Arbuscular mycorrhizal and dark septate fungi colonization in an invasive plant from Patagonian wetlands

Abstract

Arbuscular mycorrhizal and dark septate fungi are common plant symbionts,but their role in promoting host plant fitness depends on environmental variables.Particularly in wetland plants, these associations are less understood.We analysed the role of arbuscular mycorrhizal fungi (AMF) and dark septatefungi (DSF) in the roots of Potentilla anserina (Rosaceae), an invasive species ofPatagonia, widely distributed in wetlands. We tested three hypotheses: that fungicolonization varies according to soil moisture and nutrient content (nitrogen andphosphorus), that they enhance P. anserina nutrient content, and benefit plantgrowth. We measured the percentage of colonization in plants from five wetlandsacross a moisture gradient with different nutrient content, and performed agrowth experiment with soil from these wetlands to evaluate changes in mycorrhizaland endophytic fungal colonization, aerial nutrient content and biomassproduction. In the field, root colonization by AMF was high in all sites (~90%),whereas DSF was less abundant (~20%), positively related to soil organic matter,and negatively related to soil phosphorus. In the experiment, DSF colonizationwas inversely related to increasing tissue N and P content. Potentilla anserinagrew similarly in all the treatments, but biomass was positively related to DSFcolonization. Our results provide evidence that DSF, rather than AMF, confer tothis invasive species the ability to grow in soils with different water and nutrientcontent and may help to explain the wide distribution of this alien species inPatagonian wetlands.