Showing papers in "Community Ecology in 2017"
TL;DR: Using a network approach, a list of important plant and pollinator species are obtained, including three Network Hubs of utmost importance, and other hubs of particular biogeographical interest, to help to preserve the greatest number of interactions and thus support many other species.
Abstract: Conservation of species is often focused either only on those that are endangered, or on maximising the number recorded on species lists. However, species share space and time with others, thus interacting and building frameworks of relationships that can be unravelled by community-level network analysis. It is these relationships that ultimately drive ecosystem function via the transfer of energy and nutrients. However interactions are rarely considered in conservation planning. Network analysis can be used to detect key species (“hubs”) that play an important role in cohesiveness of networks. We applied this approach to plant-pollinator communities on two montane Northern Apennine grasslands, paying special attention to the modules and the identity of hubs. We performed season-wide sampling and then focused the network analyses on time units consistent with plant phenology. After testing for significance of modules, only some modules were found to be significantly segregated from others. Thus, networks were organized around a structured core of modules with a set of companion species that were not organized into compartments. Using a network approach we obtained a list of important plant and pollinator species, including three Network Hubs of utmost importance, and other hubs of particular biogeographical interest. By having a lot of links and high partner diversity, hubs should convey stability to networks. Due to their role in the networks, taking into account such key species when considering the management of sites could help to preserve the greatest number of interactions and thus support many other species.
31 citations
TL;DR: Comparisons of predation pressure on artificial caterpillars during day and night on the ground in forest fragments in Denmark do not support the idea that night activity can provide enemy-free time for solitary caterpillar on the temperate forest floor.
Abstract: Lepidoptera is one of the most diverse orders of insects, their larvae are very abundant in many habitats, and frequent prey of various predators. To decrease predation risk, caterpillars developed several means of defence, among them timing their activity to avoid predators (seeking enemy-free time). Although the enemy-free time hypothesis is often invoked to explain caterpillar behaviour, empirical evidence for it is scarce. We tested whether such enemy-free time exists in a temperate forest by comparing predation pressure on artificial caterpillars during day and night on the ground in forest fragments in Denmark. We found a high predation rate, 23.9%d−1, and higher predation rate at night (30.9%d−0.5) than during the day (17.0%d−0.5), both by invertebrate (23.3%d−0.5 vs. 12.4%d−0.5) and vertebrate (8.5%d−0.5 vs. 3.3%d−0.5) predators. The most important predators were chewing insects (73.4% of all attacks) and small mammals (19.0%). Attack rates on red caterpillars were higher (30.0%d−1) than on green ones (19.5%d−1). Overall, these data do not support the idea that night activity can provide enemy-free time for solitary caterpillars on the temperate forest floor.
22 citations
TL;DR: This review examines how the shift from a strictly linear to a dendritic network perspective influenced the thinking about the organization of fish meetacommunities in stream networks, and suggests that scaling metapopulation models up to the metacommunity level can be useful to further the understanding of the spatial structure of metacomunities.
Abstract: The metacommunity perspective has substantially advanced our understanding of how local (within community) and dispersal (between community) processes influence the assembly of communities. The increased recognition of dispersal processes makes it necessary to re-evaluate former views on community organization in different ecological systems and for specific organisms. Stream systems have long been considered from a linear perspective, in which local community organization was examined along the longitudinal profile, from source to mouth. However, the hierarchically branching (i.e. dendritic) structure of stream networks also significantly affects both local and regional scale community organization, which has just only recently been fully recognized by ecologists. In this review, I examine how the shift from a strictly linear to a dendritic network perspective influenced the thinking about the organization of fish metacommunities in stream networks. I argue that while longitudinal patterns in the structure of fish communities are relatively well known, knowledge is still limited about how the structure of the stream network ultimately affects the spatial and temporal dynamics of metacommunities. I suggest that scaling metapopulation models up to the metacommunity level can be useful to further our understanding of the spatial structure of metacommunities. However, this requires the delineation of local communities and the quantification of the contribution of dispersal to local community dynamics. Exploring patterns in diversity, spatial distribution and temporal dynamics of metacommunities is not easily feasible in continuous stream habitats, where some parts of the habitat network are exceptionally hard to sample representatively. Combination of detailed field studies with modelling of dispersal is necessary for a better understanding of metacommunity dynamics in stream networks. Since most metacommunity level processes are likely to happen at the stream network level, further research on the effects of stream network structure is needed. Overall, separation of the effect of dispersal processes from local scale community dynamics may yield a more mechanistic understanding of the assembly of fish communities in stream networks, which may also enhance the effectiveness of restoration efforts.
21 citations
TL;DR: It was found that the overall richness and diversity of community decreased along with the progression of KRD, and leaves with lower area yet higher density had the optimal adaptability in KRD regions, which can be planted as pioneer vegetation to restore land inKRD regions.
Abstract: Karst rocky desertification (KRD) is a process of soil desertification, which leads to the decline of soil quality and biomass. We conducted a plant community survey in KRD areas in Chongqing, China. Our aims were to determine key soil properties that shape plant communities and to identify essential leaf functional traits (LFTs) in responding to the progression of KRD. The vegetation survey was carried in a total of twenty study sites (five replicates for four stages of KRD) in the Wushan County in Chongqing, China. Leaves were collected from all the species in every site and measured/calculated for five LFTs, namely, specific leaf area, leaf area, leaf thickness, leaf tissue density, and leaf dry matter content. Soil samples were collected in triplicates in each site to measure soil properties. We found that the overall richness and diversity of community decreased along with the progression of KRD. Phanerophytes predominated in all the KRD areas. Soil pH was the main determinant of vegetation structure. Leaves with lower area yet higher density had the optimal adaptability in KRD regions, which can be planted as pioneer vegetation to restore land in KRD regions.
20 citations
TL;DR: The decoupled patterns of functional and phylogenetic diversity among the biogeographical regions highlight the complementarity between these dimensions and the importance of transitional regions, and suggest that several historical, environmental and ecological processes may be structuring mammal assemblages.
Abstract: The multi-dimensional analysis of biodiversity addresses several components, including the number of species, as well as their ecological and evolutionary identities. This approach can lead to key biodiversity patterns that remain covered when only species richness is studied. The convergence of the Nearctic and Neotropical biogeographic regions in Mexico suggests spatial variation in biodiversity patterns. In this study we analysed species richness, functional diversity, and phylogenetic diversity of mammal assemblages in relation to abiotic variables and their variation across the biogeographic regions. Our results showed contrasting patterns among biodiversity dimensions: 1) species richness followed the typical global pattern of a gradual increase from the Nearctic towards the Neotropical region, 2) phylogenetic diversity was highest in the Transitional region; and 3) functional diversity was highest in the Neotropical region, but not different between the Nearctic and Transitional regions. Abiotic variables had a significant relation with variation in biodiversity dimensions, but they had a higher contribution to explain functional diversity than species richness and phylogenetic diversity. The decoupled patterns of functional and phylogenetic diversity among the biogeographical regions highlight the complementarity between these dimensions and the importance of transitional regions, and suggest that several historical, environmental and ecological processes may be structuring mammal assemblages. Likewise, different approaches should be followed in accordance to variation of functional and phylogenetic traits among regions.
15 citations
TL;DR: In this article, the authors evaluated how tropical avifaunal communities respond to moderate habitat disturbances, such as shifting cultivation, selective logging and restoration from exotic plant species, in the Yagirala Forest Reserve, a fragmented tropical lowland rainforest in south-west Sri Lanka.
Abstract: Disturbed forest fragments comprise a substantial proportion of tropical landscapes, and these habitats along with associated ecotones have become important to tropical biodiversity conservation in human-modified landscapes. This study evaluated how tropical avifaunal communities respond to moderate habitat disturbances, such as shifting cultivation, selective logging and restoration from exotic plant species, in the Yagirala Forest Reserve, a fragmented tropical lowland rainforest in south-west Sri Lanka. Thirty circular plots with a 25-m fixed-radius, located to cover four prominent habitat types (secondary forest, Pinus-dominated forest, abandoned paddy lands and home gardens), were studied from March to December 2014. The results suggest that despite being fragmented and disturbed by human actions, the Yagirala Forest Reserve and associated ecotone collectively provide an important refuge for avifauna in the landscape context. The forest-home garden interface supported the highest avifaunal diversity. Edge habitats represented by home gardens and abandoned paddy lands generally supported greater bird richness. However, less disturbed secondary forest and Pinus-dominated forest were be more important for endemic and forest-specialist birds. Our results further highlight the potential value of wooded forest-home garden interfaces and forest stands restored with exotic pines in supporting native forest bird assemblages, especially in fragmented and isolated forest patches.
15 citations
TL;DR: In this article, the authors assessed habitat quality by using the Syrph The Net database and data on decreasing species richness over a 25-year period for the two largest phytophagous hoverfly genera (Merodon and Cheilosia).
Abstract: Spatial and temporal differences in landscape patterns are of considerable interest for understanding ecological processes. In this study, we assessed habitat quality by using the Syrph The Net database and data on decreasing species richness over a 25-year period for the two largest phytophagous hoverfly genera (Merodon and Cheilosia). Furthermore, within this time frame, we explored congruence between ecological responses (species richness and Biodiversity Maintenance Function for these two genera) and landscape structural changes through correlation analysis. Our results indicate that landscapes have experienced changes in aggregation, isolation/connectivity and landscape diversity, with these parameters being significantly correlated with Cheilosia species richness loss and habitat quality. We conclude that the genus Cheilosia is a good bioindicator that can highlight not only the current quality of an area but also temporal changes in landscape patterns.
13 citations
TL;DR: In this paper, the authors compared the accuracy of three widely used methods for estimating aboveground plant biomass: the visual cover estimation method, the point intercept method, and field spectroscopy.
Abstract: Aboveground plant biomass is one of the most important features of ecosystems, and it is widely used in ecosystem research. Non-destructive biomass estimation methods provide an important toolkit, because the destructive harvesting method is in many cases not feasible. However, only few studies have compared the accuracy of these methods in grassland communities to date. We studied the accuracy of three widely used methods for estimation of aboveground biomass: the visual cover estimation method, the point intercept method, and field spectroscopy. We applied them in three independent series of field samplings in semi-arid sand grasslands in Central Hungary. For each sampling method, we applied linear regression to assess the strength of the relationship between biomass proxies and actual aboveground biomass, and used coefficient of determination to evaluate accuracy. We found no evidence that the visual cover estimation, which is generally considered as a subjective method, was less accurate than point intercept method or field spectroscopy in estimating biomass. Based on our three datasets, we found that accuracy was lower for the point intercept method compared to the other two methods, while field spectroscopy and visual cover estimation were similar to each other in the semi-arid sand grassland community. We conclude that visual cover estimation can be as accurate for estimating aboveground biomass as other approaches, thus the choice amongst the methods should be based on additional pros and cons associated with each of the method and related to the specific research objective.
11 citations
TL;DR: In this paper, the authors compared and measured the restoration success of three well-established methods for grassland restoration (sod transplantation, hay transfer, seeding) with three commonly used indices (diversity, number of target species, similarity to reference sites).
Abstract: How should the somewhat vague term of restoration success be measured? This is a critical question rooted in European law, where in fact the creation of proper replacement habitats is a prerequisite for permitting projects that trigger a loss of species or habitats. Previous studies have used indices that relied on a comparison to reference sites, for example the number of a predefined pool of target species or compositional similarity. However, since restoration sites have rarely the same biotic and abiotic conditions as reference sites, plant communities in restored sites will not perfectly match the reference sites. Furthermore, such indices fail when reference sites are lacking or degraded. Hence, there is a need for an alternative approach that evaluates the conservation value of a restored site independently from reference sites. We propose that naturalness indicator values can be an option to measure restoration success. The approach of using naturalness indicator values makes use of the fact that plants are able to indicate environmental parameters, including degradation and regeneration. We compared and measured the restoration success of three well-established methods for grassland restoration (sod transplantation, hay transfer, seeding) with three commonly used indices (diversity, number of target species, similarity to reference sites). The results verified earlier studies and showed that sod transplantation led to the highest restoration success followed by hay transfer and seeding of sitespecific seed mixtures. Further, we used those well-established indices for an evaluation of novel, naturalness-based indices (unweighted and cover-weighted mean naturalness indicator values, the sum of naturalness indicator values). While calculating the means of naturalness indicator values failed to offer conclusive information on restoration success, we could show that the sum of naturalness indicator values was highly correlated with the number of target species and compositional similarity to reference sites. Thus, our case study demonstrated that naturalness indices can be an excellent option to estimate success in grassland restoration.
11 citations
TL;DR: In this paper, the authors focus on how spatial patch characteristics, such as patch area, shape and isolation, affect the natural species composition of hardwood floodplain forests and establish the relationship between fragmentation indices and the number and proportion of species in each functional species group stated in this paper.
Abstract: The present study focuses on how spatial patch characteristics, such as patch area, shape and isolation, affect the natural species composition of hardwood floodplain forests. The natural species composition is defined according to species groups obtained using phytocoenological methods. The aim of the study was to establish the relationship between fragmentation indices and the number and proportion of species in each functional species group stated in this paper. This study is based on a dataset of 118 phytocoenological releves sampled using the standard methodology of the Zurich-Montpellier School, ordered within the suballiance Ulmenion (mixed oak-elm-ash forests along the great rivers). The study area is situated in Central Europe, in the northern part of the Pannonian biogeographic region. The digital map of hardwood floodplain forests was rasterized to 25 m cell size. The FRAGSTATS software was used to obtain fragmentation indices, and generalised linear models tested the influence of forest patch fragmentation indices on species composition. Our analyses confirm that large hardwood floodplain forests are essential for natural species composition conservation, and that large fragment areas are highly susceptible to non-native species penetration. We also determined that small, compact fragments contain very valuable remnants of well-preserved natural hardwood floodplain forests with a high proportion of specialised Ulmenion species. However, disruption to hardwood floodplain forest natural borders engenders a greater threat to its natural species composition than decline in patch area, because disruption results in increased Shape index, increased contact with the surrounding environment, greater edge effect and a higher proportion of alien species in the forest community.
11 citations
TL;DR: It is concluded that differences in the elevation of these paramos and small-scale variables such as slope significantly affect the diversity and composition of terricolous communities.
Abstract: Altitudinal gradients involve macroclimatic changes that can affect the diversity of several organisms. We tested the effects of elevation and small-scale variables on the diversity and composition of terricolous communities (lichens and bryophytes) in five paramos in southern Ecuador. The altitudinal range considered (from 2700 to 4000 m a.s.l.) is associated with changes in rainfall, temperature and irradiance. At each paramo, forty 40 x 40 cm2 sample plots were randomly selected in similar areas of vegetation (grass paramo) and conservation status. The presence/absence and cover of lichens and bryophytes were recorded in 200 sample plots. A total of 90 species (46 lichens and 44 bryophytes) were identified. Our results showed that total species richness, lichen and bryophyte richness, Simpson’s inverse and Shannon’s index were related to elevation and slope. Nevertheless, the response to elevation was dependent on the organism considered. Thus, meanwhile lichens had their maximum richness at the highest elevation (3930 m a.s.l.), bryophytes had a maximum peak at middle elevation (3300 m a.s.l.). Species composition also differed significantly among the five paramos, especially in bryophytes. We conclude that differences in the elevation of these paramos and small-scale variables such as slope significantly affect the diversity and composition of terricolous communities.
TL;DR: In this article, the effects of urbanization on ground-dwelling spider assemblages along a rural-suburban-urban gradient in Hungary were studied, and the authors found that the number of hygrophilous and disturbance sensitive species was the lowest in the urban habitat.
Abstract: Urban areas have been growing radically worldwide, causing considerable changes in biodiversity of natural habitats. In floodplain forests, we studied the effects of urbanization on ground-dwelling spider assemblages along a rural-suburban—urban gradient in Hungary. We tested three traditional hypotheses (intermediate disturbance hypothesis, habitat specialist hypothesis and hygrophilous species hypothesis) and two novel expectations (shade-preferring species hypothesis, and disturbance sensitive species hypothesis) on spiders. We found that the total number of species was higher in the suburban habitat than in rural and urban ones, supporting the intermediate disturbance hypothesis. We found a decrease in the species richness of forest specialist and shade-preferring species along the urbanization gradient. We found that the number of hygrophilous and disturbance sensitive species was the lowest in the urban habitat. The spider assemblages of the rural and suburban habitats were clearly separated from the assemblages of urban habitats. Based on our findings we emphasize that low and moderate intensity of forest management contributes to the preservation of the local species richness in floodplain forests.
TL;DR: In this article, the authors studied the long-term dynamics of ant colonies for 37 years on a sandy grassland in central Hungary and showed that climate change can be linked to a fundamental change in the community structure of major ecosystem actors.
Abstract: Climate change brings along trend-like changes as well as changes in the temporal variations in environmental conditions which interact with the biological dynamics of ecological systems. Therefore, only studies covering several decades may unveil long term trends in ecological systems, such as in animal communities. To demonstrate if recent climatic changes have caused fundamental changes in the structure of a key arthropod community, I studied the long-term dynamics of ant colonies for 37 years on a sandy grassland in central Hungary. To be able to monitor colonies – the natural units of ant communities – with the possible least disturbance, I applied two grids of a total of 80 slate plates as artificial nesting sites. Prior to the presented study, a well-defined spatial ant community structure had been identified in the studied habitat, which consisted of three species groups (dune top, transitional and dune slack groups), occupying different habitat patches. During the study period 2813 nests of 11 ant species were recorded under the slates. Over the 37 years, community pattern markedly changed, dune slack species disappeared from the studied plots, while the frequency of drought-tolerant dune top species increased by a significant trend. No significant trend was observed in the case of the transitional species group. On the species population level, two species, Lasius niger and Formica cunicularia, showed an intensive population decline; while the Plagiolepis taurica population significantly increased and spatially joined the transitional species group in the dune slack in the second half of the project. These changes led to a major decline in species richness and a homogenization of species composition across habitat patches. Multiple correlation analyses revealed that the depletion of groundwater had the strongest relationship with these population trends. The study indicates that climate change can be linked to a fundamental change in the community structure of major ecosystem actors.
TL;DR: In this article, a multiscale hierarchical sampling approach along an 1000 m elevational transect was used to evaluate the contributions of the alpha and beta diversity components to overall bryophyte diversity in Terceira Island, Azores.
Abstract: How are bryophyte alpha and beta diversities distributed across spatial scales along an elevational gradient in an oceanic island? Which mechanisms and drivers operate to shape them? Starting from a multiscale hierarchical sampling approach along an 1000 m elevational transect, we used additive diversity partitioning and null modeling to evaluate the contributions of the alpha and beta diversity components to overall bryophyte diversity in Terceira Island, Azores. Substrate-level diversity patterns were explored by means of the Sorensen Similarity Index and the Lloyd Index of Patchiness. Elevation-level beta diversity was decomposed into its replacement and richness differences components, with several environmental variables being evaluated as diversity predictors. Bryophyte diversity proved to be primarily due to beta diversity between elevation sites, followed by diversity among substrates. Compositional differences between neighboring sites decreased with elevation, being mainly caused by species replacement and correlating with differences in relative humidity and disturbance. At the substrate level, we found a great homogeneity in terms of species composition, coupled with a low substrate specialization rate. We conclude that, in Terceira’s native vegetation patches, regional processes, such as environmental gradients associated with elevation, play a greater role in shaping bryophyte diversity than local processes. Moister and less disturbed areas at mid-high elevation harbor a richer bryoflora, consistently more similar and stable between neighbouring sites. Simultaneously, the different substrates available are somewhat ecologically redundant, supporting few specialized species, pointing to these areas providing optimal habitat conditions for bryophytes. Our findings provide a better understanding of how bryophyte diversity is generated in Terceira Island, indicating that management and conservation measures should focus on island-level approaches, aiming to protect and rehabilitate additional natural vegetation patches at different elevations, especially in the severely disturbed lowlands.
TL;DR: In this paper, the authors studied the co-occurrence patterns of fish in a segment of the Arauca River's floodplain and the influence of the spatial and temporal variability on them.
Abstract: The study of co-occurrence patterns has been extensively applied to propose assembly rules for community organization. Recently, a new interest has grown in the effect of gradients on these patterns and to analyze them through new approximations such as co-occurrence networks, through which keystone species can be identified. Neotropical floodplains represent interesting systems to study such patterns, because of their spatial heterogeneity, temporal variability and their high fish species richness. With this in mind, our goal was to study the co-occurrence patterns of fish in a segment of the Arauca River’s floodplain and the influence of the spatial and temporal variability on them. One stream and one floodplain lake were sampled with gill nets during 2014 – 2015 across a hydrological cycle and 5 matrices for each 5 sampled months in each water body were prepared to explore the co-occurrence patterns in each water body across months and 2 for the entire period, through a probabilistic pair-wise analysis of species co-occurrence that identified aggregated and segregated species pairs. With the observed cooccurrences × water body × month, the species weighted degrees and betweenness were calculated, and co-occurrence networks were constructed. The networks structures, in terms of the degrees of every species, were compared spatially and temporally through a generalized linear model. The stream showed the highest numbers of aggregated species pairs, and in general showed the most complex networks in terms of nodes, edges and degrees. The habitat type and the hydrological phases significantly influenced the structure of the fish co-occurrence networks. Two species, Loricariichthys brunneus and Pygocentrus cariba were identified as the core of the fish communities of the floodplain and as keystone species because they contribute to the connection of the networks by having a series of links with less frequent species.
TL;DR: Establishing whether proximity to two edges has any additive influence on Ancient Woodland Indicator (AWI) species presence relative to proximity to a single edge is established and presence of individual AWI species was significantly related to distance from the nearest and second nearest edges in isolation, but significantly more strongly by the additive effect of distance from both edges in a single model.
Abstract: The influence of edge proximity on woodland plants is a well-established research area, yet the influence of dual edge exposure has rarely been investigated. This novel research aims to establish whether proximity to two edges has any additive influence on Ancient Woodland Indicator (AWI) species presence relative to proximity to a single edge. Several AWI species are threatened and thus specific conservation priorities, while Ancient Semi-Natural Woodland (ASNW) itself is often highly fragmented: almost half of remnant patches are less than 5 ha, which increases the potential for dual edge effects. Here, systematic mapping of herbaceous AWI species was conducted in 310 vegetation plots in two formerly-connected ASNW fragments in South-West England. Linear regression modelling revealed that distance to nearest edge and distance to second nearest edge were both univariately positively correlated with AWI species richness. After distance from nearest edge was entered into a multivariate model first, distance from second edge was entered in a second optional step after meeting stepwise criteria. The resultant multivariate model was more significant, and explained more variance, than either variable in isolation, indicating an additive effect of dual edge exposure. Likewise, binary logistic regression modelling showed presence of individual AWI species (Anemone nemorosa, Hyacinthoides non-scripta, Lamiastrum galaeobdolon and Paris quadrifolia) was significantly related not only to distance from the nearest and second nearest edges in isolation, but significantly more strongly by the additive effect of distance from both edges in a single model. We discuss the implications of these findings from community ecology and conservation perspectives.
TL;DR: In this article, a benthic invertebrate assemblage of a stream that passes through pristine, rural, suburban and urban areas of a municipality located in southeastern Brazil was analyzed in a spatial and temporal scale.
Abstract: We studied a benthic invertebrate assemblage of a stream that passes through pristine, rural, suburban and urban areas of a municipality located in southeastern Brazil to investigate a possible relationship between this assemblage structure and urbanization. The environmental variables and fauna structure were analyzed in a spatial and temporal scale, sampling the four sites in a dry and wet season. We found a clear spatial pattern, with higher similarity between sites from rural and suburban area that presented intermediate environmental characteristics. The pristine site showed in both seasons the lowest values of alkalinity and fecal coliform. On the other hand, the site located in the urban area showed the lowest concentration of dissolved oxygen and higher of suspended solids, ammonia and fecal coliform. The extreme values of these three variables occurred in the wet season, probably related to the high rainfall values. The benthic invertebrate fauna structure followed the same longitudinal and seasonal pattern found for the environmental variables. The site in urban area showed the lowest richness, diversity and evenness, with a dominance of two groups resistant to adverse environmental conditions (Oligochaeta and Orthocladiinae) and absence of more sensitive groups (Coleoptera, Ephemeroptera and Trichoptera). The increase drag of the substrate and associated invertebrates can be responsible for the lower abundance and richness observed in the wet season. The environmental variables that best defined the differentiation between sites (dissolved oxygen, organic suspended solids and fecal coliform) related directly to urbanization effects, like dump effluents and removal of riparian vegetation.
TL;DR: The structure of biocoenosis at the local scale is determined mainly by current velocity/discharge, granulometry of the inorganic bottom substrate, quantity and quality of particulate organic matter, as well as water quality variables.
Abstract: The biodiversity and species richness of benthic macroinvertebrate assemblages are under the strong pressure of environmental variables compounded with geographical and historical processes. Numerous studies that have investigated biodiversity and assemblage stability have shown the importance of choosing proper methodologies and paradigms. Consequently, the use of diversity measures and the partitioning of biodiversity at different spatial and temporal scales are of particular significance. Within habitats, only those species whose preferences remain within a tolerable range of the variability of abiotic factors are able to survive. The structure of biocoenosis at the local scale is determined mainly by current velocity/discharge, granulometry of the inorganic bottom substrate, quantity and quality of particulate organic matter, as well as water quality variables. Dispersion plays a key role in shaping regional diversity gradients, which supports the permanent inflow of individuals and their exchange between riverine basins. However, dispersion is also one of the basic aspects of the saturation/non-saturation of local communities with species from the regional species pool; a respective concept tries to determine how, why and to what degree local species richness is dependent on regional species richness.
TL;DR: It is argued that these results likely indicate risk aversion and a fear of reprisal among conspecifics.
Abstract: Cannibalism is a common phenomenon among insects. It has raised considerable interest both from a theoretical perspective and because of its importance in population dynamics in natural ecosystems. It could also play an important role from an applied perspective, especially when using predatory species in biological control programmes. The present paper aims to study the cannibalistic behaviour of Nabis pseudoferus Remane and the functional response of adult females. In a non-choice experiment, adult females showed clear acceptance of immature conspecifics as prey, with relatively high mortality values (51.89 ± 2.69%). These values were lower than those occurring for heterospecific prey, Spodoptera exigua Hubner, under the same conditions (80.00 ± 2.82%). However, the main result was that the rate of predation on heterospecific prey was reduced to 59.09 ± 7.08% in the presence of conspecific prey. The prey-capture behaviour of adult females differed when they hunted conspecific versus heterospecific prey. This was shown in the average handling time, which was 23.3 ± 3.3 min in the first case (conspecific) versus 16.6 ± 2.5 min in the second (heterospecific). Furthermore, the values increased in the former case and declined in the latter according to the order in which the prey were captured. The difference in handling time was not significant when adjusting the adult female functional response to conspecific nymphs. We argue that these results likely indicate risk aversion and a fear of reprisal among conspecifics.
TL;DR: In this article, the authors presented the results of two experiments on the use of chemical fertilizers in permanent grasslands, one in Italy and the other in Slovakia, which showed that chemical fertilization should be carefully planned according to soil conditions, since different treatments may have the same effect on the floristic and vegetation patterns of grasslands.
Abstract: The 2013 reform of the European Common Agricultural Policy tries to support farmers willing to follow environment- friendly rural practices, by the so called “green payment”. Within this framework, it is suggested that governments and regions should maintain a certain ratio of the area of permanent grasslands to the total Utilized Agricultural Area according to the greening rules of the reform. However, the weak economic performance of permanent grasslands does not encourage farmers to invest into their conservation. This fact persuaded us to revisit our old unpublished data, obtained by experiments on the use of chemical fertilizers in permanent grasslands. By this reanalysis we hope to further support the new European policy with the perspective to find a trade-off between the conservation of the biodiversity and the economic productivity of permanent grasslands. Of the many possibilities we have chosen to present the results of two experiments, one in Italy and the other in Slovakia. The main reason for this choice was that these two studies followed complementary strategies of fertilization that appeared useful to detect both the single and the synergistic effects of N, P, and K on the relationships between yield and species diversity. The results of cluster and diversity analysis suggest that chemical fertilization should be carefully planned according to soil conditions, since different treatments may have the same effect on the floristic and vegetation patterns of grasslands. These results, according to similarity theory, allow to choose the least expensive and polluting combination of N, P and K from those that, according to the species combinations, are assigned to the same cluster.
TL;DR: A significant negative correlation was found between condition and asymmetry for C. nemoralis and N. brevicollis in the suburban as well as urban forest fragments, indicating a complex interaction between tolerance limits, feeding conditions and stress levels during advancing urbanisation, emphasising the importance of using multiple criteria for assessing its impact on biodiversity.
Abstract: Physiological condition of an animal is flexible and can quickly change in relation to the quality of its environment. This makes it potentially suitable as an estimator of environmental stress. We studied the condition in three predatory ground beetles, Carabus nemoralis, Nebria brevicollis and Pterostichus melanarius along an urbanisation gradient (forest-suburban area - forest fragments in urban park) in Soro, Denmark to test whether urbanisation-related stress is reflected in body condition. We also considered the interaction between condition and the true asymmetry using a local polynomial regression model. Females showed consistently better condition than males in all studied species. The condition indices in C. nemoralis and N. brevicollis were higher in the urban habitats than the other sites, while P. melanarius showed better condition in the suburban forest fragments than the forest or urban habitats. A significant negative correlation was found between condition and asymmetry for C. nemoralis and N. brevicollis in the suburban as well as urban forest fragments. This indicates a complex interaction between tolerance limits, feeding conditions and stress levels during advancing urbanisation, emphasising the importance of using multiple criteria for assessing its impact on biodiversity.
TL;DR: It is found that the indices of taxonomic distinctness were the most sensitive indicators of eutrophication, and the importance to examine multiple facets for mapping biodiversity or for assessing the effects of anthropogenic disturbances on biological communities is supported.
Abstract: Modern biodiversity research focuses on multiple diversity facets because different indices may describe different ecological and environmental processes, as well as the effects of varied disturbances of natural and anthropogenic origins. We investigated littoral macroinvertebrate diversity in a large boreal lake system and specifically explored congruence of indices within and between the three diversity facets: species diversity, functional diversity and taxonomic distinctness. First, we found that the indices of taxonomic distinctness were the most sensitive indicators of eutrophication. Second, we observed that most correlations between the indices within the same diversity facet, and between the indices of functional and species diversity, were relatively strong. However, the indices of taxonomic distinctness (Δ+ and Λ+) were weakly associated with other metrics of diversity, emphasising the importance of taxonomic distinctness as a complementary dimension of biodiversity. Therefore, our observations support the importance to examine multiple facets for mapping biodiversity or for assessing the effects of anthropogenic disturbances on biological communities.
TL;DR: The research showed a significant influence of C. epigejos necromass on the recruitment of mesic meadow species, connected with the emergence of a mechanical barrier to seedlings, which impedes their sprouting.
Abstract: Calamagrostis epigejos produces a large amount of litter in patches dominated by this expansive species in degraded meadows. Two studies were carried out in the area of the Central Sudetes Mountains (SW Poland). The goals of these surveys were to address the following questions: How do active manipulations regarding the removal of necromass and C. epigejos tillers, as well as seeding of additional species, influence the meadow species seedling recruitment? How is the organic matter decomposed in the consecutive stages of mountain grassland degradation caused by C. epigejos expansion? How do environmental factors influence litter decomposition? The results of the research showed a significant influence of C. epigejos necromass on the recruitment of mesic meadow species. The influence is connected with the emergence of a mechanical barrier to seedlings, which impedes their sprouting. No relation was found between the degradation stage and the rate of necromass decomposition. The study showed the influence of some environmental factors on the rate of necromass decomposition – in the case of C. epigejos there was a negative impact of exchangeable magnesium forms, whereas in the case of mixed meadow plant litter there was a positive effect of nitrogen and C:N ratio, and negative correlations with Ellenberg’s light and soil humidity indices.
TL;DR: Phenotypic responses of kin recognition in unconstrained environment confirm phenotypic response of decreased competition in roots rather than in shoots in Xanthium italicum.
Abstract: Unlike vagile organisms, plants perform a wide range of phenotypic responses to cope with environmental stresses. A special case of interaction with external factors is the ability of plants to recognize genetic relatedness of neighbour plants, actually well known as kin recognition. The present work aimed to provide a valuable contribution to the field of kin recognition in plants through a common garden experiment. To avoid bias involved in pot experiments, we perform an experiment in unconstrained root growth conditions comparing the development of coupled kin, non-kin and solitary plants of Xanthium italicum. Biometrics of plants with different genetic relatedness were measured, then architecture and competitive interaction were assessed using the relative interaction index (RII) for above and belowground portions of plants. X. italicum showed different allocation depending on the neighbourhood. Root biomass was declined in plants growing with kin compared to non-kin coupled plants, while plants coupled with kin allocated more shoot than roots compared to solitary plants. RII explains phenotypic response of decreased competition in roots rather than in shoots. Despite high values of RII for the aboveground portion, the architectural analysis of shoot, number, angle and length of branches and roots reveals dramatic but indistinctive change in the structure of plants growing near kin or non kin compared to a solitary plant. These results confirm phenotypic responses of kin recognition in unconstrained environment.
TL;DR: This finding for a direct relationship between DGW and plant species composition provides important reference information on the ecological condition of these mesic woodlands in the absence of groundwater extraction, vital for setting ecological thresholds that ensure sustainable extraction of groundwater.
Abstract: Groundwater-dependent ecosystems (GDEs) are threatened by over-extraction of groundwater for human needs across the world. A fundamental understanding of relationships between naturally occurring gradients in depth-to-groundwater (DGW) across landscapes and the ecological properties of vegetation assemblages is essential for effective management of the impacts of groundwater extraction. Little is known, however, about relationships between DGW and the ecology of mesic woodlands in GDEs. Here, we investigated relationships between a naturally occurring DGW gradient and plant species composition, richness and abundance in mesic Eucalyptus woodlands of eastern Australia. Across 16 sites varying in DGW from 2.4 m to 43.7 m, we found that plant species composition varied significantly in relation to DGW, independently of a range of 14 physical and chemical attributes of the environment. Nine understorey species, representing only 7% of the pool of 131 plant species, were identified as contributing to up to 50% of variation in species composition among the study sites. We suggest this dominant pattern driver in the understorey is explained by differential abilities among understorey species in their ability either to tolerate extended dry conditions at deeper DGW sites during periods of low rainfall, or to withstand periodically waterlogged conditions at shallow sites. Plant species richness and total plant abundance (a measure of plant productivity) were not significantly and independently related to DGW or any of the other 14 environmental attributes. Our finding for a direct relationship between DGW and plant species composition provides important reference information on the ecological condition of these mesic woodlands in the absence of groundwater extraction. Such information is vital for setting ecological thresholds that ensure sustainable extraction of groundwater.
TL;DR: Seed predation losses strength as forests become more stressed either by loss of soil fertility or by flooding with nutrient-poor water, Conversely seed pathogens become more important with water-logged soils and with flooding.
Abstract: Because of the importance of the Amazon to our shared human future and because we need to understand how its forests regenerate, I set out seeds for a week in igapo, palm, terra firme, varzea and white sand forests and then collected them, scoring seed losses to predators, seed losses to pathogens and seeds that germinated. I found (1) terra firme forest, white sand forest, varzea forest and igapo forest under water 1 month every year, were significantly different for seed mechanisms and tolerances, terra firme forest, palm forest, varzea forest and igapo forest under water 1 month per year, were significantly different among species, and the interaction term was significant for all forests except for the two most flooded igapo forests, (2) in terra firme forest seed predators took most seeds regardless of species, (3) in palm forest species were different regardless of seed mechanism and tolerance, (4) in white sand forest seed predators took most seeds regardless of species, (5) in varzea forest seed predators took most seeds but with some species differences and (6) in igapo forest under water 1 month per year, there were differences in predation, pathogens and germination, and in species variation. I conclude that seed predation losses strength as forests become more stressed either by loss of soil fertility or by flooding with nutrient-poor water. Conversely seed pathogens become more important with water-logged soils and with flooding. Seed loss variation among species within forests was always a secondary factor.
TL;DR: The conclusion is that Correspondence Analysis on presence/absence data seems the most appropriate method to use, and Multiple Correlation Analysis provides interesting information on the species distribution while showing a pattern of releves very similar to that issued by PCA.
Abstract: Two simulated coenoclines and a real data set were differently recoded with respect to the Braun-Blanquet coding (including presence/absence) and analysed through the most common multidimensional scaling methods. This way, we aim at contributing to the debate concerning the nature of the Braun-Blanquet coding and the consequent multidimensional scaling methods to be used. Procrustes, Pearson, and Spearman correlation matrices were computed to compare the resulting sets of coordinates and synthesized through their Principal Component Analyses (PCA). In general, both Procrustes and Pearson correlations showed high coherence of the obtained results, whereas Spearman correlation values were much lower. This proves that the main sources of variation are similarly identified by most of used methods/transformations, whereas less agreement results on the continuous variations along the detected gradients. The conclusion is that Correspondence Analysis on presence/absence data seems the most appropriate method to use. Indeed, presence/absence data are not affected by species cover estimation error and Simple Correspondence Analysis performs really well with this coding. As alternative, Multiple Correlation Analysis provides interesting information on the species distribution while showing a pattern of releves very similar to that issued by PCA.
TL;DR: In this paper, the effect of anthropogenic activities, seasonality, and vegetation types was studied on the contamination level of surface water of oxbows in the Upper Tisza region in Eastern Hungary.
Abstract: The contamination level of oxbows depends on both natural and anthropogenic effects. The aim of our study was to identify those abiotic and biotic factors that determine the contamination level of oxbows. The effect of anthropogenic activities, seasonality, and vegetation types was studied on the contamination level of surface water of oxbows. The following chemical variables were measured: suspended solid, ammonium, nitrate, chlorophyll-a, Al, Ba, Fe, Mn, Pb, Sr and Zn from eight oxbows from 2013 summer to 2014 autumn in the Upper Tisza region in Eastern Hungary. Three of the studied oxbows were protected, four oxbows were used for fishing and one oxbow was contaminated with wastewater. Our findings revealed that anthropogenic activities had remarkable effect on the contamination level of oxbows. Seasonality also influenced the contamination level, except the concentration of suspended solid, chlorophyll-a and manganese. Significant differences were found among vegetation types for the concentration of suspended solids, aluminium, iron, manganese and lead. The high level of iron concentration was not explained by the anthropogenic activities, suggesting that the quality of oxbows depends on both natural and anthropogenic effects.
TL;DR: The present findings demonstrate the need for a unified terminology in research on community overlap as well as for pairwise and multiple measures for quantifying the phenomenon.
Abstract: Although overlap of communities is a key issue in studies ranging from community ecology to biogeography, a clear definition of community overlap and related terms hinder the development of the field. The absence of a unified terminology is remarkable even when the overlap of a pair or multiple communities is characterized. As a remedy, I suggest a definition of community overlap and two measures of it (number of overlapping species and total overlap size). Although both measures quantify different aspects of community overlap, in studying pairs of communities they yield identical results. The present findings demonstrate the need for a unified terminology in research on community overlap as well as for pairwise and multiple measures for quantifying the phenomenon.
TL;DR: In this paper, the authors applied the concept of hemeroby and generalism at community level, on a set of birds occurring in various habitats of central Italy characterized by different level of disturbance.
Abstract: We tested the application of the concept of hemeroby and generalism at community level, on a set of birds occurring in various habitats of central Italy characterized by different level of disturbance. In each habitat-related bird community, we applied the recently published species-specific score in hemeroby (a proxy of habitat-related disturbance; HSi) and hemerobiotic diversity (a proxy of generalism; H’Hi) to local species frequency, obtaining weighted values at community level (HStot and H’Htot). The relationship between HStot vs. H’Htot showed an increasing trend moving from reed beds through forests and mosaics to urban communities. Quadratic model (best fit) evidenced a significant correlation between these variables and a tendency toward a hump-shaped curve, corroborating results already observed at species level (intermediate generalism hypothesis). The co-inertia analysis discriminated four groups of habitat-related communities, characterized by species with different levels of disturbance-sensitivity (expressed by HSi) and generalism (expressed by hemerobiotic diversity; H’Hi): (i) forest type-related, where mature wood communities were separated from a coppiced wood one; (ii) communities of moderately disturbed agricultural habitats; (iii) communities embedded in highly disturbed mosaics, and (iv) a group including either a highly disturbed urban habitat or a low disturbed wetland reed bed, with highly specialized species (respectively, synanthropic species and water-related species). Total scores in hemeroby and hemerobiotic diversity, expressing the composition in species with different disturbance preference and generalism, might act as good community-based indicators of degree of naturalness, especially for forest habitat types.