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

Abstract

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.

Combining paleo-data and modern exclosure experiments to assess the impact of megafauna extinctions on woody vegetation

“…Whereas some niche separation was evident (57,61,62), recent multiproxy data on megaherbivore paleodiets suggests that many were mixed feeders that adapted their diets to local plant availability (62)(63)(64). Similarly, extant megaherbivores are mostly mixed feeders with a few grazing specialists like the hippopotamus (Hippopotamus amphibius) and white rhinoceros (Ceratotherium simum) (65). Further work comparing the guild structures of megaherbivores both in the present and the Late Pleistocene would provide better understanding of the potential impact of these species on vegetation structure.…”

Extinction‐driven changes in frugivore communities on oceanic islands

“…For tortoises, body mass was calculated with morphometric data from 182 Aldabra giant tortoises (Aldabrachelys gigantea) (Supplementary material Appendix 2). The amount of fruit in the diet of each of the species was predominantly derived from existing databases (Kissling et al 2009(Kissling et al , 2014, but also from the primary literature, genus means or surrogate species (Table 1). Because the diet of extinct species could not be quantified at the same level of detail as the diet of extant species, we used three categories to harmonize diet estimates across species and vertebrate classes: low ( 30%), medium (40-60%) or high (70-100%) amounts of fruit in the diet.…”

“…For birds, we used the proportion of fruits in the diet (Kissling et al 2009) relative to other dietary components mentioned in the literature (Del Hoyo et al 2011). For mammals, we used the MammalDIET database (Kissling et al 2014) and assigned data from rank 1, rank 2 and rank 3 as high, medium and low amounts of fruit, respectively. For reptiles as well as mammal and bird species without diet information from existing diet databases, additional primary literature, books and websites (Supplementary material Appendix 1) were used to assign the most likely diet category.…”

“…For reptiles as well as mammal and bird species without diet information from existing diet databases, additional primary literature, books and websites (Supplementary material Appendix 1) were used to assign the most likely diet category. In case species-specific diet descriptions were not available, the diet of close taxonomic relative(s) or the genus mean from existing databases (Kissling et al 2009(Kissling et al , 2014) was used as a surrogate.…”

Towards global interoperability for supporting biodiversity research on essential biodiversity variables (EBVs)

“…(e.g. Kattge et al 2011;Kissling et al 2014;Naeem and Bunker 2009) (Poelen, Simons, and Mungall 2014), but the limited availability of data for modelling species interactions across large spatial scales remains a challenge (e.g. Blois et al 2013;Kissling et al 2012;Morales-Castilla et al 2015;Wisz et al 2013).…”