Understanding how species' ecological partitioning 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 at a broad geographical scale. Using species-level data from over 3600 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 a 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., This work was supported by the European Research
Council under the European Union’s Horizon 2020 research
and innovation program (grant agreement 947921; SV) as
part of the MAPAS project. This paper is part of the LOST
project (PID2021-123202NA-I00) funded by the MCIN/
AEI/10.13039/501100011033/ and FEDER funds. This
research was partially funded by PID2020-116220GB-I00 and
PID2022-138275NB-I00 projects (Ministerio de Ciencia e
Innovación, Spain). This is a contribution by the Paleoclimatology,
Macroecology, and Macreoevolution of Vertebrates team (PMMV)
as part of the research group UCM 910607 on Evolution of
Cenozoic Mammals and Continental Palaeoenvironments. SaG
was funded by the Spanish Ministry of Universities and the Next
Generation European Union programme through a Margarita Salas
Grant from Universidad Complutense de Madrid, grant CT31/21.
SoG was funded by the Universidade de Vigo through a predoctoral
fellowship PREUVIGO-2022 (00VI 131H 6410211). This research
was also funded by an ‘Axuda Complementaria beneficiario axuda
StG do ERC’ from Xunta de Galicia GAIN Oportunius programme
and Consellería de Educación (Galicia, Spain). Funding for Open
Access charge: Universidade de Vigo/ CISUG., Peer reviewed