Do pollinators respond in a dose-dependent manner to flower herbivory?: An experimental assessment in Loasa tricolor (Loasaceae) Responden los polinizadores en forma dosis-dependiente a la herbivoría floral?: Una evaluación experimental en Loasa tricolor (Loasaceae)

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. Los polinizadores son capaces de discriminar entre diferentes fenotipos florales. Por lo tanto, flores más atractivas para los polinizadores usualmente reciben más visitas a sus estructuras reproductivas. Sin embargo, este efecto de atracción no ocurre necesariamente de una forma binaria, todo o nada. Loasa tricolor KerGawl. es una hierba anual cubierta con pelos urticantes. Sus flores presentan una corola con cinco pétalos amarillos y escamas nectarinas rojas. En este estudio, evaluamos si la variación en el fenotipo floral de L. tricolor afecta la discriminación por polinizadores, siguiendo una respuesta de tipo dosis-dependiente. Este estudio fue llevado a cabo en un área protegida de Chile donde L. tricolor muestra altos niveles de herbivoría floral, probablemente afectando su atracción hacia los polinizadores. Modificamos experimentalmente el fenotipo de la corola, removiendo tres o todos sus pétalos. Medimos la tasa de visita, riqueza y diversidad de especies de polinizadores en las flores tratadas y control.