Abstract

Non-native plant species with a taxonomic affinity to co-occurring natives may perform best as invaders into plant-pollinator networks because their similarity in floral morphologies with natives enabled them to co-opt their pollinators. However, non-native species may impact the reproduction of natives by altering their pollination only if they share pollinators and if natives depend on pollinators for seed-set, premises that are often assumed but seldom tested. The non-native invasive species Taraxacum officinale (Asteraceae) co-exist and co-flower with other asteraceous species in the high elevation of the central Chilean Andes. In this study we determined the dependence on pollinators for seed-set in five co-occurring and co-flowering native asteraceous species and assessed the similarity in insect pollinators between the non-native and this five native species that differ in their floral similarity with the former species. Pollinator exclusion experiments were performed to determine the dependence of pollinators for seed-set in the native species. Characteristics such as capitula size and colour were measured to quantitatively assess the similarity in the floral morphology between T. officinale and the native species. The identity and visitation rates of insect pollinators that visit T. officinale and the five native species were determined. Native species were highly dependent on the transport of pollen by insects to produce seeds. T. officinale shared a moderate to high proportion (34-94%) of insect pollinators with the five asteraceous native species studied, but the level of overlap in pollinators was not related with the floral similarity between the non-native and the native species. The presence of the non-native species T. officinale has the potential to alter the pollinator services to co-flowering native species in the Andes of central Chile, with no higher impacts on those species with the most similar flowers.