The invasions of species may not be breaking news on television the way an invading army is, but the problem has jumped to priority number one in the last few decades for those concerned with protecting our natural spaces and resources. Invasive species are posed to displace native plant and animal communities as their ranks move ever forward. But how fast does the takeover happen? And is it always happening at the same speed?
A study conducted by T. Alex Perkins at the University of California, Davis and published in the February 2012 issue of The American Naturalist set out to tackle these questions. In the paper, he outlined a mathematical model that could be used to predict the rate at which an invasive predatory species could invade the range of its native prey. Perkins took it a step further than the models other scientists have created: he accounted for the gradual evolution of the invading species. Perkins is applying a theory of invasion that recognizes that invasion is a strategy for an organism in and of itself, not just something that happens. Invasive species are adapting to a new way of life, one that demands that they overtake new territory quickly and fully.
Rewarding these invasion tactics brings the possibility of rapid evolution in some invading species. Perkins' model shows that if species are ever so slightly evolving as they multiply and spread across the landscape, they are adapting to take over new habitats faster and faster. This idea of an accelerating invasion goes counter to many of our intuitive ideas about evolution and invasion: namely, that an invasion is going to happen much faster than evolution, making evolution irrelevant to many invasive species concerns.
This change is not evenly spread though. Once all the numbers were plugged in, Perkins noticed an interesting trend in the projected locations of the population. After the first accelerating front of the invasion, subsequent waves were much more constant in their rate of spread and evolution. This is because adaptations for invading were more strongly selected for at the front lines of an invasion where improvements to speed and physique were greatly rewarded and dissonance in the ranks quickly squashed out.
Perkins’ mathematical model helps us to demonstrate a few simple truths that were previously hard to quantify, though it is somewhat limited. The mathematical relationships built into it assumes that we know a lot about the mechanisms of invasion and this sort of rapid evolution, when we really still have many questions. Still, it shifts our paradigm from considering evolution as just a slow, lumbering force to one that also has a more targeted, fast acting component.
Scientists are increasingly finding the world is not static. Evolution can act faster than we ever expected, and plays a key role in invasions around the globe. Moving closer to the facts and nuances of ecological invasions puts us closer to winning the fight against them. Many questions remain to be investigated on all fronts.
No comments:
Post a Comment