Figure 1.

Range‐limit theory (RLT) (a) predicts that abiotic factors (blue) constrain the high‐latitude/altitude (upper) limit of the potential range (grey dashed lines) and biotic interactions (green) constrain the low‐latitude/altitude (lower) edge of the potential range, resulting in the black outlined observed range. Interactive range‐limit theory (iRLT) (b) extends RLT to predict that the interaction of abiotic and biotic factors forms limits at either edge of a range. Positive biotic factors can expand the range along upper limits despite negative abiotic factors, and expansion along lower edges can result if negative biotic interactions are ameliorated by stress from abiotic factors. RLT posits that (c) species like bobcat (Lynx rufus), (bottom) are limited by abiotic factors (e.g. climate) on the upper edge, and (e) those such as Canada lynx (Lynx canadensis) are limited by biotic interactions (e.g. competition for prey) along the lower limit. iRLT predicts that (d) positive biotic factors (more prey for bobcats) can ameliorate negative abiotic factors along high‐latitude/altitude limits and (f) positive abiotic factors (increase in snow for lynx) mediate negative biotic interactions along lower limits