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The co-occurrence of species and the co-diversity of sites in neutral models of biodiversity.

Trejo-Barocio P, Arita HT - PLoS ONE (2013)

Bottom Line: The nearly covariance among species, in contrast, implies low variance in species richness of sites and very slim frequency distributions.In real world assemblages of Mexican volant and non-volant mammals, patterns of range-size and species-richness frequency distribution are similar to those generated by neutral models.However, when the comparison includes the covariance both for species (co-occurrence) and for sites (co-diversity), empirical patterns differ significantly from the predictions of neutral models.

View Article: PubMed Central - PubMed

Affiliation: Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, México, D. F., México.

ABSTRACT
Patterns of co-occurrence of species are widely used to assess the fit of ecological neutral models to empirical patterns. The mathematically equivalent patterns of co-diversity of sites, in contrast, have been considered only indirectly and analyses normally are focused on the spatial distribution of species richness, rather than on the patterns of species sharing. Here we use two analytical tools (range-diversity plots and rank plots) to assess the predictions of simple neutral models in relation to patterns of co-occurrence and co-diversity. Whereas a fully stochastic model predicts zero average among species and among sites, neutral models generate systems with low levels of covariance among species and high levels of positive covariance among sites. These patterns vary with different combinations of dispersal and speciation rates, but are always linked to the shape, symmetry, and spread of the range-size and species-richness frequency distributions. Non-homogeneous patterns of diversity and distribution arise in neutral models because of the spatial arrangement of sites and their concomitant similarity, which is reflected also in the spread of the range-size frequency distribution. The nearly covariance among species, in contrast, implies low variance in species richness of sites and very slim frequency distributions. In real world assemblages of Mexican volant and non-volant mammals, patterns of range-size and species-richness frequency distribution are similar to those generated by neutral models. However, when the comparison includes the covariance both for species (co-occurrence) and for sites (co-diversity), empirical patterns differ significantly from the predictions of neutral models. Because of the mathematical links between the covariance in the distribution of species and the variance of species-richness values and between the covariance in species sharing among sites and the variance of range-size values, a full understanding of patterns of diversity calls for the simultaneous analysis of co-occurrence and co-diversity.

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Range-diversity plots by sites for different combinations of the speciation and dispersal parameters in neutral models.Information as in Figure 2B.
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pone-0079918-g004: Range-diversity plots by sites for different combinations of the speciation and dispersal parameters in neutral models.Information as in Figure 2B.

Mentions: The extreme case with no speciation ( and no dispersal () yielded systems with the 136 species having very small ranges, producing presence-absence matrices with very low fill (), meaning that on average only 1.3% of species occurred in a given cell and 1.3% of sites were included in the range of a given species. Points in the RD plot for species are concentrated on the lower sector of the graph and along the vertical line, indicating that all species had very small ranges and average covariance close to zero (Fig. 3 top left panel). Similarly, points for sites concentrated on the lower left sector of the RD plots, indicating very low species richness values and average covariance with other sites close to zero (Fig. 4 top left panel). The resulting rank plots were extremely flat, indicating the very low degree of variation both in range size of species and in species richness of sites (Figs. 5 and 6, top left panels).


The co-occurrence of species and the co-diversity of sites in neutral models of biodiversity.

Trejo-Barocio P, Arita HT - PLoS ONE (2013)

Range-diversity plots by sites for different combinations of the speciation and dispersal parameters in neutral models.Information as in Figure 2B.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3823601&req=5

pone-0079918-g004: Range-diversity plots by sites for different combinations of the speciation and dispersal parameters in neutral models.Information as in Figure 2B.
Mentions: The extreme case with no speciation ( and no dispersal () yielded systems with the 136 species having very small ranges, producing presence-absence matrices with very low fill (), meaning that on average only 1.3% of species occurred in a given cell and 1.3% of sites were included in the range of a given species. Points in the RD plot for species are concentrated on the lower sector of the graph and along the vertical line, indicating that all species had very small ranges and average covariance close to zero (Fig. 3 top left panel). Similarly, points for sites concentrated on the lower left sector of the RD plots, indicating very low species richness values and average covariance with other sites close to zero (Fig. 4 top left panel). The resulting rank plots were extremely flat, indicating the very low degree of variation both in range size of species and in species richness of sites (Figs. 5 and 6, top left panels).

Bottom Line: The nearly covariance among species, in contrast, implies low variance in species richness of sites and very slim frequency distributions.In real world assemblages of Mexican volant and non-volant mammals, patterns of range-size and species-richness frequency distribution are similar to those generated by neutral models.However, when the comparison includes the covariance both for species (co-occurrence) and for sites (co-diversity), empirical patterns differ significantly from the predictions of neutral models.

View Article: PubMed Central - PubMed

Affiliation: Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, México, D. F., México.

ABSTRACT
Patterns of co-occurrence of species are widely used to assess the fit of ecological neutral models to empirical patterns. The mathematically equivalent patterns of co-diversity of sites, in contrast, have been considered only indirectly and analyses normally are focused on the spatial distribution of species richness, rather than on the patterns of species sharing. Here we use two analytical tools (range-diversity plots and rank plots) to assess the predictions of simple neutral models in relation to patterns of co-occurrence and co-diversity. Whereas a fully stochastic model predicts zero average among species and among sites, neutral models generate systems with low levels of covariance among species and high levels of positive covariance among sites. These patterns vary with different combinations of dispersal and speciation rates, but are always linked to the shape, symmetry, and spread of the range-size and species-richness frequency distributions. Non-homogeneous patterns of diversity and distribution arise in neutral models because of the spatial arrangement of sites and their concomitant similarity, which is reflected also in the spread of the range-size frequency distribution. The nearly covariance among species, in contrast, implies low variance in species richness of sites and very slim frequency distributions. In real world assemblages of Mexican volant and non-volant mammals, patterns of range-size and species-richness frequency distribution are similar to those generated by neutral models. However, when the comparison includes the covariance both for species (co-occurrence) and for sites (co-diversity), empirical patterns differ significantly from the predictions of neutral models. Because of the mathematical links between the covariance in the distribution of species and the variance of species-richness values and between the covariance in species sharing among sites and the variance of range-size values, a full understanding of patterns of diversity calls for the simultaneous analysis of co-occurrence and co-diversity.

Show MeSH
Related in: MedlinePlus