Pollination systems are mostly mutualistic, meaning that the plant benefits from the pollinator's transport of male gametes and the pollinator benefits from a reward, such as pollen or nectar. As nectar robbers receive the rewards without direct contact with the reproductive parts of the flower, their behaviour is easily assumed to be cheating. However, the effect of robbery on the plant is sometimes neutral or even positive. For example, the proboscis of "Eurybia elvina" does not come in contact with the reproductive parts of the flower in "Calathea ovandensis," but this does not lead to significant reduction in fruit-set of the plant. In another example, when 80 percent of the flowers in a study site were robbed and the robbers did not pollinate, neither the seed nor fruit set were negatively affected.