Volcanic ash from Puyehue-Cordón Caulle eruptions affects running performance and body condition of Phymaturus lizards in Patagonia, Argentina

Abstract

The Puyehue-Cordón Caulle eruption of 4 June 2011 dispersed about 100 million tonnes of pyroclastic materials resulting in ash accumulations of 30 cm depth on the Patagonian steppe, an area occupied by several lizard species. Herein we analysed, by experimental trials, the effects of ash and slope on running performance of two endemic and vulnerable species, Phymaturus excelsus and Phymaturus sinervoi, restricted to volcanic rock outcrops in Patagonia. We also determined the effect of ash fall on body condition by comparing the same populations before and after the volcanic eruption. Locomotion of P. excelsus, adapted to rocky and steep outcrops, was more affected in a negative way by ash. In contrast, P. sinervoi, which lives in mixed habitats with flat rocks and sandy substrates, ran more slowly on the inclined surface but was unaffected by ash, suggesting the two species are well adapted to the habitats they occupy. In spite of impacts of ash deposition on locomotion and potentially the feeding, reproduction and dispersal activity of P. excelsus, lizards captured 18 months after ash deposition showed improved body condition. Our study site for P. sinervoi received less ash deposition and hence body condition was similar before and after ash fall. We hypothesize that negative effects of ash on lizards were counteracted by competitive release; ash deposition caused an acute and significant increase in mortality of herbivorous competitors such as hares and sheep that feed upon the same flowers and fruits included in the Phymaturus diet.