**5. Conclusions**

Interaction is often formed between invasive plants and native flower visitors, and their invasion is often reliant on these interactions. Despite the widespread belief that invasive plants have a detrimental effect on native flower tourists, there is no evidence to back this up [48]. In view of the challenges of studying so many flower-visiting taxa, it is not surprising that the direct effects on the diet of individual flower visitors, their health, and fitness by the invasive plants are poorly understood. Given the complexity of performing experiments to assess the effects and the wide variety of responses that can be measured, we are only likely to be able to evaluate impacts for a small percentage of the potentially affected species (most likely insect species that are commercially accessible and/or can be manipulated in a laboratory setting). Moreover, since the effects of invasive plants are likely to be specific to plant species and ecological background-specific, our knowledge is likely to be restricted to globally distributed, problematic plant species. However, better predictions of impacts can be made by designing suitable studies [49] and integrating more knowledge of plant and insect species traits (including plant the breeding system, pollination syndrome, nectar chemistry, insect body size, and diet breadth). As a result, more research into invasive plants and the ecology of flower visitors is needed before broad conclusions regarding direct impacts can be drawn.
