Predator and floral traits change pollinator behaviour, with consequences for plant fitness

Abstract

1. Flower-dwelling predators may interfere in plant–pollinator interactions through changes in pollinator behaviour, leading to a reduction in pollination services. Although the context-dependency of tri-trophic interactions is often acknowledged, the relative contribution of predator, pollinator and flower traits in shaping pollinator behaviour has been rarely studied simultaneously. 2. Pollinators' responses to predation risk were evaluated using artificial spiders on Alstroemeria aurea flowers in order to experimentally test whether predator traits (colour and size) and nectar availability affect their behaviour and plant fitness. 3. Regarding the predator's traits, both sizes of artificial spiders used were similarly rejected, but spider colour was detected differently. In particular, red and black artificial spiders were more strongly rejected than the rest. In turn, nectar availability increased the time spent in the inflorescences, yet most pollinators rejected flowers with artificial spiders independently of nectar availability. Furthermore, responses to artificial spider colour and nectar availability varied significantly between dipterans and hymenopterans. Finally, artificial spiders reduced seed set and fruit weight of plants owing to changes in the behaviour of the most efficient pollinators. 4. It was shown that poorly studied predator traits such as colour and size may affect pollinator behaviour in different ways among taxa. In addition, feeding necessity in a rich-resource environment was a weaker selecting force than predation risk. Hence, it is argued here that trade-offs between predation and flower reward may arise depending on predator detection, relationship between pollinator and predator size, and resource availability in the ecosystem with consequences for plant fitness.