Tropical-temperate comparison of landscape-scale arbuscular mycorrhizal fungal species distributions

Aim: Mycorrhizas are among the most common symbioses on Earth, impacting plant community structure and ecosystem functioning, yet little landscape-scale data linking mycorrhizal fungal diversity to biotic and abiotic properties exist to inform conservation. We examined arbuscular mycorrhizal (AM) fungal diversity in tropical and temperate locations and identified potential drivers of species distributions and diversity for use as proxy indicators in biodiversity conservation. Location: AM fungal communities were documented at 60 sites in the Colorado Plateau in south-western United States and La Gran Sabana in south-eastern Venezuela. Methods: Communities of plants and AM fungi and abiotic variables were measured along 50-m transects in three vegetation types (shrublands, forests, and traditional agricultural fields). Model selection and multivariate analyses were used to evaluate environmental predictors of AM fungal diversity and community structure. Results: AM fungal species richness (alpha diversity) and community structure, but not among-site turnover (beta diversity), differed between tropical and temperate locations; only 15% of taxa were present in both locations. In unmanaged sites, AM fungal richness was not correlated with plant richness, but instead predicted by soil pH and temperature (temperate) or precipitation and latitude (tropics). The structure of AM fungal communities was influenced by plant identity but not plant diversity in both locations. Traditional, sedentary Hopi agriculture influenced AM fungal communities on the Colorado Plateau, but Pemon shifting slash-and-burn agriculture did not alter AM fungal communities at La Gran Sabana. At both locations, AM fungal community structure was linked to soil texture and nitrogen. Main conclusions: Our study demonstrates similarity between tropical and temperate regions in the biotic and abiotic drivers of landscape-scale AM fungal species distributions. Soil and climate as well as habitat heterogeneity may serve as proxy indicators of AM fungal communities for use in conservation planning to preserve the ecosystem functions and services of mycorrhizas.