Assessing the potential for predator-prey interactions in mesofaunal arthropod communities through temperature dependence of locomotion

Thermal performance curves (TPCs) have become an important part of the thermal biologists' toolbox in understanding how organisms may respond to temperature variation. The aim of this study was to investigate how temperature affects the locomotion of soil arthropods (Collembola and Acari), and explore how these responses might influence the potential for predator-prey interactions under different environmental conditions. Locomotion-based thermal performance curves of four species of Acari and three species of Collembola were estimated across seven test temperatures through automated tracking of individuals. Acari (predators) generally exhibited broader thermal tolerances compared to Collembola (prey), with overlapping thermal optima observed for some species, such as Parasitus sp. and Ceratophysella cf. gibbosa. However, differences in maximum thermal limits could influence predator-prey dynamics under warmer conditions. There were no significant effects of temperature on distance traveled or maximum walking speed for most species (Folsomina sp. p = 0.21, Ceratophysella cf. gibbosa p = 0.55, Mucrosomia sp. p = 0.36), with subclass-level analyses also showing no significant effects for Acari (p = 0.6) or Collembola (p = 0.96). Among Acari, Linopodes sp. exhibited a clear TPC, peaking at 30 °C (175 mm/s), while Parasitus sp. and Ceratophysella cf. gibbosa displayed broad thermal tolerances, with the temperature at which performance is maximized (Rmax) near 20 °C and 30 °C, respectively. Among the Acari species tested, Linopodes sp. and Parasitus sp. did show typical TPCs. Among Collembola, Folsomina sp. and Ceratophysella cf. gibbosa showed typical TPCs. These sit-and-wait predators with jump escaping prey groups are likely to be poorly captured by a TPC approach, suggesting other functional traits such as feeding rates, handling times and/or digestion efficiency should be employed in the future to better characterize temperature-dependent interactions.