Downsizing of animal communities triggers stronger functional than structural losses in seed-dispersal networks

DONOSO, ISABEL; SORENSEN, MARJORIE C.; BLENDINGER PG; KISSLING, W. DANIEL; NEUSCHULZ, EIKE LENA; MUELLER, THOMAS; SCHLEUNING, MATTHIAS

Corbet

Simposio; 7th Frugivores and Seed Dispersers Symposium; 2020

Downsizing of animal communities due to defaunation is prevalent in many ecosystems. Yet, we know little about the consequences of downsizing for ecosystem functions such as seed dispersal. Here, we use eight empirical seed-dispersal networks sampled across the Andes and simulate how downsizing of avian frugivores impacts the structural stability and ecosystem function of these networks. We use a trait-based modelling framework to quantify the consequences of downsizing?relative to random extinctions?for both secondary plant extinctions (as a measure of structural stability) and long-distance seed dispersal (as a measure of ecosystem function). We found that downsizing led to stronger functional than structural losses. For instance, 10% size-structured loss of bird species resulted on average in 35% decline of longdistanceseed dispersal, but only in few secondary plant extinctions. Our simulations reveal that structural changes in ecological networks are insufficient to represent the consequences of animal extinction and downsizing for ecosystem functioning.