Species and individual replacements contribute more than nestedness to shape vertebrate scavenger metacommunities

Abstract

Understanding the mechanisms that organize biodiversity is central in ecology and conservation. Beta diversity links local (alfa) and regional (gamma) diversity, giving insight into how communities organize spatially. Metacommunity ecology provides the framework to interpret regional and local processes interacting to shape communities. However, the lack of metacommunity studies for large vertebrates may limit the understanding and compromise the preservation of ecosystem functions and services. We aim to understand the mechanisms underlying differences in species composition among vertebrate scavenger communities ‒ which provide key ecosystem functions, e.g. carrion consumption ‒ within a metacommunity context. We obtained species richness and abundances at scavenger communities consuming ungulate carcasses monitored through motion‐triggered remote cameras in seven terrestrial ecosystems in Spain. We partitioned beta diversity to decompose incidence‐based (species presence/absence) and abundance‐based dissimilarities into their components (turnover/balanced variation and nestedness/abundance gradient, respectively). We identified the environmental factors explaining the observed patterns. The vertebrate scavenger metacommunity consisted of 3101 individuals from 30 species. Changes in composition among ecosystems were mostly (> 84%) due to species or individual replacement (i.e. turnover or balanced variation). Species or individual loss/gain (i.e. nestedness or abundance gradient) accounted for 13–16% of these changes. Mean carcass weight, elevation and habitat diversity were the main factors explaining species/individual replacement. Our findings suggest that local processes such as species‐sorting through habitat heterogeneity would dominate scavenger metacommunity dynamics together with stochastic forces (i.e. related to carrion unpredictability and scavenging being a widespread strategy among vertebrates). The presence of structured patterns (i.e. nestedness) in beta diversity could reflect a role of deterministic processes: mass‐effects through dispersal and defaunation. Vultures are long‐distance foragers and functionally dominant species, which would connect local assemblages within the metacommunity, supporting scavenger diversity and functions across space. These results highlight the importance of managing vertebrate scavenger assemblages within a metacommunity context.

Large home range scavengers support higher rates of carcass removal

“…In particular, species home range size seems to be a key characteristic in predicting carrion removal rates. Our results also reinforce the idea of the pivotal role of mobile link organisms in ecosystem functioning (Lundberg & Moberg, 2003), which has already been highlighted for vultures in scavenger assemblages (Mateo‐Tomás, Olea, Selva, & Sánchez‐Zapata, 2019), and as providers of ecosystem services at the landscape level (Kremen, Williams, Bugg, Fay, & Thorp, 2004). Most of these links have been explored for specific taxonomic guilds and functions (i.e.…”

Scavenging in the Anthropocene: Human impact drives vertebrate scavenger species richness at a global scale

“…The latter species may benefit from warm and wet climatic conditions, reducing the temporal window of carcass consumption, and outcompeting vertebrates (DeVault, Brisbin, & Rhodes, 2004;Ray, Seibold, & Heurich, 2014). On the other hand, habitat modification and loss, or direct persecution may reduce the population viability of many scavenger species, reducing community diversity and richness (Mateo-Tomás, Olea, Selva, & Sánchez-Zapata, 2018). Moreover, modern human-mediated factors may override evolved latitudinal or ecological patterns, and affect scavenger richness and diversity in both positive and negative ways.…”

“…On the one hand, humans may increase the availability of carrion from hunting, livestock, or roadkills (Lambertucci, Speziale, Rogers, & Morales, 2009;Oro, Genovart, Tavecchia, Fowler, & Martínez-Abraín, 2013), as well as the predictability of carcasses available through wild harvesting (Read & Wilson, 2004), or artificial feeding stations (Cortés-Avizanda et al, 2016), ultimately benefitting scavengers. On the other hand, habitat modification and loss, or direct persecution may reduce the population viability of many scavenger species, reducing community diversity and richness (Mateo-Tomás, Olea, Selva, & Sánchez-Zapata, 2018). Here, we used the largest compilation of vertebrate scavenging studies to date to identify the major drivers of scavenger richness and diversity at a global scale.…”

Fear the reaper: ungulate carcasses may generate an ephemeral landscape of fear for rodents

“…Animal carcasses and the scavengers that use them are important for ecosystem processes and structure [1][2][3]. These processes are underpinned by ecological and species interactions [4][5][6]. Animals take advantage of carrion either through the direct consumption of detritus or indirectly by feeding on arthropod 'blooms' in and around carcass sites [7][8][9].…”

“…only carcass density was used from a range of search radii as a covariate, and an interaction with year (2017 and 2018) was added to assess how each rodent presence, bird abundance and mammal abundance responses varied between years and with carcass density. Model selection (AICc) was used across each response and with the search radius of carcass density ranging(1,2,3,4,5,6,7,8,9,10,15,20,30,40,50, 100, 200 m). A residual autocovariate (RAC) was used in model structures for mesopredator and bird abundance responses, as those models depicted spatial autocorrelation (SAC; Moran's I test) in the residuals.…”