A new family (Intraornatosporaceae), two new genera (Intraornatospora, Paradentiscutata), two new species (P. bahiana, P. maritima), and a new combination (I. intraornata) are presented in the Gigasporales. The genera, both with diagnostic introverted ornamentations on the spore wall, are distinguished by spore wall structure and germ shield characteristics. The new species, detected in NE Brazil, can be differentiated by their projections on the outer spore surface. Partial sequences of the LSU rRNA gene place both species next to I. intraornata in a monophyletic major clade related to Gigasporaceae and Dentiscutataceae.

Tropical forests concentrate most of the world’s biodiversity. In the Northeast of Brazil it is possible to record mosaics of tropical dry and moist forests growing nearby but with completely different biotic and abiotic characteristics. These forests are constantly threatened by intense environmental devastation that affect not only above-ground communities but also those hidden below-ground, such as arbuscular mycorrhizal fungi (AMF), which act in maintaining ecosystem balance. This work aimed to determine the composition of native AMF communities in areas of humid forest (HF) and dry forest (DF) in northeastern Brazil. A total of 70 taxa of AMF were identified in the study areas, with Acaulospora (17) and Glomus (16) being the most representative genera. The sampling effort allowed the evaluation of 70%–73% of the species estimated for the areas. AMF communities differed between HF and DF areas. Species of the genus Glomus occurred predominantly in humid forest areas, whereas representatives of the order Gigasporales were associated more specifically with the dry forest area. Four soil attributes showed approximately 50% correlation with the composition of the AMF community (silt, clay, K, and CEC). Humid and dry forest areas presented a high diversity of AMF, and the soil properties were an important factor for the community composition of these fungi.

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Increasing elevation affects many abiotic factors, such as a temperature decrease and an increase in radiation, as well as multiple biotic characteristics such as richness and composition of plant communities, both of which contribute to the formation of different habitats in mountainous landscapes. Both biotic and abiotic factors also affect belowground arbuscular mycorrhizal fungi (AMF) communities, but there is scarce information available from tropical mountain ecosystems. The objective of this study was to determine the diversity and distribution of AM fungi in different mountainous habitat types in the Chapada Diamantina mountain range in Bahia (NE Brazil). Soil samples were collected in five habitats types: high‐altitude cerrado savannas (HAC), natural grasslands (GRA), gallery forests (GAF), in natural rocky rupestrian fields (shrublands; CAR) and in rocky, rupestrian field in the regeneration stage (CRR). A total of 49 AMF species were identified, of which Glomeraceae and Acaulosporaceae species were the most representative families. The AMF communities did not follow the shifts in plant communities. The composition of the AMF communities differed only between CAR and HAC and between CRR and GAF, while the other habitats had similar AMF communities. Our conclusion is that the AMF community assemblages in tropical mountains are related to the heterogeneity of habitats of these ecosystems. In our study, silt and coarse sand contents were the main factors related to the community composition of AMF in the different habitats.

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