Overlooked stories beneath the rocks: Rodents as potential columnar cactus seed dispersers in the campo rupestre ecosystem

Although small rodents are typically considered seed predators, recent evidence indicates they may also serve as endozoochoric dispersers for small-seeded plants. In this context, Thrichomys apereoides (Rodent) is one of the main consumers of Cipocereus minensis fruits, an endemic cactus within the campo rupestre ecosystem, a high-elevation rocky grassland. However, the full extent of its potential as a seed dispersal agent for this plant remains unknown. We investigated the effects of seed scarification following gut passage by T. apereoides on cactus seeds, evaluating the gut passage effects on seed fate (germinability and viability). We also explore possible mechanisms involved in germination changes by evaluating the morphological changes in seeds after gut passage. We found that 92 % of seeds found in T. apereoides feces appeared undamaged. However, we observed a divergent effect of gut passage on seed fate: while it had no effect on the seed viability, it reduced seed germination from 11.9 % (Seeds without pulp, extracted directly from ripe fruits) to 4.3 %. An anatomical analysis of seeds reveals that while the seed coat is thick and resistant to gut passage, microfissures in some seeds allow for embryo digestion. Despite those limitations, our results provide the first evidence for the potential contribution of T. apereoides dispersing viable seeds of C. minensis, a vital process to seed bank formation and plant establishment.