Inconsistent responses of alpine arthropod communities to experimental warming and thermal gradients

How alpine arthropods respond to climate warming is poorly understood. Empirical approaches to address this issue include experimental warming and characterizing changes in community composition across environmental gradients. Here we compare these short- and longer-term approaches in understanding the likely effects of warming on arthropods from grassland-heathland vegetation in the Australian sub-alpine zone. Arthropod communities showed relatively small changes in composition in response to passive experimental warming in open topped chambers (OTCs) under the ITEX (International Tundra Experiment) protocol. Collembola, Katiannidae (Collembola), Australotomurus nr. barbatus (Collembola; Entomobryidae) and Saprophytic Coleoptera increased in abundance; however none of these patterns were evident when considering a similar range of natural temperature variation (11.3 to 13.6°C) associated with elevation (1676 to 1891 m). Thus, experimental warming using OTCs was a poor predictor of likely changes along natural gradients. Responses to OTCs appear to be associated with thermal extremes and secondary effects such as increases in resources. These findings suggest caution is required when extending results from experimental warming to likely shifts in arthropod abundance along elevation gradients.Michael A. Nash, Philippa C. Griffin, Ary A. Hoffman