Quantifying the geographic mosaic of coevolutionary temperature: from coldspots to hotspots

The Geographic Mosaic Theory of Coevolution (GMTC) predicts that reciprocal evolutionary effects vary across landscapes, generating hotspots and coldspots. Traditionally, these states are treated as discrete categories, even though the intensity of coevolutionary selection can vary continuously. To capture this variation, we introduce a concept of coevolutionary temperature, ranging from coldspot to hotspot. We propose two complementary metrics to quantify it: reciprocity and strength of pairwise evolutionary effects. We also extend the GMTC framework beyond its traditional focus on pairwise systems to species-rich communities. Applying this approach to empirical plant-pollinator networks in a fragmented landscape, we find pronounced geographic mosaics in coevolutionary temperature. Smaller habitat patches support small, highly connected, and weakly nested communities with high reciprocity and strength, suggesting that they act as coevolutionary hotspots. In contrast, larger patches host species-rich, poorly connected, and highly nested communities with low reciprocity and strength, consistent with coldspots. At the interaction scale, reciprocity depends on degree similarity, with interactions between species that have similar numbers of partners exhibiting higher reciprocity. Together, these results highlight the strong dependence of coevolutionary effects on spatial variation in community structure and show how extending the geographic mosaic framework to species-rich communities can deepen our understanding of coevolution in complex systems.