Seed dispersal by carnivorous mammals into burnt forests: An opportunity for non-indigenous and cultivated plant species

Some species of carnivorous mammals are important seed dispersers of wild, cultivated and ornamental fleshy-fruited plants, and can transport seeds to long distances. In recently disturbed areas, such seed dispersal may have a role in vegetation dynamics, and may support the introduction of non-indigenous plants into such areas. In this study we aimed to assess the importance of carnivorous mammals as vectors of fleshy-fruited plants into areas recently affected by wildfires, and whether they may contribute to weed colonization and spread. We also wanted to study the hypothetical influence of the distance from fruit sources on the spatial distribution of dispersed seeds. Moreover, we examined the emergence success and survival rates of most dispersed species, predicting that gut passage would improve germination. We collected carnivore scats along transects in paths and dirt roads in a burnt area in Catalonia (Spain), recording the distance of each scat to the fire border. Germination trials were carried out both in the field and in a greenhouse, using seeds obtained from scats, from ripe fruits (manually removing the pulp), and using fruits with the pulp intact. Seeds of the same three treatments were planted in the field. We confirmed that carnivore species, especially red fox, disperse seeds into burnt areas. Most seeds belonged to non-indigenous species, with the Mediterranean hackberry being the most abundant one. Seed dispersal took place more intensely near the unburnt area, while scats that did not contain seeds were distributed independently of the distance from the fire border. Gut passage improved germination of hackberry seeds, both in field and greenhouse trials, but the survival rate of hackberry seedlings was very low. Although the efficiency of carnivores as dispersers was limited in the case of hackberry, we should not underestimate their importance in other species, or under different conditions. Therefore, it is important to minimize the availability of invasive fleshy-fruited plants that could be transported into disturbed areas by carnivores.