 Within the same geographic region, hummingbird clades co-evolved with nectar-bearing plant clades, affecting mechanisms of pollination.The same is true for the sword-billed hummingbird ("Ensifera ensifera"), one of the morphologically most extreme species, and one of its main food plant clades ("Passiflora" section "Tacsonia").Hummingbirds exhibit sexual size dimorphism according to Rensch's rule, in which males are smaller than females in small species, and males are larger than females in large-bodied species.