Revealing suitable micro- and macrohabitat characteristics to save the critically endangered Chilean saproxylic beetle Sclerostomulus nitidus (Coleoptera: Lucanidae)

Saproxylic insect species have deadwood-specific requirements to survive, such as advanced decay stages. However, in some parts of the world, deadwood is currently considered an endangered resource. The Poqui's stag beetle Sclerostomulus nitidus (Coleoptera: Lucanidae)—a critically endangered saproxylic species—was rediscovered during the 2010s, but non-academic collection currently threatens it with extinction in a projected 10-year span. Our main aim was to identify key macro- and microhabitat tools to restore this species' population by associating the abundance of S. nitidus with deadwood micro- and macrohabitat variables such as vegetation type (pure Nothofagus stands vs. hygrophilous forest stands) and elevation. We measured decay stage (low, medium and high), volume and length of dead logs and the vegetation type and elevation of where they were available inside the restricted habitat of S. nitidus and assessed these variables as predictors of S. nitidus abundance using GLM analysis. We found that abundance (current and projected) is strongly associated (90%) with high stages of wood decay and lower elevations. Microhabitat restoration by (i) replacement of low-quality highly decayed deadwood but keeping equal volumes and (ii) injection of highly suitable habitat as a novel fieldwork experiment could be the best short-term to mid-term alternative for saving S. nitidus.