Intraspecific diversity affects stress response and the ecological performance of a cosmopolitan aquatic fungus

Fungi play an important role in organic matter turnover and ensure key ecosystem services in freshwaters. The relationships between intraspecific fungal diversity and key ecological processes remain largely unknown. We examined the effects of intraspecific diversity of Articulospora tetracladia, a cosmopolitan fungal decomposer thriving on plant detritus in streams. Alder leaves were inoculated with 1 or mixtures of 2-8 fungal strains for 35 d, and leaf litter decomposition and fungal reproduction were quantified in the presence and absence of 2 mg L-1 of cadmium (Cd), a common stressor in polluted streams. Intraspecific diversity and identity affected fungal reproduction, but not leaf decomposition. Under metal stress, leaf decomposition slightly increased with intraspecific diversity. Fungal reproduction increased with intraspecific diversity and was greater in mixed assemblages, either in the absence or presence of Cd. Effect size of intraspecific diversity was higher under Cd stress for fungal reproduction, but no differences were found for leaf mass loss, with or without metal. The impacts of intraspecific diversity loss may jeopardize fungal survival and fungal functions, namely microbial leaf decomposition and leaf litter condition for invertebrate shredders in streams, particularly under metal stress. (C) 2019 Elsevier Ltd and British Mycological Society. All rights reserved.This work was supported by the strategic programme UID/BIA/04050/2019 and the STREAMECO project (PTDC/CTA-AMB/31245/2017) funded by national funds through the FCT I.P. and by the ERDF through the COMPETE2020-Programa Operacional Competitividade e Internacionalizacao (POCI). Support from FCT to Sofia Duarte (SFRH/BPD/47574/2008 and SFRH/BPD/109842/2015) and to Seena Sahadevan (SFRH/BPD/103865/2014) is also acknowledged. The authors also want to thank to Felix Barlocher, Lynne Boddy and to two anonymous reviewers for the suggestions made on the earlier versions of the manuscript