Tree diversity promotes functional dissimilarity and maintains functional richness despite species loss in predator assemblages (original) (raw)
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Canadian Journal of Forest Research, 2020
The majority of natural forest steppes in Central-Europe were converted to forest plantations, a significant part of plantations are composed of exotic pine trees. This brings dramatic changes in habitat structure. The formerly open-canopy forest patches and grasslands became closed-canopy forests and key habitat factors were altered, such as microhabitat diversity, plant species composition, microclimate, and amount of dead organic matter. Here we studied the difference in spider species richness, assemblage composition, and functional diversity of native forest steppes, exotic pine plantations, their edges, and adjacent grasslands. We selected 10 native forest patches and 10 pine plantations in commercial maturity, all plantations had direct interface with extensive forest steppe areas. We sampled spiders in forests, forest edges, and adjacent steppe grasslands, resulting in 60 sampling plots. We found different species composition in natural forest patches and pine plantations; however forest edges and grasslands near forest edges did not differ significantly. Spiders with preferences for shaded and humid habitats were associated with forests. Web builders were associated with pine plantations and their edges, large vegetation dwelling spiders had preferences for grasslands and native forest edge, and ballooning spiders were associated with grasslands and edges. Pine forest belts around natural forest steppe patches, besides being low quality secondary habitats for forest steppe spiders, also hamper effective dispersal; the high density of trees and the lower wind speed may act as barriers for effective ballooning. Contrary to our expectations, we found lower functional diversity at natural sites than at pine plantations. The hot and dry microclimate of natural forest steppes favours some trait states (e.g., drought-tolerant, preferences for open habitats), and this may lead to convergence in trait values and a lower functional diversity of forest steppe spider assemblages than the that of assemblages in pine plantations.
Journal of Arachnology, 2010
Understanding the variation of diversity patterns requires analysis at multiple spatial scales. In this study we estimated the diversity components (alpha, beta and gamma) of the spider community at El Vínculo Natural Regional Park, using the additive partitioning of diversity (species richness, Shannon's diversity index and Simpson's index) for the first time on this taxon in Colombia. We collected the specimens following a nested sampling design that consisted of two spatial scales. At the local scale, we quantified additive diversity components in 238 sampling units, and at the regional scale in five vegetation types. Total observed regional diversity (c) was partitioned into its additive components: within sampling units (a 1), among sampling units (b l) and among vegetation types (b 2). We used the same approach to compare common and infrequent spider species and to compare sampling methods. A total of 1565 adult spiders and 72 identifiable juveniles, including 193 morphospecies from 36 families, was sampled during the study. In all cases (entire community, infrequent species, common species and four different sampling methods) we found that a significant percentage, relative to that of randomization tests, of the diversity measurements used was attributed to beta diversity among vegetation types. The relative contributions of alpha and beta diversity to total observed regional diversity depended on the diversity measurement used. The contribution of beta diversity with respect to alpha diversity was low using Simpson's index (less than 20%), whereas with species richness and Shannon's index the contribution was high (up to 90% and up to 66%, respectively). Our results suggest that beta diversity is the main component of diversity in the natural park. We concluded that the maintenance of a large variety of vegetation types can be an important tool for the conservation of spider richness at the natural park.
Macroecological patterns of spider species richness across Europe
Biodiversity and Conservation, 2008
We analysed the pattern of covariation of European spider species richness with various environmental variables at different scales. Four layers of perception ranging from single investigation sites to the whole European continent were selected. Species richness was determined using published data from all four scales. Correlation analyses and stepwise multiple linear regression were used to relate richness to topographic, climatic and biotic variables. Up to nine environmental variables were included in the analyses (area, latitude, elevation range, mean annual temperature, local variation in mean annual temperature, mean annual precipitation, mean July temperature, local variation in mean July temperature, plant species richness). At the local and at the continental scale, no significant correlations with surface area were found, whereas at the landscape and regional scale, surface area had a significant positive effect on species richness. Factors that were positively correlated with species richness at both broader scales were plant species richness, elevation range, and specific temperature variables (regional scale: local variation in mean annual, and mean July temperature; continental scale: mean July temperature). Latitude was significantly negatively correlated with the species richness at the continental scale. Multiple models for spider species richness data accounted for up to 77% of the total variance in spider species richness data. Furthermore, multiple models explained variation in plant species richness up to 79% through the variables mean July temperature and elevation range. We conclude that these first continental wide analyses grasp the overall pattern in spider species richness of Europe quite well, although some of the observed patterns are not directly causal. Climatic variables are expected to be among the most important direct factors, although other variables (e.g. elevation range, plant species richness) are important (surrogate) correlates of spider species richness.
Applied ecology and environmental research, 2015
One of the crucial issues in nature conservation studies refers to the significant investment of time and energy required for a reliable estimation of biodiversity. To overcome this problem we designed a short survey for the estimation the richness of spider species in comparable habitats based on a semi-quantitative approach. Carrying out the survey in protected and unprotected temperate forest in the north-east Slovenia provided sufficient data for evaluation and relative comparison of spider diversity between the forests. High diversity of spiders observed in both forests indicates their importance as refuge habitats in agriculturally degraded landscape. At the same time, the comparison between surveyed forests shows a significantly higher level of spider diversity in the protected one, which supports the current conservation acts and provides a base-line for future monitoring of spider diversity in the forest. Modified set of sampling methods used in the survey revealed high level of efficiency in sampling by hand-held suction device and suggests its potential as an additional method in spider diversity studies in temperate forests with dense undergrowth. As the study is based on one of the most diverse and abundant animal groups in terrestrial ecosystems, it provides a reliable comparison of estimated biodiversity between comparable sites and exhibits the potential to complement the current criteria for assignment and monitoring of the biodiversity required for efficient conservation planning.
Forest Ecology and Management, 2020
Variable retention mitigates negative effects of traditional harvesting on biodiversity, maintaining legacies in harvested forests as habitat for sensitive species, and generating other habitats for early-seral species. Their assessment, including drivers, has a high concern for society. Likewise, species association with ecosystems in the landscape (as different forest types, grasslands and peatlands) are unknown for some taxa and regions, and could explain species flow into harvested areas. Therefore, we evaluated the forest harvest impact on grounddwelling spiders and vascular plants, their diversity and association to vegetation types in the landscape matrix, and richness and abundance correlations with forest structure. Six natural common habitats were studied in Tierra del Fuego (Argentina), where variable retention has been implemented: aggregated (AR) and dispersed (DR) retention in harvested Nothofagus pumilio forests, unharvested primary forests (NPF) as reference, grasslands (G), peatlands (P), and unharvested N. antarctica forests (NAF). We surveyed spiders (N = 432, by 6 habitats × 6 replicates × 6 collections × 2 years), and vascular plants (N = 36, by 6 habitats × 6 replicates), and characterized forest structure in wooded ecosystems. We determined for both taxa richness, relative abundance (total captures/ground cover) and Shannon-Wiener and Pielou indices, compared assemblage composition and indicator species among harvesting treatments and vegetation types, and analyzed correlations. We sampled 752 individuals of spiders from 33 species (six families), and 79 vascular plant species (28 families) that averaged 52% total vegetation cover. Total spider captures and overall richness were higher in DR > NPF > AR, although differences were not detected at plot level for any variable. For understory vascular plants, richness and cover were the highest on DR, followed by AR and NPF, as well as at plot level, with no affectation in indices. Likewise, highest richness and abundance occurred in NAF and NPF for spiders, and in NAF and G for vascular plants, with unique assemblages in each vegetation type despite the shared species. Assemblages also differed in harvested areas, including species of other vegetation types mainly in DR, where new conditions were generated by reduction of forest structure variables (evidenced by negative correlations), while AR maintained species composition similar to NPF, contributing to the conservation of forest specialists. Indicators occurred for both taxa in several habitats. This study highlights the importance of different vegetation types for spider and plant conservation at landscape level, while provides tools for developing monitoring strategies and conservation policies.
Journal of Arachnology, 2014
We studied how forest stand characteristics influence spider assemblage richness and composition in a forested region of Hungary. Deciduous-coniferous mixed forests dominate in the Ő rség National Park. Thirty-five plots were established and sampled for spiders for three years in 70-110 year-old stands with a continuum of tree species composition. Detailed background information was acquired for stand structure, tree species composition, forest-floor-related variables and spatial position of the plots. The effect of variables was analyzed by nonparametric multiplicative regression on rarefied spider species richness and by redundancy analysis on species composition. The relative importance of variable groups was assessed by variation partitioning. Spider species richness was positively and strongly affected by tree species richness, and the species composition of the spider assemblage was influenced by the proportion of the most important tree species. This study established the importance of tree species composition, but variance partitioning analysis also showed that tree species identity and forest floor variables together explain much of the variation. These findings may guide management and conservation efforts to maintain regional diversity of the spider fauna.
Journal of Tropical Ecology, 2020
Human activities change the biodiversity of ecological communities in at least three dimensions: ecologically, taxonomically and functionally. Gathering information on these three dimensions allows the improvement of biodiversity assessments and the increased understanding of anthropogenic impact on natural communities. In this study, we analysed the spider community associated with the tropical plant Heliconia aurantiaca in two contrasting habitat types: continuous forest and forest fragments in south-eastern Mexico. We examined the foliage, stems and bracts of H. aurantiaca individuals in both habitats. We categorized each spider species according to its behavioural and functional traits. We analysed ecological diversity using Hill numbers, taxonomic distinctness and functional diversity using the FRic index. Overall, we collected a total of 110 spiders, of which 44 individuals from 29 species were found in continuous forests, with 66 individuals from 36 species in forest fragments. We found greater ecological diversity in continuous forest than in fragments. In contrast, we found lower functional diversity in continuous forest than in fragments. Taxonomic diversity showed no significant difference between habitats. Forest fragmentation affected the biodiversity of spiders by disrupting species composition and function, which may lead to other ecological changes such as predator–prey interactions and other aspects of ecosystem functioning.
Animal Biodiversity and Conservation, 2016
The influence of vegetation structure on spider species richness, diversity and community organization in the Apšuciems calcareous fen, Latvia.-Calcareous fens are considered to be among the most threatened ecosystems of Europe. They are also one of the most diverse habitats as they support an incredibly rich and diverse range of plant and animal species. However, in spite of their diversity, calcareous fens are still poorly investigated, especially when referring to fen invertebrates, such as spiders. Because spiders are good bioindicators, knowledge of their ecology in rare and threatened habitats is of interest. The aim of this study was to document the composition and diversity of spider species, families and foraging guilds in the ground-and grass-layers of the Apšuciems calcareous fen, and to evaluate the influence of vegetation structure on spider community organization. In summer 2012, we collected ground-dwelling spiders using pitfall traps and grassdwelling spiders using sweep-netting. A total of 2,937 spider individuals belonging to 19 families and 80 species was collected in the Apšuciems fen. Our results indicate that spider species and families tend to be stratified across the vertical structure of the habitat; the spider composition in the ground stratum differed from that in the grass stratum. On the contrary, however, the spider foraging guild structure between the ground-layer and the grass-layer was similar. Each of the two studied strata presented similar guilds in similar proportions. Our results also showed that spider composition differed considerably between fen parts and that much of this variability could be explained by the architectural properties of the habitat. More diverse vegetation generally supported a higher number of spider species.
Book preface: The protection of forests and forest-related biodiversity has received increasing attention both at the national and international level. At the same time, increasing demands are being made on European forests with respect to the products and energy they can and do provide on a renewable, climate-friendly, and domestic basis. Forests provide income for many farmers, forest owners, and the forest industry and offer valuable recreation opportunities and protection from various hazards, especially for urban dwellers, and are thus subject to many questions on the state of their biodiversity and their protection. The positive or negative impacts of forest management practices and the question whether biodiversity in multi-functional forests can be better enhanced by integrative or segregative approaches are subjects of ongoing debate. Spiders in Forest Ecosystems: Introductory section Spiders are a key component of forest ecosystems, occupying a unique position in food webs...