Why are species invasive?

Answer 1

Invasive species spread because they get introduced - either intentionally or accidentally - into areas where they have no natural controls or predators to check their population growth.

How they get into new places varies:

• A common way is hitching the boat, trailer, boating equipment and fishing gear, including bait buckets. Zebra mussels are an example of that.
• Cars, trucks and other motor vehicles can transport pests to new areas - like the Gypsy Moth.
• Shipments from abroad can bring in new pests. The Asian Longhorn beetle was thought to have come in via wood pallets from China.
• Asian carp were purposefully imported into the U.S. to eat algae and unwanted vegetation in catfish farms and sewage plants. They escaped during flooding.
• Snakehead fish are thought to be purchased live and then purposely released.
• Brown tree snakes might have gotten to Hawaii by hitching a ride on planes.
• Dandelion was brought to America by European settlers who grew it for food and medicine.

Invasive species usually get here when someone byes a pet such as a snake and then puts it out in the wild and over time it makes its way to our area and becomes an invasive species. Or when we are in a different area the animal gets into our vehicle and comes to our normal location.

Answer 2

There are numerous ways in which invasive species can be transported. Mile-a-minute weed first became established in the U.S. in the late 1930’s and slowly began to spread. Natural causes tend to be the primary methods of spreading. Birds eat the fruit and carry the seed for long distances before depositing the seeds along with their feces. Waterways also play a significant role in spreading the seeds. This weed produces vines that tend to hang over waterways. As the seeds ripen and fall, they may float for a week and be carried over long distances downstream. Over shorter distances, ants may be involved in distributing mile-a-minute seeds. Another example of natural causes spreading an invasive species is that of wind. This is especially important when considering plant diseases. Fungi produce spores that can be carried by the wind and quickly and widely distributed. An Internet interactive model has been developed that predicts the potential for infestation of tobacco by the wind distributed plant pathogen, Tobacco Blue Mold. This type of information immediately available can literally save a farmer’s crop. Female Gypsy moths cannot fly, so human involvement greatly increases the rate at which this pest expands its range. The females lay their egg masses on just about anything, cars, recreational vehicles, and even lawn furniture. If this egg mass is carried into an uninfested area before the eggs hatch, a new infestation is started. It is estimated that the Gypsy moth invades an additional 15,600 square miles each year (three times the area of Connecticut). Giant Salvina, a water fern from southeastern Brazil, is a tremendous threat to waterways. Under optimal conditions, it can double its numbers within a week. This weed has been illegally sold for use in residential ponds from Florida to California and currently is known to infest waterways in Alabama, Arizona, California, Florida, Hawaii, Louisiana, Mississippi, and Texas. Once established in a lake the weed can easily be caught on boats and boat trailers then moved from one lake to another. Cattle are a major source of transporting Tropical Soda Apple seeds. If cattle eat Tropical Soda Apple fruit growing in one field then are moved to another field the seeds will then be deposited in manure in the new the location. This can rapidly spread this weed when cattle are sold from and infested region and transported across state lines, if proper holding and shipping procedures are not followed.

Answer 3

A species can be invasive if 1) it is well suited to utilize or adapt to take advantage of, a new environment (living conditions and resources). 2) it can out-compete the existing organisms in the new environment that utilize the same resources. IE. flourish in its new niche.