Endozoochory decreases environmental filtering imposed to seedlings

Questions Recruitment microsites are imposed on plants, first by seed dispersal and then by the environment. Different seed dispersal vectors could decrease or increase the environmental filtering imposed on seedlings, depending on their specificity to deliver seeds to suitable microsites for germination and establishment. We addressed the hypothesis that endozoochory reduces the environmental filtering imposed to seedlings to a larger extent than does anemochory. We predicted that seedlings from animal-dispersed species should show a higher degree of environmental coupling. Location Northern Patagonian Andean region of Argentina, 40-42 degrees S. Methods We characterized the relationship of seedlings, saplings and reproductive individuals to total radiation, air temperature and relative humidity for 16 woody species growing in 25 plant communities of different post-fire ages in temperate forests of southern South America. Results Seedlings and saplings of endozoochorous species occurred under more similar environmental conditions than seedlings and saplings of anemochorous species. Basically, the mean difference in plantenvironment correlation coefficients between saplings and seedlings was <0.2 for all endozoochorous species and >0.2 for all anemochorous species for all environmental variables. Comparisons between dispersal modes were also statistically significant before and after controlling for phylogenetic relationships among species. Even though saplings and seedlings of endozochorous species tended to occur under similar environmental conditions, we did not find evidence that saplings and seedlings co-occur in the same physical microsites. Finally, we did not find evidence either that seedlings of endozoochorous species tended to occur differentially underneath reproductive individuals of the same species (i.e. more seeds falling by gravity beneath maternal plants). Conclusions The tighter coupling between seedlings of endozoochorous species and environmental factors persisting to the sapling stage suggests that relying on animals for seed dispersal reduces mortality costs during the early stages of recruitment by reducing the environmental filtering imposed on seedlings.