Do pollinators respond in a dose-dependent manner to flower herbivory?: An experimental assessment in Loasa tricolor (Loasaceae)

Abstract

Pollinators are able to discriminate among different floral phenotypes. Thus, flowers more attractive to pollinators usually receive more visits to their reproductive structures. However, this effect of attraction does not necessarily occur in a binary way, all-or-nothing. Loasa tricolor KerGawl. is an annual herb covered with stinging hairs. Flowers present a corolla with five yellow petals and red nectarine scales. In this study, we assess whether the variation in the floral phenotype of L. tricolor affects discrimination by pollinators, following a dose-dependent type of response. This study was carried out in a protected area of Chile where L. tricolor shows high levels of florivory, probably affecting its attraction to pollinators. We experimentally modified the corolla phenotype, removing three or all petals. We measured visitation rate, richness and diversity of pollinator species in treated and control flowers. Results show that three-petal-removal did not reduce the visitation rate compared to control, while complete-petal-removal significantly reduced the visitation rate. Most pollinator species were recorded in the three-petal-removal treatment (nine species), while complete-petal-removal treatment obtained the lowest richness value (four species). These results suggest that species diversity, richness and visitation rates are affected by flower phenotype variation, but probably for complete petal loss only. We suggest that different levels of florivory on L. tricolor do not affect pollinator discrimination in a dose-dependent way.