Shared phylogeography of Arachnitis uniflora and its mycorrhizal fungi

RENNY, M. E.; ACOSTA, M. C.; COFRÉ, N.; DOMÍNGUEZ, L. S.; BIDARTONDO, M. I.; SÉRSIC, A. N.

Valdivia

Workshop; Mycorrhizal symbiosis in the Southern cone of South America International Workshop; 2017

Universidad Austral de Chile y otros

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