Fig. 2.

Variation between indigenous and alien springtails in thermal tolerance from tropical to polar habitats. For each trait, the x axis shows median or maximum soil microhabitat temperature for the sites at which species’ populations were collected. Lines represent the fits of ordinary least-squares regression for indigenous (green symbols) and alien (orange symbols) species separately with 95% confidence bands (gray shading). No interaction terms were significant, indicating no slope differences between indigenous and alien species in any of the traits (analytical outcomes, excluding interaction terms, in Table 1). (A) Critical thermal maximum, (B) critical thermal minimum, (C) critical thermal range, (D) warming tolerance calculated as the difference between the highest microhabitat temperature of the warmest month and the critical thermal maximum. For comparative purposes, plots against minimum and maximum environmental temperatures are provided as SI Appendix, Fig. S3.