Random amplified polymorphic DNA markers reveal genetic variation in the symbiotic fungus of leaf-cutting ants

Abstract

RAPD markers were used to examine the degree of genetic variation within the putatively asexual basidiomycete fungus (Lepiotaceae: provisionally named Leucoagaricus gongylophorus) associated with the leaf-cutting ant species Atta cephalotes. We analyzed fungal isolates from ant nests in two geographically distant sites, two isolates from Panama and five isolates from Trinidad. Ten decamer primers were used to amplify total DNA from these seven fungal isolates, and RAPD banding patterns were compared. Genetic similarity among isolates was determined by pair-wise comparisons of the shared number of DNA bands on an agarose gel. There was considerable genetic variation among isolates of the symbiotic fungus even within sites. Pairs of fungal isolates from the two different sites shared an average of only 36% of the bands in their RAPD profiles, while pairs from the within sites shared an average of 72% of the bands. RAPD markers may be useful for further investigation of the genetic structure of the fungal symbiont within species of leaf-cutting ants.

• Atta cephalotes
• fungal DNA
• genetic variation
• leaf-cutting ants
• Leucoagaricus gongylophorus (Lepiotaceae)
• population differentiation
• RAPD markers
• symbiosis

We would like to thank Randy Morgan of the Cincinnati Zoo Insectarium for the fungal isolates from Trinidad, Cameron Currie at the University of Kansas for the fungal isolates from Panama, and Andy McCall for initiating the laboratory fungal strains. This research was made possible through a Carleton College Faculty Development Endowment Grant to Dr. Stephan Zweifel and Dr. Mark McKone, and a Howard Hughes summer internship to Katherine Doherty.