The division of food space among mammalian species on biomes

Understanding how species ecological partition functions across biomes is
fundamental to macroecology and conservation biology. Here, we examine the
global distribution of dietary strategies in terrestrial mammals, focusing
on how biome specialization modulates trophic diversity and structure on a
broad geographical scale. Using species-level data from over 3,600
terrestrial mammal species, we constructed a multivariate dietary space
and quantified the area, redundancy, dispersion, uniqueness, and turnover
of trophic strategies across ten major biomes. Species were classified as
biome specialists, moderate generalists, or extreme generalists based on
their biome breadth. By analysing biome specialists and generalists
separately, we show that biome specialists tend to exhibit more
constrained and compositionally distinct dietary niches in less productive
biomes, while generalists, particularly moderate generalists, dominate
functional space occupancy in all biomes, even the harsher ones such as
tundra and taiga. This highlights how environmental constraints and
ecological roles shape trophic strategies at global scale. Notably,
extreme generalists tended to exhibit more carnivorous or insectivorous
diets, suggesting a strategy based on mobile predation or opportunism
rather than a highly diversified omnivory. Despite these general patterns,
highly productive biomes supported the greatest diversity of dietary
strategies, with higher functional redundancy and niche packing.
Nestedness and turnover analyses revealed that biome specialists diets are
often subsets of generalists diets, but with significant compositional
shifts across biomes. These findings underscore the dual role of biome
generalists as both functional stabilizers and potential limiters of
ecological diversity, and highlight the vulnerability of specialist
species to global change. Our study offers a mechanistic framework for
understanding how dietary strategies interact with environmental
filtering, and for identifying functional risks in changing ecosystems.