Abstract
Species assemblages often have a non-random nested organization, which in vertebrate scavenger (carrion-consuming) assemblages is thought to be driven by facilitation in competitive environments. However, not all scavenger species play the same role in maintaining assemblage structure, as some species are obligate scavengers (i.e., vultures) and others are facultative, scavenging opportunistically. We used a database with 177 vertebrate scavenger species from 53 assemblages in 22 countries across five continents to identify which functional traits of scavenger species are key to maintaining the scavenging network structure. We used network analyses to relate ten traits hypothesized to affect assemblage structure with the "role" of each species in the scavenging assemblage in which it appeared. We characterized the role of a species in terms of both the proportion of monitored carcasses on which that species scavenged, or scavenging breadth (i.e., the species "normalized degree"), and the role of that species in the nested structure of the assemblage (i.e., the species "paired nested degree"), therefore identifying possible facilitative interactions among species. We found that species with high olfactory acuity, social foragers, and obligate scavengers had the widest scavenging breadth. We also found that social foragers had a large paired nested degree in scavenger assemblages, probably because their presence is easier to detect by other species to signal carcass occurrence. Our study highlights differences in the functional roles of scavenger species and can be used to identify key species for targeted conservation to maintain the ecological function of scavenger assemblages.
Highlights
IntroductionUnderstanding the structure of communities may reveal critical insights on their functioning, such as understanding the role of keystone species, ecological engineers, and interactions among species (Hooper et al 2005)
How natural communities organize has interested ecologists for decades (Elton 1966)
We identified relevant functional traits that characterize those species that are critical to maintaining the structure of scavenger networks in terms of proportion of carcasses visited and how good a species is in predicting the use of the carcass by another species (i.e., “paired nested degree,” AlmeidaNeto et al 2008)
Summary
Understanding the structure of communities may reveal critical insights on their functioning, such as understanding the role of keystone species, ecological engineers, and interactions among species (Hooper et al 2005). The species in an assemblage, differ in their contribution to community structure. Ecologists have recently realized that the most important species for network structure may share several key functional traits (Coux et al 2016). In seed-dispersal assemblages, frugivorous birds play the most important network roles at a global scale (Schleuning et al 2014). Functional traits, regarded as any property of organisms that influence performance (McGill et al 2006), offer an ideal framework to better understand the mechanisms driving assemblage structure and how different geographic areas may be characterized by functionally similar species
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