Data from: Establishing macroecological trait datasets: digitalization, extrapolation, and validation of diet preferences in terrestrial mammals worldwide

Ecological trait data are essential for understanding the broad-scale
distribution of biodiversity and its response to global change. For
animals, diet represents a fundamental aspect of species’ evolutionary
adaptations, ecological and functional roles, and trophic interactions.
However, the importance of diet for macroevolutionary and macroecological
dynamics remains little explored, partly because of the lack of
comprehensive trait datasets. We compiled and evaluated a comprehensive
global dataset of diet preferences of mammals (“MammalDIET”). Diet
information was digitized from two global and cladewide data sources and
errors of data entry by multiple data recorders were assessed. We then
developed a hierarchical extrapolation procedure to fill-in diet
information for species with missing information. Missing data were
extrapolated with information from other taxonomic levels (genus, other
species within the same genus, or family) and this extrapolation was
subsequently validated both internally (with a jack-knife approach applied
to the compiled species-level diet data) and externally (using independent
species-level diet information from a comprehensive continentwide data
source). Finally, we grouped mammal species into trophic levels and
dietary guilds, and their species richness as well as their proportion of
total richness were mapped at a global scale for those diet categories
with good validation results. The success rate of correctly digitizing
data was 94%, indicating that the consistency in data entry among multiple
recorders was high. Data sources provided species-level diet information
for a total of 2033 species (38% of all 5364 terrestrial mammal species,
based on the IUCN taxonomy). For the remaining 3331 species, diet
information was mostly extrapolated from genus-level diet information (48%
of all terrestrial mammal species), and only rarely from other species
within the same genus (6%) or from family level (8%). Internal and
external validation showed that: (1) extrapolations were most reliable for
primary food items; (2) several diet categories (“Animal,” “Mammal,”
“Invertebrate,” “Plant,” “Seed,” “Fruit,” and “Leaf”) had high proportions
of correctly predicted diet ranks; and (3) the potential of correctly
extrapolating specific diet categories varied both within and among
clades. Global maps of species richness and proportion showed congruence
among trophic levels, but also substantial discrepancies between dietary
guilds. MammalDIET provides a comprehensive, unique and freely available
dataset on diet preferences for all terrestrial mammals worldwide. It
enables broad-scale analyses for specific trophic levels and dietary
guilds, and a first assessment of trait conservatism in mammalian diet
preferences at a global scale. The digitalization, extrapolation and
validation procedures could be transferable to other trait data and taxa.