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Specificity of the fungi used in carton runway galleries in the (ant - plant) Azteca brevis - Tetrathylacium macrophyllum association

Tuesday, 25 June 2013: 09:15
La Paz - B West (Herradura San Jose)
Maximilian Nepel , Structural and Functional Botany, University of Vienna, Austria
Veronika E. Mayer , Structural and Functional Botany, University of Vienna, Austria
Hermann Voglmayr , Systematic and Evolutionary Botany, University of Vienna, Austria
Jürg Schönenberger , Structural and Functional Botany, University of Vienna, Austria
In the past few years, more and more ant-fungus associations have been discovered in arboreal ant species. Most of these (usually unknown) fungi belong to the order Chaetothyriales (Ascomycetes), the “black yeasts”. Chaetothyriales are known to have two types of interactions with ants: (1) as components in ant-built carton-like structures, e.g. ant nests or runway galleries, and (2) as fungal patches within living chambers (so-called domatia), provided by myrmecophytic plants. In carton as well as in domatia, the fungi have been regarded to be specific for the respective ant-association. The research presented here was focused on the tripartite association among Azteca brevis (Formicidae, Dolichoderinae), Tetrathylacium macrophyllum (Salicaceae), and Chaetothyriales. A. brevis is building extensive carton-like runway galleries on branches of T. macrophyllum which are overgrown by hyphae of chaetothyrialean fungi. The aim was to find whether specific fungi are cultivated on the carton walls beside opportunistic ones, or whether the mutualism between these ants and fungi is unspecific and only opportunistic. Carton fungi of 19 trees colonized by A. breviswere cultivated in pure cultures and analysed molecularly, using mainly the ITS region. In total 128 different black-yeast genotypes were documented. These genotypes were found to be distributed all over the phylogenetic tree of Chaetothyriales. This unexpected high biodiversity of chaetothyrialean genotypes of carton fungi suggests low specificity for this type of interaction. As the specificity is indicated by the fungal frequency of occurrence, the community of isolated fungi was analyzed on each tree. On genotype level as well as on approximated species level, the most common fungus was present on half of the investigated trees. The available data indicates that A. brevis does not cultivate specific carton fungi and point to a stochastic distribution of Chaetothyriales on the carton galleries of A. brevis.