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Regularities in species’ niches reveal the world’s climate regions

  1. Joaquín Calatayud  Is a corresponding author
  2. Magnus Neuman
  3. Alexis Rojas
  4. Anton Eriksson
  5. Martin Rosvall
  1. Integrated Science Lab, Department of Physics, Umeå University, Sweden
  2. Departamento de Biología, Geología, Física y Química inorgánica, Universidad Rey Juan Carlos, Spain
Research Article
Cite this article as: eLife 2021;10:e58397 doi: 10.7554/eLife.58397
13 figures, 1 table and 1 additional file

Figures

Workflow to identify niche domains and climatic regions.

Using the climatic conditions a given species experiences within its range (A), we project species niches into a climatic space discretized in an optimal number of bins (Appendix 1) (B). We translate the binned data into a weighted bipartite network, where climatic bins and species form the nodes and the probabilities of finding the species in the bins form the weighted links (C). Using a network community detection algorithm, we identify domains of the climatic space with similar species (D, upper). The climatic conditions defining these domains delineate the corresponding climatic regions of the Earth (D, lower). The striped climatic bin links to species classified in both climatic domains, and, therefore, it represents a diffuse transition with low specificity.

Tetrapods’ niche domains across the climatic space.

The climatic niche domains of each group shown across a space defined by potential evapotranspiration (PET) as a surrogate of energy and annual precipitation (AP) as a surrogate of water inputs. Tetrapods’ domains are labeled so that E and W represent energy and water, respectively, and superscripts H, M, and L mean high, medium, and low, respectively. Numerical subscripts differentiate domains of similar climates. Numbers between 0 and 1 indicate the bootstrap support. The dotted line represents the domains at the highest hierarchical level. Domains of less than 50 species are colored dark gray. Domain colors across groups only indicate similar climatic regions. To characterize the climatic space, we used 17 divisions of both PET and AP for all groups except for amphibians, where we used 18 (see Appendix 1).

Figure 2—source data 1

niches domains and the species associated to them.

https://cdn.elifesciences.org/articles/58397/elife-58397-fig2-data1-v2.zip
Tetrapod groups and Köppen’s climatic regions.

(A) Geographic location of tetrapods’ niche domains and Köppen’s climatic regions. See also Appendix 1—figure 1. Colors according to Figure 2. (B) Tetrapods’ climatic regions are labeled according to Figure 2.

Figure 3—source data 1

rasters with climate regions for each studied group.

https://cdn.elifesciences.org/articles/58397/elife-58397-fig3-data1-v2.zip
The geographic location of climatic domains and their associated species provides insights into the mechanism underlying the climatic regions.

(A) Geographic projection of the specificity of climatic bins to their niche domain. (B) An example showing a bird’s niche domain with a low geographical signal. The distribution of the climatic conditions (black line) and the species (colored richness values) belonging to the same niche domain was mostly congruent. (C) An example of an amphibian’s niche domain showing a high geographical signal, reflected in a substantial mismatch between the distribution of climatic conditions and species belonging to the same domain. (D) A quantitative approximation of the geographical signal, ranging between 0 and 1, for the different taxonomic groups (see 'Materials and methods').

Appendix 1—figure 1
Tetrapod groups and Köppen’s climatic regions.

(A) Geographic location of tetrapods’ niche domains and Köppen’s climatic regions. (B) Alluvial diagram comparing the climatic regions between classifications. In the stacks of boxes, one for each classification, a box represents a climatic region, and the height of the box is proportional to the number of raster cells of the climatic region. Streamlines connecting boxes in different stacks depict the number of raster cells shared between climatic regions of different classifications. Colors according to Figure 2.

Appendix 1—figure 2
Geographic projection of the specificity of the climatic bins (SP) for the studied groups.
Appendix 1—figure 3
Distribution of the climatic conditions (black line) and the species (colored richness values) belonging to the same niche domains of amphibians.
Appendix 1—figure 4
Distribution of the climatic conditions (black line) and the species (colored richness values) belonging to the same niche domains of reptiles.
Appendix 1—figure 5
Distribution of the climatic conditions (black line) and the species (colored richness values) belonging to the same niche domains of birds.
Appendix 1—figure 6
Distribution of the climatic conditions (black line) and the species (colored richness values) belonging to the same niche domains of mammals.
Appendix 1—figure 7
Distribution of the climatic conditions (black line) and the species (colored richness values) belonging to the same niche domains of tetrapods.
Appendix 1—figure 8
Distribution of (a) annual precipitation and (b) potential evapotranspiration values.

Seventeen divisions of each climatic variable are presented with red dotted lines.

Appendix 1—figure 9
Predictions of piecewise regression of the increment in Jensen–Shannon divergence (ΔJSD) as a function of the number of divisions in the variables defining the climatic space of all studied groups.

The breakpoints and the coefficient of determinations are also provided.

Tables

Table 1
Similarity of climatic regions measured by adjusted mutual information.
KöppenTetrapodsAmphibiansReptilesBirds
Tetrapods0.44
Amphibians0.400.66
Reptiles0.450.700.58
Birds0.450.770.610.64
Mammals0.470.720.570.660.68

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