What Makes a Successful Invader?

Only a handful of factors always influence whether a plant or animal successfully moves into territory outside its native range. Various studies have consistently found that three circumstances universally predict whether a fish, bird, mammal, reptile, amphibian, insect or plant can establish in new environments.

A new site's climate and habitat need to first of all match the conditions where the plant or animal already reside. Where these correspond well, a species has a better chance of becoming established when lots of individuals get released into the new area. Also, plants or animals with a track record of being invasive elsewhere seem most apt to survive introductions.

For a species to not only establish but also become invasive and harm the environment it has moved into, the only factor that corresponds with success for all types of organisms is a matching of climate and habitat. Among plants, invaders also share certain reproductive traits. Invasive plant species usually reproduce vegetatively, bear flowers over a long period, and quickly reach maturity.

Besides these, many other features found in some studies of successfully spreading species, did not appear important in other studies of different types of animals or plants. Furthermore, many characteristics of birds, mammals and fish consistently have no bearing on how likely they'll establish or become invasive beyond their native range. These include what they eat, their size, how many offspring they produce, and how long young take to mature.

The findings come from a review of 49 investigations into the traits that enable species to establish or become invasive in a new area. The review mainly reveals that not much can yet be generalized about the essential attributes of a proficient invader.