RODENT DISPERSAL OF VESICULAR-ARBUSCULAR MYCORRHIZAL FUNGI IN AMAZONIAN PERU

We quantitatively assessed rodent dispersal of vesicular-arbuscular mycorrhizal fungi in a lowland tropical rain forest. We examined fecal pellets from seven rodent species of the genera Proechimys, Oryzomys, and Mesomys trapped each month from August 1983 through July 1984 at the Cocha Cashu field station in Manu National Park, Peru. We found sporocarps of Sclerocystis coremioides and spores of four Glomus species in 69.3% of fecal samples, with 37.5% of samples containing 2-4 fungus species. There were median numbers of 8.6 S. coremioides sporocarps and 712 Glomus spores/0.1 g feces. S. coremioides and all Glomus species comprised up to 4.1 and 5.4% of fecal mass, respectively. We did not detect differences in fungus consumption by rodent species or sex, but did find significant differences between rodent genera. More than 60% of Proechimys samples contained glomalean fungi in contrast to approximate to 37% of Oryzomys samples. Occurrence of the two fungus genera in feces differed seasonally but was generally congruent between Proechimys and Oryzomys. Glomus presence in feces is significantly positively associated with the dry season. Both rodent genera together annually pass 2.96 x 10(5) S. coremioides sporocarps and 7.30 x 10(7) Glomus spores/ha at Cocha Cashu. We concluded that Proechimys and Oryzomys are likely to be important agents of vesicular-arbuscular mycorrhizal fungus spore dispersal.