Okay, we all know that jewelweed leaves have a natural antihistamine in them when applied externally (handy that they grow near poison ivy).
It seems that jewelweed populations are not affected well when deer eat them — not the first year, anyway. But apparently they gradually get used to it and deal with it. The article thinks they evolve; but of course it could be that jewelweed has a range of responses to environmental conditions which only express themselves under those conditions.
There’s a nice picture of jewelweed in flower.
Cornell’s doe deer are of course famous as the ones that received tubal ligations, continued to produce pheromones because they never got pregnant, and thus seduced every buck in several counties to visit campus for their neverending “mating season.” Ooooops.