Communities of arbuscular mycorrhizal fungi on a vegetation gradient in tropical coastal dunes

Abstract

The community composition of arbuscular mycorrhizal fungi (AMF) was studied related to AMF species richness, abundance and frequency in coastal dune areas, northeastern Brazil. Soil samples were collected periodically in 2010 and 2011 in three dune areas (herbaceous, shrubby and arboreal) that form an environmental gradient from the beach to the inland tropical rainforest. Fifty AMF species were identified belonging to 18 glomeromycotan genera and 10 families. Several remarkable observations were made: higher AMF spore density was observed in the arboreal dune compared to the shrubby and herbaceous dunes, while the highest number of infective propagules was observed in the herbaceous dune, followed by the shrubby and arboreal dunes. Although AMF species richness and AMF root colonization were similar in all dunes, the Shannon's diversity and Pielou's evenness indices were higher in the herbaceous dune than in the shrubby and arboreal dunes, which was the opposite in relation to the Simpson dominance index. Thus, surprisingly, the areas closest to the sea had greater diversity compared to the later successional dunes in farer distance from the sea. Funneliformis halonatus was the indicator species of the arboreal dune, Ambispora appendicula, Gigaspora gigantea and Paradentiscutata maritima were the indicator species of the shrubby dune, while two undescribed Cetraspora species and Sclerocystis sinuosa were the indicator species of the herbaceous dune. The study areas can be considered as hotspots for the conservation of diversity of AMF.