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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 (

The annual range of Balkan chamois (Rupicapra rupicapra balcanica) in Giona mountain was found to be 5502 ha, with a low population density (2 individuals/100 ha). Seasonal range patterns varied significantly, with a minimum extent in summer and a maximum in winter (30% and 79% of the annual range, respectively). Summer stress and the rutting period might be associated with the observed aggregated distributions during the summer and autumn (core areas of 28% and 22% of seasonal ranges, respectively, defined after the Fixed Kernel Density Estimator). Chamois were found to use significantly lower altitude habitats in winter (1212 m) than in summer (2223 m), and significantly steeper slopes in winter (35°); aspect was not found to have a significant effect on habitat use. Population structure consisted of kids (21%), yearlings (8%), females (35%) and males (36%). Conservation management for the species should consider poaching, livestock competition and global warming.

Worldwide, there is a well-documented crisis for bees and other pollinators which represent a fundamental biotic capital for wild life conservation, ecosystem function, and crop production. Among all pollinators of the world, bees (Hymenoptera: Apoidea) constitute the major group in species number and importance, followed by hover flies (Diptera: Syrphidae). The Aegean constitutes one of the world’s hotspots for wild bee and other pollinator diversity including flies (mainly hover flies and bee flies), beetles, and butterflies. Despite this advantage, our present knowledge on Greek pollinators is poor, due to a lack of focused and systematic research, absence of relevant taxonomic keys, and a general lack of taxonomic experts in the country. As a result, assessments of pollinator loss cannot be carried out and the causes for the potential pollinator loss in the country remain unknown. Consequently, the desperately needed National Red Data list for pollinators cannot be compiled. This new research (2012–2015) aims to contribute to the knowledge of the pollinator diversity in Greece, the threats pollinators face, as well as the impacts these threats may have on pollination services. The research is conducted in the Aegean archipelago on >20 islands and several mainland sites in Greece and Turkey. Prime goals are: i. the assessment of bee and hover fly diversity (species, genetic); ii. their pollination services; and iii. the effects of climate change, grazing, intensive bee-keeping, fires, electromagnetic radiation on bee diversity and ecology, as well as on plant–pollinator networks. At the same time, this research contributes to the taxonomic capital in Greece and the Eastern Mediterranean, focusing on the creation of the first identification keys for pollinators, the training of new scientists, as well as the enrichment and further development of the Melissotheque of the Aegean, a permanent reference collection of insect pollinators established at the University of the Aegean. En todo el mundo hay una crisis bien documentada para las abejas y otros polinizadores los cuales representan un capital biótico fundamental para la conservación de la vida silvestre, la función de los ecosistemas, y la producción de cultivos. Entre todos los polinizadores del mundo, las abejas (Hymenoptera: Apoidea) constituyen el grupo principal en cuanto al número de especies y su importancia, seguido por los sírfidos (Diptera: Syrphidae). El Egeo constituye uno de los puntos importantes de diversidad de abejas silvestres y otros polinizadores del mundo, incluyendo moscas (principalmente sírfidos y bombílidos), escarabajos y mariposas. A pesar de esta ventaja, los conocimientos actuales sobre los polinizadores griegos son reducidos, debido a la falta de una investigación focalizada y sistemática, la ausencia de claves taxonómicas pertinentes, y una falta general de expertos en taxonomía en el país. Como resultado, no se pueden llevar a cabo evaluaciones de la pérdida de polinizadores y las causas de la pérdida potencial de polinizadores en el país siguen siendo desconocidas. En consecuencia, la imperiosamente necesitaba Lista Roja de datos para polinizadores no se puede compilar. Esta nueva investigación (2012-2015) tiene como objetivo contribuir al conocimiento de la diversidad de polinizadores en Grecia, enfrentarse a las amenazas para los polinizadores, así como investigar el impacto que estas amenazas pueden tener sobre los servicios de polinización. La investigación se llevará a cabo en el archipiélago del mar Egeo en más de 20 islas y en varios sitios del continente en Grecia y Turquía. Los principales objetivos son: i. la evaluación de la diversidad de abejas y sírfidos (especies, genética); ii. sus servicios de polinización, y iii. los efectos del cambio climático, el pastoreo, la apicultura intensiva, los incendios y las radiaciones electromagnéticas sobre la diversidad de abejas y la ecología, así como en las redes planta-polinizador. Al mismo tiempo, esta investigación contribuirá a la taxonomía en Grecia y el Mediterráneo Oriental, centrándose en primer lugar en la creación de las claves de identificación para polinizadores, la formación de nuevos científicos, así como el enriquecimiento y el desarrollo de la Melisoteca del Egeo, una colección de referencia permanente de los insectos polinizadores establecidos en la Universidad del Egeo. This research is co-financed by the European Union (European Social Fund—ESF) and Greek national funds through the Operational Program “Education and Lifelong Learning” of the National Strategic Reference Framework (NSRF) - Research Funding Program: Thales -Investing in knowledge society through the European Social Fund.

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.

Chlorophyll-α fluorescence induction kinetics of dark-adapted leaves of Sonchus spp. were measured in plants from areas of differing levels of urban pollution. Significant increases (∼ 200%) in the minimal (Fo) and maximal (Fm) fluorescence and decreases (∼ 50%) in the half-rise time from Fo to FM (t12) were observed for plants in areas of high pollution. A stress index factor (SIF) was derived based on the variation in these variables, using canonical variance analysis, which increased with increasing pollution levels. Significant linear relationhips between the fluorescence parameters of Sonchus spp. and Taraxacum spp. indicate that both plants exhibit the same changes in their chlorophyll fluorescence patterns in response to the pollution gradient. The ratio of Fm/Fo had a mean value of 5.2 ± 0.24 for Taraxacum spp. and 4.9 ± 0.23 Sonchus spp. No significant variation in the ratio of variable to maximal fluorescence (Fv/Fm) was observed (0.75–0.82) which indicated that the efficiency of the primary photochemistry of photosystem II was not directly affected by pollution level. The concentrations of Pb, Zn and Cu in the soil and plant tissue were higher in areas of higher traffic density and air pollution. Individual or combinations of the metal concentrations significantly accounted for at least 53% of the variation in SIF for both Taraxacum spp. and Sonchus spp.

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.

We analysed the dynamics of a plant-pollinator interaction network of a scrub community surveyed over four consecutive years. Species composition within the annual networks showed high temporal variation. Temporal dynamics were also evident in the topology of the network, as interactions among plants and pollinators did not remain constant through time. This change involved both the number and the identity of interacting partners. Strikingly, few species and interactions were consistently present in all four annual plant-pollinator networks (53% of the plant species, 21% of the pollinator species and 4.9% of the interactions). The high turnover in species-to-species interactions was mainly the effect of species turnover (c. 70% in pairwise comparisons among years), and less the effect of species flexibility to interact with new partners (c. 30%). We conclude that specialization in plant-pollinator interactions might be highly overestimated when measured over short periods of time. This is because many plant or pollinator species appear as specialists in 1 year, but tend to be generalists or to interact with different partner species when observed in other years. The high temporal plasticity in species composition and interaction identity coupled with the low variation in network structure properties (e.g. degree centralization, connectance, nestedness, average distance and network diameter) imply (i) that tight and specialized coevolution might not be as important as previously suggested and (ii) that plant-pollinator interaction networks might be less prone to detrimental effects of disturbance than previously thought. We suggest that this may be due to the opportunistic nature of plant and animal species regarding the available partner resources they depend upon at any particular time.

Understanding how the ecological niches of species are formulated across space is critical for modeling the current and predicting future distributions under climate change. Here, we examine how stable are the realized niches of distinct populations of the endangered green sea turtle (Chelonia mydas) which are defined on the basis of genetic and demographic data and are distributed around the globe. We used 906 georeferenced records of green turtle nesting sites that are embedded within eight Regional Management Units to compare climatic niche for each one of the distinct units. We used an asymmetric overall index and a decision-tree model to assess niche conservatism through a comparison of temperature- and precipitation-based bioclimatic variables that characterize the climatic niche breadth of the spatially distinct population segments. We found a high degree of variance in climatic space, which also lacks any latitudinal pattern. Environmental determinants vary significantly across the studied population units: variables that have been long-recognized as critical for nesting (e.g., maximum temperature of the warmest month) showed only low overlap between some of different regional entities. Our results contribute substantially to the current debate on the predictive power of species distribution models that use only climate variables as predictors when aggregating data from various populations. We argue that studies on climatic-niche evolution and divergent ecological selection mechanisms are required before attempting to identify suitable habitats for a species, describe climatic widths and search for plausible expansions of geographical shifts attributed to climate change.

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