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Abstract:
Ambrosia beetles farm ascomycetous fungi in tunnels within wood. These ambrosia fungi are regarded
asexual, although population genetic proof is missing. Here we explored the intraspecific genetic diversity
of Ambrosiella grosmanniae and Ambrosiella hartigii (Ascomycota: Microascales), the mutualists of
the beetles Xylosandrus germanus and Anisandrus dispar. By sequencing five markers (ITS, LSU, TEF1a,
RPB2, b-tubulin) from several fungal strains, we show that X. germanus cultivates the same two clones of
A. grosmanniae in the USA and in Europe, whereas A. dispar is associated with a single A. hartigii clone
across Europe. This low genetic diversity is consistent with predominantly asexual vertical transmission
of Ambrosiella cultivars between beetle generations. This clonal agriculture is a remarkable case of
convergence with fungus-farming ants, given that both groups have a completely different ecology and evolutionary history.
