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.

真菌在有机物周转中发挥重要作用，并确保淡水中的关键生态系统服务。种内真菌多样性与关键生态过程之间的关系仍然未知。我们检查了四瓣Articulospora的种内多样性的影响，Articulospora tetracladia是一种大都会真菌分解剂，对植物碎屑在河流中tus壮成长。将1木叶片接种1种或2-8种真菌菌株的混合物35 d，并在存在和不存在2 mg L ^-1的情况下对凋落物的分解和真菌繁殖进行定量镉（Cd），一种在污染流中的常见压力源。种内多样性和同一性影响真菌繁殖，但不影响叶片分解。在金属胁迫下，叶片分解随种内多样性的增加而略有增加。不论有无镉存在，真菌的繁殖都随着种内多样性的增加而增加，在混合组合中的真菌繁殖也更大。在Cd胁迫下，真菌繁殖的种内多样性的影响量较大，但无论有无金属，叶片质量损失均无差异。种内多样性丧失的影响可能会危害真菌的存活和真菌功能，即微生物叶片的分解以及溪流中无脊椎动物切碎机的叶片凋落条件，特别是在金属胁迫下。