Biological invasions are well documented phenomena.
In fact, they are the hottest topic in conservation these days. You've probably driven through Connecticut on a major state highway in the summer and noticed the lush clumps of flowery purple spikes growing in profusion along the roadside. You may have paused and wondered at their natural beauty, particularly at dusk when they reflect the vivid colors of the evening sky. But looks can be deceiving. It now pervades wetlands throughout the northern United States and is displacing native vegetation at an alarming rate.