Herbivore digestion as environmental filter - which seed traits help species survive?

Abstract

Abstract Herbivorous animals are one of the vectors for seed dispersal of open-landscape plant species. The plant species are expected to be adapted to this type of dispersal and researchers presume they have specific seed traits. To find which traits help seeds survive the passage through digestion of wild herbivores, we conducted a comprehensive feeding experiment with almost forty species of plants and four species of herbivorous mammals. We fed specified numbers of seeds to the animals, collected the dung and germinated the dung content. We explored whether seed morphological traits and seed nutrient contents are good predictors of seed survival after passage through the herbivore digestive system. We also tested how the seed survival differed after the passage through different herbivore species. We found that species survival and germination success was positively correlated to seed nitrogen content and negatively to seed elongation. However, when we tested species from main families separately, i.e., legumes, grasses, and all other species, these trends changed directions. This suggests that seed dispersal by free-ranging wild herbivores is more a random process than driven by seed traits.