Rapid recovery of the beetle richness-elevation relationship and its environmental correlates after a major volcanic event in northwestern Patagonia, Argentina

Abstract

Volcanic eruptions often modify the structure and function of ecosystems at large geographical scales. However, the extent to which species diversity patterns respond to these major natural disturbances is still poorly known. We tested the shape of the species richness – elevation relationship (SRER) and its environmental correlates (thermal environment at ground level, vegetation structure and soil attributes) before and 6 months after (in the first summer) the most recent eruption of the Puyehue Cordon Caulle volcanic complex (PCCVC), which caused an extensive ash accumulation in northwestern Patagonia, Argentina. We re-established 32, 100-m2 sampling plots of nine pitfall traps, placed every 100 m of altitude from the base to the summit of three mountains differentially affected by ash deposition, and from which we had pre-eruption data on richness and environmental variables. Coverage-based rarefaction/extrapolation curves showed a local post-eruptive decrease in richness on only one mountain. Generalised additive models (GAMs) showed no significant differences between pre- and post-eruptive SRER shapes. Partial least squares structural equation modelling (PLS-SEM) showed that woody vegetation and the thermal environment accounted for most of the variation in richness before and after the eruption. Soil attributes were only indirectly associated with beetle richness and the association was mediated by woody vegetation. Ash accumulation ameliorated the thermal environment, promoting a local increase in beetle richness. The rapid recovery of the SRER shape and its environmental correlates suggest that the structuring of local diversity patterns at temperate latitudes of the southern hemisphere is resilient to major volcanic eruptions.