Prevalence dynamics of two endosymbiont fungi (Orphella spp. Harpellales: Kickxellomycotina) and host shift among different Leuctra (Plecoptera) species in a stream community

• Temporal dynamics of Plecopteran-associated fungi (Harpellales) have been studied.
• Temporal oscillations are more directly dependent on biotic than abiotic factors.
• In situ host shift promoted alterations on the prevalence of Orphella spp.
• Orphella helicospora survived in the environment, linked to its lower host specificity.
• Orphella catalaunica nearly disappeared at the studied site after host community alteration.

This study was conducted to increase the understanding of the temporal dynamics of the plecopteran-associated endosymbiont species Orphella helicospora and Orphella catalaunica (Harpellales, Zygomycota) in the middle reaches of a stream in Montseny Natural Park (Barcelona, Spain). Previous studies addressing the temporal dynamics of Harpellales have focused on Diptera-related species. Statistical analyses revealed that the temporal dynamics of Plecoptera-associated Harpellales do not respond directly to environmental factors but are more directly dependent on biotic factors, such as the particular preference and fitness of each Orphella species towards a specific Leuctra host, the relative host abundance, and its annual cycle. We report that an in situ host shift linked to Leuctra species replacement occurred during the years 2012–2013, with a resulting decline of O. catalaunica in this environment. The ecological implications of the specificity range and fitness of the host are discussed. We also provide information about the possible causes of this macroinvertebrate shift and the effects on the associated endozoic community.