Invasion impact is conditioned by initial vegetation states Abstract Biological invasion is a crucial problem in the world because of its negative consequences for protected areas. The degradation stage of vegetation might affect the success of invasion. One of the most abundant and threatening invasive species is the common milkweed (Asclepias syriaca L.) which has invaded already 23 countries of Europe and in several habitat types its further spreading is promoted by climate change. Pannonian sand grassland is one of the most threatened habitat by common milkweed invasion. Therefore, invasion in sand grassland vegetation is an important issue. However, the effects of the invasive plant in the open sand grassland are rather controversial. In order to clarify the existing contradictory results, the study was carried out in a strictly protected area, near Fülöpháza (Hungary) in a reserve core area in a UNESCO biosphere reserve. Microcoenological study was applied to determinate the fine-scale community characteristics of non-invaded and invaded stands in natural and seminatural vegetation and data were processed by Juhász-Nagy’s information theory models. Shannon diversity of species combinations (compositional diversity) which describes the ways of the coexistence of species, and the number of realized species combinations were used for measuring beta diversity. Differences between stands were analyzed by two-way ANOVA. The maximum compositional diversity of species and main life-forms (annuals, perennials and cryptogams) did not differ significantly between the non-invaded and invaded stands. In contrast, significantly larger characteristic areas of compositional diversity were detected in the invaded stands. Based on these results, it could be concluded that diversity of species combinations did not change but those values have shifted to coarser scales in case of invaded stands. The direction of this change suggests a kind of impoverishment in the presence of Asclepias. Thus, it is worth mentioning from the invasion management point of view that protection of the habitats against disturbance is a more cost-effective and successful way than protection against the establishment or extirpation of invasive species, since disturbance facilitates the invasions throughout the impoverishment of the community.

Technical review on derivation methods for behavior dependent functional responses Abstract Functional responses measure the trophic interactions between species, taking into account the density and behavior of the interacting species. In predator-prey interactions, the prey preference of the predator and the antipredator behavior of the prey together determine the feeding rate of the predator and the survival rate of the prey. Consequently, the behavior dependent functional responses make it possible to establish dynamic ecological models providing insight, among others, into the coexistence of predator and prey species and the efficiency of agents in biological pest control. In this paper the derivation methods of functional responses are reviewed. Basically, there are three classes of such methods: heuristic, stochastic and deterministic ones. All of them can take account of the behavior of the predator and prey. There are three main stochastic methods for the derivation of functional responses: renewal theory, Markov chain and the Wald equality-based method. All these methods assume that during the foraging process the prey densities do not change, which provides a mathematical basis for heuristic derivation. There are two deterministic methods using differential equations. The first one also assumes that during the foraging process the prey densities do not change, while the second one does not use that assumption. These derivation methods are appropriate to handle the behavior dependent functional responses, which is essential in the derivation of ecological games, when the payoff of prey and predator depends on the strategies of the prey and predator at the same time.

Abundance and size of birds determine the position of the species in plant-frugivore interaction networks in fragmented forests Abstract The relationships between frugivorous animals and plants are of vital importance particularly in tropical forests. The way species interact and how they are organized within interaction networks could be determined by their ecological and morphological characteristics. This study evaluates the hypothesis that the topological position of species within an interaction network is determined by their degree of frugivory, body size, and abundance. Thus, we constructed the frugivory network between birds and plants in a rainforest fragment in northwestern Colombia. The position of the species within the network was calculated based on three centrality measures (degree, betweenness, and closeness), and its association with relative abundance, degree of frugivory, and body size of each bird species was evaluated by means of a generalized linear model. We found that the species that were most abundant and had the smallest body size had central positions in the interaction network. This pattern is contrary to what has been observed in pristine forests, where species with large body size are more important for network stability. Our results suggest that forest fragmentation modifies the roles of species within the network structure, in part, due to changes in the makeup of the original frugivore community. The information presented may be useful to evaluate the effects of the loss of species as a result of anthropic actions, with the aim of generating ecosystem restoration strategies.

Factors shaping distribution and abundance of raptors wintering in two large Mediterranean islands Abstract A growing number of ecological studies suggest that animal distributions are not only influenced by classical ecological features such as habitat availability, but also by the motion capacity of the studied animal. Here we analyse the diversity and density of two wintering raptor communities from Crete and Sicily, two large Mediterranean islands located along migratory flyways. We performed 611 and 1030 km of transects in Crete and Sicily respectively, examining the spatial distribution of raptors in relation to land use, topography, raptor species diversity and abundance. Our results show that community diversity and specific abundance are strictly related in accordance with the ‘More Individuals Hypothesis’. Comparing the two most common raptors, the density of the Eurasian kestrel was the highest in Sicily and that of the common buzzard in Crete. An overall positive effect of Eurasian kestrel density on that of the common buzzard was found in both islands, but higher in Crete. Our findings suggest that the distribution and density of the Eurasian kestrel, because of its higher movement ability, are less influenced by the presence of ecological barriers along potentially migratory flyways. We cannot exclude that higher inter specific competition with common buzzards in Crete might have pushed the smaller species to cross the Mediterranean Sea in order to overwinter in Africa.

Can we trust the chord (and the Hellinger) distance? Abstract To avoid the problems associated with the Euclidean distance for the calculation of plot-to-plot dissimilarity, a variety of alternative measures have been proposed. Among them, the chord and the Hellinger distances are both obtained by first transforming separately the species abundances in each plot vector and then by calculating the Euclidean distance on the chord-transformed or the Hellinger-transformed data. However, although both measures are routinely used by ecologists as substitutes for the Euclidean distance, they have very different properties. In this paper, using a modified version of Dalton’s principle of transfers, I will show that, unlike the Euclidean distance, the chord and the Hellinger distances are not monotonic to changes in absolute abundances. Therefore, they are not interchangeable with the Euclidean distance. The moral of this story is that although dissimilarity may appear an intuitively simple concept, the properties of even the best-known indices are not fully understood. Therefore, a clear understanding of old and new coefficients is needed to evaluate their ability to highlight relevant aspects of compositional dissimilarity among plots.

Do pioneer species enhance early performance of native species in subtropical shrublands? An examination involving six native species in South China Abstract This paper examines the following questions: (1) Do early pioneer species have a greater impact on the survival and growth of different successional native trees compared to the shrub Rhodomyrtus tomentosa? (2) Do canopy treatments affect soil nutrients and light availability? (3) What is the mechanism underlying the interaction between nurse species and target species? Degraded shrubland sites (Heshan, Guangdong, China), under moist subtropical conditions were studied. About 1-year-old seedlings of Pinus massoniana, Schima wallichii, Schefflera heptaphylla, Castanopsis hystrix, Cryptocarya chinensis and Castanea chinensis were transplanted under the canopy of R. tomentosa, Dicranopteris dichotoma and in open interspaces without vegetation. Survival and growth were recorded from the first growing season after planting. Leaf gas exchange, water potential, soil physicochemical characters and irradiation were then measured. Canonical redundancy analyses (RDA) were used to evaluate the relationships between environmental factors and seedling survival and growth conditions. Both R. tomentosa and D. dichotoma canopy treatment facilitated seedling survival and growth either directly or indirectly. Irradiance/radiation was considered the most important resource (factor) for seedling growth in subtropical regions, however, soil nutrients and species are yet to be examined simultaneously with irradiance/radiation under field conditions. We conclude that early successional species facilitates the survival and growth of late successional species in subtropical shrublands. However, further predictions of successional trajectories remain elusive and are influenced by stochastic processes, including arrival order, shade tolerance, physiological character of the colonizing species and their competitive interactions.

Taxonomic resolution refinement does not improve understanding of invertebrate’s role on leaf litter breakdown Abstract The invertebrate biodiversity of subtropical streams depends on the seasonal input of organic matter, as much as the leaf decomposition process on stream system. However, one of the challenges in determining the importance of invertebrates for leaf breakdown in subtropical streams is the low taxonomic resolution applied in most studies. To overcome this limitation, here we used litter bags with senescent leaves to evaluate the impact of different taxonomic resolutions of trophic group classification to assess the seasonal importance of invertebrate community for leaf litter breakdown in a subtropical stream (Atlantic Forest in western of Paraná state, Brazil). Litterfall was quarterly measured over a year. The leaf litter accumulated in an interval of 30 days was retrieved, weighed, and used for the leaf breakdown experiments (by litter bags). We found a lower importance of invertebrate community richness and density (shredders and scrapers) in leaf breakdown process irrespective of the taxonomic resolution (family or genus level used). Hyphomycetes biomass and fungi sporulation also did not present changes among sample times, and consecutively, importance for leaf breakdown. However, the richness and density of Chironomidae taxa respond differently depending on the taxonomic resolution used. Low litter breakdown may be explained by the increase of consumption of microorganisms, due to high density of Chironomidae scrapers evaluated at the genus level. Moreover, temperature is the main factor responsible for breakdown over the year, in a positive way. Therefore, our results indicated the family level as the taxonomic resolution sufficient to assess the role of shredders and scrapers in the leaf litter breakdown process of this subtropical stream system.

Interactions of soil moisture and plant community properties in meadows restored from abandoned farmlands on the Sanjiang Plain, China Abstract Soil moisture is a major driving force of plant community succession in restored meadows. Existing studies mainly focus on diversity-productivity relationships. However, studies which determine the effects of soil moisture on the plant community properties in restored meadows are lacking. In this study, we conducted a chronosequence analysis of the interactions between soil water content variation and plant community properties in meadows following passive restoration (3-, 5-, 9-, 14-, 17-, 21-year restoration) of abandoned farmlands on the Sanjiang Plain, China. Results showed that the plant community was characterized by ruderal plants in the initial year of succession, and then by perennial plants such as Calamagrostis angustifolia and Carex spp. in older restored meadows. Similarity of restored community to target site increased across succession time whereas species diversity gradually decreased. Plant height, coverage and biomass increased with restoration time, with plant density being the exception. The community height, coverage and root/shoot ratio were positively related to the water content in the surface soil layer (0–10 cm). Conversely, plant density was significantly and negatively related with soil moisture at 0–10 cm soil depth. Plant diversity (Shannon index, Richness index and evenness) was closely correlated to soil water content at the soil depth of 0–10 cm. Our findings indicate that vegetation of cultivated meadows could be effectively restored by passive restoration. Change of plant species diversity is an especially important response to hydrological recovery in restored meadows on the Sanjiang Plain.

Key factors affecting the diversity of Sphagnum cover inhabitants with the focus on ground beetle assemblages in Central-Eastern European peat bogs Abstract A key structural component in peat bog formation is Sphagnum spp., which determines very specific associated environmental conditions. The aim of this study was to characterise some of the key factors affecting the diversity, species richness and abundance of sphagnum inhabiting ground beetles and to examine the maintenance of stable populations of cold adapted specialised peat bog species. A total of 52 carabid species were recorded by pitfall traps along six main habitats, such as the lagg zone, pine bog, hollows, hummock open bog and dome. The results are characterised by a low diversity, which vary significantly among habitat types, and include a high abundance of a few carabid species. Among the variables influencing carabid species richness and abundance were plant cover, pH and the conductivity of the Sphagnum mat water. Vascular plant cover was a key factor shaping carabid beetle assemblages in the slope and the dome, while electric conductivity affected carabid beetle assemblage in the lagg. Whereas, the water level was the most important factor for the hollows. At the same time, peat bog specialists showed low sensitivity to the gradient of the analysed variables. Most of the specialised species are protected boreal beetles in the temperate zone of Europe, and therefore Belarusian peat bogs are a significant repository of cold adapted specialised bog species and potentially represent a significant refugia for these species in the context of global warming.

Contrasting responses of lizard occurrences to burrowing by a critically endangered seabird Abstract Seabirds are considered ecosystem engineers, because they facilitate ecosystem functioning (e.g., nutrient cycling), crucial for other marine and terrestrial species, including reptiles. However, studies of seabird-reptile interactions are limited. Here, we assessed the influence of the ‘Critically Endangered’ Whenua Hou Diving Petrel (Pelecanoides whenuahouensis) on the occurrence of two threatened skinks, Stewart Island green skink (Oligosoma aff. chloronoton) and southern grass skink (O. aff. polychroma). We surveyed skinks for 26 consecutive days at 51 sites with and 48 sites without Diving Petrel burrows in the dunes on Codfish Island (Whenua Hou), New Zealand. We used occupancy modelling to assess the influence of burrows on the occurrence of skinks, while accounting for other factors affecting occupancy (Ψ) and detection probabilities (p). Diving Petrel burrows had a contrasting effect on the occurrence of skinks. On average, ̂Ψ of Stewart Island green skinks was 114% higher at sites with burrows compared to sites without, while ̂Ψ of southern grass skinks was only 2% higher. Occurrence of both skinks was negatively influenced by the presence of the other skink species. On average ̂p were low: 0.013 and 0.038 for Stewart Island green and southern grass skinks, respectively. Stewart Island green skinks appear attracted to burrows, which might facilitate thermoregulation (i.e., shelter from temperature extremes). The larger Stewart Island green skinks may subsequently exclude the smaller southern grass skinks at burrows, causing the contrasting relationships. We suggest that these interspecific interactions should be considered when implementing conservation management, e.g., through the order of species reintroductions.