| 1. |
- Astor, Tina, et al.
(författare)
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Importance of environmental and spatial components for species and trait composition in terrestrial snail communities
- 2017
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Ingår i: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 44, s. 1362-1372
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Tidskriftsartikel (refereegranskat)abstract
- AimDespite the huge diversity of soil animals and their recognized contribution to many ecosystem functions, little is known about the relative importance of factors controlling their abundance and distribution. We examined the relative importance of environmental and spatial factors in explaining the species and functional trait composition of terrestrial snail communities at the level of meta-communities (spatial extent c.100x100km) in a heterogeneous, intensively used landscape. We hypothesized that both spatial and environmental factors contribute to the variation in community structure across the landscape, but expected environmental variables describing local habitat conditions to be most important.LocationCounty of Skane, south Sweden.MethodsWe quantified community structure in terms of species composition and as functional trait composition, because functional traits directly link species performance to environmental conditions. To disentangle the unique and shared contribution of environmental and spatial factors to the variation in snail community structure (in terms of species and trait composition) we applied a partial redundancy analysis.ResultsSpecies traits explained more of the variance in community composition than species identity. Snail traits such as tolerance to environmental stress (related to soil moisture content) and niche width were correlated with the main environmental gradient. Environmental variables (i.e. soil moisture content, vegetation characteristics and soil pH) contributed considerably more to variation in community composition (species: 11.4%; traits: 24.9%) than the spatial variables (species: 6.5%; traits: 4.2%).Main conclusionsThe results highlight that both environmental and spatial variables are required to understand the relative importance of niche-based and intrinsic population processes as drivers of terrestrial snail community structure. However, at the scale of our study niche-based community structuring explained by the trait-environment relationship is considerably more important than spatial patterning independent of the environment.
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| 2. |
- Astor, Tina, et al.
(författare)
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Measuring feeding traits of a range of litter-consuming terrestrial snails: leaf litter consumption, faeces production and scaling with body size
- 2015
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 178, s. 833-845
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Tidskriftsartikel (refereegranskat)abstract
- Plant litter decomposition is an essential ecosystem function that contributes to energy and nutrient cycling above- and belowground. Terrestrial gastropods can affect this process in various ways: they consume and fragment leaf litter and create suitable habitats for microorganisms through the production of faeces and mucus. We assessed the contributions of ten litter-feeding terrestrial snail species to leaf litter mass loss and checked whether consumption rate and faeces production scale with body size (i.e. shell size and shape), which may indicate that morphological traits can serve as proxies for consumption rate. Additionally, we compared the consumption rates of a subset of these species among litter types of two plant species which differ in resource quality (Fraxinus excelsior and Betula pendula). These snail species differed in their litter consumption rates. Consumption rates differed between the two litter types, whereas the rank order of litter consumption by the different species was independent of litter quality. Consumption rate and faeces production were positively related to shell size, whereas relative consumption rate and faeces production were related to shell shape, with more elongated snail species having lower relative consumption rates and faeces production rates. Our results show that easily measurable morphological traits scale with the feeding traits of snails, and represent useful proxies for consumption rate and faeces production, which are laborious to measure. Thus, estimated potential total consumption rates of snail communities along environmental gradients may be inferred from shell-size distributions. Our study contributes to a systematic trait-based evaluation of the importance of gastropods to litter decomposition.
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| 3. |
- Astor, Tina
(författare)
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The importance of species traits in biodiversity-ecosystem functioning research
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Biodiversity‐ecosystem functioning research is a major field in ecology. Currently research on biodiversity and ecosystem functioning is shifting from focusing on species diversity to focus on functional diversity. From this point of views species traits play a central role, because it is the traits that determine how a species reacts to environmental change, and how this reaction influences ecosystem functions. In this essay, I present an overview over the nature and measurement of traits, and highlight examples of trait based approaches from different ecosystems. Despite that there is an increasing numbers of studies dealing with this topic, there is still confusion about the terminology of traits and functional groups. A new concept, dividing species traits into response‐ and effect traits seems to be a promising step forward. So far, focus has been placed on plants, because these are the most studied organisms in this field. Some key plant traits, such as leaf dry matter content (LDMC) and specific leaf area (SLA), are identified to be important factors determining species responses to environmental change, and seem to affect ecosystem functioning. Although decomposition is an ecosystem function of fundamental importance, the knowledge about soil communities is still limited. Despite that they are known to have considerable effects on decomposition rates, soil animal traits are rarely considered in decomposition studies. A change may, however be on its way, as the interest of the role of soil animal traits recently seem to be increasing.
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| 4. |
- Astor, Tina, et al.
(författare)
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Underdispersion and overdispersion of traits in terrestrial snail communities on islands
- 2014
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 4:11, s. 2090-2102
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Tidskriftsartikel (refereegranskat)abstract
- Understanding and disentangling different processes underlying the assembly and diversity of communities remains a key challenge in ecology. Species can assemble into communities either randomly or due to deterministic processes. Deterministic assembly leads to species being more similar (underdispersed) or more different (overdispersed) in certain traits than would be expected by chance. However, the relative importance of those processes is not well understood for many organisms, including terrestrial invertebrates. Based on knowledge of a broad range of species traits, we tested for the presence of trait underdispersion (indicating dispersal or environmental filtering) and trait overdispersion (indicating niche partitioning) and their relative importance in explaining land snail community composition on lake islands. The analysis of community assembly was performed using a functional diversity index (Rao's quadratic entropy) in combination with a null model approach. Regression analysis with the effect sizes of the assembly tests and environmental variables gave information on the strength of under- and overdispersion along environmental gradients. Additionally, we examined the link between community weighted mean trait values and environmental variables using a CWM-RDA. We found both trait underdispersion and trait overdispersion, but underdispersion (eight traits) was more frequently detected than overdispersion (two traits). Underdispersion was related to four environmental variables (tree cover, habitat diversity, productivity of ground vegetation, and location on an esker ridge). Our results show clear evidence for underdispersion in traits driven by environmental filtering, but no clear evidence for dispersal filtering. We did not find evidence for overdispersion of traits due to diet or body size, but overdispersion in shell shape may indicate niche differentiation between snail species driven by small-scale habitat heterogeneity. The use of species traits enabled us to identify key traits involved in snail community assembly and to detect the simultaneous occurrence of trait underdispersion and overdispersion.
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| 5. |
- Astor, Tina
(författare)
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What do snails do in ecosystems? it is a matter of traits
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Current environmental changes demand the ability to predict possible consequences for ecosystems performing important functions regulating the Earth system, and providing essential services for human well-being. Indirect impacts can occur through changes in biotic communities. Functional traits determine organisms' performance, and thus their fitness in a given environment. Therefore, traits can be used to assess communities' response to environmental variation (via response traits) and their effects on ecosystem processes (via effect traits). In this thesis, I used terrestrial snails as study organisms to examine different aspects of their response to environmental and spatial factors, and their potential effects on leaf litter decomposition, as mediated by their traits. I investigated which factors determine the assembly of communities and found that trait underdispersion was more common than trait overdispersion, indicating the dominance of environmental filtering over biotic interactions. Testing the relative importance of environmental and spatial factors, I found that both environment and space significantly contributed to the variation in community trait composition, whereby the environment had the strongest effect. This indicates that intrinsic population processes (e.g. dispersal) that are independent from the environment play only a subordinate role. Moreover, I conducted microcosm experiments to measure snail traits that affect leaf litter decomposition (consumption rate, faeces production and assimilation efficiency) testing two litter types differing in quality. With the observed relationship between species specific shell size and consumption rate as proxy I assessed snail communities' potential influence on leaf litter decomposition along an acidification gradient. Several traits responded to environmental factors in all three observational studies (shell size, number of offspring, reproduction mode, and microhabitat occurrence), or in two of the three studies (survival of dry period, and humidity preference) suggesting some generality of certain trait-environment relationships. Three traits (shell size, calcium affinity, and self-fertilization) and one measure of functional diversity (functional richness) responded both to environmental variation, and influenced the snails' potential contribution to leaf litter decomposition.
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