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Evaluating multiple spatial scales to understand the distribution of anuran beta diversity in the Brazilian Atlantic Forest

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ABSTRACT

We partitioned the total beta diversity in the species composition of anuran tadpoles to evaluate if species replacement and nestedness components are congruent at different spatial resolutions in the Brazilian Atlantic Forest. We alternated the sampling grain and extent of the study area (among ponds at a site, among ponds within regions, among sites within regions, and among sites within regions pooled together) to assess the importance of anuran beta diversity components. We then performed variation partitioning to evaluate the congruence of environmental descriptors and geographical distance in explaining the spatial distribution of the species replacement and nestedness components. We found that species replacement was the main component of beta diversity, independent of the sampling grain and extent. Furthermore, when considering the same sampling grain and increasing the extent, the values of species replacement increased. On the other hand, when considering the same extent and increasing the sampling grain, the values of species replacement decreased. At the smallest sampling grain and extent, the environmental descriptors and geographic distance were not congruent and alternated in the percentage of variation explaining the spatial distribution of species replacement and nestedness. At the largest spatial scales (SSs), the biogeographical regions showed higher values of the percentage explaining the variation in the beta diversity components. We found high values of species replacement independently of the spatial resolution, but the processes driving community assembly seem to be dependent on the SS. At small scales, both stochastic and deterministic factors might be important processes structuring anuran tadpole assemblages. On the other hand, at a large spatial grain and extent, the processes restricting species distributions might be more effective for drawing inferences regarding the variation in anuran beta diversity in different regions of the Brazilian Atlantic Forest.

No MeSH data available.


Proportion of the variation in the pairwise Jaccard dissimilarity components, species replacement (βjtu—a) and nestedness (βjne—b), explained by the correlations with climatic descriptors, geographic distance (i.e., space), and forest types considering sites as the sampling units and the three forest types (semideciduous seasonal forest, dense rain forest, and mixed rain forest) pooled together as the extent. Climate = variation explained purely by climatic descriptors; space = variation explained purely by space; regions = variation explained purely by forest types; environment ∩ space = spatially structured environment; forest types ∩ space = spatially structured forest types; climate ∩ forest types = climate together with forest types; climate ∩ forest types ∩ space = variation shared among the three descriptors, unexplained = residual. “‐” = not associated with variation in beta diversity components. Boxplot showing values of species replacement (c) and nestedness (d) components between sites in the same region and in different regions. “*” indicates significance at level of .05
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ece32852-fig-0005: Proportion of the variation in the pairwise Jaccard dissimilarity components, species replacement (βjtu—a) and nestedness (βjne—b), explained by the correlations with climatic descriptors, geographic distance (i.e., space), and forest types considering sites as the sampling units and the three forest types (semideciduous seasonal forest, dense rain forest, and mixed rain forest) pooled together as the extent. Climate = variation explained purely by climatic descriptors; space = variation explained purely by space; regions = variation explained purely by forest types; environment ∩ space = spatially structured environment; forest types ∩ space = spatially structured forest types; climate ∩ forest types = climate together with forest types; climate ∩ forest types ∩ space = variation shared among the three descriptors, unexplained = residual. “‐” = not associated with variation in beta diversity components. Boxplot showing values of species replacement (c) and nestedness (d) components between sites in the same region and in different regions. “*” indicates significance at level of .05

Mentions: The relative importance of the environmental descriptors and geographical distance within and among regions, with exception of SS1 that showed different results, was congruent (Figures 2b and 4). From the 12 sites analyzed in SS1, variation in values of species replacement for four sites was explained by environmental descriptors; for one site by geographical distance, while for seven sites was not associated with environmental descriptors or geographical distance (Figure 4SS1). Variation in values of nestedness for two sites was explained by environmental descriptors, while for ten sites was not associated with environmental descriptors or geographical distance (Figure 4SS1). For SS2, we found that variation in beta diversity components was explained by geographical distance in the three regions (Figure 4SS2). For SS3, we found that variation in beta diversity components was not explained either by climatic variables or by geographical distance (Figure 4SS3). For SS4, the regions in which the sites were located explained 17% of the variation in species replacement and 5% of the variation in nestedness (Figure 5). We observed that values of species replacement between sites in the same region were on average 0.51 lower than between sites in different regions (F1,64 = 252.5, p < .001; Figure 5).


Evaluating multiple spatial scales to understand the distribution of anuran beta diversity in the Brazilian Atlantic Forest
Proportion of the variation in the pairwise Jaccard dissimilarity components, species replacement (βjtu—a) and nestedness (βjne—b), explained by the correlations with climatic descriptors, geographic distance (i.e., space), and forest types considering sites as the sampling units and the three forest types (semideciduous seasonal forest, dense rain forest, and mixed rain forest) pooled together as the extent. Climate = variation explained purely by climatic descriptors; space = variation explained purely by space; regions = variation explained purely by forest types; environment ∩ space = spatially structured environment; forest types ∩ space = spatially structured forest types; climate ∩ forest types = climate together with forest types; climate ∩ forest types ∩ space = variation shared among the three descriptors, unexplained = residual. “‐” = not associated with variation in beta diversity components. Boxplot showing values of species replacement (c) and nestedness (d) components between sites in the same region and in different regions. “*” indicates significance at level of .05
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ece32852-fig-0005: Proportion of the variation in the pairwise Jaccard dissimilarity components, species replacement (βjtu—a) and nestedness (βjne—b), explained by the correlations with climatic descriptors, geographic distance (i.e., space), and forest types considering sites as the sampling units and the three forest types (semideciduous seasonal forest, dense rain forest, and mixed rain forest) pooled together as the extent. Climate = variation explained purely by climatic descriptors; space = variation explained purely by space; regions = variation explained purely by forest types; environment ∩ space = spatially structured environment; forest types ∩ space = spatially structured forest types; climate ∩ forest types = climate together with forest types; climate ∩ forest types ∩ space = variation shared among the three descriptors, unexplained = residual. “‐” = not associated with variation in beta diversity components. Boxplot showing values of species replacement (c) and nestedness (d) components between sites in the same region and in different regions. “*” indicates significance at level of .05
Mentions: The relative importance of the environmental descriptors and geographical distance within and among regions, with exception of SS1 that showed different results, was congruent (Figures 2b and 4). From the 12 sites analyzed in SS1, variation in values of species replacement for four sites was explained by environmental descriptors; for one site by geographical distance, while for seven sites was not associated with environmental descriptors or geographical distance (Figure 4SS1). Variation in values of nestedness for two sites was explained by environmental descriptors, while for ten sites was not associated with environmental descriptors or geographical distance (Figure 4SS1). For SS2, we found that variation in beta diversity components was explained by geographical distance in the three regions (Figure 4SS2). For SS3, we found that variation in beta diversity components was not explained either by climatic variables or by geographical distance (Figure 4SS3). For SS4, the regions in which the sites were located explained 17% of the variation in species replacement and 5% of the variation in nestedness (Figure 5). We observed that values of species replacement between sites in the same region were on average 0.51 lower than between sites in different regions (F1,64 = 252.5, p < .001; Figure 5).

View Article: PubMed Central - PubMed

ABSTRACT

We partitioned the total beta diversity in the species composition of anuran tadpoles to evaluate if species replacement and nestedness components are congruent at different spatial resolutions in the Brazilian Atlantic Forest. We alternated the sampling grain and extent of the study area (among ponds at a site, among ponds within regions, among sites within regions, and among sites within regions pooled together) to assess the importance of anuran beta diversity components. We then performed variation partitioning to evaluate the congruence of environmental descriptors and geographical distance in explaining the spatial distribution of the species replacement and nestedness components. We found that species replacement was the main component of beta diversity, independent of the sampling grain and extent. Furthermore, when considering the same sampling grain and increasing the extent, the values of species replacement increased. On the other hand, when considering the same extent and increasing the sampling grain, the values of species replacement decreased. At the smallest sampling grain and extent, the environmental descriptors and geographic distance were not congruent and alternated in the percentage of variation explaining the spatial distribution of species replacement and nestedness. At the largest spatial scales (SSs), the biogeographical regions showed higher values of the percentage explaining the variation in the beta diversity components. We found high values of species replacement independently of the spatial resolution, but the processes driving community assembly seem to be dependent on the SS. At small scales, both stochastic and deterministic factors might be important processes structuring anuran tadpole assemblages. On the other hand, at a large spatial grain and extent, the processes restricting species distributions might be more effective for drawing inferences regarding the variation in anuran beta diversity in different regions of the Brazilian Atlantic Forest.

No MeSH data available.