Effect of passage through the gut of Greater Rheas on the germination of seeds of plants of cerrado and caatinga grasslands

Frugivorous seed-dispersers play an important role in the maintenance or regeneration of plant populations and communities. Greater Rheas are potentially one of the most import dispersers of seeds in South American grassland biomes owing to their capacity to swallow large seeds and their habitat of walking long distances each day. We studied the potential role of Greater Rheas in the dispersion of seeds of plants of the cerrado and caatinga grassland biomes through germination experiments. We evaluated the rate of seed germination and the mean time of germination of passage through the gut (seeds that passed through the digestive system of Rheas) compared with a control (seeds extracted directly from fruits). Nine species of plant from cerrado grasslands and three plant species from caatinga grasslands were tested. All three caatinga plant species germinated at a lower rate and took longer to germinate after passage through the gut, whereas two of nine cerrado plant species germinated at a higher rate and in less time after passage through the gut. Greater Rheas are probably good dispersers of some of the plant species we examined and may therefore be important in maintenance and regeneration of habitat. Future experiments will investigate the factors causing the variation in germination of seeds seen in this experiment.