Gopher Tortoise (Gopherus polyphemus) Gut Passage Can Alter Seed Germinability

Abstract

Seed dispersal by animals is an important plant-animal mutualism, but saurochory, the dispersal of seeds by reptiles, is an understudied phenomenon despite its prevalence in many taxa. The effects of seed ingestion by the gopher tortoise (Gopherus polyphemus) were investigated in eight central Florida plant species by comparing germination of ingested seeds to seeds that did not pass through tortoises. Seeds from both treatments were also planted with and without tortoise scat. Both the percentage of seeds germinating and the time to germination were recorded. Ingested seeds from two fleshy-fruited plant species germinated in greater proportions and in less time than control seeds. The presence of scat also increased germination proportion following gut passage and decreased time to germination in both these species. Germination proportions in five dry-fruited native species were either not affected, or lowered, and time to germination was either not affected, or slower. Similarly, the effects of scat had either no effect on germination percentage in these species or caused a decrease, and either had no effect on time to germination or caused an increase. One non-native dry-fruited species was also tested, and although germination percentage following gut passage was unaffected, time to germination decreased. Similarly, while the addition of scat increased germination percentage, there was no effect on time to germination. In summary only seeds from fleshy-fruited plant species were consistently positively impacted by passage through gopher tortoise guts and by gopher tortoise scat.