Shared phylogeography of Arachnitis uniflora and its mycorrhizal fungi

RENNY, M.; ACOSTA, C.; COFRÉ, N.; DOMINGUEZ, L.; BIDARTONDO, M.I.; SÉRSIC, A.N.

Valdivia

Workshop; Mycorrhizal Symbiosis in the Southern Cone of South America; 2017

Universidad Austral de Chile, Universidad de La Frontera, Universidad de Concepción, Centro de Estudios Avanzados en Fruticultura, EarthShape Project (DFG)

Arachnitis uniflora Phil. (Corsiaceae) is a mycoheterotrophic plant; it is unable to assimilate carbon and depends on mycorrhizal fungi to obtain nutrients from autotrophic plants. Arachnitis grows mainly along the Andean-Patagonian forests of Argentina and Chile, in south-central Bolivia and in the Malvinas Islands. Morphological and molecular studies showed that the fungi involved belong to the Glomeromycotina but have intracellular structures different from those of typical arbuscular mycorrhizas. Another noticeable feature is the presence of plant propagules in the roots containing Glomeromycotina and potentially favouring the maintenance of the symbiosis.We studied the genetic variability of A. uniflora and its mycorrhizal fungi using molecular markers along the plant´s geographic range. We found that A. uniflora associates with three families - Glomeraceae, Claroideoglomeraceae and Acaulosporaceae - the first present in every plant, while the others are rare and appear to be facultative. Molecular dating revealed that the origin of Arachnitis coincided with the diversification of Glomeromycotina in the Oligocene-Miocene. The Andes uplift and the Great Patagonian Glaciation shaped the diversification of A. uniflora and we found four common geographic barriers latitudinally structured. Both plants and fungi have three overlapping hot spots of genetic diversity related to Pleistocene glacial refuges where genetic diversity was maintained.