually reproducing N. laevigatum had higher genetic diversity than the predominantly asexual N. parile. Conclusions: This new set of markers is suitable for studying population structure and providing insights into gene flow among populations and for understanding processes of diversification. Compared between the species, they will facilitate an understanding of the influence of contrasting reproductive strategies on population and community structure.

The current trend of declining epiphytic richness caused by human activities (forest fragmentation, logging, agriculture, and livestock grazing) and the greater efforts required to sample and identify the most inconspicuous species have necessitated the use of indicators of the species richness. In this study, we examined the potential of predicting epiphytic lichen richness based on the richness of a single taxon (family) of the most conspicuous lichens (macrolichens) in Mediterranean woodlands. Since our working hypothesis is that the richness of some conspicuous elements is tightly connected with the total richness, we expect this connection is maintained even after composition shifts (for instance composition changes between coniferous and oak forests). In order to control the large set of confounding factors at macro- and microclimate scales our present study was conducted in 504 forest stands, which represented a wide range of Mediterranean climates, management intensity levels, canopy cover types, and tree sizes. The presence/absence of epiphytic lichens were determined in 7560 trees, which were dominated by coniferous (Pinus nigra and P. sylvestris) and oak (Quercus ilex ssp. ballota, Q, faginea, and Q. pyrenaica) species. In oak forests, the increased richness of Collemataceae and the complex known as "rest of Peltigerales" was followed by an increase in the overall epiphytic richness, whereas there was a strong positive correlation between Parmeliaceae and total epiphytic richness in coniferous forests. In both cases, the richness of these predictors increased in well-preserved forest stands with dense canopies. Thus, we propose the potential use of Parmeliaceae (for coniferous forests) and the Collemataceae and the "rest of Peltigerales" (for oak forests) as indicators in the Mediterranean region because they have a cosmopolitan distribution, grow in a wide range of environmental conditions, and are correlated with changes in the epiphytic richness caused by forest disturbances. (C) 2013 Elsevier B.V. All rights reserved.

It is necessary to understand how environmental changes affect plant fitness to predict survival of a species, but this knowledge is scarce for lichens and complicated by their formation of sexual and asexual reproductive structures. Are the presence and number of reproductive structures in Lobaria pulmonaria, a threatened lichen, dependent on thallus size, and is their formation sequential? Does any size-dependence and sequential formation vary along a climate gradient? Generalized linear mixed models were used to explore the effect of environmental predictors on the size and presence/abundance of each reproductive structure and to determine the probability of a given-sized thallus to develop any reproductive structure. The largest individuals are more likely to develop reproductive structures, and the lichen uses a mixed strategy of early asexual reproduction and late sexual. Macro and microclimatic variables also influenced reproductive capacity. Relationships among climate conditions and lichen size and reproductive capacity can compromise the future viability of the species in the most southern populations of Europe.

The co-occurrence pattern of epiphytic lichen communities was evaluated relative to micro-environmental heterogeneity along an edge-interior forest gradient. We collected data on the occurrence of 57 epiphytic lichen species from 452 plots in a Mediterranean forest remnant. We used two realistic null models to test for non-randomness in the structure of epiphytic lichen communities and generalized linear models to test the influence of micro-environmental variables on co-occurrence indices along the edge-interior gradient. We found that epiphytic lichen communities co-occurred less often than expected by chance, although the segregation pattern was not highly structured or recurrent. Less species co-occurrence was detected in the assemblage structure in the forest interior and with a southerly exposure. However, there were no significant relationships between co-occurrence and the number of coexisting species, the dominant species coverage or bryophyte coverage. In summary, our co-occurrence analyses suggested that epiphytic lichens were competitively structured, while we found no evidence of facilitation in more stressful conditions, as predicted by the stress-gradient hypothesis. Nevertheless, these results should be treated with caution because co-occurrence patterns may involve specific unknown modes of facilitation and competition, which relate to the life history of these organisms.

Persistence and abundance of species is determined by habitat availability and the ability to disperse and colonize habitats at contrasting spatial scales. Favourable habitat fragments are also heterogeneous in quality, providing differing opportunities for establishment and affecting the population dynamics of a species. Based on these principles, we suggest that the presence and abundance of epiphytes may reflect their dispersal ability, which is primarily determined by the spatial structure of host trees, but also by host quality. To our knowledge there has been no explicit test of the importance of host tree spatial pattern for epiphytes in Mediterranean forests. We hypothesized that performance and host occupancy in a favourable habitat depend on the spatial pattern of host trees, because this pattern affects the dispersal ability of each epiphyte and it also determines the availability of suitable sites for establishment. We tested this hypothesis using new point pattern analysis tools and generalized linear mixed models to investigate the spatial distribution and performance of the epiphytic lichen Lobaria pulmonaria, which inhabits two types of host trees (beeches and Iberian oaks). We tested the effects on L. pulmonaria distribution of tree size, spatial configuration, and host tree identity. We built a model including tree size, stand structure, and several neighbourhood predictors to understand the effect of host tree on L. pulmonaria. We also investigated the relative importance of spatial patterning on the presence and abundance of the species, independently of the host tree configuration. L. pulmonaria distribution was highly dependent on habitat quality for successful establishment, i.e., tree species identity, tree diameter, and several forest stand structure surrogates. For beech trees, tree diameter was the main factor influencing presence and cover of the lichen, although larger lichen-colonized trees were located close to focal trees, i.e., young trees. However, oak diameter was not an important factor, suggesting that bark roughness at all diameters favoured lichen establishment. Our results indicate that L. pulmonaria dispersal is not spatially restricted, but it is dependent on habitat quality. Furthermore, new spatial analysis tools suggested that L. pulmonaria cover exhibits a distinct pattern, although the spatial pattern of tree position and size was random.

La mayor parte de paisajes forestales en gran parte del planeta se han visto transformados en un mosaico de fragmentos de diferentes tamaños y grado de aislamiento, inmersos en una matriz de vegetación con diferentes estados de degradación. Esta transformación del paisaje ha afectado a la dinámica poblacional de las especies y a la riqueza y diversidad de las comunidades. En este contexto, los conocimientos que tenemos del estado de las poblaciones de organismos "no carismáticos", como pueden ser los líquenes en general, es muy escaso. Los pocos estudios desarrollados hasta el momento, indican que la calidad del hábitat de los fragmentos de bosque y el tipo de matriz que los rodea, y no su tamaño y grado de aislamiento, son determinantes de la riqueza, distribución, vitalidad, fertilidad, abundancia y diversidad genética de las especies y comunidades liquénicas que crecen sobre los árboles. Nuestros resultados pueden sugerir que quizás las poblaciones de especies liquénicas todavía no estén respondiendo con pérdidas de diversidad genética o cambios en abundancia de los individuos a los cambios en la configuración del paisaje en el que habitan y que necesitaremos más tiempo para poder ver una respuesta.

Fragmentation represents a serious threat to biodiversity worldwide, however its effects on epiphytic organisms is still poorly understood. We study the effect of habitat fragmentation on the genetic population structure and diversity of the red-listed epiphytic lichen, Lobaria pulmonaria, in a Mediterranean forest landscape. We tested the relative importance of forest patch quality, matrix surrounding fragments and connectivity on the genetic variation within populations and the differentiation among them. A total of 855 thalli were sampled in 44 plots (400 m2) of 31 suitable forest fragments (beeches and oaks), in the Sierra de Ayllón in central Spain. Variables related to landscape attributes of the remnant forest patches such as size and connectivity and also the nature of the matrix or tree species had no significant effects on the genetic diversity of L. pulmonaria. Values of genetic diversity (Nei's) were only affected by habitat quality estimated as the age patches. Most of the variation (76%) in all populations was observed at the smallest sampled unit (plots). Using multiple regression analysis, we found that habitat quality is more important in explaining the genetic structure of the L. pulmonaria populations than spatial distance. The relatively high level of genetic diversity of the species in old forest patches regardless of patch size indicates that habitat quality in a highly structured forest stand determines the population size and distribution pattern of this species and its associated lichen community. Thus, conservation programmes of Mediterranean mountain forests have to prioritize area and habitat quality of old forest patches.

QuestionWhat are the responses of epiphytic lichens to the intensity of management along a large environmental gradient in Mediterranean Quercus forests?LocationCentral Spain.MethodsThis study was carried out on 4590 trees located in 306 forest stands dominated by Quercus faginea or Quercus ilex ssp. ballota. The effect of forest management and other predictor variables on several species diversity indicators were studied. Variables modelled were total species richness, cyanolichen richness and community composition. A large number of predictor variables were included: forest fragmentation (patch size, stand variability), climate and topographic (altitude, slope, sun radiation, annual rainfall and mean annual temperature) and intensity of management. General linear models and constrained ordination techniques were used to model community traits and species composition, respectively.ResultsTotal richness and especially cyanolichens richness were significantly and negatively affected by the intensity of management. Lichen composition was influenced by management intensity, climatic and topographic variables and stand variability.ConclusionsIn Mediterranean forests, human activities related to forestry, agricultural and livestock use cause impoverishment of lichen communities, including the local disappearance of the most demanding species. The conservation of unmanaged forests with a dense canopy is crucial for lichen diversity.

Destruction and fragmentation of habitats represent one of the most important threats for biodiversity. Here, we examined the effects of fragmentation in Mediterranean forests on the epiphytic lichen Lobaria pulmonaria (Lobariaceae). We tested the hypothesis that not only the level of fragmentation affects L. pulmonaria populations, but also the quality of the habitat and the nature of the surrounding matrix affect them. The presence and abundance of the lichen was recorded on 2039 trees in a total of 31 stands. We recorded habitat quality and landscape variables at three hierarchical levels: tree, plot, and patch. We found that L. pulmonaria tends to occur in trees with larger diameters in two types of surveyed forests. In Quercus pyrenaica patches, the mean diameter of colonized trees was smaller, suggesting the importance of bark roughness. Factors affecting the presence and cover of the lichen in each type of forest were different. There was a strong positive influence of distance from a river in beech forests, whereas proximity to forest edge positively affected in oak forests. The influence of the surrounding matrix was also an important factor explaining the epiphytic lichen abundance.

Se propone un nuevo indice de diversidad liquenica epifitica (IDLE) que incorpora valores de riqueza, frecuencia y calidad. El estudio se realizo sobre 346 manchas de bosque distribuidas por todo el territorio de Castilla-La Mancha. Se seleccionaron variables relacionadas con la orografia y paisaje, con la estructura y manejo del bosque y variables climaticas. Mediante Modelos Lineares Generalizados (GLMs) evaluamos el efecto de cada una de ellas sobre los valores de IDLE. Los resultados indican que la diversidad de liquenes esta principalmente relacionada con la intensidad de manejo, cobertura arborea y edad del bosque. Con los resultados obtenidos se establecieron cinco clases de valores cuantitativos a los que relacionamos con una valoracion cualitativa de diversidad: muy alta, alta, moderada, baja y muy baja. Posteriormente analizamos la coincidencia de las manchas con valores de diversidad “muy alta” y “alta” con los espacios que van a conformar la Red Natura 2000 en Castilla-La Mancha y comprobamos que la mayoria de ellos quedarian integrados en dicha Red.