Tropical mammal functional diversity increases with productivity but decreases with anthropogenic disturbance

Abstract

A variety of factors can affect the biodiversity of tropical mammal communities, but their relative importance and directionality remain uncertain. Previous global investigations of mammal functional diversity have relied on range maps instead of observational data to determine community composition. We test the effects of species pools, habitat heterogeneity, primary productivity and human disturbance on the functional diversity (dispersion and richness) of mammal communities using the largest standardized tropical forest camera trap monitoring system, the Tropical Ecology Assessment and Monitoring (TEAM) Network. We use occupancy values derived from the camera trap data to calculate occupancy-weighted functional diversity and use Bayesian generalized linear regression to determine the effects of multiple predictors. Mammal community functional dispersion increased with primary productivity, while functional richness decreased with human-induced local extinctions and was significantly lower in Madagascar than other tropical regions. The significant positive relationship between functional dispersion and productivity was evident only when functional dispersion was weighted by species' occupancies. Thus, observational data from standardized monitoring can reveal the drivers of mammal communities in ways that are not readily apparent from range map-based studies. The positive association between occupancy-weighted functional dispersion of tropical forest mammal communities and primary productivity suggests that unique functional traits may be more beneficial in more productive ecosystems and may allow species to persist at higher abundances.

Productivity correlates positively with mammalian diversity independently of the species’ feeding guild, body mass, or the vertical strata explored by the species

“…There are indications that mammalian assemblages are more likely to be able to withstand human anthropogenic disturbance in areas of higher productivity (Peres 2000, Swan et al 2020). More productive sites, associated with more rapid forest turnover, are usually associated with higher food availability (Phillips et al 2004) so that ecosystem productivity may lead to increased population sizes and mammal diversity, and promotes lower extinction rates (Hawkins et al 2003, Evans et al 2005, Luo et al 2012, Gorczynski et al 2021). Even with increasing anthropogenic activities, the recovery of some groups of mammals can be more rapid in more productive locations, because the higher resource availability and diversity in these locations allow both larger populations and quicker population recovery (Peres & Dolman 2000).…”

“…As a consequence, species will be less susceptible to local extinctions (Chase 2010), mitigating the impact of anthropogenic disturbance. This has conservation implications, since a higher ecosystem carrying capacity presupposes higher energetic levels to meet the high metabolic requirements of mammals, sustaining more individuals and a more diverse array of species (Hubbell 2001, Allen et al 2007, Hurlbert & Stegen 2014, Gorczynski et al 2021). Thus, ecosystem productivity could be assumed to be an ecological factor, which increases environmental resilience to anthropogenic disturbance.…”

Functional diversity loss and change in nocturnal behavior of mammals under anthropogenic disturbance

“…Changes in functional composition and diversity of a community can alter or impair key ecosystem functions (Tilman et al., 1997 ). Hence, measures of functional diversity provide insights into ecological processes and inform effective conservation (Gorczynski et al., 2021 ). Body size, trophic guild (i.e., diet), and diel activity appear to be key functional traits closely correlated with anthropogenic disturbances (Gaynor et al., 2018 ; Mazel et al., 2017 ; Weideman et al., 2020 ).…”

Low level of anthropization linked to harsh vertebrate biodiversity declines in Amazonia

“…Concerning mammals, the absence of the largest and smallest mammal species at most of the anthropized sites parallel the trends reported elsewhere in the world 36 , 37 . The absence of top predators such as jaguars, giant otters, and bush dogs ( Speothos venaticus ) in anthropized sites could disturb top-down trophic chain control 38 and thus can deeply impact terrestrial and aquatic ecosystems functioning 39 . Consequently, the ecological roles performed and the ecological services provided by these taxa are jeopardized.…”