Effects of terrestrial mammals on plant functional diversity in a Neotropical forest

It is well established that the presence or absence of herbivorous mammals can change the species richness and diversity of plant communities. The impact of mammals on the functional diversity of plant communities has received less investigation, particularly in tropical forests. We measured functional traits and abundance of woody saplings in a thirteen year-old terrestrial mammal exclosure experiment on Barro Colorado Island, Panama. We hypothesized that traits of exclosure communities would favor competitive ability while traits of plants communities with mammals present would favor defense. Our results suggest that plant communities lacking mammals do have a higher community mean specific leaf area (p = 0.03) and lower community mean leaf toughness (p = 0.03) than communities with ambient mammal exposure, but do not show a significant difference in mean seed mass. Furthermore, within species there was a consistent trend of lower leaf water contents inside exclosures (p < 0.001), suggesting that an increase in plant density following mammal exclosure may increase competition for water.