Seed dispersal by carnivores in temperate and tropical dry forests

The seed dispersal mechanisms and regeneration of various forest
ecosystems can benefit from the actions of carnivores via endozoochory.
This study aims to evaluate the role of carnivores in endozoochory and
diploendozoochory, as well as their effect on seed viability,
scarification, and germination in two forest ecosystems: temperate and
tropical dry forest. We collected carnivore scat in the Protected Natural
Area of Sierra Fría in Aguascalientes, Mexico, for two years to determine
the abundance and richness of seeds dispersed by each carnivore species,
through scat analysis. We assessed seed viability through optical
densitometry using X-rays, analyzed seed scarification by measuring seed
coat thickness using a scanning electron microscope, and evaluated seed
germination in an experiment as the percentage of seeds germinated per
carnivore disperser, plant species, and forest type. In the temperate
forest, four plant species (but mainly Arctostaphylos pungens) were
dispersed by four mammal species. The gray fox dispersed the highest
average number of seeds per scat (66.8 seeds). Bobcat dispersed seeds
through diploendozoochory, which was inferred from rabbit (Sylvilagus
floridanus) hair detected in their scats. The tropical dry forest
presented higher abundance of seeds and richness of dispersed plant
species (four species) than in the temperate forest, and the coati
dispersed the highest number of seeds (8639 seeds). Endozoochory and
diploendozoochory did not affect viability in thick testas
seeds in temperate forest and thin testas seeds in
tropical dry forest. Endozoochory improved the selective germination of
seeds. Nine plant species were dispersed by endozoochory, but only one
species (Juniperus sp.) by diploendozoochory. These results suggest that
carnivores can perform an important ecological function by dispersing a
great abundance of seeds, scarifying these seeds causing the formation of
holes and cracks in the testas without affecting viability and promoting
the selective germination of seeds.