Functional diversity and redundancy of tropical forest mammals over time

Globally, tropical rain forests comprise some of the most diverse and
functionally rich ecosystems but are increasingly degraded by human
impacts. Protected areas have been shown to conserve species diversity,
but their effectiveness at maintaining functional diversity over time is
less well known, despite the fact that functional diversity likely reveals
more ecological information than taxonomic diversity. By extension, the
degree to which species loss decreases functional diversity within
protected areas is also unknown; functional redundancy may buffer
communities from loss of functional diversity from some local extinctions.
Using eight years of camera trap data, we quantified annual functional
dispersion of the large mammal community in the Volcán Barva region of
Costa Rica and tested for changes in functional dispersion over time in
response to environmental and anthropogenic predictors. We quantified
functional redundancy based on modeled declines in functional dispersion
with species loss. Functional dispersion did not change significantly over
time and was not associated with measured environmental or anthropogenic
predictors. Quantitative modeling of change in functional traits over time
did not identify significant changes. We did however find qualitative
trends in relative trait proportions, which could be indicative of
functional change in the future. We found high functional redundancy, with
average functional dispersion declining significantly only after 9 out of
21 large mammal species were lost from the community. We cautiously
suggest that protected tropical rain forests can conserve functional
diversity over the course of a decade even in heavily fragmented
landscapes.