Shared phylogeography of Arachnitis uniflora and its mycorrhizal fungi

MAURICIO RENNY, M. CRISTINA ACOSTA, NOELIA COFRÉ, LAURA S. DOMÍNGUEZ, MARTIN I. BIDARTONDO, ALICIA N. SÉRSIC. ; DOMINGUEZ LS

Valdivia

Workshop; International workshop "Mycorrhizal symbiosis in the southern cone of South America", Universidad Austral de Chile; 2017

Universidad Austral de Chile

Arachnitis uniflora Phil. (Corsiaceae) is a mycoheterotrophic species unable to assimilate carbon by itself depending on its mycorrhizal fungi to obtain nutrients from autotrophic plants. The species grow mainly along the Andean-Patagonian forests of Argentina and Chile, in south-central Bolivia and in Malvinas Islands. Morphological root studies showed that the fungi involved belong to the Glomeromycotina (confirmed by molecular studies) showing distinct intracellular structures different from those of the typical arbuscular-mycorrhizal fungi (AMF). Another noticeable feature is the presence of propagules in the roots containing AMF which favours the maintenance of this symbiosis.We studied the genetic variability of A. uniflora and its AMF using molecular markers along the whole geographic range. We found that A. uniflora was associated with three AMF families (Glomeraceae, Claroideoglomeraceae and Acaulosporaceae), being the first the predominant, while the others appear to be facultative. Molecular dating revealed that the origin of AMF initiated in the Lower Cretaceous, while their diversification was coincident with the origin of Arachnitis in the Oligocene-Miocene. The Andes uplift, and the Great Patagonian Glaciation were the events shaping the diversification of A. uniflora. We found four common geographic barriers latitudinally structured. Finally, both genetic diversity partners presented three coincident hot spots of genetic diversity related to Pleistocene glacial refuges where the genetic diversity was maintained.