2013. szeptember 27., péntek

Giokas et al. (2013) Evolutionary Ecology

Morphological variation is often attributed to differential adaptations to diverse habitats, but adaptations to a similar environment do not necessarily result in similar phenotypes. Adaptations for water and heat budget are crucial for organisms living in arid habitats, and in snails, variation in shell morphology has been frequently attributed to selection by stressful environmental factors. However, their phenotypic divergence often is not accompanied by a relevant niche differentiation and consistent relationships with environmental correlates are lacking. In the pulmonate genus Albinaria, there is great size and shape variation between and within species, and there are two major shell sculpture morphotypes, ribbed and smooth. We used 62 populations of 28 Albinaria species, taking into account their phylogeny, to examine the variation of shell traits (sculpture, size, shape), their effect on water and heat budget, and their association with geographical and climatic gradients. We found unambiguous size and shape discrimination between the two morphotypes. Ribbed shells are lighter, taller, and slimmer and have a smaller aperture than the smooth ones. Moreover, significant correlations between shell traits and heat/moisture budget and climate/geography were revealed. Ribbed and taller shells retain more water on their shell surface, and on the other hand, smooth shells exhibit lower water permeability. Therefore, two strategies are being used to prevent water loss, active retention or resistance to loss. Consequently, different alternative solutions evolved and were retained as responses to the same stressful factor by the two distinct shell morphotypes. Larger shells occur in southern latitudes, mostly on islands, and at sites where there is a shortage of rainfall. Therefore, the variation of the examined traits is nonrandom with respect to location and to climate and their evolution can be attributed to selection by environmental factors, with water availability being the key driving agent of body-size variation.

Sculpture, Size, Shape, Adaptation, Tradeoff, Environmental gradients

2013. szeptember 25., szerda

Habel et al. (2013) Biodiversity and Conservation

Jan Christian Habel, Jürgen Dengler, Monika Janišová, Péter Török, Camilla Wellstein, Michal Wiezik (2013) European grassland ecosystems: threatened hotspots of biodiversity.Biological Conservation 22(10): 2131-2138.

Biodiversity is not homogenously distributed over the globe, and ecosystems differ strongly in the number of species they provide. With this special issue we highlight the ecology and endangerment of one of the most diverse ecosystem of Europe: the European grassland ecosystems. The selected 16 contributions describe interactions from below-ground to the atmosphere and focus on (1) effects of abiotic and biotic on species diversity, (2) the impact of various factors along spatial and temporal gradients, (3) the relevance of falling abandoned and eutrophication—including countervailing management strategies like encroachment; and (4) intraspecific effects based on physiology, genetics and intraspecific plasticity. The contributions cover fungi, plants, and invertebrates and highlight effects taking place at the level of ecosystem, species community, species, populations, and also within individuals (physiology and genetics).

Abandonment, Animal assemblage, Conservation management, Diversity hotspot, Eutrophication, Plant community, Species richness

2013. szeptember 17., kedd

Endresz et al. (2013) Community Ecology

Recent research indicates that the soil microbial community, particularly arbuscular mycorrhizal fungi (AMF), can influence plant invasion in several ways. We tested if 1) invasive species are colonised by AMF to a lower degree than resident native species, and 2) AMF colonisation of native plants is lower in a community inhabited by an invasive species than in an uninvaded resident community. The two tests were run in semiarid temperate grasslands on grass (Poaceae) species, and the frequency and intensity of mycorrhizal colonisation, and the proportion of arbuscules and vesicles in plant roots have been measured. In the first test, grasses representing three classes of invasiveness were included: invasive species, resident species becoming abundant upon disturbance, and non-invasive native species. Each class contained one C3 and one C4 species. The AMF colonisation of the invasive Calamagrostis epigejos and Cynodon dactylon was consistently lower than that of the non-invasive native Chrysopogon gryllus and Bromus inermis, and contained fewer arbuscules than the post-disturbance dominant resident grasses Bothriochloa ischaemum and Brachypodium pinnatum. The C3 and C4 grasses behaved alike despite their displaced phenologies in these habitats. The second test compared AMF colonisation for sand grassland dominant grasses Festuca vaginata and Stipa borysthenica in stands invaded by either C. epigejos or C. dactylon, and in the uninvaded natural community. Resident grasses showed lower degree of AMF colonisation in the invaded stand compared to the uninvaded natural community with F. vaginata responding so to both invaders, while S. borysthenica responding to C. dactylon only. These results indicate that invasive grasses supposedly less reliant on AMF symbionts have the capacity of altering the soil mycorrhizal community in such a way that resident native species can establish a considerably reduced extent of the beneficial AMF associations, hence their growth, reproduction and ultimately abundance may decline. Accumulating evidence suggests that such indirect influences of invasive alien plants on resident native species mediated by AMF or other members of the soil biota is probably more the rule than the exception.

Arbuscular mycorrhizal fungi, Calamagrostis epigejos, Cynodon dactylon, Grasses, Invasive plants, Semiarid temperate grassland

2013. szeptember 11., szerda

Horváth et al. (2013) Biodiversity and Conservation

Roland Horváth, Tibor Magura, Csaba Szinetár, János Eichardt, Béla Tóthmérész (2013): Large and least isolated fragments preserve habitat specialist spiders best in dry sandy grasslands in Hungary. Biodiversity and Conservation 22 (10): 2139-2150.

The role of fragment size, isolation and habitat diversity in the conservation of spider assemblages living in fragmented landscape were studied in dry sandy grasslands (East Hungary, Nyírség). Spiders were collected using pitfall traps at eight dry grassland fragments from 2001 to 2009 from March to October fortnightly. We tested the rules of island biogeography, which suggest that the species richness increases with the size and decreases with the isolation of fragments. The habitat diversity is an important factor for species richness, since large areas usually have more habitats; therefore, the number of species may be higher in these areas. During the 9-year study period, altogether 10,544 individuals belonging to 106 species were collected. Contradicting the classical theory, we found a significant negative relationship between the total number of spider species and the grassland size, while the ratio of sandy grassland specialist spider species increased with fragment size. The relationship between the ratio of generalist species and the fragment size was not significant. The overall species richness and the isolation of studied grasslands did not show a significant relationship. The ratio of sandy grassland specialist species decreased, while the ratio of generalist species increased with the increasing of isolation. The habitat diversity did not show any effect on spider species richness. We concluded that to conserve the habitat specialist species it is recommended to preserve the large and least isolated grassland fragments, furthermore to increase the size of small fragments with the restoration of the adjacent croplands.

Island biogeography, Fragmentation, Species richness, Sandy grassland specialist species, Generalist species, Habitat heterogeneity

Bácsi et al. (2013) Hydrobiologia

István Bácsi, Tamás Török, Viktória B-Béres, Péter Török, Béla Tóthmérész, Alex Sándor Nagy, Gábor Vasas (2013): Laboratory and microcosm experiments testing the toxicity of chlorinated hydrocarbons on a cyanobacterium strain (Synechococcus PCC 6301) and on natural phytoplankton assemblages. Hydrobiologia 710 (1): 189-203.

In the last few years, halogenated hydrocarbons have been detected in the soil, in the aquatic environment, in organisms, and even in drinking water. The toxic effects of three chlorinated aliphatic hydrocarbons (trichloroethylene, tetrachloroethylene and tetrachloroethane) were studied in laboratory experiments (using the cyanobacterium Synecococcus elongatus PCC 6301 as test organism) and in field-like circumstances (natural phytoplankton assemblages enclosed in microcosms). The results of the laboratory experiments showed that all of the tested compounds significantly inhibited the growth of the cultures within the first 4 h. Enzymatic changes of the treated cultures suggested that oxidative stress occured—all of the three compounds caused an increase in the activity of peroxidases and superoxide dismutase, and also increased the levels of lipid peroxidation. Observed changes in microcosms were comparable with the results of the laboratory experiments: the number of individuals and chlorophyll contents decreased in the treated assemblages. The elevated levels of peroxidation on the second day in the assemblages treated with tetrachloroethane and tetrachloroetylene suggest that oxidative stress could occur in field conditions. One of the most important findings is the decrease in species number. Our results showed that cryptomonads, some green algae species and the cyanobacterium Limnothrix gradually disappeared from the treated beakers during the experiment.

Chlorinated hydrocarbons, Growth inhibition, Oxidative stress, Laboratory experiments, Phytoplankton assemblages

2013. szeptember 8., vasárnap

Sólymos et al. (2013) Methods in Ecology and Evolution

Sólymos, P., Matsuoka, S. M., Bayne, E. M., Lele, S. R., Fontaine, P., Cumming, S. G., Stralberg, D., Schmiegelow, F. K. A. & Song, S. J. (2013): Calibrating indices of avian density from non-standardized survey data: making the most of a messy situation. Methods in Ecology and Evolution, DOI: 10.1111/2041-210X.12106, URL: http://onlinelibrary.wiley.com/doi/10.1111/2041-210X.12106/abstract

  1. The analysis of large heterogeneous data sets of avian point-count surveys compiled across studies is hindered by a lack of analytical approaches that can deal with detectability and variation in survey protocols.
  2. We reformulated removal models of avian singing rates and distance sampling models of the effective detection radius (EDR) to control for the effects of survey protocol and temporal and environmental covariates on detection probabilities.
  3. We estimated singing rates and EDR for 75 boreal forest songbird species and found that survey protocol, especially point-count radius, explained most of the variation in detectability. However, environmental and temporal covariates (date, time, vegetation) affected singing rates and EDR for 73% and 59% of species, respectively.
  4. Unadjusted survey counts increased by an average of 201% from a 5-min, 50-m radius survey to a 10-min, 100-m radius survey (n = 75 species). This variability was decreased to 8·5% using detection probabilities estimated from a combination of removal and distance sampling models.
  5. Our modelling approach reduced computation when fitting complex models to large data sets and can be used with a wide range of statistical techniques for inference and prediction of avian densities.


boreal forest songbirds, conditional maximum likelihood, distance sampling, generalized linear models, point counts, predictive mapping, removal sampling, statistical offsets