Multi-host and multi-taxon experiment reveals the overlooked importance of small-sized carrion for biodiversity

The diversity of resources, such as plants or dung of different mammal species, is an essential basis for the diversity of consumers at higher trophic levels. Here, animal carcasses provide an ephemeral and unpredictable resource of high nutrient content used by microbes, insects and vertebrates. While succession stage or season have already been identified as important for the composition and diversity of scavengers, the role of the carrion species is, compared to other necromass resources such as deadwood, not well understood. In this study, we investigated the role of ten mammal carrion species for the diversity of fungi, bacteria, Dipterans, Coleoptera and vertebrates. To do so, we exposed 100 carcasses of ten vertebrate species with varying body sizes in a low-mountain range area (Bavarian Forest National Park, Bavaria, Germany). To quantify the role of carrion species identity on the carcass necrobiome groups, we used sample coverage standardized diversity estimates of α-, β- and γ-diversity and uniqueness in composition. Despite a range in carcass size from 0.04kg (single stoat carcass) to more than 100 kg (single red deer carcass), we found no significant differences in α- and β-diversity, except for bacteria. Thus, the highest γ-diversity was found in small-sized carrion species for vertebrate scavengers (stoat) and fungi (marten), and in medium-sized species for Coleoptera (beaver), bacteria (red fox) and Diptera (red fox). However, carcass size alone did not explain diversity. The uniqueness of Coleoptera was highest for beaver carcasses, while all other groups showed the highest uniqueness for stoat. Our findings suggest that particular small and medium-sized carcasses can make an important contribution to necrobiome diversity at the landscape scale, although the mechanisms underlying these patterns and their management implications require further studies.