DOI: 10.5061/dryad.nk98sf7st
title: Biogeography of bird and mammal trophic structures

description: Does climate determine the trophic organization of communities around the
 world? A recent study showed that a limited number of community trophic
 structures emerge when co-occurrence of trophic guilds among large mammals
 is examined globally. We ask whether the pattern is general across a all
 terrestrial mammals (n=5272) and birds (n=9993). We found that the six
 community-trophic structures previously identified with large mammals are
 largely maintained when all mammals and birds are examined, both together
 and separately, and that bioclimatic variables, including net primary
 productivity (NPP), are strongly related to variation in the geographical
 boundaries of community trophic structures. We argue that results are
 consistent with the view that trophic communities are self-organized
 structures optimizing energy flows, and that climate likely acts as the
 main control parameter by modulating the amount of solar energy available
 for conversion by plants and percolated through food webs across trophic
 communities. Gradual changes in climate parameters would thus be expected
 to trigger abrupt changes in energy flows resulting from phase transitions
 (tipping points) between different dynamical stable states. We expect
 future research to examine if our results are general across organisms,
 ecosystems, scales, and methodologies, and whether inferences rooted in
 complex systems theory are supported. The emergence of general patterns in
 the functional properties of animal communities at broad scales supports
 the emergence of food-web biogeography as a sub-discipline of biogeography
 focused on the analysis of the geographical distributions of trophic
 relationships among organisms.
description: Methods: How was this
 dataset collected? How has it been processed? Three sources of geographical
 data were extracted and plotted in a world terrestrial 1º×1º grid system:
 (1) global distributional ranges of non-marine mammal and bird species;
 (2) bioclimatic variables; and (3) net primary productivity. The global
 species distributions were derived from IUCN Global Assessment
 distributional data for native ranges (IUCN 2014). Specific occurrences in
 grid cells were used to produce a presence/absence matrix with names of
 9993 non-marine birds and 5272 terrestrial mammals (15265 species) as
 columns and 15370 1º × 1º grid cells as rows. In the global species-level
 compilation published by Wilman et al. (2014), trophic resources are
 classified into 10 categories. The trophic profile of each species
 (Data_I) is obtained from the estimated percentage of each type of
 resource in their diet. The result is a matrix with the 10 trophic
 resources categories as columns, 15265 species of birds and mammals as
 rows, and values representing the estimated percentage of each type of
 resource. The eleventh column in Data_I is the trophic guild (TG) in which
 these species were classified. These trophic guilds were obtained using
 c-means clustering, on the basis of the Euclidean distance between the
 15265 species in the 10-dimensional ‘species-level trophic space’ defined
 by the estimated percentage of each type of resource in their
 diet. In Data_II,
 15370 1º × 1º terrestrial grid cells are identified by their coordinates
 (latitude and longitude). To obtain their trophic profile, we assigned
 species to their correspondent guild (Data_I) and then counted the number
 of species of each guild within the cell. The result is a matrix with the
 9 trophic guilds as columns, 15370 communities as rows, and values
 representing numbers of species. The trophic profile of every community is
 thus a point in a 9-dimensional ‘trophic space’ defined by the number of
 species from each trophic guild (a vector of dimension 9). The tenth
 column in Data_II is the type of trophic structure found in the cell.
 These trophic structures (TS1 to TS6) correspond to well-defined clusters
 across this 9-dimensional ‘community-level trophic space’ identified with
 the help of the AMD index.  Bioclimatic data for the
 terrestrial surface of the Earth (Data_III) were obtained from WorldClim -
 Global Climate Data (Hijmans et al. 2005).