Is there variation in the effects of primate size as seed dispersers?: Seed and seedling performance after gut simulation treatments in hydrochloric acid

Abstract

Primates are reliable seed dispersers due to their foraging patterns and ability to transport seeds several hundred kilometers away from the parent tree. It has been observed in the wild that seeds defecated by primates with longer digestive tracts have more successful seed germination. Within the primate stomach, hydrochloric acid (HCl) is a major gastric acid that helps digest and breakdown foods. Hydrochloric acid may also be beneficial to plants as well; the acid provides corrosion of the seed coat to reduce the time a seed spends dormant. Therefore organisms that swallow seeds indirectly treat seeds with HCl acid baths and provide beneficial seed modifications. In this study, seeds were treated with HCl for two hour intervals to determine the effect on germination and growth to stimulate varying time in the gut of various primate species with varying gut lengths. We found that larger primates (i.e., those with longer digestive tracts) may be more effective seed dispersers as seeds germinated earlier and seedlings performed better the longer the time they spent in the acid (i.e., stimulated gut), although they were also more susceptible to herbivory. These findings demonstrate the positive effects of primates on seedling germination and their potential as seed dispersers.

Keywords: acid baths, endozoochory, gut length, plant-animal interaction, primate, seed dispersal, seed dormancy