DNA-based fungal diversity in Madagascar and arrival of the ectomycorrhizal fungi to the island

Madagascar is known for its high diversity and endemism of fauna and flora. Fungi, however, have been largely overlooked in diversity and evolution studies on the island, and whether fungi exhibit the same patterns as animals and plants has yet to be further examined. We collected fungal sporocarps and ectomycorrhizal (EcM) roots during three opportunistic surveys in five forests in Madagascar and generated a dataset of fungal Internal Transcribed Spacer (ITS) DNA sequences. We analyzed them together with all publicly available fungal ITS DNA sequences and identified 620 Operational Taxonomic Units (OTUs) from Madagascar, 10% of which contained only sequences from our surveys. Two hundred and ninety-two OTUs belonged to EcM species with /russula-lactarius, /boletus, /tomentella-telephora, /cortinarius, and /amanita being the most abundant EcM lineages. Overall, 60% of all fungi and 81% of the EcM species from Madagascar appear to be endemic. We conducted a phylogenetic analysis using all the OTUs in Amanitaceae, Boletaceae, and Russulaceae families to elucidate their relative timing of arrival in Madagascar. We found that most EcM species from Madagascar in the three families diverged less than 22 million years ago (mya), long after the separation of India and Madagascar (88 mya), which is consistent with a dispersal mediated process of arrival to the island. Our study provides the first comprehensive view of the overall DNA-based fungal diversity in Madagascar and the current state of knowledge of EcM fungi based on DNA sequences, useful for further ecological and evolutionary studies.Abstract in Malagasy is available with online material.

Automated summary

Madagascar is known for its rich diversity and endemism of fauna and flora. However, little attention has been given to fungi in diversity and evolution studies on the island. This study collected fungal sporocarps and ectomycorrhizal roots in Madagascar and analyzed their DNA sequences to reveal the overall fungal diversity and endemic species. The study also investigated the timing of arrival of ectomycorrhizal species in Madagascar through phylogenetic analysis.