Leaving the web: Testing the link between predation style and resting metabolic rate using closely related spiders...

Resting metabolic rate is influenced by numerous biotic and abiotic factors, as well as complex interactions between these factors. Behavior and lifestyle traits have significant influence on metabolic rates, but they closely interact with other influential factors, such as environmental conditions and evolutionary history. This makes distinguishing the influence of behavior and lifestyle on metabolism independent of any other factors difficult. Spiders are an ideal system for studying predation behavior, as they broadly exhibit two methods of prey capture: web-building and cursorial hunting. A spider's web represents a large energy sink, and the loss of web-building is expected to have a significant effect on energy budget and allocation. In order to determine the influence of predation style on resting metabolic rate, we use two co-occurring, closely related clades of Hawaiian long-jawed orb weaver spiders (Tetragnatha, Tetragnathidae), one that builds webs, and one that adopts a cursorial lifestyle. Using stop-flow respirometry, we measured the resting metabolic rates of four species, two web-building and two cursorial, at 20 °C. As predicted, the cursorial Tetragnatha species have higher resting metabolic rates than the web-building species. By using this unique natural system and eliminating confounding factors, our results show that predation style has a direct influence on spider metabolism.