*Grünig, Christoph R.; Queloz, Valentin; Sieber, Thomas N. Black is beautiful – Exploring the population biology and ecology of dark septate endophytes. In: International Meeting on "Population and Evolutionary Biology of Fungal Symbionts", Ascona, Switzerland, 2007. AB-37. Click here to download the presentation on pdf format or the Poster AB-37.

Dark septate endophytes (DSE) are ubiquitous colonizers of non-mycorrhizal roots of many plant species. Phialocephala fortinii Wang & Wilcox was shown to be the dominant DSE in coniferous and ericaceous roots in heathlands, forests, and alpine ecosystems in the Northern hemisphere. In contrast, little data is available about the abundance of species belonging to P. fortinii in the Southern Hemisphere. Despite the ubiquitous distribution of P. fortinii, the ecological significance of root-P. fortinii symbioses is largely unknown. Conflicting results in root-endophyte interaction studies have been published describing P. fortinii as beneficial, neutral or pathogenic. Contradictory results are mainly due to the use of undefined isolates and a multitude of experimental designs and that either favour P. fortinii or the host.

Indeed, recent population genetic studies showed that P. fortinii is composed of an as yet unknown number of reproductively isolated but morphologically indistinguishable species. Single-copy RFLP analyses of more than 2000 strains collected in Europe and sequencing showed that at least 14 cryptic species (CSP) of P. fortinii are present and additional ones will probably be discovered in future. The index of association was zero within CSP indicating recombination. A morphotype which is known to be closely related to P. fortinii s.l. was recently described as Acephala applanata. Up to six CSP of P. fortinii including A. applanata were shown to occur sympatrically within the same forest plot and strains belonging to different CSP were isolated repeatedly from the same 5-mm-long root segment. Communities of P. fortinii s.l. and A. applanata seem to be temporarily and spatially stable over several years. Whereas no host specificity was evident for any CSP of P. fortinii, host specificity was observed for A. applanata. In the presentation we will summarize the actual knowledge about the population genetics of this species complex and highlight how these data will help to elucidate the ecological significance of these ubiquitous root endophytes.

Keywords: Acephala applanata, Phialocephala fortinii, speciation, species recognition, species boundaries, migration rates, reproduction

*Institution: ETH Zürich

Email: christoph.gruenig@env.ethz.ch