Warming is here: using locomotor performance to infer thermal parameters and vulnerability for an endemic Argentinean tarantula Grammostola vachoni

Abstract

Because of global climate change and its consequences, estimating the physiological responses of ectothermicorganisms to temperature is of high priority. The thermal increase and changes in fire frequency are some of the consequences of global warming, which could challenge the physiological performance and thermal tolerance of individuals. The present study estimates the thermal parameters from field individuals of the tarantula Grammostola vachoni. To achieve this, we determined the critical thermal limits for locomotor performance, the thermal optimum, and the preferred temperatures. We also calculate the thermal performance breadth and thermal tolerance zone. Temperature strongly affected the locomotor performance of spiders; the sprint speeds were significantly different between temperatures, and at 5 ∘C and 25 ∘C the parameter was significantly different between females and juveniles. The preferred temperature showed a mean value of 26.5 ∘C, and females preferred lower temperature than juveniles. Grammostola vachoni showed a wide thermal tolerance range (close to 43 ∘C) and thermal performance breadth (B80), an index defined as the range of temperatures at which performance is at least 80% of the maximum. For G. vachoni, these large breadths in the sprint speed represent a substantial buffer against future increases in habitat temperature and shows that the locomotor performance of this species is an adaptable parameter. Understanding the impact of warming in performances is important to make predictions about if this species can remain ecologically viable while facing global change, given the massive worldwide declines in arthropod populations.