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We investigated the effect of drought in spring (earlier onset of summer drought) on litter decomposition in a Mediterranean pine forest, in Greece. We exposed litterbags filled with decomposed or fresh pine litter in the forest floor from January to November and simulated drought from April to May (season with usually high activity in soil). The drought treatment resulted in a significant increase of microbial respiration and litter weight loss and a decrease of microbial C. Both litter types were similarly affected by drought, but differed in parameters related to decomposer community succession (Collembola and Acari abundances, organic C and N, microbial N). Our results indicate that drought during the highly biologically active season might have significant implications for soil Carbon sequestration/storage.

Angiosperm flowers have evolved a dazzling palette of colours and a rich bouquet of scents, principally serving to attract pollinators. Despite recent progress in the ecology of pollination, the sensory floral traits that are important for communication with pollinators (for example, colour and scent) have not been assessed in an unbiased, integrative sense within a community context. Nonetheless, floral sensory stimuli are known key factors that mediate flower visitation, thus affecting community dynamics. Here we show that flowers of the phrygana, a natural Mediterranean scrubland, display integrated patterns of scent composition and colour (as perceived by pollinators). Surprisingly, the data reveal predictive relationships between patterns of volatile composition and flower reflectance spectra. The presence of nectar is related to visual cues and the qualitative composition of floral aromas. Our results reveal a coordinated phenotypic integration consistent with the sensory abilities and perceptual biases of bees, suggesting potential facilitative effects for pollination and highlighting the fundamental importance of bees in Mediterranean-type ecosystems. We offer our unbiased approach as a starting point for more extensive, global investigations of the diversity of floral sensory phenotypes and its role in the community ecology of plant-pollinator interactions.

DIDSON acoustic cameras provide a way to collect temporally dense, high-resolution imaging data, similar to videos. Detection of fish targets on those videos takes place in a manual or semi-automated manner, typically assisted by specialised software. Exploiting the visual nature of the recordings, tools and techniques from the field of computer vision can be applied in order to facilitate the relatively involved workflows. Furthermore, machine learning techniques can be used to minimise user intervention and optimise for specific detection and tracking scenarios. This study explored the feasibility of combining optical flow with a genetic algorithm, with the aim of automating motion detection and optimising target-to-background segmentation (masking) under custom criteria, expressed in terms of the result. A 1000-frame video sequence sample with sparse, smoothly moving targets, reconstructed from a 125 s DIDSON recording, was analysed under two distinct scenarios, and an elementary detection method was used to assess and compare the resulting foreground (target) masks. The results indicate a high sensitivity to motion, as well as to the visual characteristics of targets, with the resulting foreground masks generally capturing fish targets on the majority of frames, potentially with small gaps of undetected targets, lasting for no more than a few frames. Despite the high computational overhead, implementation refinements could increase computational feasibility, while an extension of the algorithms, in order to include the steps of target detection and tracking, could further improve automation and potentially provide an efficient tool for the automated preliminary assessment of voluminous DIDSON data recordings.

Nematode community indices have been broadly used to assess and monitor soil conditions. Most studies focused on agricultural or other disturbed soils and were usually applied at local-field scale. In this study, we focused on the variation of nematode community indices across fine (among microhabitats) and landscape level scales with the aim to identify indices or combinations of indices that are efficient at distinguishing microhabitats and landscape properties. We calculated nematode community indices in five microhabitats to account for variability in basal resources/organic input (soils, mosses on soil, mosses on rocks, as well as mosses on the lower and the upper part of trees trunks). The different microhabitats were located across the landscape in sites that differed in vegetation cover type (forested and non-forested), altitude (low, high) and aspect (North, East, South). Results of our models showed that microhabitat type could be predicted by all indices except the Maturity Index (MI) and the Fungivore/Bacterivore (F/B) ratio. Soil could be distinguished from mosses by the higher Plant Parasitic Index (PPI) and Enrichment Index (EI) and the lower Channel Index (CI). The different moss microhabitats could be distinguished from each other by the Summed Maturity Index (SMI) the Structure Index (SI) as well as the Basal Index (BI). At the larger scale, among landscape properties, variation by altitude was more pronounced compared to vegetation cover type and aspect. Samples originated from low altitudes were characterized by higher EI and F/B ratio. Indices for predicting landscape properties of the site a sample was taken from were more efficient when analyzed separately within each microhabitat. The interaction of the BI and the F/B ratio was able to predict vegetation cover type in soils while the same holds for BI, SI and their interaction in mosses. We conclude that nematode community structure is strongly shaped by variation in basal resources in the different microhabitats and microhabitats can be well predicted by most nematode community indices. Landscape properties constitute gradients of exposure of basal resources to ambient conditions, which affects basal resource transformations and availability. This variation across the landscape can also be predicted by some nematode community indices.

Fire is an important and frequent disturbance in Mediterranean-type ecosystems affecting the structure and dynamics of bee communities. We explored the effect of fire history on taxonomic and functional composition of wild bees on Rhodes Island, Greece, using UV-bright pan trap sampling. We carried out a fourth-corner analysis based on Generalized Linear Models to identify significant interactions between functional traits (nesting preferences, trophic specialization, and body size) and fire history, defined by fire frequency and post-fire age of sites. Our analysis showed that species diversity and abundance at various taxonomic levels did not display significant differences among different fire history regimes (twice-burnt, recently-burnt, old-burnt, and unburnt). The effect of fire was detected when focusing on functional traits rather than species. Ground nesting bees were positively associated with recently-burnt sites, which provide bare soil and therefore nesting sites for this group of bees. Polylectic bees were positively associated with twice-burnt sites, indicating the dominance of generalist bee species. Larger bees were positively associated with post-fire age, probably due to the larger foraging range of larger bees that enables a more efficient exploitation of aggregated resources. Our results show that responses of wild bee species to fire are driven by nesting preference, trophic specialization, and body size.

Nematode metabolic footprints (MFs) refer to the lifetime amount of metabolized carbon per individual, indicating a connection to soil food web functions and eventually to processes supporting ecosystem services. Estimating and managing these at a convenient scale requires information upscaling from the soil sample to the landscape level. We explore the feasibility of predicting nematode MFs from temperature-based bioclimatic parameters across a landscape. We assume that temperature effects are reflected in MFs, since temperature variations determine life processes ranging from enzyme activities to community structure. We use microclimate data recorded for 1 year from sites differing by orientation, altitude and vegetation cover. At the same sites we estimate MFs for each nematode trophic group. Our models show that bioclimatic parameters, specifically those accounting for temporal variations in temperature and extremities, predict most of the variation in nematode MFs. Higher fungivorous and lower bacterivorous nematode MFs are predicted for sites with high seasonality and low isothermality (sites of low vegetation, mostly at low altitudes), indicating differences in the relative contribution of the corresponding food web channels to the metabolism of carbon across the landscape. Higher plant-parasitic MFs were predicted for sites with high seasonality. The fitted models provide realistic predictions of unknown cases within the range of the predictor's values, allowing for the interpolation of MFs within the sampled region. We conclude that upscaling of the bioindication potential of nematode communities is feasible and can provide new perspectives not only in the field of soil ecology but other research areas as well.

Soil biodiversity plays a key role in regulating the processes that underpin the delivery of ecosystem goods and services in terrestrial ecosystems. Agricultural intensification is known to change the diversity of individual groups of soil biota, but less is known about how intensification affects biodiversity of the soil food web as a whole, and whether or not these effects may be generalized across regions. We examined biodiversity in soil food webs from grasslands, extensive and intensive rotations in four agricultural regions across Europe: in Sweden, the UK, the Czech Republic and Greece. Effects of land use intensity were quantified based on structure and diversity among functional groups in the soil food web, as well as on community-weighted mean body mass of soil fauna. We also elucidate land use intensity effects on diversity of taxonomic units within taxonomic groups of soil fauna. We found that between regions soil food web diversity measures were variable, but that increasing land use intensity caused highly consistent responses. In particular, land use intensification reduced the complexity in the soil food webs, as well as the community-weighted mean body mass of soil fauna. In all regions across Europe, species richness of earthworms, Collembolans and oribatid mites was negatively affected by increased land use intensity. The taxonomic distinctness, which is a measure of taxonomic relatedness of species in a community that is independent of species richness, was also reduced by land use intensification. We conclude that intensive agriculture reduces soil biodiversity, making soil food webs less diverse and composed of smaller bodied organisms. Land use intensification results in fewer functional groups of soil biota with fewer and taxonomically more closely related species. We discuss how these changes in soil biodiversity due to land use intensification may threaten the functioning of soil in agricultural production systems. This article is protected by copyright. All rights reserved.

The species–area relationship (SAR) is one of the few generalizations in ecology. However, many different relationships are denoted as SARs. Here, we empirically evaluated the differences between SARs derived from nested-contiguous and non-contiguous sampling designs, using plants, birds and butterflies datasets from Great Britain, Greece, Massachusetts, New York and San Diego. The shape of SAR depends on the sampling scheme, but there is little empirical documentation on the magnitude of the deviation between different types of SARs and the factors affecting it. We implemented a strictly nested sampling design to construct nested-contiguous SAR (SACR), and systematic nested but non-contiguous, and random designs to construct non-contiguous species richness curves (SASRs for systematic and SACs for random designs) per dataset. The SACR lay below any SASR and most of the SACs. The deviation between them was related to the exponent f of the power law relationship between sampled area and extent. The lower the exponent f, the higher was the deviation between the curves. We linked SACR to SASR and SAC through the concept of “effective” area (Ae), i.e. the nested-contiguous area containing equal number of species with the accumulated sampled area (AS) of a non-contiguous sampling. The relationship between effective and sampled area was modeled as log(Ae) = klog(AS). A Generalized Linear Model was used to estimate the values of k from sampling design and dataset properties. The parameter k increased with the average distance between samples and with beta diversity, while k decreased with f. For both systematic and random sampling, the model performed well in predicting effective area in both the training set and in the test set which was totally independent from the training one. Through effective area, we can link different types of species richness curves based on sampling design properties, sampling effort, spatial scale and beta diversity patterns.

Several abiotic and biotic factors were investigated as possible predictors of local species richness in two sub-alpine grasslands of Jenna and Belles Mountains in Northern Greece. For species richness modelling a hierarchical modelling framework based on generalized additive models was adopted. The two sub-alpine grasslands differed in aspect, altitude and soil parent material (volcanic origin, mostly trachyte, and andesite (TA) for Jenna and metamorphic rocks, mostly gneiss (G) for Belles). 12 fenced squared plots, 16 m2 each, were used per grassland, where soil properties, herbage production, species presence and cover of grasses, legumes and forbs were estimated. Mean herbage production was significantly affected by slope and altitude, soil K content and floristic composition as expressed by an ordination axis. Soil pH, floristic composition and average herbage production were significant predictors of forbs and total species richness. For the former, soil N content and for the latter the occurrence of Agrostis capillaris, were also included as significant terms in the predictive model. The predictors for grasses species richness were N content, having a positive effect, and average herbage production. In all cases higher species richness was predicted for intermediate values of average herbage production. Differential responses were found between forbs and grasses. The predictors of their species richness were different while for the case of the common predictor (N) the responses of the two groups were also different (grasses species numbers increase and forbs species numbers decreased with increasing N). Maximum species richness of grasses was observed at relatively low production levels while forbs species richness maximized at relatively high production levels.

The combined study of movement patterns and habitat selection, behaviors that are affected by landscape structure, is of critical importance for effective conservation of wildlife. In the same context, maintaining connectivity is a key component for facilitating movement and ensuring species persistence. The brown bear is a wide-ranging predator that moves across large areas, crossing various habitats of different quality. Here, we provide a methodological framework that allowed us to explore the relative importance of habitat quality upon movement patterns and connectivity. First, we developed habitat-suitability models by using telemetry data of eight male brown bears (12,893 radio-locations) collected in Greece. Next, we combined habitat-suitability maps with real movement data to develop graph models that represent movement networks as inter-connected patches of different quality. Network analyses revealed that movement networks demonstrate some well-studied properties regarding their structure and robustness (i.e. scale-free and small-world), providing insights on the contribution of patches of different quality to connectivity. Less suitable patches were found to play a critical role for facilitating brown bear's movement and landscape connectivity. Our findings raise the importance of considering the entire habitat of brown bear in conservation planning rather than isolated patches of high quality, as it might have been revealed by simple habitat-suitability models. Our results highlight the need of assessing the importance of the intervening matrix for facilitating connectivity and movement specifically in the case of large and highly mobile species that do not perceive landscape as strictly dichotomous.

Recent anthropogenic climate change is strongly associated with average shifts toward earlier seasonal timing of activity (phenology) in temperate-zone species. Shifts in phenology have the potential to alter ecological interactions, to the detriment of one or more interacting species. Recent models predict that detrimental phenological mismatch may increasingly occur between plants and their pollinators. One way to test this prediction is to examine data from ecological communities that experience large annual weather fluctuations. Taking this approach, we analyzed interactions over a four-year period among 132 plant species and 665 pollinating insect species within a Mediterranean community. For each plant species we recorded onset and duration of flowering and number of pollinator species. Flowering onset varied among years, and a year of earlier flowering of a species tended to be a year of fewer species pollinating its flowers. This relationship was attributable principally to early-flowering species, suggesting that shifts toward earlier phenology driven by climate change may reduce pollination services due to phenological mismatch. Earlier flowering onset of a species also was associated with prolonged flowering duration, but it is not certain that this will counterbalance any negative effects of lower pollinator species richness on plant reproductive success. Among plants with different life histories, annuals were more severely affected by flowering–pollinator mismatches than perennials. Specialized plant species (those attracting a smaller number of pollinator species) did not experience disproportionate interannual fluctuations in phenology. Thus they do not appear to be faced with disproportionate fluctuations in pollinator species richness, contrary to the expectation that specialists are at greatest risk of losing mutualistic interactions because of climate change.

a b s t r a c t The contribution of common species to overall species richness in many cases is greater than that of rare species. However, the explanation of this phenomenon remains vague. One hypothesis is that this is a sampling issue and not a biological one. Therefore standardization methods like the information index and empirical variance have been proposed. But, these standardizations do not explicitly compare the significance of the dataset size of the common and rare sub-assemblage. Here, we investigate the role of dataset size in accounting for the capacity of common and rare species to contribute to diver- sity spatial patterns. We used a dataset of 5148 vascular plant species recorded in 16,439 sample plots in the Greek Natura 2000 network. Species were ranked according to the number of sample plots they occupied in ascending (rare to common), descending (common to rare) and random order. We analyzed the correlation between the richness of each sub-assemblage and total species richness. When com- paring among sub-assemblages with equal number of species, common species are clearly the better predictors of total species richness. But, when comparing among sub-assemblages with equal number of occurrence records, the patterns changed. Common and rare species contribution to the overall richness pattern was comparable, with rare species contributing slightly less than widespread species in some cases and the opposite in other cases. However in all cases, sub-assemblages of random species remark- ably outperformed the equal sized sub-assemblages of common or rare species. Our results suggest that common and rare species are biased samples of the community and that equal sized random samples are more representative; thus the greater contribution of common species than rare species to biodiversity patterns might be more a sampling issue than a biological effect of commonness or rarity.

The universality of the shape of the species–area relationship (SAR) is subject to regular debate. Recently, Storch et al. (2012) argued that species–area relationships collapse into a single curve at continental scales after the axes are rescaled adjusting the area-axis being to the mean range size of species and the species-axis to the species richness of an area equal to mean range size. It has been claimed that this rescaling generates a universal model, invariant of taxon and continent, and that it is driven by differences in range sizes. Here, we test the universality of the rescaled SAR across scales smaller than the continental level, using presence data for plants, birds and butterflies. We also test an alternative rescaling approach, by using the total extent of the study area and total species richness. At the scales analysed here, we found that the proposed rescaling by Storch et al. adjusts for differences in the extent of the study area and for variation in gamma diversity. Consequently, while the rescaled curves were closely aligned, they did not converge into a single curve. The observed remaining variation is independent of scale and biogeographical region, and is correlated with beta diversity; thus, it reflects the differentiation of species composition in space.

The aims of organic farming are to protect: (a) the environment, by using organic management practices that do not have the adverse effects of conventional practices, and (b) the health of consumers, by the provision of organic products. Using the Greek organic farming sector as an example, it is shown that while this sector is well-developed, it fails to provide the market with labeled organic products. While farmers follow the rules of organic management, thus achieving the first aim, products from just one third of organically managed areas are labeled, thus failing the second aim. Several phenomena indicate an unbalanced development of the organic agricultural sector in Greece, with respect to both farming and marketing. For example, organic green fodder is grown 10 times more than demanded for organic livestock farming. Furthermore, while many other products are imported to cover the country's demand for organic produce, Greek (unlabeled) organic products are sold as conventional. As also documented in most other European member states, financial support to farmers is calculated based on the amount of land being organically cultivated, rather than the overall performance of organic farms. This study highlights the importance of establishing a monitoring procedure that evaluates the performance of organic farming systems, including the outcome of labeled organic products. The development of a sustainable organic agricultural sector, where farming, marketing, economy, and knowledge are interconnected, requires the development of research toward implementing a more sophisticated approach of financing organic farming.

Summary Beta diversity provides a link between species diversity in a region to species diversity within sites. Many metrics have been proposed for its estimation each reflecting a different aspect of the phenomenon. Many of them are more informative of the variation in alpha diversity among samples and the sampling effort (number of sampling units) rather than of the species assemblage differentiation. Here, we propose an index based on the sampling effort needed to fulfil a certain criterion and accounts for the relationship between the initial slope of the species accumulation curve and mean alpha diversity. For defining the index, we consider a set of n samples with S(n) species among R(n) total occurrences. The shared species occurrences are I(n) = R(n) − S(n). The proposed new index (N*) is defined as the point, in terms of n, where I(n) crosses S(n). Samples taken beyond that point (N*) contribute, cumulatively, more to the shared occurrences rather than to new species. For the estimation of N*, we provide the R function ‘Nstar’ based on the specaccum function in the vegan package. We tested the properties of N* on simulated datasets with known community assembly patterns and on a dataset of plant diversity of Greek Natura 2000 protected areas. N* is not mathematically confounded with alpha or gamma diversity. It depends on the relationship between gamma and alpha (Whittaker's index) but, furthermore, it reflects the variation in species occupancies. Thus, if a number of random samples, sufficient for the reliable estimation of mean alpha diversity and the species accumulation curve, is collected, N* converges to a value that does not change by the inclusion of more samples from the same region. N* depends primarily on the proportion of new species expected in each next sample. N* declines with nestedness in community structure, while it increases with species turnover. This holds for plant diversity of Greek Natura 2000, where N* exhibited lower values in island compared to continental regions reflecting the increased nestedness of island communities.

Intensive land use reduces the diversity and abundance of many soil biota, with consequences for the processes that they govern and the ecosystem services that these processes underpin. Relationships between soil biota and ecosystem processes have mostly been found in laboratory experiments and rarely are found in the field. Here, we quantified, across four countries of contrasting climatic and soil conditions in Europe, how differences in soil food web composition resulting from land use systems (intensive wheat rotation, extensive rotation, and permanent grassland) influence the functioning of soils and the ecosystem services that they deliver. Intensive wheat rotation consistently reduced the biomass of all components of the soil food web across all countries. Soil food web properties strongly and consistently predicted processes of C and N cycling across land use systems and geographic locations, and they were a better predictor of these processes than land use. Processes of carbon loss increased with soil food web properties that correlated with soil C content, such as earthworm biomass and fungal/bacterial energy channel ratio, and were greatest in permanent grassland. In contrast, processes of N cycling were explained by soil food web properties independent of land use, such as arbuscular mycorrhizal fungi and bacterial channel biomass. Our quantification of the contribution of soil organisms to processes of C and N cycling across land use systems and geographic locations shows that soil biota need to be included in C and N cycling models and highlights the need to map and conserve soil biodiversity across the world.

Nowadays that biodiversity monitoring is a legal obligation in many countries, monitoring implementation still lags behind the needs for efficient conservation. This is mainly due to three limiting factors that are rarely available for an exhaustive diversity survey, i.e. time consuming, expensive and demands high level of expertise. We propose an alternative monitoring scheme based on the higher taxon approach. This approach allows rapid tracking of biodiversity changes and the utilization of data collected by non-expert volunteers. Here we show, for the first time, that temporal changes in genera or family richness are strongly correlated to, and have similar spatial pattern characteristics as changes in species richness for the breeding birds in New York State. Changes in genera richness proved more reliable in predicting changes in species richness than changes in family richness.

Soil disturbances that exert strong impacts on biota and their resources are also expected to induce changes in the web of interactions among soil variables. The objective of this paper was to explore the hypothesis that during the first years after the conversion from conventional to organic farming gradual changes occur in the correlations among the nematode, microbial and nutrient flow components, resulting in increased complexity of the soil system. To test this hypothesis, we used network analysis techniques to analyze data from conventional (Conv) and organic asparagus cultivations, as well as from the adjacent hedgerows (Hedg). Organic cultivations were managed organically for 2, 3 and 5 years (Org-2, Org-3, Org-5), representing thus steps along a gradient that corresponds to the duration of organic farming. The estimated network cohesion and centrality, as well as the key player metrics, showed that the correlation network of the newest organic systems, and mostly that of Org-3, was disorganized compared with that of Conv. This trend was reversed, and a complex and more cohesive network was formed in Org-5. In addition, by employing QAP techniques and Spearman rank correlation coefficients, inter-network correlations were estimated and similarities were found between the correlation network from Org-2 and that of Org-3. The structure of the latter was correlated with that from Org-5. Our results indicated that the conversion of a conventional system to organic induces a disturbance into the soil system routine, probably launching secondary successional changes in the interactions among soil components. These changes seem to involve the gradual destruction of existing interactions leading to the disorganization of the correlation network and the reconstruction of a more complicated one after 3–5 years.

Summary 1. Halting biodiversity loss, a major environmental challenge, relies on the understanding of species richness patterns. The assessment of species richness is often hampered by limited taxonomic knowledge and the general dearth of trained systematists. Research has shown that we can predict the number of species in a community by the number of higher order taxonomic units present. Here, we test whether we need to know all the genera, families or orders in order to do so. Further, the number of common species in a region is a good predictor of total richness and we test if this predictability translates to using higher taxa. 2. We used data from 240 sites from the Natura 2000 network of protected areas in Greece, including 5148 plant species and subspecies, which are grouped in 1113 genera 174 families and 56 orders. We correlated species richness with the number of common genera, families or orders present. The analysis was repeated using the number of the most speciose higher orders instead of the most common. 3. We found that we do not need to know all higher order taxa present, in order to predict species richness. If we know how many out of the 30 most common orders are present, we can reliably predict the number of species. Similar results were obtained if we know how many of the 60 most common families or 200 most common genera are present. 4. Equally good results were obtained using the same numbers of the most speciose higher orders. 5. Synthesis and applications. Our analysis demonstrates that species richness can be predicted from the number of common or more speciose genera, families and orders present. These predictions hold without complete sampling of these higher taxa. The implication is that we need only limited systematic knowledge, resources and effort in order to predict species richness. Assuming these findings hold in other taxonomic groups and in other regions, we argue that the uncertainty introduced by limited knowledge of the systematics of less studied taxa should not be used as an excuse to avoid making conservation decisions.

The sea surface temperature (SST) in loggerhead turtle breeding areas affects the species reproductive biology. Less is known about the effects of changes in SST in the species foraging grounds. We used nesting data for the Mediterranean loggerhead turtle population breeding on the Greek island of Zakynthos to study the effect of SST in the population foraging grounds upon the initiation of nesting and the number of clutches laid. We found that the climatic conditions (SST) in the foraging grounds affected the population nesting phenology in the short term (i.e. within the same year); warmer years triggered an earlier onset of nesting. However, the effect of foraging grounds SST upon nesting is comparatively less important than the local conditions at the nesting ground. Although nesting phenology seems to depend on current's year foraging grounds SST the number of nests in our study rookery were negatively correlated with SSTs recorded 2 years prior nesting, with higher SST leading to fewer nests. From this point of view, climate change at the foraging grounds may influence the reproductive phenology of loggerheads.

– We examined the relative contribution of environmental heterogeneity and dispersal limitation on freshwater fish community composition in 18 Greek protected lakes and reservoirs. Environmental heterogeneity was measured by spatial pattern metrics (calculated by digital map processing, e.g., patch richness density, area-weighted mean patch area), altitude, maximum lake depth and trophic status. Dispersal limitation was measured by straight-line distances among lake centres. Ecosystems were clustered according to species composition. We examined the correlation of similarity in species composition among ecosystems with that of environmental heterogeneity and with straight-line distances, for the entire dataset, as well as for the occurring clusters. Fish species richness increased with ecosystem area and decreased with altitude. The clusters identified (aquatic ecosystems of Northern vs. ecosystems of Western Greece), implied an underlying biogeographical pattern as defined, with Pindus range acting as a natural barrier. Between ecosystems similarity, based on fish species composition, showed a weak to insignificant correlation with environmental heterogeneity, but was significantly correlated to dispersal limitation for the entire dataset as well as within each occurring cluster. Thus, natural barriers, species biogeography and dispersal limitation played a more significant role in shaping freshwater fish communities than environmental heterogeneity.

Common farmland birds are declining throughout Europe; however, marginal farmlands that escaped intensification or land abandonment remain a haven for farmland species in some Mediterranean mountains. The purpose of this study is to identify the most important anthropogenic microhabitat characteristics for Red-Backed Shrike (Lanius collurio), Corn Bunting (Miliaria calandra) and Common Whitethroat (Sylvia communis) in three such areas within the newly established Northern Pindos National Park. We compare land use structural and physiognomic characteristics of the habitat within 133 plots containing birds paired with randomly selected "non-bird" plots. Using logistic regression and classification-tree models we identify the specific habitat requirements for each of the three birds. The three species show a preference for agricultural mosaics dominated by rangelands with scattered shrub or short trees mixed with arable land. Areas with dikes and dirt roads are preferred by all three species, while the presence of fences and periodically burned bushes and hedges are of particular importance for Red-Backed Shrike. Across the gradient of vegetation density and height, M. calandra is mostly found in grasslands with few dwarf shrubs and short trees, S. communis in places with more dense and tall vegetation of shrub, trees and hedges, and L. collurio, being a typical bird of ecotones, occurs in both habitats and in intermediate situations. In all cases those requirements are associated with habitat features maintained either directly or indirectly by the traditional agricultural activities in the area and particularly by the long established extensive controlled grazing that prevent shrub expansion.

Plant–pollinator interaction networks are characterized by several features that cannot be obtained from a totally random network (e.g. nestedness, power law distribution of degree specialization, temporal turnover). One reason is that both plants and pollinators are active for only a part of the year, and so a plant species flowering in spring cannot interact with a pollinator species that is active only in autumn. In this paper we build a stochastic model to simulate the plant–pollinator interaction network, taking into account the duration of activity of each species. To build the model we used an empirical plant–pollinator network from a Mediterranean scrub community surveyed over four years. In our simulated annual cycle we know which plant and pollinator species are active, and thus available to interact. We can obtain simulated plant–pollinator interaction networks with properties similar to the real ones in two different ways: (i) by assuming that the frequency distribution of both plant and pollinator duration of activity follow an exponential function, and that interaction among temporally coexisting species are totally random, and (ii) by assuming more realistic frequency distributions (exponential for pollinators, lognormal for plants) and that the interaction among coexisting species is occurring on a per capita basis. In the latter case we assume that there is a positive relationship between abundance and duration of activity. In our model the starting date of the species activity had little influence on the network structure. We conclude that the observed plant–pollinator network properties can be produced stochastically, and the mechanism shaping the network is not necessarily related to size constraints. Under such conditions co-evolutionary explanations should be given with caution.

Global climate change is likely to have an important influence on the phenology, behaviour and population dynamics of many species. We investigate climatic related changes in the breeding phenology of Mediterranean loggerhead marine turtles Caretta caretta over a 19 year period and the potential relationship between these changes and reproductive success and performance. We found that the studied population has experienced fluctuating sea surface temperatures (SST) with an increasing trend during the last century. With increasing spring SST there is a trend towards earlier nesting. However, there is no significant relationship between SST and nesting season, defined as the duration between the first recorded emergence and the last nest laid. Our analyses indicate that marine turtles display phenological changes, and thus maintain favorable thermal conditions at the nesting sites. Furthermore, increasing spring SST was correlated with decreasing clutch size and increasing hatching success that resulted in an apparent lack of correlation between SST and hatchling production. This apparent independence might be misleading since it only holds for a limited range of SST values. Thus, if we estimate the effect of climate change on loggerhead population growth as neutral, based on the apparent independence between SST and total number of hatchlings, we will be underestimating the population extinction risk.

Aim To examine the way in which ‘area’ and ‘habitat diversity’ interact in shaping species richness and to find a simple and valid way to express this interaction. Location The Natura 2000 network of terrestrial protected areas in Greece, covering approximately 16% of the national territory. Methods We used the Natura 2000 framework, which provides a classification scheme for natural habitat types, to quantify habitat heterogeneity. We analysed data for the plant species composition in 16,143 quadrats in which 5044 species and subspecies of higher plants were recorded. We built a simple mathematical model that incorporates the effect of habitat diversity on the species–area relationship (SAR). Results Our analysis showed that habitat diversity was correlated with area. However, keeping habitat diversity constant, species richness was related to area; while keeping area constant, species richness was related to habitat diversity. Comparing the SAR of the 237 sites we found that the slope of the species–area curve was related to habitat diversity. Main conclusions Discussion of the causes of the SAR has often focused on the primacy of area per se versus habitat heterogeneity, even though the two mechanisms are not mutually exclusive and should be considered jointly. We find that increasing habitat diversity affects the SAR in different ways, but the dominant effect is to increase the slope of the SAR. While a full model fit typically includes a variety of terms involving both area and habitat richness, we find that the effect of habitat diversity can be reduced to a linear perturbation of the slope of the species accumulation curve.

The breeding biology of the spur‐winged plover Hoplopterus spinosus was studied in the Evros Delta during 2003. Nest selection was studied at a microhabitat level. The factors found to affect this selection were: distance from the nearest bush, sum of angles of optical scope on a radius of 50m, sum of angles of optical scope on a radius of 100m and distance from the nearest conspecific nest. The logistic regression model identified the factors: sum of angles of optical scope on a radius of 100m, surface covered by water, surface covered by bare ground and surface covered by the dominant plant as important microhabitat features for the prediction of the nest location. Regarding breeding performance, hatching success was estimated at 42%, while fledging success was estimated at 41%. Irregular flooding and trampling by grazing animals were the main factors found to affect nest failure. Management proposals for the protection of the species were given in relation to these factors.

Different environmental factors act as driving forces of diversity at different scales of analysis; and also the effect of one environmental factor changes as the scale of analysis changes. Most studies rely on multiple regression models, and such models tend to mix-up the effect of all factors and assume that factors effects are additive. We believe that the effect of environment on diversity should be characterized by a hierarchical structure with coarse scale factors, like geographical tropics to poles gradients, defining the envelope of possible diversity conditions, and other more local factors, like habitat structure, being responsible for the fine tuning of diversity. This structure is most efficiently modeled with regression trees. We show that for six habitat types in Greek protected areas regression tree models were able to describe plant species richness based upon environmental factors considerably more efficiently than multiple regression models. More importantly when the models were extrapolated to other sites in Greece, outside their domain, the differences between the predictive ability of the two approaches was magnified. The tree models picked up important ecological characteristics, and a hierarchical structure that used coarse scale factors, like latitude and longitude, for the coarse scale estimate of alpha diversity, and finer scale factors like fragmentation, for the fine-tuning of the estimation. Therefore, we advocate that the regression tree methodology is most appropriate for modeling the relationship between diversity and environmental factors, and the use of the classical regression approaches might be misleading.

The temporal and spatial distribution, and the life strategies, of fifteen grass species in a Mediterranean evergreen sclerophyllous formation at Petralona (Chalkidiki, Greece) were studied in order to identify the relationships between species, and among species and the environment, which allows for the coexistence of species. The grass species were grouped into (i) early annual species that were characterized by early germination and a relatively long growth period; they did not need excessive resources and were distributed over the entire site, (ii) late annuals that were characterized by late germination and a short growth period; they required resources within this limited period and were competitive in capturing them and so were confined to the most productive sites of the site and (iii) perennial grasses that were characterized by early germination and vegetative reproduction; they were tolerant to nutrient shortages and hence maintained their distribution on the site. The spatial arrangement of species can be considered as a response to the selective pressures of the seasonal water and resource availability in a Mediterranean environment. This environment posed temporal limitations on the activity of early annual and late annual species, which restricts them in time and space. The perennial species overcame this by being flexible in their resource capture and use, because of their ability to store nutrients.

In this study we experimentally manipulated the precipitation pattern (frequency and intensity) in a Mediterranean pine forest on Mt. Holomon (northern Greece) in order to investigate the response of soil microarthropods (Collembola and oribatid mites). Our experimental treatments included drought, frequent and infrequent irrigation and lasted for 4 months. The treatments affected soil water content, maximum soil temperature and diversity of soil microarthropods. Compared to the undisturbed surrounding area, drought decreased soil water content as well as microarthropod species richness and increased maximum soil temperature. Irrigation treatments increased soil water content and microarthropod species richness. Infrequent irrigation increased maximum soil temperature. Oribatid mites and Collembola responded differently to the irrigation treatments. The collembolan community showed higher species evenness and diversity in the frequently irrigated plots and the oribatid mite community in the infrequently irrigated ones. Our results indicate that irrigation pattern (and the corresponding changes in soil moisture) will have an impact on soil ecosystems in complicated non-linear ways.

Recent extinction models generally show that spatial aggregation of habitat reduces overall extinction risk because sites emptied by local extinction are more rapidly recolonized. We extended such an investigation to include spatial structure in the disturbance regime. A spatially explicit metapopulation model was developed with a wide range of dispersal distances. The degree of aggregation of both habitat and disturbance pattern could be varied from a random distribution, through the intermediate case of a fractal distribution, all the way to complete aggregation (single block). Increasing spatial aggregation of disturbance generally increased extinction risk. The relative risk faced by populations in different landscapes varied greatly, depending on the disturbance regime. With random disturbance, the spatial aggregation of habitat reduced extinction risk, as in earlier studies. Where disturbance was spatially autocorrelated, however, this advantage was eliminated or reversed because populations in aggregated habitats are at risk of mass extinction from coarse-scale disturbance events. The effects of spatial patterns on extinction risk tended to be reduced by long-distance dispersal. Given the high levels of spatial correlation in natural and anthropogenic disturbance processes, population vulnerability may be greatly underestimated both by classical (nonspatial) models and by those that consider spatial structure in habitat alone. Resumen: Los modelos recientes de extincion generalmente muestran que la agregacion espacial de habitat reduce el riesgo de extincion debido a una recolonizacion mas rapida de sitios vacios por extincion local. Extendimos la investigacion para incluir la estructura espacial en el regimen de perturbacion. Desarrollamos un modelo metapoblacional espacialmente explicito en el que el patron espacial tanto del habitat como de los regimenes de perturbacion podia variar aleatoriamente de fractal a completamente agregado (bloque) y con una amplia gama de distancias de dispersion. El incremento de la agregacion espacial de la perturbacion generalmente incremento el riesgo de extincion. El riesgo relativo que enfrentan poblaciones en paisajes diferentes fue muy variable, dependiendo del regimen de perturbacion. Con perturbacion aleatoria, la agregacion espacial de habitat redujo el riesgo de extincion, como en estudios anteriores. Sin embargo, cuando la perturbacion estaba autocorrelacionada espacialmente, esta ventaja se eliminaba o invertia debido a que las poblaciones en habitats agregados estan en riesgo de extincion masiva por eventos perturbadores a escala gruesa. Los efectos de patrones espaciales sobre el riesgo de extincion tendieron a reducirse por la dispersion de larga distancia. Debido a los altos niveles de correlacion espacial en los procesos naturales y humanos de perturbacion, la vulnerabilidad puede estar enormemente subestimada tanto por modelos clasicos (no espaciales) como por los que solo consideran la estructura espacial del habitat. Los modelos que consideran la estructura espacial del habitat solo subestiman el riesgo en comparacion con modelos que consideran la estructura especial de la perturbacion.

Fractals have found widespread application in a range of scientific fields, including ecology. This rapid growth has produced substantial new insights, but has also spawned confusion and a host of methodological problems. In this paper, we review the value of fractal methods, in particular for applications to spatial ecology, and outline potential pitfalls. Methods for measuring fractals in nature and generating fractal patterns for use in modelling are surveyed. We stress the limitations and the strengths of fractal models. Strictly speaking, no ecological pattern can be truly fractal, but fractal methods may nonetheless provide the most efficient tool available for describing and predicting ecological patterns at multiple scales.

Summary In this paper we describe and compare the oribatid distribution patterns at two scales: a regional scale corresponding to an altitudinal gradient and a local one created by the variation of vegetation cover. Distribution patterns at the local scale are assessed by sampling under the canopy of the Juniperus sp. shrubs, which are scattered all along the altitudinal gradient, and at the adjacent grass-covered openings. Our results showed that the two scale effects are not equally important in shaping the oribatid communities. Altitude per se does not induce clear distribution patterns, acting mostly indirectly through the effect on the formation of local vegetation. In contrast, profound differences in the structure of oribatid communities are imposed by the local scale effect, which consists of strong microclimatic fluctuations in the exposed grassy sites and litter accumulation in the sheltered shrubby sites. Oribatids respond to the two scale effects, forming separate communities with distinct characteristics. The temporal heterogeneity of the exposed habitats at all altitudes leads to a temporal separation of oribatid niches and to a seasonal succession of communities. The structural heterogeneity of the shrubby habitats is responsible for a more complicated and site-specific differentiation of communities; oribatid species of shrubby sites are either capable of inhabiting the open sites as well or persist throughout the whole year.

We carry out a simulation study of the estimation of fractal dimension in a grid-based setting typical of ecological species distributions, using null landscape models. We calculate the box-counting dimension for samples taken in various types of sampling geometry. Sampler geometries include simple blocks,Cantor grids and line transects. This method may be used to measure fractal dimension of a species distribution, but the accuracy depends on a number of criteria. The most important is sampling effort: any estimate will be inaccurate if the sampling effort is low. We also find the geometry of the sampler to be important. For a given sampling effort, schemes based on the Cantor grids performed better than either line transects or simple blocks. Sampling effort can be improved either by using a bigger sampler over a larger area or by repeated sampling of a smaller area: optimum performance is often a trade-off between these two mechanisms. However, performance is also highly sensitive to the type of fractal object being sampled, with certain types of object requiring a much greater effort for an accurate estimate of fractal dimension. These results raise the possibilities of using novel sampling techniques to estimate fractal dimension, when confronted with limited resources and time, but underline also the need for an understanding of the “type” of fractality expected in ecological situations.

Apparent leaf photosynthesis of the grass Stipa bromoides was measured in the field in two sites of Northern Greece. For predicting apparent photosynthesis from irradiance, temperature and relative air humidity data, we applied and compared two modelling approaches: ordinary statistical modelling and automatic model construction based on machine learning procedures. Ordinary statistical models were constructed based on background knowledge concerning the response of photosynthesis to irradiance. A Michaelis–Menten type light saturation curve was selected among six candidate models and was extended to include air temperature effects. A bell-shaped function of temperature was substituted for the parameter describing the asymptotic maximum photosynthesis. The final model accounted for 67.3% of data variation and was further improved by splitting the data set by experimental site. Site-specific differences were detected regarding the half saturation constant for light and the optimal temperature for photosynthesis. Automatic model construction produced a number of regression trees that enabled a detailed but simple description of the way irradiance, temperature and relative humidity affect photosynthesis. Photosynthesis increases with increasing irradiance, temperature affects photosynthesis when irradiance is close to saturation levels and relative humidity has an effect when both irradiance and temperature are high. There is a threshold value of relative humidity (at about 35%), below which photosynthesis is independent of irradiance within the observed range, decreasing with increasing temperature when temperature is high (>25°C) and increasing with increasing relative humidity when temperature is low (

In this study the morphological ontogeny, distribution and ecology of Edwardzetes edwardsii (Nicolet, 1855) and Sphaerozetes orbicularis (C.L. Koch, 1835) were investigated. The latter species looks strikingly similar to S. piriformis (Nicolet, 1855), and was recognized by a rounded distal part of lamellar cusp, which in S. orbicularis had an outer spine. However, the shape of the lamellar cusp varies in Norwegian adults of S. orbicularis being rounded or with one or two spines, which puts in question the validity of S. piriformis. Our study on the morphology of juveniles of these two morphological forms of S. orbicularis also indicates that they are identical, so we provisionally consider S. piriformis as a junior synonym of S. orbicularis (syn. nov.). The juveniles of E. edwardsii and S. orbicularis have a humeral organ and a humeral macrosclerite, which is common in Sphaerozetinae, and carry seta c1 on the humeral macrosclerite. In the juveniles of E. edwardsii most gastronotal setae are of medium size and blunt, but the gastronotal shield of the larva is divided in two parts, whereas in the nymphs this shield is uniform. In all juvenile stages of S. orbicularis the gastronotal setae are short and the gastronotal shield is uniform. The adult of E. edwardsii has a rounded rostrum and 10 pairs of long notogastral setae, including c2, whereas that of S. orbicularis has rostrum with two deep incisions and 11 pairs of short notogastral setae, including c2 and c3, which is typical of Sphaerozetes Berlese, 1885, but unique in Sphaerozetinae. Edwardzetes edwardsii has a holarctic distribution, whereas S. orbicularis is a Palaearctic species. The former species prefers forest litter, whereas the latter species prefers moss.

The phenology ofAsphodelus aestivus Brot. is described by means of a phenological model which has been formulated to fit skewed phenological data. Based on the model parameters the timing of different phenophases of biomass accumulation were determined. The biomass oscillations of leaves, inflorescence stalks and tubers were found to be synchronized with the predictable seasonal climatic changes. In addition, the plant seems to respond to minor random climatic variations. The emergence of leaves and inflorescence stalks depends on stored material in the tubers while leaf and inflorescence stalk elongation as well as flowering depends on current production. The storage part of the tubers seems to be a regulating structure, which is responsible for the synchronization ofA. aestivus productivity with the seasonality of the Mediterranean climate.A. aestivus is considered to be a Competitor Ruderal and Stress tolerant (C-R-S) strategist which may explain the wide distribution of this plant over the Mediterranean Basin.

The combustion of petroleum fuel and exhaust emissions are major sources of atmospheric pollution in cities which result in the deposition of toxic substances, particularly heavy metals, in the surface layers of soils. Lead in particular enters the environment from the use of tetraethyl lead as an antiknock agent for petrol engines constituting 21% of fine particles emitted from cars burning leaded petrol. Antiwear protectants incorporated in lubricants often contain Cd, Cr, Cu, Hg, Ni, Pb and/or Zn which are also released into the environment by inefficient engines and irresponsible dumping of engine oils. Zn from tyre wear and Cu from diesel engines also add considerably to the environmental metal burden. Lowering of the permitted lead content of petrol and the growing use of unleaded fuel are expected to lead to reductions in the environmental lead burden, however, until unleaded fuel becomes universally accepted lead contamination, particularly of roadside soils and vegetation is a major cause for concern. A direct relationship between car exhaust, the Pb content of needles of Abies alba and reduced growth has been observed and can extend hundreds of metres from major highways. Lead tolerance has been observed in higher plants growing mine waste soils andmore » to a lesser extent on lead-contaminated roadside soils. Automobiles which are responsible for line sources of pollution emissions in rural and suburban areas have a more far-reaching impact on roadside vegetation, already under considerable stress, in urban areas. Information on heavy metal effects on vegetation in urban environments however, are scarce. Modeling and multivariate analysis of a few of the factors involved have provided only limited data related to plant performance in these complex environments. Therefore in this study, the extent of heavy metal pollution by Pb, Zn, Cu and Cd in soils and in dandelion plants in the city of Thessaloniki has been examined. 20 refs., 2 figs., 3 tabs.« less

The effect of a summer wildfire on the abundance and community composition of soil macroinvertebrates of a phryganic ecosystem was studied. The numerical responses of macroinvertebrates to fire were variable, most notably the reduction of the saprophagous fauna. The magnitude of the changes in abundance due to fire was comparable or even lower than the variations imposed by the seasonality of the mediterranean climate. fire did not seem to affect strongly the community composition of the soil inhabiting fauna, but caused considerable changes in the composition of the litter-dwellers. Furthermore, seasonal changes in community composition were less pronounced in the burnt site compared to those in the control. The observed effects of fire should be attributed to the destruction of the litter layer and the above ground vegetation cover, rather than to the immediate death of the animals, since most of them were absent from the upper soil layers during summer, that is when fire occured.

A model is formulated aiming to describe census data for populations changing non-symmetrically with time. The model is based on the concept of ecological time, conceived as an environmental gradient. A method of changing time scales. by using a periodic equation relating ecological to standard clock time unit, is presented. The model has been applied to simulate phenological curves of population abundance for oribatid mites and Collembola from a Mediterranean ecosystem