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Janne Soininen - One of the best experts on this subject based on the ideXlab platform.
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regional occupancy in unicellular eukaryotes a reflection of Niche Breadth habitat availability or size related dispersal capacity
Freshwater Biology, 2006Co-Authors: Jani Heino, Janne SoininenAbstract:Summary 1. The distribution patterns of unicellular and multicellular organisms have recently been shown to differ profoundly, with the former probably being mostly cosmopolitan, whereas the latter are mostly restricted to certain regions. However, the within-region distribution patterns of these two organism groups may be rather similar. 2. We predicted that the degree of regional occupancy in unicellular eukaryotes would be related to Niche characteristics, dispersal ability and size, as has been found previously for multicellular organisms. The Niche characteristics we considered were Niche position, that measures marginality in species habitat distribution, and Niche Breadth, that measures amplitude in species habitat distribution. Niche characteristics were determined using Outlying Mean Index (OMI) analysis. 3. We found that the regional occupancy in our model group of unicellular eukaryotes, stream diatoms, was primarily a reflection of the Niche position of a species or, more generally, habitat availability. Thus, non-marginal species (i.e. species that occupied common habitat conditions across the region) tended to be more widely distributed than marginal species (i.e. species that were restricted to a limited range of rare habitat conditions). This finding was further supported by the general linear model, with Niche position, Niche Breadth, maximum size and attachment mode as explanatory variables: Niche position was by far the most important variable accounting for variability in regional occupancy, with significant amounts of additional variation related to Niche Breadth and maximum size of diatoms. 4. Thus, the degree of regional occupancy among unicellular eukaryotes may be primarily governed by habitat availability, supporting former findings for multicellular organisms.
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Regional occupancy in unicellular eukaryotes: a reflection of Niche Breadth, habitat availability or size‐related dispersal capacity?
Freshwater Biology, 2006Co-Authors: Jani Heino, Janne SoininenAbstract:Summary 1. The distribution patterns of unicellular and multicellular organisms have recently been shown to differ profoundly, with the former probably being mostly cosmopolitan, whereas the latter are mostly restricted to certain regions. However, the within-region distribution patterns of these two organism groups may be rather similar. 2. We predicted that the degree of regional occupancy in unicellular eukaryotes would be related to Niche characteristics, dispersal ability and size, as has been found previously for multicellular organisms. The Niche characteristics we considered were Niche position, that measures marginality in species habitat distribution, and Niche Breadth, that measures amplitude in species habitat distribution. Niche characteristics were determined using Outlying Mean Index (OMI) analysis. 3. We found that the regional occupancy in our model group of unicellular eukaryotes, stream diatoms, was primarily a reflection of the Niche position of a species or, more generally, habitat availability. Thus, non-marginal species (i.e. species that occupied common habitat conditions across the region) tended to be more widely distributed than marginal species (i.e. species that were restricted to a limited range of rare habitat conditions). This finding was further supported by the general linear model, with Niche position, Niche Breadth, maximum size and attachment mode as explanatory variables: Niche position was by far the most important variable accounting for variability in regional occupancy, with significant amounts of additional variation related to Niche Breadth and maximum size of diatoms. 4. Thus, the degree of regional occupancy among unicellular eukaryotes may be primarily governed by habitat availability, supporting former findings for multicellular organisms.
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Latitudinal gradients in Niche Breadth and position-regional patterns in freshwater fish.
Die Naturwissenschaften, 2006Co-Authors: Jyrki Lappalainen, Janne SoininenAbstract:The latitudinal gradient in diversity is widely acknowledged, but the mechanisms contributing to this pattern are still poorly known. Given that the species have environmental optima, a central issue is how species’ Niche parameters, i.e. Niche Breadth and Niche position, vary along the latitudinal gradient. In this study, we examined the determinants of fish distribution and the variability in species’ Niche Breadth and position along latitudinal gradient using a regional data set of boreal lakes. Results of the Outlying Mean Index analysis showed that the fish community structure was jointly controlled by a number of environmental factors, ranging from water chemistry and temperature to local physical factors such as lake area and depth. Corroborating the number of earlier findings, the regional occupancy of species was more strongly governed by the Niche position than the Niche Breadth, although both showed a significant relationship with the regional distribution. When the latitudinal variability in Niche parameters of the main taxonomic groups was analysed, both percids and cyprinids, being cool water species, showed significant decrease in Niche Breadth northwards as we predicted. By contrast, the Niche position and latitude were non-significantly correlated in percids and salmonids, and negatively correlated in cyprinids, the latter showing the opposite pattern as we predicted. However, even if only a part of our predictions was supported, the results generally implied that the examination of latitudinal variability in the Niche properties is potentially highly rewarding, not only in estimation of present community structure in lakes but also for predictions of species’ responses to climate change.
Jani Heino - One of the best experts on this subject based on the ideXlab platform.
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Predicting occupancy and abundance by Niche position, Niche Breadth and body size in stream organisms.
Oecologia, 2017Co-Authors: Mariana Perez Rocha, Luis Mauricio Bini, Tadeu Siqueira, Jan Hjort, Mira Grönroos, Marja Lindholm, Satu-maaria Karjalainen, Jani HeinoAbstract:The regional occupancy and local abundance of species are thought to be strongly correlated to their body size, Niche Breadth and Niche position. The strength of the relationships among these variables can also differ between different organismal groups. Here, we analyzed data on stream diatoms and insects from a high-latitude drainage basin to investigate these relationships. To generate measures of Niche position and Niche Breadth for each species, we used sets of local environmental and catchment variables separately, applying the outlying mean index analysis. Beta regression and negative binomial generalized linear models were run to predict regional occupancy and mean local abundance, respectively. We found a positive occupancy-abundance relationship in both diatoms and insects, and that Niche-based variables were the main predictors of variation in regional occupancy and local abundance. This finding was mainly due to local environmental Niche position, whereas the effects of Niche Breadth on regional occupancy and local abundance were less important. We also found a relationship between body size and local abundance or regional occupancy of diatoms. Our results thus add to current macroecological research by emphasizing the strong importance of Niche position rather than Niche Breadth and body size for regional occupancy and local abundance in rarely studied organisms (e.g., diatoms and insects) and ecosystems (i.e., wilderness streams).
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regional occupancy in unicellular eukaryotes a reflection of Niche Breadth habitat availability or size related dispersal capacity
Freshwater Biology, 2006Co-Authors: Jani Heino, Janne SoininenAbstract:Summary 1. The distribution patterns of unicellular and multicellular organisms have recently been shown to differ profoundly, with the former probably being mostly cosmopolitan, whereas the latter are mostly restricted to certain regions. However, the within-region distribution patterns of these two organism groups may be rather similar. 2. We predicted that the degree of regional occupancy in unicellular eukaryotes would be related to Niche characteristics, dispersal ability and size, as has been found previously for multicellular organisms. The Niche characteristics we considered were Niche position, that measures marginality in species habitat distribution, and Niche Breadth, that measures amplitude in species habitat distribution. Niche characteristics were determined using Outlying Mean Index (OMI) analysis. 3. We found that the regional occupancy in our model group of unicellular eukaryotes, stream diatoms, was primarily a reflection of the Niche position of a species or, more generally, habitat availability. Thus, non-marginal species (i.e. species that occupied common habitat conditions across the region) tended to be more widely distributed than marginal species (i.e. species that were restricted to a limited range of rare habitat conditions). This finding was further supported by the general linear model, with Niche position, Niche Breadth, maximum size and attachment mode as explanatory variables: Niche position was by far the most important variable accounting for variability in regional occupancy, with significant amounts of additional variation related to Niche Breadth and maximum size of diatoms. 4. Thus, the degree of regional occupancy among unicellular eukaryotes may be primarily governed by habitat availability, supporting former findings for multicellular organisms.
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Regional occupancy in unicellular eukaryotes: a reflection of Niche Breadth, habitat availability or size‐related dispersal capacity?
Freshwater Biology, 2006Co-Authors: Jani Heino, Janne SoininenAbstract:Summary 1. The distribution patterns of unicellular and multicellular organisms have recently been shown to differ profoundly, with the former probably being mostly cosmopolitan, whereas the latter are mostly restricted to certain regions. However, the within-region distribution patterns of these two organism groups may be rather similar. 2. We predicted that the degree of regional occupancy in unicellular eukaryotes would be related to Niche characteristics, dispersal ability and size, as has been found previously for multicellular organisms. The Niche characteristics we considered were Niche position, that measures marginality in species habitat distribution, and Niche Breadth, that measures amplitude in species habitat distribution. Niche characteristics were determined using Outlying Mean Index (OMI) analysis. 3. We found that the regional occupancy in our model group of unicellular eukaryotes, stream diatoms, was primarily a reflection of the Niche position of a species or, more generally, habitat availability. Thus, non-marginal species (i.e. species that occupied common habitat conditions across the region) tended to be more widely distributed than marginal species (i.e. species that were restricted to a limited range of rare habitat conditions). This finding was further supported by the general linear model, with Niche position, Niche Breadth, maximum size and attachment mode as explanatory variables: Niche position was by far the most important variable accounting for variability in regional occupancy, with significant amounts of additional variation related to Niche Breadth and maximum size of diatoms. 4. Thus, the degree of regional occupancy among unicellular eukaryotes may be primarily governed by habitat availability, supporting former findings for multicellular organisms.
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positive relationship between regional distribution and local abundance in stream insects a consequence of Niche Breadth or Niche position
Ecography, 2005Co-Authors: Jani HeinoAbstract:A positive relationship between regional distribution and local abundance of species is almost ubiquitous macroecological pattern, yet the mechanisms behind this pattern remain poorly understood. I tested for the relationship between regional distribution and local abundance of stream insect species in a boreal drainage system, with a specific aim to examine if this relationship follows the mechanistic basis of either the Niche-based (Niche Breadth and Niche position) or metapopulation models. There was a positive relationship between regional distribution and local abundance of stream insects, and there also were significant relationships between distribution/abundance and Niche Breadth or Niche position. These results thus suggest that widely distributed species tend to be, on average, locally more abundant, have wider Niches and lower marginality of Niche position with regard to environmental factors than species that have more restricted distributions. However, although significant, there was much unexplained variability around these relationships, suggesting that other mechanisms (e.g. metapopulation dynamics) besides differences in species' Niches are likely to affect the distribution and abundance of stream insects, at least within a drainage system. The results thus showed that 1) although Niche position was more consistently related to the positive distribution-abundance relationship, ecologists should not abandon Niche Breadth as a potential mechanism behind this relationship, and 2) that several mechanisms are likely to act in concert in determining the relationship between distribution and abundance of species.
Anthony Herrel - One of the best experts on this subject based on the ideXlab platform.
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is dietary Niche Breadth linked to morphology and performance in sandveld lizards nucras sauria lacertidae
Biological Journal of The Linnean Society, 2013Co-Authors: Shelley Edwards, Krystal A. Tolley, Bieke Vanhooydonck, John G Measey, Anthony HerrelAbstract:The functional characteristics of prey items (such as hardness and evasiveness) have been linked with cranial morphology and performance in vertebrates. In lizards particularly, species with more robust crania generally feed on harder prey items and possess a greater bite force, whereas those that prey on evasive prey typically have longer snouts. However, the link between dietary Niche Breadth, morphology, and performance has not been explicitly investigated in lizards. The southern African genus Nucras was used to investigate this link because the species exhibit differing Niche Breadth values and dietary compositions. A phylogeny for the genus was established using mitochondrial and nuclear markers, and morphological clusters were identified. Dietary data of five Nucras species, as reported previously, were used in correlation analyses between cranial shape (quantified using geometric morphometrics) and dietary Niche Breadth, and the proportion of hard prey taken and bite force capacity. Dietary Niche Breadth and the proportion of hard prey eaten were significantly related to cranial shape, although not once phylogeny was accounted for using a phylogenetic generalized least squares regression. The proportion of evasive prey eaten was a significant predictor of forelimb length when phylogeny was taken into account. We conclude that, in Nucras, the percentage of evasive prey taken co-evolves with forelimb morphology, and dietary Niche Breadth co-evolves with cranial shape. However, although head width is correlated with the proportion of hard prey eaten, this appears to be the result of shared ancestry rather than adaptive evolution.(c) 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110, 674-688.
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Is dietary Niche Breadth linked to morphology and performance in Sandveld lizards Nucras (Sauria: Lacertidae)?
Biological Journal of the Linnean Society, 2013Co-Authors: Shelley Edwards, Krystal A. Tolley, Bieke Vanhooydonck, G. John Measey, Anthony HerrelAbstract:The functional characteristics of prey items (such as hardness and evasiveness) have been linked with cranial morphology and performance in vertebrates. In lizards particularly, species with more robust crania generally feed on harder prey items and possess a greater bite force, whereas those that prey on evasive prey typically have longer snouts. However, the link between dietary Niche Breadth, morphology, and performance has not been explicitly investigated in lizards. The southern African genus Nucras was used to investigate this link because the species exhibit differing Niche Breadth values and dietary compositions. A phylogeny for the genus was established using mitochondrial and nuclear markers, and morphological clusters were identified. Dietary data of five Nucras species, as reported previously, were used in correlation analyses between cranial shape (quantified using geometric morphometrics) and dietary Niche Breadth, and the proportion of hard prey taken and bite force capacity. Dietary Niche Breadth and the proportion of hard prey eaten were significantly related to cranial shape, although not once phylogeny was accounted for using a phylogenetic generalized least squares regression. The proportion of evasive prey eaten was a significant predictor of forelimb length when phylogeny was taken into account. We conclude that, in Nucras, the percentage of evasive prey taken co-evolves with forelimb morphology, and dietary Niche Breadth co-evolves with cranial shape. However, although head width is correlated with the proportion of hard prey eaten, this appears to be the result of shared ancestry rather than adaptive evolution.(c) 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110, 674-688.
Christoph Leuschner - One of the best experts on this subject based on the ideXlab platform.
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The relationships between abundance, range size and Niche Breadth in Central European tree species
Journal of Biogeography, 2009Co-Authors: Benjamin Köckemann, Holger Buschmann, Christoph LeuschnerAbstract:Aim Range size and Niche Breadth have been found to be positively related to abundance in many plant and animal groups. We tested these two relationships for the tree species flora of Central Europe; that is, for all 25 species that have their distribution centre in this region. Location Eurasia, with a focus on Central Europe. Methods We devised an abundance and Niche variable classification system to transform the existing literature data into a semi-quantitative assessment of abundance and Niche Breadth (in terms of soil chemical and physical variables, and temperature) for each of the 25 tree species. Regression analyses between abundance, range size and Niche Breadth were conducted for the entire species sample and for subsets of species defined by their ecology or phylogeny. Results The relationship between abundance in the distribution centre and range size was weak for the Central European tree species. However, significant abundance–range size relationships were found for phylogenetically or ecologically more homogenous species groups (for example for trees of the order Rosales and for mid-successional tree species). Realized Niche Breadth was positively related to range size in the case of temperature, but not for soil-related variables. No relationship existed between Niche Breadth and abundance in the distribution centre. Main conclusions We hypothesize that the weak relationship between abundance and range size is primarily a consequence of substantial ecological and phylogenetic heterogeneity within this rather species-poor assemblage. The positive relationship between realized temperature Niche Breadth and range size emphasizes the strong influence of climatic variables on plant distribution patterns over continental or global scales.
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Abundance, Niche Breadth, and Niche occupation of Central European tree species in the centre and at the margin of their distribution range
Forest Ecology and Management, 2009Co-Authors: Christoph Leuschner, Benjamin Köckemann, Holger BuschmannAbstract:Abstract How abundance, Niche Breadth and Niche occupation of species change within the distribution range remains unresolved for tree floras. We compared populations of three common and three rare European tree species in the distribution centre and at the eastern margin with respect to abundance, Niche Breadth, and preferential occurrence along several soil-related Niche axes. We hypothesised: (i) that abundance is higher, and Niche Breadth greater, in the distribution centre than at the margin, (ii) that the occupied Niche differs between central and marginal populations with species being restricted to more favourable soils at the margin, and (iii) that common and rare species show different patterns. We characterised the occupied Niche and Niche Breadth in a semi-quantitative way and discuss the role of human impact on tree abundance in the light of evidence from paleoecology and forest dynamics research. Five of the six species are more abundant in the centre than at the margin, at least in the natural vegetation prior to human intervention. In contrast to soil Niche Breadth, the preference for soil chemical and hydrological properties differed between centre and margin. Contrary to expectation, a shift to less fertile and partly also drier sites at the margin was observed, although bedrocks which give rise to the development of fertile soils were more frequent in Slovakia (ca. 49% of the total area compared to 20% in Central Germany) and bedrock types which produce infertile soils were more abundant in Central Germany (about 23% vs. 2% in Slovakia). While the abundant-centre-distribution hypothesis is supported by our data, we found no conclusive evidence of competitive displacement of weaker competitors and of a Niche shift of superior competitors to more favourable sites at the range margin. Factors other than competition must be responsible for the observed Niche shifts. Higher drought stress does not seem to be a limiting factor at the eastern margin, where dry sites were occupied more frequently compared to the centre.
Holger Buschmann - One of the best experts on this subject based on the ideXlab platform.
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The relationships between abundance, range size and Niche Breadth in Central European tree species
Journal of Biogeography, 2009Co-Authors: Benjamin Köckemann, Holger Buschmann, Christoph LeuschnerAbstract:Aim Range size and Niche Breadth have been found to be positively related to abundance in many plant and animal groups. We tested these two relationships for the tree species flora of Central Europe; that is, for all 25 species that have their distribution centre in this region. Location Eurasia, with a focus on Central Europe. Methods We devised an abundance and Niche variable classification system to transform the existing literature data into a semi-quantitative assessment of abundance and Niche Breadth (in terms of soil chemical and physical variables, and temperature) for each of the 25 tree species. Regression analyses between abundance, range size and Niche Breadth were conducted for the entire species sample and for subsets of species defined by their ecology or phylogeny. Results The relationship between abundance in the distribution centre and range size was weak for the Central European tree species. However, significant abundance–range size relationships were found for phylogenetically or ecologically more homogenous species groups (for example for trees of the order Rosales and for mid-successional tree species). Realized Niche Breadth was positively related to range size in the case of temperature, but not for soil-related variables. No relationship existed between Niche Breadth and abundance in the distribution centre. Main conclusions We hypothesize that the weak relationship between abundance and range size is primarily a consequence of substantial ecological and phylogenetic heterogeneity within this rather species-poor assemblage. The positive relationship between realized temperature Niche Breadth and range size emphasizes the strong influence of climatic variables on plant distribution patterns over continental or global scales.
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Abundance, Niche Breadth, and Niche occupation of Central European tree species in the centre and at the margin of their distribution range
Forest Ecology and Management, 2009Co-Authors: Christoph Leuschner, Benjamin Köckemann, Holger BuschmannAbstract:Abstract How abundance, Niche Breadth and Niche occupation of species change within the distribution range remains unresolved for tree floras. We compared populations of three common and three rare European tree species in the distribution centre and at the eastern margin with respect to abundance, Niche Breadth, and preferential occurrence along several soil-related Niche axes. We hypothesised: (i) that abundance is higher, and Niche Breadth greater, in the distribution centre than at the margin, (ii) that the occupied Niche differs between central and marginal populations with species being restricted to more favourable soils at the margin, and (iii) that common and rare species show different patterns. We characterised the occupied Niche and Niche Breadth in a semi-quantitative way and discuss the role of human impact on tree abundance in the light of evidence from paleoecology and forest dynamics research. Five of the six species are more abundant in the centre than at the margin, at least in the natural vegetation prior to human intervention. In contrast to soil Niche Breadth, the preference for soil chemical and hydrological properties differed between centre and margin. Contrary to expectation, a shift to less fertile and partly also drier sites at the margin was observed, although bedrocks which give rise to the development of fertile soils were more frequent in Slovakia (ca. 49% of the total area compared to 20% in Central Germany) and bedrock types which produce infertile soils were more abundant in Central Germany (about 23% vs. 2% in Slovakia). While the abundant-centre-distribution hypothesis is supported by our data, we found no conclusive evidence of competitive displacement of weaker competitors and of a Niche shift of superior competitors to more favourable sites at the range margin. Factors other than competition must be responsible for the observed Niche shifts. Higher drought stress does not seem to be a limiting factor at the eastern margin, where dry sites were occupied more frequently compared to the centre.