That is a good question. This is an active area of research but I will try to give you the best answer that I can from what we know about the subject at this time. Generally speaking, the levels of nicotine that are naturally occurring in tobacco flowers are not acutely toxic to pollinators. In fact, some pollinators seem to seek out flowers containing low levels of nicotine. This benefits the plant because it is more likely to produce viable seeds if pollinators only visit flowers of their same species. We do not know of any long-term negative impacts on the pollinators from exposure to low levels of natural nicotine. Studies of synthetic nicotine analogs (neonicotinoids) have shown some adverse long-term effects, at least for some pollinators, but this another active area of research and has not been accepted by the entire scientific community. It is also important to remember that naturally occurring nicotine is very different from synthetic neonicotinoids and pollinator species have had millions of years to evolve the ability to detoxify naturally occurring nicotine. In other words, it is probably okay to plant nicotiana in your garden.
Thank you Nate.