Hongos asocIados con dos poblacIones de acromyrmex lobIcornIs (FormIcIdae) de san luIs, argentIna

Summary: Fungi associated with two populations of Acromyrmex lobicornis (Formicidae) from San Luis, Argentina. The ant genera Atta and Acromyrmex (Tribe Attini) include the mowers or trimmers of leaves called leaf-cutting ants, which are the only ants that show an obligate dependence of fungal symbionts as a food source. Fragments of plants collected by these ants are used to grow the fungal symbionts, which produce gongylidia for the larvae and queen of the colony to feed on. The aim of this study was to isolate and characterize both, genetically and taxonomically the fungi cultured by two populations of Acromyrmex lobicornis from San Luis province. Samples were collected from the most superficial chambers of the nests and fungal isolates were cultured in malt extract (ME) and potato dextrose agar (PDA) media. The fungal symbiont associated to A. lobicornis nests was identified as Leucoagaricus gongylophorus (Moller) Singer (Holobasidiomycetes, Agaricales) through its morpho-anatomic characteristics and sequencing of ITS1, ITS2 and 5.8S ribosomal gene. Fungal growth in ME was higher than in PDA, and symbiont isolates showed differential growth rates depending on ant populations from where they originated. Fungal symbiont nutritional features and distributional aspects are discussed.