Seed dispersal from animals is an important component of seed success in the tropical plant genus Piper. Fungi can have beneficial interactions with seeds, and an important knowledge gap centers on the seed fungal community that establishes after seeds pass through the gut of their disperser. Our research has three objectives: 1) Identify changes to the seed fungal community of Piper sancti-felicis after passage through the bat gut, 2) Evaluate the antifungal properties of alkenylphenols extracted from fruit as a potential filter for fungal colonization prior to dispersal, and 3) Analyze morphological changes to the seeds for evidence of scarification. To answer these questions, we used the diverse plant genus, Piper (Piperaceae), which is dispersed primarily by bats and has diverse defensive compounds. We caught 22 short tailed fruit bats from 3 different species that specialize on Piper infructescences (Carollia spp., Phyllostomidae), fed them seeds of Piper sancti-felicis and then collected their guano to recollect seeds. Seeds were surface sterilized either immediately or after a sitting in guano for a week. We performed a microdilution assay with 10 different fungi isolated from Piper seeds to detect antifungal activity. Seed scarification was determined through image analysis.
Results/Conclusions
We found that the fungal communities that colonized seeds differed between undigested and digested seeds, with undigested seeds hosting the greatest diversity of fungi. Moreover, a few fungi colonized the interior of seeds in digested seeds. Alkenylphenols present in the fruit of P. sancti-felicis exhibited antifungal properties, with decreased fungal growth over 48 hours. Finally, scarification occurred through the digestion through the bat gut. The seed microbiome is one of the least explored axes of plant-fungal symbioses and deserves more attention because of its consequences for plant fitness. Moreover, Piper has become a tropical model system for studying tri-trophic interactions because of our growing understanding of its evolutionary history, distribution, plant chemistry, genomics and species interactions, which puts this experiment into a well understood ecological context. In particular, Piper and Carollia have a tight knit interaction where infructescences of Piper sancti-felicis ripen at dusk, when Carollia become active. Connecting the antifungal properties of the fruit, via alkenylphenols, with isolated seed fungi provides insight into the interaction between fruit mutualisms (e.g., dispersers) and antagonisms (e.g., pathogens).