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Announcements Oct. 4, 2006. Key on course web site (link on lectures page) click on “Test 1 (key)” after Sept. 20 You can pick up error sheets after class today. Invasive Species II. Lecture Objectives: Be introduced to biological invasions Know several examples of invasive species

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AnnouncementsOct. 4, 2006

Key on course web site (link on lectures page)

click on “Test 1 (key)” after Sept. 20

You can pick up error sheets after class today.

invasive species ii
Invasive Species II

Lecture Objectives:

  • Be introduced to biological invasions
  • Know several examples of invasive species
  • Learn what you can do to stop the spread of invasive species


5 October, 2004

Deadly ladybird' sighted in UK

A ladybird which has already caused havoc to native insects in America has been spotted near a pub in Essex. Harmonia axyridis posed a "deadly threat" to butterflies, lacewings and many other ladybirds. The ladybird is an Asian species which was introduced into North America 25 years ago to fight aphids. It has since spread to Europe and last month was discovered in the gardens of the White Lion pub in Sible Hedingham. It is critical to monitor this ladybird now, before it gets out of control and starts to annihilate our own British ladybirds. H. axyridis is still sold in North America as a pest control. "It is now the commonest ladybird in North America.


Laurentian Great Lakes


Mills et al. 1993

Over 140 exotic species


Many fish species were (and continue to be) released intentionally




Many other exotics have entered the lake accidentally:


Escape from captivity

Ballast water

Bait buckets, live wells and gear


Sea Lamprey

(Petromyzon marinus)

Invaded the Great Lakes after the opening of the Welland Canal

Devastated native fish stocks, especially lake trout


Other fish (>25 species)

Round goby (1990)

(Neogobius melanostomus)

Ballast water

Alewife (1873)

(Alosa pseudoharengus)


Chinook salmon (1873)

(Oncorhynchuys tshawytscha)

Deliberate release

Coho salmon (1933)

(Oncorhynchus kisutch)

Deliberate release


Exotic Crustaceans (>6 species)

Bythotrephes cederstromi (1984)

Ballast water

Cercopagis pengoi (1998)

Ballast water


Exotic mollusks (> 14 species)

Quagga mussel (1990s)

(Dreissena bugensis)

Ballast water

Asiatic clam (1980)

(Corbicula fluminea)

Aquarium release


ZEBRA MUSSEL — Dreissena polymorpha

Found in 1988 in Lake St. Clair (Lake between Huron and Erie, just off of Detroit, MI).

Up to 70,000 individuals per m2

Likely came to North America in ballast water


One of the most expensive exotic species

Will biofoul and restrict the flow of water through intake pipes (drinking, cooling, processing and irrigating water)

Also attaches to boat hulls, docks, locks, breakwaters and navigation aids, increasing maintenance costs and impeding waterborne transport.


Characteristics of zebra mussels:

Can attach to hard surfaces

They have a free-living planktonic larval stage— veliger

Females can produce 40,000 veligers

These are typical characteristic of marine species


Veligers are easily transported in bait buckets and livewells and anywhere else water collects

Adults can attach to hulls and survive outside of water for several days.

Cover most hard surfaces


Negative effects on native clams

Zebra mussels cover them and prevent them from feeding and moving


Plants (> 59 species)

Purple Loosestrife (early 1800s)

Lythrum salicaria

Eurasian Watermilfoil (1881)

Myriophyllum spicatum


How to prevent the spread of aquatic nuisance species?

Never dump bait buckets!!

Before leaving site, inspect gear, boats and trailers for exotics

Empty all water before leaving site

Rinse your boat and equipment with high pressure hot water, especially if moored for more than a day

Let equipment dry for several days (does not work for species with resting eggs)


Lake Victoria

zmax = 100m

More than 30 million people depend on the lake for survival


Lake Victoria Cichlids

Over 300 endemic species described from Lake Victoria

Haplochromis obliquidens

Rock scraper

Crab eater

Plant scraper

Parasite picker

Snail crusher

Egg snatcher

Scale eater

Rock-reef low-foraging zooplanktivore


The traditional fishery was dominated by hundreds of native species.

But the introduction of gill nets and other gear by the British in the early 1900s resulted in over-fishing


In the 1950s, several new species were introduced to Lake Victoria to compensate for the declining stock of native species

Oreochromis niloticus

Nile tilapia

eats zooplankton

Lates niloticus

Nile perch

eats fish


One major life-history difference between the native and exotics:

All cichlids provide parental care

Many cichlids brood a relatively small number (5 to 100) of large eggs

The exotics have much higher birthrates and no parental care


Before 1980, Haplocromines contributed about 80% of the biomass and Nile perch less than 2%

Figure from Kaufman 1992

Most rapid vertebrate mass extinction in recent history


What had been a fishery of > 400 species now was dominated by three:

80% Nile perch

20% Nile tilapia and omena

As the native fish species declined, Nile perch shifted to feeding on the native shrimp Cardina nilotica


Other problems with Nile perch:

Destroys gear

Cannot be sun-dried

Can be smoked, but smoking required wood

Favors large-scale fishing operations, which results in malnutrition, unemployment and poverty

what kind of ants are pests
What kind of ants are “pests”
  • Both native and introduced species can become problematic
    • Leaf cutting ants, “sugar ants”, fire ants
  • Most damaging species are introduced
  • Biggest problems may occur

on islands that have no native ant species.

why worry about introduced ants
Why worry about introduced ants?
  • Agricultural
    • Some direct damage to crops
    • Tend and protect aphids
    • Disrupt biological control programs
  • Urban pests
    • Mostly nuisance but can spread bacteria (in hospitals)
  • Ecological pests - ecosystem level effects
why worry about introduced ants30
Why worry about introduced ants?
  • Ecological pests - ecosystem level effects

Phrynosoma coronatum

Declining throughout its range.

A “sit and wait” ant specialist.


Argentine ants disrupt ant-mediated seed dispersal.

Dendromecon rigida - tree poppy (Papaveraceae)

how do we control invasive species
How do we control invasive species?
  • In urban and agricultural areas pesticide use still common
  • Natural enemies - Biological Control
  • Manage the landscape to minimize disturbance
    • Turn off the water; landscape with native plants
results of pesticide use
Results of pesticide use
  • Killed native competitors
  • May select for resistance
  • Health risks for people

Biological Control:

The use of one species to control another.

Usually a specialist predator or parasite of an invasive species.

Needs to be species specific or could cause even worse problems.


Phorid flies



Priorities for future research:

  • Comparisons of native & introduced populations
  • (determining native range)
  • More experimental, large-scale & long-term studies
  • Better estimates of density & biomass
  • Prevention & control


  • Education is key
  • Research is still needed - generalities?
  • Monitoring programs - early detection
  • Prevent establishment - quarantine
  • Increased communication among agencies
  • Increase regulations
what can you do to stop the spread of exotics
What can you do to stop the spread of exotics?

points to know oct 2 4
Points to know, Oct. 2-4
  • Name two reasons we should be concerned about exotic, invasive species. How are they often introduced?
  • Why are some exotic species so successful? Why are certain ecosystems more vulnerable to exotic species?
  • Be able to recognize the exotic species from these lectures by name. Additionally, know the Lake Victoria and Laurentian Great Lakes stories in detail.
  • Know how individual people can help prevent the spread of invasive species.