Which of following will be fewer in number for an invasive species in a new ecosystem?

I. Ecological niches

II. Predators

III. Suitable food sources

An invasive species is an organism that is new to environment where it is not native. A key factor that makes many species invasive is a lack of predators in the new environment. This is complex and results from thousands of years of evolution in a different place. Predators and prey often co-evolve in a phenomenon called the co-evolutionary arms race. What this means is that as prey evolve better defenses, predators in turn evolve better ways of exploiting prey. The classic example of this comes from the cheetah and antelope. Faster antelope survive better because they can better escape cheetahs. The fastest cheetahs then survive better because they can better catch the faster antelope. Neither species ultimately gains an advantage because they continually evolve in response to one another. However, when a plant or animal enters a new environment, they will likely encounter predators who have not been evolving with them, which makes these predators unable to successfully exploit the prey. Defense mechanisms like venom, size or speed that have been matched by adaptation in predators are suddenly without match in the new environment. This can allow the species to proliferate rapidly as it no longer faces any predators.