The geographic mosaic theory of coevolution suggests that reciprocal e
volution involves three processes that operate among populations: sele
ction mosaics, coevolutionary hotspots, and trait remixing. These proc
esses, in turn, produce three patterns: population differences in trai
ts favored by an interaction, a combination of trait matches and misma
tches among populations, and few species-level coevolved traits (i.e.,
coevolved traits that have spread to all populations). Here I show ho
w studies of the interactions between the pollinating floral parasite
Greya politella and its host plants provide evidence for most of the c
omponents of this view of the coevolutionary process, including indica
tions of the ecological conditions that can prevent coevolutionary cha
nge. These studies are suggesting that the dynamics of coevolution in
these interactions are interpretable only when analyzed over broad geo
graphic scales.