Small carnivores contribute surrogate seed dispersers for a megafaunal-fruited liana in subtropical Asia

Abstract

The megafaunal seed dispersal hypothesis posits that mega-fruits co-evolved for seed dispersal by extremely large mammals, such as elephant-like gomphotheres, which became extinct during the Pleistocene. Nevertheless, various plants in subtropical Asia still produce oversized fruits as a seed dispersal syndrome anachronism. Here, we investigated how a mega-fruited perennial woody liana, Akebia trifoliata achieves the consumption of its large, sweet, edible fruits to disperse its seeds in a subtropical region on China where the mega frugivores are absent nowadays. We hypothesized that some other surrogate species may be fulfilling this dispersal function. From 2926 fecal samples from 13 species of mammal and various unidentified birds, collected over two years, we identified A. trifoliata seeds in only 13 feces from the masked palm civet (Paguma larvata). Our systematic sampling allowed us to eliminate any role being played by all other plausible dispersal mutualists; not least, these fruits rarely fall to the ground and deteriorate quickly, and so must be picked from the vine by species able to reach 2–5m above the ground. Of 338 masked palm civet feces examined during the August to September fruiting season only 3.85% (frequency of occurrence) contained A. trifoliata seeds, although when seeds were present, they were abundant (c. 600/feces). All seeds passing through the gut of masked palm civets were intact. Moreover, masked palm civets mainly dispersed A. trifoliata seeds in degraded habitats (i.e., the logged, and selectively logged forests). These results showed that although masked palm civets dispersed A. trifoliata seeds in low proportion, they could play a surrogate seed dispersal role for this mega-fruit vine species, especially in degraded forests. Our findings highlight that, in subtopical Asia, small frugivorous carnivores can act as surrogate seed dispersers for oversized fruit plants, advancing knowledge on how past species interactions and defaunation underlie modern plant distributions.