Experimental assessment of endozoochorous dispersal of Prosopis flexuosa seeds by domestic ungulates

Abstract

Question: The spatial and temporal dynamics of plant communities in various ecosystems are shaped by the movements of seeds expressed as different dispersal modes. In desert rangeland, many plants produce relatively large fruits that are limited in their long-distance dispersal abilities and, therefore, depend on transport inside animals, a process termed endozoochory. Evaluating the effectiveness of this process from experimental data is crucial for assessing the potential of domestic ungulates as effective long-distance seed dispersers and, consequently, as management and restoration tools in degraded rangelands. Methods: In this study we jointly estimated recovery, gut retention time (RT) and germination probability of Prosopis flexuosa seeds (a tree species of Monte desert in Argentina) transported by goats, horses and cattle (n = 4) through a seed-feeding experiment. Also, in horses and cattle, we used plastic particles to distinguish between seed loss due to mastication and due to degradation in the gut. Results: Results showed higher seed recovery in horses (26%) than in cattle (3%) and goats (5%), and different values of RT and germination of seeds among species (in decreasing order, RT was: cattle > goats > horses; and germination was: goat > horses > cattle = control seeds). Conclusions: We concluded that the quality of seed treatment by horses is better than by the other species, because of the high seed recovery and high germination compared to control seeds. To get a complete picture of this mutualistic interaction, future studies could inquire about the physical and chemical properties of faeces as substrate and the environmental conditions of sites where seeds are deposited.