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Invasive Species. Welcome to our new course. An exciting topic which may be the most important conservation issue today. Instructor: Robert C. Whitmore, Ph.D. Professor of Wildlife Ecology. Office: 312-b Percival Hall Phone: 304-293-3196

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Invasive Species

Welcome to our new course

An exciting topic which may be the most important conservation issue today


Instructor: Robert C. Whitmore, Ph.D. Professor of Wildlife Ecology

Office: 312-b Percival Hall

Phone: 304-293-3196

email: rwhitmor@wvu.eduOffice Hours- MTWR 8:30 am-noon


"The world, that understandable and lawful world, was slipping away."- William Golding, Lord of the Flies, Ch. 5

Mud & freshwater from a Hawaiian habitat degraded by the actions of feral pigs washes into the ocean and kills a reef system


“Nowadays we live in a very explosive world, and while we may not know where or when the next outburst will be, we might hope to find ways of stopping it or at any rate damping down its force”. Charles Elton, The Ecology of Invasions by Plants and Animals, 1958 University of Chicago Press, page 15

Asian Silver Carp, introduced into the Mississippi River drainage system.

so what is an invasive species
So, what is an invasive species?

Monk Parakeet colony nearChicago, Illinois


Following the most rigorous of definitions: “Invasion occurs when a species colonizes and persists in an area which it previously had not inhabited” (Shigesada and Kawasaki 1997).

For example, the Cattle Egret moved into South America from Africa and up into the United States without the aid of man. But, the definition is fuzzy, because of the myriad of plant and animal species that find themselves in a new area as a result of the direct actions of man. Both groups of species are covered in this course and both can result in either beneficial or harmful effects to local ecosystems.


Can you find Guam and New Guineaon a map of the world?

Brown Tree Snake introduced to Guam, but they are native to New Guinea

"Exotic," "alien," "introduced," non-indigenous," and "non-native" are all synonyms for plant or animal species that are intentionally or unintentionally introduced into an area outside of their natural range.


New Guinea

New Guinea


One must realize that, historically, all of the continents have been connected (and broken apart several times) and while connected, within ecological limits, species were able to move more freely between different geographic areas.

The general topic of the movement of large land masses, e.g. continents, is known as continental drift, the subject of which has had a great deal of study in the past 30 years. The continents are continuing to move and it is estimated that North America and Europe are moving apart at a rate of about 3-6 cm per year.



San AndreasFault

If you ever lived in Southern California, then you already know a lot about continental drift, just check with my buddy, Good ‘Ol Sam Andreas, who is selling “beachfront property” in Palmdale.


For example, in Charles Elton’s classic book, he was quick to point out that Dinosaur fossils are found worldwide. “But the significance of these dinosaurs for the serious historical evidence is that you couldn’t then get an animal the size of a lorry from one continent to another except by land; therefore the continents must have been joined together, at any rate fairly frequently, as geological time is counted.” page 31-(note a “lorry” is a large truck in the U.K.)


Of course, movement was prevented by natural barriers such as bodies of water (inland seas, etc.), mountain ranges, deserts and other geographic barriers.


Geologic Time Scale

= periods of “Mass Extinction”


So, about 200 million years ago (mya) Pangaea began the break-up which led to the creation of the current continents. For visual representation of the break-up go to the next slide. The break-up link to a video died over the weekend- sorry. The tiger picture is still sexy, though.


Distribution of continents with respect to the Equator, starting about 225 million years ago


Our course focuses on the movement and establishment of species into a new area. We will deal only slightly with human health issues, leaving that to courses in epidemiology. But, past invasion of certain species has led to huge human health disasters. For, example after the first World War a pandemic influenza outbreak circled the globe, killing in excess of 100 million humans. Currently, outbreak levels of several human diseases are feared, including host locations within North America. The tick being removed from the mouse, above, contained the pathogen responsible for Lyme Disease in humans (about 21,000 new cases were reported in the United States last year).


“Ecological explosions differ from some of the rest by not making such a loud noise and in taking longer to happen” Charles Elton.

Kudzu infestation along the Atlanta Highway between Athens and Atlanta, Georgia


We will also examine the roll of the new species to the ecology of the area, for example Sea Lamprey in the Great Lakes

Two Sea Lamprey attached to a Lake Trout

or wild pigs on a tropical island
Or wild pigs on a tropical island

“This head is for the beast. It's a gift. "- William Golding, Lord of the Flies, Ch. 8


We will cover the mechanisms of introduction/invasion including;

1. Intentional

Such as European Rabbits in Australia


Methods of Introduction, continued

2. Inadvertent, but human caused such as the ruffe

Would you want to swallow this?

Native to lakes and rivers in Eurasia, the ruffe was introduced to Duluth Harbor on Lake Superior via ballast water of an ocean going vessel and first collected in fish surveys in 1986. Capable of explosive population growth.


3. Natural Invaders

The Cattle Egret, perched atop the Cape Buffalo in this photo, is native to Africa and first crossed to South America then into the United States in the 1940’s


Current distribution of the Cattle Egret- a natural invasive species from Africa, by way of South America


Most invaders, whether introduced or natural, either fail to establish or if they establish they fail to cause measurable impact to the ecosystem, e.g. become pests. This rule was developed by Mark Williamson and has been called “The Rule of 10s.”10% of invading species become established and, of those, 10% are harmful (Biological Invasions, 1996 page 33, Chapman and Hall Publishing.

Zebra Mussel- introduced into the Great Lakes in the ballast of oceanic ships


House Sparrow- intentionally introduced into the U.S.from the U.K.

Sadly, things in nature are never quite that simple and there are a lot of exceptions to the “10s rule”. But, it does emphasize the fact that invasions are continually occurring and that because of world commerce the rate of invasion has increased greatly in the past 50 years. In essence, the continents have been re-united.So, our course will also look at, not only how species re-locate, but also what determines whether or not they become established and subsequently become pests.


We will look at determinants of impact

1. Ecological distinctiveness- highly successful invaders are usually different in structure, physiology or behavior from native forms

Keystone Exotics

Kudzu, a keystone exotic species infestation in Georgia. Keystone species are those, that if added or lost, would precipitate an extinction cascade or vortex, meaning the subsequent loss of many additional species. More on this later

Kudzu takes Atlanta


Determinants for Impact

2. Potential for competitive exclusion- when one species out-competes another, to the detriment of the latter

Zebra Musses attached to the shell of a native mussel in the Ohio River


3. Potential for disease transmission

Chestnut Blight

Fungi accidently introduced on Chinese Chestnut trees imported to the United States, the map documents the timing of the spread


4. Potential for genetic swamping- example rainbow trout

The species is native to Pacific Coast drainages in Western North America and Asia and has been introduced for food or sport to at least 45 countries, and every continent except Antarctica.

The first “Rainbow” hatcheries were located in California.1. 1871 on San Leandro Creek, a tributaryof San Francisco Bay, in 1870 with trout production beginning in 1871. The source population was likely obtained from “pure genetic lines” in California.2. A second California hatchery was located on a tributary of the McCloud River in Northern California. The genetic make-up of this hatchery is mixed and of were questionable origin.Fish from both of these hatcheries have been transported world wide, upsetting the genetic make-up of local native populations………………

Rainbow trout


McCloud River Fish Hatchery constructed in 1870s. The river is in the foreground and the hatchery, is in the background. This classic photograph was taken by Thomas Houseworth in 1882 and provided through the courtesy of Ned Kirstein of Pittsburgh PA


Rainbow trout are easily cultured and with the advent of “modern” railroad widely dispersed. Once introduced for anglers, they readily hybridize with native species such as; cutthroat trout naturally found on the west slope of the Rockies, Apache Trout in Arizona, and the Gila Trout found in Arizona and New Mexico. Of major importance is the genetic purity of the Lahontan Cutthroat Trout of the Walker and Pyramid Lake drainages on the California/Nevada border. This subspecies is now listed as Threatened under the U.S. Endangered Species Act and has been the subject of intensive management to protect it from “swamping” by hatchery raised rainbow trout introduced for sport fishing.

Lahontan Cutthroat trout


General Concepts to consider when dealing with detrimental exotics

1. Prevention of entry

2. Control of spread

3. Creation of pristine areas

4. Local eradication

5. Protection of individuals

6. General population reduction


To summarize- a species may be a natural invader or an introduced exotic (for which millions of dollars have been spent on their establishment, such as this ring-necked pheasant, which is prized by hunters because they taste mighty fine). None-the-less they are not native species and, therefore, special concern needs to be given to their affect on the ecosystem- before they are introduced.