DISPERSAL AND GERMINATION OF SEEDS INGESTED BY CARNIVORES IN A MEXICAN TROPICAL DRYLAND

Resumen

Seed dispersal by animals influences plant recruitment depending on the number of dispersed seeds, the treatment given to seeds in gut, and the germination and seedling survival in sites where seeds are dropped in the field. Seed dispersal by carnivores influences plant recruitment in temperate and tropical ecosystems. However, data on seed dispersal by carnivores in tropical drylands are limited. In these ecosystems, plants produce large numbers of fruits that may be eaten by carnivores, yet we ignore whether seed dispersal potentially influences plant recruitment. Hence, we investigated seed dispersal, seed germination after gut passage, and seed deposition of plants eaten by carnivores in the Tehuacán-Cuicatlán Valley. We collected scats to quantify the number of seeds per scat, percentage of damaged seeds per scat, and number of scats in the field. We also examined the relationship between seed number and seed weight, and compared the germination between seeds removed from fruits and scats in laboratory experiments. We found seeds from 18 plant species in scats collected in the field. Scats had an average of 133 seeds and 0.3% of damaged seeds. Seed number was negatively related to seed weight. Scats were dropped more frequently than expected in open areas and less frequently than expected in rocky and canopy areas. Gut passage had positive effects on germination in two species, neutral effects in six species, and negative effects in four species. Our data showed that carnivore scats had large numbers of viable seeds and gut passage increases seed germination or allows seed transportation to particular sites in fourteen species. However, gut passage decreases germination in four species. These results suggest that seed dispersal by carnivores potentially influences plant recruitment in the Tehuacán-Cuicatlán Valley.