The effects of arbuscular mycorrhizal fungal species and taxonomic groups on stressed and unstressed plants: a global meta-analysis.

The great majority of plants gain access to soil nutrients and enhance their performance under stressful conditions through symbiosis with arbuscular mycorrhizal fungi (AMF). The benefits that AMF confer vary among species and taxonomic groups. However, a comparative analysis of the different benefits among AMF has not yet been performed. We conducted a global meta-analysis of recent studies testing the benefits of individual AMF species and main taxonomic groups in terms of plant performance (growth and nutrition). Separately, we examined AMF benefits to plants facing biotic (pathogens, parasites, and herbivores) and abiotic (drought, salinity, and heavy metals) stress. AMF had stronger positive effects on phosphorus nutrition than on plant growth and nitrogen nutrition and the effects on the growth of plants facing biotic and abiotic stresses were similarly positive. While the AMF taxonomic groups showed positive effects on plant performance either with or without stress, Diversisporales were the most beneficial to plants without stress and Gigasporales to plants facing biotic stress. Our results provide a comprehensive analysis of the benefits of different AMF species and taxonomic groups on plant performance and useful insights for their management and use as bio-inoculants for agriculture and restoration.

Can arbuscular mycorrhizal fungi from non-invaded montane ecosystems facilitate the growth of alien trees?

It is generally assumed that recruitment and expansion of alien species along elevation gradients are constrained by climate. But, if plants are not fully constrained by climate, their expansion could be facilitated or hindered by other factors such as biotic interactions. Here, we assessed the composition of arbuscular mycorrhizal fungi (AMF) in soils along an elevation gradient (i.e. 900 m, 1600 m, 2200 m and 2700 m a.s.l.) through a fungal DNA meta-barcoding approach. In addition, we studied in the greenhouse the effects of AMF on growth and phosphorous (P) nutrition of seedlings of the alien trees Gleditsia triacanthos, Ligustrum lucidum and Pyracantha angustifolia cultivated in soils from those elevations, spanning the elevation at which they already form monospecific stands (below 1450 m a.s.l.) and higher elevations, above their current range of distribution in montane ecosystems of Central Argentina. For comparison, we also included in the experiment the dominant native tree Lithraea molleoides that historically occurs below 1300 m a.s.l. Arbuscular mycorrhizal fungal community composition showed strong community turnover with increasing elevation. The effects of these AMF communities on plant growth and nutrition differed among native and alien trees. While P nutrition in alien species' seedlings was generally enhanced by AMF along the whole gradient, the native species benefited only from AMF that occur in soils from the elevation corresponding to its current altitudinal range of distribution. These results suggest that AMF might foster upper range expansion of these invasive trees over non-invaded higher elevations.

Chytridiomycosis in endemic amphibians of the mountain tops of the Córdoba and San Luis ranges, Argentina.

Chytridiomycosis is a major threat to amphibian conservation. In Argentina, the pathogenic fungus Batrachochytrium dendrobatidis has been recorded in several localities, and recently, it was registered in amphibians inhabiting low-elevation areas of mountain environments in Córdoba and San Luis provinces. In the present study, we searched for B. dendrobatidis in endemic and non-endemic amphibians on the mountain tops of Córdoba and San Luis provinces. We collected dead amphibians in the upper vegetation belt of the mountains of Córdoba and San Luis. Using standard histological techniques, the presence of fungal infection was confirmed in 5 species. Three of these species are endemic to the mountain tops of both provinces. Although there are no reported population declines in amphibians in these mountains, the presence of B. dendrobatidis in endemic species highlights the need for long-term monitoring plans in the area.

Ectomycorrhizal fungal communities associated to Nothofagus species in Northern Patagonia.

Ectomycorrhizal fungi constitute an important component of soil biota in Nothofagus forests in Patagonia. However, ectomycorrhizal fungal community is poorly known in this region. Here, we assess biodiversity and community compositions of ectomycorrhizal fungal species associated with Nothofagus dombeyi, N. obliqua and N. alpina. We selected three monospecific Nothofagus forest sites for each species within the boundaries of the Lanin National Park in Northern Patagonia. Ectomycorrhizal fungal species were identified based on morphotyping and rDNA (ITS and 28S rDNA) sequence analysis using both universal and taxon-specific primers. Contrary to previous studies on congeneric host trees, our results showed no significant differences among Nothofagus forest types in terms of fungal biodiversity and community composition. However, altitude had a strong effect on the structure of the ectomycorrhizal fungal community associated with Nothofagus spp.

Ocurrence of ectomycorrhizal, hypogeous fungi in plantations of exotic tree species in central Argentina.

Eleven hypogeous, ectomycorrhizal species of Basidiomycota, including two new species, and one of the Zygomycota were collected in exotic tree plantations in C6rdoba Province, Argentina. Descomyces fusisporus sp. nov., D. varians sp. nov., Hydnangium archeri (Berk.) Rodway, H. carneum Wallr., Hysterangium gardneri E. Fisch. and Setchelliogaster tenuipes (Setch.) Pouzar were associated with Eucalyptus spp. Endogone lactiflua Berk., Hymenogaster lycoperdineus Vittad., H. griseus Vittad., H. rehsteineri Bucholtz, Rhizopogon couchii A.H. Sm. and R. roseolus (Corda) Th. Fr., were associated with various northern hemisphere tree species. Descriptions are provided to aid identification of the hypogeous fungi in exotic plantations of Argentina.