Consumption of arbuscular mycorrhizal fungi by spiny rats (Proechimys semispinosus) in eight isolated populations

The consumption of arbuscular mycorrhizal fungi (AMF) by Proechimys semispi nosus (Central American spiny rat) was assessed via microscopic examination of faecal material for the presence of AMF spores. Mycophagy (indicated by the presence of spores) was compared among individual spiny rats residing on eight isolated islands in Gatun Lake, Panama during January and July 199 6. Spores and sporocarps of Sclerocystis coremioides and spores from at lea st four species of Glomus were present in 77% of the 231 faecal samples exa mined. The proportion of faecal samples that contained AMF spores did not d iffer between spiny rat sex, age classes or months of sampling or with isla nd area. However, there was a positive relationship between the proportion of samples containing spores and rodent density in January, and a marginall y significant positive trend in July. Increased consumption of AMF on islan ds that supported high densities of spiny rats may have resulted from incre ased competition for primary food resources (fruits and seeds).