Species Co-occurrence Analysis Research Articles

Spatial patterns and species associations of earthworms in relation to micro-topography and insolation

Despite significant advancements in our understanding of the relationship between soil animal life and environmental gradients, as well as their impact on ecosystem functioning, there is a growing need for quantitative research that considers the spatial and temporal heterogeneity of soil biodiversity. Such research can help to address current knowledge gaps and support the development of legislation and conservation measures aimed at preserving soil biodiversity in the future. Earthworms, one of the most important group of soil animals, show patchy horizontal distribution in response to spatial heterogeneity in soil physico-chemical parameters, food availability and biological interactions at various scales.The aim of this study was to explore whether the spatial and temporal variability and co-occurrence probability of earthworm species and ecological categories (epigeic, endogeic and anecic) can be characterized by exploiting habitat micro-topography and insolation.Field research was carried out in spring and summer at seven locations using a regular grid of 49 sampling points with 5 m inter-sample distance over an altitudinal gradient. The results of Geary's C and Moran's I indices, as well as the semivariograms calculated for each species, season and location confirmed a patchy spatial distribution. The range of semivariograms varied from 3.2 m to 32.8 m in spring, and from 0.3 m to 32.8 m in summer. Overall (all locations and both seasons), the mean range was similar for adult (8.4 m) and juvenile (9.2 m) earthworms. In spring, epigeic species had a larger range than endogeic species. Abundances of juvenile earthworms were negatively correlated with microtopographic elevation in spring (at most locations) and in summer (at all locations). The relationship between adult earthworms and microtopographic elevation could not be interpreted generally within season. Additionally, correlations between earthworm abundance and average monthly insolation were weak. Pairwise analysis of species co-occurrence revealed a random pattern for most species. In the analysis of co-occurrence of ecological categories, endogeics and epigeics had more positive probabilities than other pairs. The obtained results could be useable in soil biodiversity assessments, or creation of monitoring protocols.

On the efficiency of indicator species for broad-scale monitoring of bird diversity across climate conditions

Multiple constraints (e.g., time, funding, expertise) can impede the broad-scale monitoring of human-induced loss of biodiversity. Non-random species co-occurrence provides an opportunity to estimate local species richness by tracking only a few species that are indicators of more global assemblages. Despite promising fine-scale studies, it remains unclear whether such indicator species remain effective over broad spatial extents. We assessed the value of indicator species to consistently predict species richness despite variation in short-term (5–9 years) climate conditions. Our study involves 22,041 point-count stations distributed over 1.75 M km2 of Canadian boreal forest, where 197,000 birds from 216 species were detected. Using null model analysis of species co-occurrence followed by regression analysis, we identified the minimum set of indicator species that can predict 70% of spatial variation in local bird richness in each of eight short-term climate regions. We found that indicators were non-random subsets of the species pool, as they were species whose presence explained a relatively high percentage of variations in species richness within the short-term climate region, and those sharing a relatively high number of significant pairwise associations. Although only 11 to 26 indicator species were needed to predict species richness at the regional scale, 57 of the 216 species pool (26%) were necessary to make predictions over the entire study area. This large number reflects regional variations in the best indicator species, and those that remained indicators in several regions were representative of different species assemblages. Our observations thus cast doubts on the use of indicator species as an effective and efficient tool for biodiversity monitoring under changing climate conditions. Broad-scale (spatial or temporal) use of indicators thus comes with the colossal challenge of having to determine under which new conditions a given set of indicators must be replaced by another, and by which one.

Decapods Associated with the Southern King Crab (Lithodes santolla) Fishery in Central Patagonia (44° S, Chile)

The southern king crab, Lithodes santolla, is an important fishery resource in the inner seas of Chilean Patagonia. The fishing gear used to catch southern king crab (bait trap) and its operation at different depths over several months provide the opportunity to gather information about relative abundance. The aim of the present study was to analyze the information collected from the catches of southern king crab and its associated fauna in the Magdalena Fjord to study the biodiversity and ecology of scavenging decapod crustaceans. Specifically, the study aimed to determine the bathymetric patterns of abundance by species, to model the abundance by season (winter and spring) and to determine the structuring pattern of scavenging decapods assemblage. Samples were collected between June and November 2019 by deploying traps in four bathymetric strata: 1 = 0–50 m; 2 = 51–100 m; 3 =101–150 m; 4 = 151–200 m. We registered a total of 673 decapod specimens associated with the southern king crab fishery, representing five species: Lithodes santolla (n = 96), Libidoclaea smithii (n = 10), Metacarcinus edwardsii (n = 58), Munida gregaria (n = 507) and Peltarion spinulosum (n = 2). The abundance of decapod species varied by month and bathymetric strata. We found bathymetric patterns for L. santolla abundance, M. gregaria, M. edwardsii, and total species abundance. The most informative model to explain scavenging decapod abundance by generalized linear model (GLM) included species and season. The null model of species co-occurrence analysis revealed that all species associations during the sampled months were random. Our study is the first that provides evidence about patterns of bathymetrical and temporal variation of scavenging decapod abundance and expands the body of knowledge regarding the biodiversity of scavenger decapods in the Magdalena Sound.

Prediction and evaluation of allelopathic plants species in Algerian Saharan ecosystem

Allelochemicals involved in plant-plant interaction (Allelopathy) are a potential source for alternative agrochemicals to solve the negative effects caused by synthetic herbicides. The present study is focused on the prediction and evaluation of allelopathic plants species in Saharan ecosystem from the Souf region in the southeastern of Algeria. The study was articulated through three steps of investigation: (1) a floristic survey, including a general inventory with notation of abundance and sociability scores for each species to understand the floristic composition of the study area, (2) Species co-occurrence analysis, using a presence/absence of data species in restricted sampling plots, which allowed to identify eight negatively associated species pairs with only one positive association and (3) allelopathic bioassays were performed with the aqueous extracts of the three species negatively associated species. The results showed a significant effect of aqueous extracts of Halocnemum strobilaceum (Pall.) M. Bieb, Retama raetam Forssk. Webb and Limoniastrum guyonianum Boiss on seed germination or seedling growth of target species (Lactuca sativa L., Daucus carota L., Triticum durum Desf. and Zea mays L.) at concentrations of 10 % and 15 %. H.strobilaceum showed the highest phytotoxic activity with 0% germination rate of all target species at concentration of 15 %, followed by R. raetam and L. guyonianum, and D. carota was the most sensitive target species with total inhibition of germination in most of treatments. Besides, plumule length was most affected then radicle length. It was conducted that some of these extracts may be represent a promising alternative bioherbicides from Saharan plants in agricultural and environmental management.

Freshwater Releases Into Estuarine Wetlands Change the Determinants of Benthic Invertebrate Metacommunity Structure

In recent years, the relative importance of the processes driving metacommunity composition has aroused extensive attention and become a powerful approach to identify community patterns and their regulatory mechanisms. We investigated variations in the composition of benthic community in restored wetlands and natural wetlands in the Yellow River Delta (Shandong Province, China). First, spatial structures within each wetland were modeled with Moran eigenvector maps. Next, the variation in community structure among local environmental and spatial variables was partitioned using constrained ordination, and the “elements of metacommunity structure” analysis was used to determine the patterns of best fit for species distributions within metacommunities. Finally, the null model was used to analyze non-random patterns of species co-occurrence. The community structure of benthic invertebrates in restored wetlands and natural wetlands differed significantly. The benthic invertebrate metacommunity structure showed a nested distribution in restored wetlands and a quasi-Clementsian structure in natural wetlands. Pure environmental fractions and pure spatial fractions were critical in regulating benthic invertebrate metacommunities of restored wetlands. In natural wetlands, pure spatial fractions and the interaction between environmental and spatial factors (shared fractions) played a major role in the metacommunity. A species co-occurrence analysis showed that species co-occurred more frequently than expected by chance, demonstrating that biotic interactions were not the main driver of metacommunity structures in both wetland types. Accordingly, the benthic invertebrate metacommunity in estuarine wetlands following freshwater releases was mostly determined by environmental and spatial effects, which resulted in a metacommunity with nested distribution. These results are important for biodiversity protection and ecosystem management of estuarine wetlands in the Yellow River Delta.

Co-occurrence of true truffle mycelia in Tuber magnatum fruiting sites.

Tuber magnatum (the white truffle) is the most precious species of the genus Tuber which comprises the hypogeous ectomycorrhizal species called "true truffle." Despite its high economic value, the knowledge on its ecology is scant, principally due to the difficulty to find its mycorrhizas in the soil. The possibility to detect its mycelium by DNA extracted from soil has given a new chance for studying this truffle species. In this work, the co-occurrence of other Tuber species with T. magnatum mycelium was investigated by using species-specific primers in several productive areas located in central and northern Italy. Most (82%) of the examined soil samples showed at least one other Tuber species in addition to T. magnatum. The most common was T. maculatum (72% of soil samples) followed by T. borchii, T. rufum, T. brumale, T. dryophilum, T. macrosporum, and T. melanosporum (40%, 37%, 22%, 19%, 12%, and 1% of soil samples, respectively). Tuber aestivum was never detected in T. magnatum productive patches. Analysis of species co-occurrence showed that the pairwise associations between T. dryophilum-T. brumale, T. brumale-T. borchii, and T. borchii-T. dryophilum was significant. The results suggest that Tuber mycelial network in white truffle grounds is much more extensive than the distribution of their ectomycorrhizas and competitive exclusion between different Tuber species seems to take place only for root colonization.

Effect of sampling intensity on understanding species co-occurrence pattern of fish community using null model analysis

Species co-occurrence pattern is fundamental in community ecology. Co-occurrence analysis identifies mechanisms for species coexistence in fish community. Different sampling intensity may result in different patterns at certain scales. In this study we conducted a simulation study to evaluate differences in the three species co-occurrence indices under different levels of sampling intensity. We used the fixed–fixed (FF) and fixed-equiprobable (FE) algorithm models to generate new matrices with different sampling intensities for a simple random sampling (SRS) and a systematic sampling (SS) survey. The estimated indices tended to approach the ‘true’ values of the co-occurrence indices of fish communities when sampling intensity increased. Sampling intensity showed a relatively low influence on the estimates of co-occurrence indices when the null hypothesis was accepted and high influence when the null hypothesis was rejected. As for checkerboard score (C-score) and Checker, when the index under both FF and FE algorithm models simultaneously indicated that the community structure was non-random, the overall error rate of FF algorithm model was lower than that of FE algorithm model for both indices. The C-score was a commonly used index of species segregation. We generated new occurrence matrix to investigate the relationships between C-score and the slope of species-area curves of fish communities for exploring the effect of species composition on species co-occurrence analysis. The C-score showed decreasing trends when the slopes of the species-area curves increased for the simulated fish communities and when the sampling intensity increased from 5 to 35 sampling grids in four seasons. The relatively low sampling intensity was needed for fish communities with more widespread species, and relatively high sampling intensity was required for communities with more rare species to ensure the representative data for species co-occurrence analysis. We conclude that sampling intensity and fish community attributes could influence the results of species co-occurrence analysis using null model analysis.

Invasive Ants Affect Spatial Distribution Pattern and Diversity of Arboreal Ant Communities in Fruit Plantations, in Tarakan Island, Borneo

Human activities influence ant community structure. In tropical areas, the habitat characteristics of crop plantations frequently shape the structure of arboreal ant communities. The present study investigated the spatial distribution of arboreal ants dwelling in durian Durio zibethinus and citrus Citrus amblycarpa plantations in the Tarakan Island, North Kalimantan. Specifically, it was investigated whether ant communities are dominated by native or invasive species; and if ant arboreal mosaics occur. This study included two sites (A and C) comprising durian and citrus plantations and one site B with only citrus plantations. Ant workers dwelling on crop trees were collected by branch beating, and subsequently identified and counted. Across all sites, a total of 64,360 workers, from 22 ant species, were collected from 59 durian and 63 citrus trees. In site A, the invasive species Tapinoma melanocephalum and the native species Oecophylla smaragdina were numerically dominant. A null model analysis of species co-occurrence revealed that species segregation existed in this site. Conversely, in sites B and C the invasive species T. melanocephalum and Technomyrmex albipes were dominant, and native arboreal ants almost co-occurred with the two species. Moreover, the number of T. melanocephalum and T. albipes workers was negatively correlated with the species diversity index of arboreal ants. However, the number of O. smaragdina workers showed no significant correlation. The results suggest that the invasion and domination of non-native species dissasemble spatial structures and reduce the species diversity in arboreal ant communities. The community structures of arboreal ants in fruit plantations were varied, depending on the fruit species and the properties of dominant ants.

A Probabilistic Co-Occurrence Approach for Estimating Likelihood of Spatial Overlap Between Listed Species Distribution and Pesticide Use Patterns.

Characterizing potential spatial overlap between federally threatened and endangered ("listed") species distributions and registered pesticide use patterns is important for accurate risk assessment of threatened and endangered species. Because accurate range information for such rare species is often limited and agricultural pesticide use patterns are dynamic, simple spatial co-occurrence methods may overestimate or underestimate overlap and result in decisions that benefit neither listed species nor the regulatory process. Here, we demonstrate a new method of co-occurrence analysis that employs probability theory to estimate spatial distribution of rare species populations and areas of pesticide use to determine the likelihood of potential exposure. Specifically, we 1) describe a probabilistic method to estimate pesticide use based on crop production patterns; 2) construct species distribution models for 2 listed insect species whose ranges were previously incompletely described, the rusty-patched bumble bee (Bombus affinis) and the Poweshiek skipperling (Oarisma poweshiek); and 3) develop a probabilistic co-occurrence methodology and assessment framework. Using the principles of the Bayes' theorem, we constructed probabilistic spatial models of pesticide use areas by integrating information from land-cover spatial data, agriculture statistics, and remote-sensing data. We used maximum entropy methods to build species distribution models for 2 listed insects based on species collection and observation records and predictor variables relevant to the species' biogeography and natural history. We further developed novel methods for refinement of these models at spatial scales relevant to US Fish and Wildlife Service (FWS) regulatory priorities (e.g., critical habitat areas). Integrating both probabilistic assessments and focusing on USFWS priority management areas, we demonstrate that spatial overlap (i.e., potential for exposure) is not deterministic but instead a function of both species distribution and land use patterns. Our work serves as a framework to enhance the accuracy and efficiency of threatened and endangered species assessments using a data-driven likelihood analysis of species co-occurrence. Integr Environ Assess Manag 2019;00:1-12. © 2019 SETAC.

Disentangling the drivers of ground-dwelling macro-arthropod metacommunity structure at two different spatial scales

Research on factors determining soil metacommunity patterns across multiple spatial scales is quite rare. In this study, we aimed to compare the mechanisms that drive species co-occurrence and consequently form the ground-dwelling macro-arthropod metacommunity structure at local (104 m) and regional (106 m) scales. For the comparison, we used three distant (approximately 200 km from each other) locations within the northeast black soil region of China. At each location, we had five sampling plots (at a distance of 500 m from each other), and at each plot, we had five sampling sites within agrolandscapes (10 m away from each other). At each site, we set three pitfall traps. Animals were collected three times: in May, July and September 2015. The analysis of the elements of metacommunity structure showed that the regional level of the metacommunity always demonstrated a Clementsian structure (a grouped distribution of species along environmental gradients), while the local scale metacommunity structure was dependent on sampling month and varied between Clementsian, random and nested distributions. Based on the results of a variance partitioning analysis, including pure environmental (environmental filtering) and pure spatial predictors (dispersal), as well as the interaction of environmental and spatial factors (shared fraction), we observed that the shared fraction at the regional scale was 30% larger than at the local scale. A species co-occurrence analysis further demonstrated that the observed C-scores were not significantly higher than simulated indices for each guild separately at the local scale. Our results suggest that biotic interactions are not the key drivers of metacommunity structure at the local scale in agriculture, while environmental filtering and dispersal appear to be key drivers of metacommunity structure at the regional scale.

Species co-occurrence analysis predicts management outcomes for multiple threats.

Mitigating the impacts of global anthropogenic change on species is conservation's greatest challenge. Forecasting the effects of actions to mitigate threats is hampered by incomplete information on species' responses. We develop an approach to predict community restructuring under threat management, which combines models of responses to threats with network analyses of species co-occurrence. We discover that contributions by species to network co-occurrence predict their recovery under reduction of multiple threats. Highly connected species are likely to benefit more from threat management than poorly connected species. Importantly, we show that information from a few species on co-occurrence and expected responses to alternative threat management actions can be used to train a response model for an entire community. We use a unique management dataset for a threatened bird community to validate our predictions and, in doing so, demonstrate positive feedbacks in occurrence and co-occurrence resulting from shared threat management responses during ecosystem recovery.

Activity patterns and spatial co-occurrence of sympatric mammals in the moist temperate forest of the Kashmir Himalaya, India

Little is known about the activity pattern and co-occurrence of mammalian species coexisting sympatrically in the rugged terrains of the Himalaya. By using camera traps we quantified diel activity patterns and temporal overlap as well as probabilistic model of spatial species co-occurrence amongst eight species. The jungle cat and the Indian porcupine tended to be strictly nocturnal whereas the leopard cat and the red fox were primarily nocturnal and crepuscular, yellow-throated marten was diurnal. The Asiatic black bear, leopard and the hangul showed no clear pattern. We found highest temporal overlap (Δ1 = 0.84, 95%CI = 0.54-0.86) between leopard and Asiatic black bear followed by pairs between red fox and leopard cat (Δ1 = 0.83, 95%CI = 0.72-0.91) and jungle cat (Δ1 = 0.82, 95%CI = 0.60-0.91). The lowest temporal overlap was found between yellow-throated marten and Indian porcupine (Δ = 0.11, 95%CI = 0.08-0.20). The results from probabilistic pairwise species co-occurrence analysis suggest that out of 28 possible species pairs 25 had random associations and one pair was unclassifiable. The remaining two species pairs had positive associations of co-occurrences between leopard cat and hangul (Pgt < 0.05) and Indian porcupine and hangul (Pgt < 0.05). Our results provided new insights into this unique community of mammals of the western Himalaya and will facilitate future studies on the mechanism determining coexistence of animal species within complex system.

Co-occurrence patterns of fish species in two aquatic habitats of the Arauca River floodplain, Venezuela

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.

Island biogeography of insect conservation in urban green spaces

SUMMARYBecause of their isolation, biotic communities of urban green spaces are expected to be similar to those of oceanic islands. This should be particularly true for insects, which represent an important component of urban faunas. The equilibrium theory of island biogeography (ETIB) allows for the formulation of some hypotheses regarding the influence of the geographical characteristics of green spaces on insect species richness and extinction risk. Based on island biogeography principles, we present eight predictions on how green space characteristics should influence insect species richness and loss. We analysed the current literature in order to determine which predictions were supported and which were not. We found that many studies gave outcomes that support ETIB predictions about the effects of area and isolation of green spaces; we found no strong support for predictions about shape and extent of native habitat in the literature that we reviewed. Most of the available studies dealt with patterns in species richness, whereas insect species loss has been rarely investigated. Future developments in the application of island biogeography principles to urban insect conservation should address temporal trends in species persistence and the analysis of species co-occurrence and nestedness.

Complex relationships between species niches and environmental heterogeneity affect species co-occurrence patterns in modelled and real communities.

Species co-occurrence analysis is commonly used to assess how interspecific interactions dictate community assembly. Non-random co-occurrences, however, may also emerge from niche differences as well as environmental heterogeneity. The relationships between species co-occurrence patterns, environmental heterogeneity and species niches are not fully understood, due to complex interactions among them. To analyse the relationships among these patterns and processes, I developed synthetic community models and analysed a large dataset of tree species across the conterminous United States. Niche overlap and environmental heterogeneity had significant and contrasting effects on species co-occurrence patterns, in both modelled and real communities. Niche breadth, in turn, affected the effect sizes of both variables on species co-occurrence patterns. The effect of niche breadth on the relationship between co-occurrence and niche overlap was markedly consistent between modelled and real communities, while its effect on the relationship between co-occurrence and environmental heterogeneity was mostly consistent between real and modelled data. The results of this analysis highlight the complex and interactive effects of species niche overlap, niche breadth and environmental heterogeneity on species co-occurrence patterns. Therefore, inferring ecological processes from co-occurrence patterns without accounting for these fundamental characteristics of species and environments may lead to biased conclusions.

Morphometric and biotic variables as potential predictors ofLudwigia sedoides(Humb. &amp; Bonpl.) Hara in a large Amazonian reservoir

Reservoirs cause hydrological changes (i.e. , water level stabilization) that favor the colonization of aquatic macrophytes. Knowing the ecological factors that determine the occurrence of these plants is critical for water management (e.g. , plant control) and biodiversity conservation. In this sense, the present study investigated colonization patterns of Ludwigia sedoides in Lajeado reservoir (Tocantins River, Amazon Basin), in order to identify variables that influence colonization at habitat scale. We investigated the relationship between colonization (coverage area and occurrence) and morphometric (fetch, slope, depth and distance from shoreline) and biotic variables (local diversity of macrophytes and co-occurrence patterns). Stepwise regression selected fetch, depth and slope as the best variables to explain the variation in L. sedoides coverage, which together explained 46% of data variability. Fetch and slope were negatively correlated with coverage, whereas depth showed a positive correlation. No biotic variable was included in the model (P >0.05). However, the investigation of the geometric shape of bivariate correlations (null models) showed positive relationships with local species richness and richness of life forms (i.e. , submerged, emergent, floating and epiphytic). In addition, an analysis of species co-occurrence (C -score) revealed that L. sedoides is negatively associated with some macrophyte species. We believe, however, that these results may be associated with species preferences for particular environmental conditions. In conclusion, the present study indicated that morphometric variables are potential predictors of the colonization of L. sedoides in Lajeado reservoir. Sheltered sites with low slope and moderate depths represent favorable environment for colonization and growth.

Copepodos (Crustacea) intermareales en islas oceanicas chilenas: un enfoque por modelos nulos y por biogeografia de islas

Chilean intertidal copepods have been a littleies studied group, there are isolated reports for the central Chilean coast and island territories. The aim of this study was to analyze intertidal copepod assemblies on Chilean islands territories (Easter Island, San Felix, San Ambrosio, Alejandro Selkirk and Robinson Crusoe islands) and compare them with respect to an area of the continental coastal zone (Montemar, Valparaiso), through null model analysis of species co-occurrence and a cluster analysis. Null model results indicated. for a simulation, the existence of regulatory factors, while two simulations showed no regulatory factors, that would presumably due to the low number of species reported. Moreover, cluster analysis revealed the existence of a core group comprising the islands Alejandro Selkirk, San Felix, and Robinson Crusoe, followed later by Easter Island, and finally Montemar. Ecological topics were analyzed, mainly related with regulation patterns of species richness, as possible explanations for the observed results.

Regulatory factors in crustacean zooplankton assemblages in mountain lakes of northern Chilean Patagonia (38 41°S): a comparison with Bulgarian counterparts (42°N)

Chilean Patagonia has protected mountainous areas with evergreen native forests; in which the lakes and rivers, of volcanic or glacial origin, are oligotrophic. In Bulgaria, there are mountainous zones with native forests and associated lakes of volcanic origin. The aim of the present study is to carry out a preliminary comparison of zooplanktonic crustaceans in lake ecosystems associated with native forests of Chilean Patagonia and of Bulgarian mountains. The study revealed that the lakes studied in Chilean Patagonia are associated mainly with Nothofagus forests; they are oligotrophic, with a low number of zooplanktonic crustacean species. Similar results were observed for Bulgarian mountain lakes associated with Fagus forests. A null model analysis of species co-occurrence was applied to the two groups of lakes, and the result revealed the absence of regulatory factors in species associations. These studies agree with similar descriptions of lakes in Andean Patagonia and New Zealand. They highlight the important role of native Nothofagus forests in Argentina and Chile, and of Fagus forests with associated soil properties in Bulgaria, in the oligotrophy of the lakes studied.

Spatial patterns in the distribution of European springtails (Hexapoda: Collembola)

Using a large database on the spatial distribution of European springtails (Collembola) we investigated how range sizes and range distribution across European countries and major islands vary. Irrespective of ecological guild, islands tended to contain more endemic species than mainland countries. Nestedness and species co-occurrence analysis based on country species lists revealed latitudinal and longitudinal gradients of species occurrences across Europe. Species range sizes were much more coherent and had fewer isolated occurrences than expected from a null model based on random colonization. We did not detect clear postglacial colonization trajectories that shaped the faunal composition across Europe. Our results are consistent with a multiregional postglacial colonization. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 498–506.

Spatial distributions of European clearwing moths (Lepidoptera: Sesiidae)

Although the sizes of the geographical ranges of plant and animal species are of major interest to macroecologists, the spa- tial distributions and environmental correlates of only a small group of animals and plants are well studied. Here data on the spatial distributions of 116 European clearwing moths (Sesiidae) was used to determine the patterns in spatial distribution, postglacial colo- nization and endemism. The spatial distributions of sesiids are significantly more coherent and there are fewer isolated occurrences and unexpected absences than predicted by a random sample null model. After correcting for environmental correlates, islands and mainland countries did not differ significantly in the number of species with small ranges. Polyphagous wood attending species were more widespread than those with other life histories. Species of Siberian origin had wider ranges than those of Mediterranean origin. Nestedness and species co-occurrence analysis did not support a unidirectional postglacial colonization from a Southern European refuge but colonization from both Southern and Eastern Europe.