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Invasive species

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Invasive species

„But the cardoon (Cynara cardunculus) has a far wider range.: it now occurs in these latitudes on both sides of the Cordillera across the continent. I saw it in unfrequented spots in Chile, Entre Rios, and Banda oriental. In the latter country alone, very many (probably several hundred) square miles are covered with one mass of these prickly plants, and are impenetrable by man or beast. Over the undulating plains, where these great beds occur, nothing else can live. Before their introduction, however, I apprehend the surface supported as in other parts a rank herbage. I doubt whether any case is on record of an invasion of so grand scale of one plant over the aborigines”

Charles Darwin 1839: Voyage of the Beagle.


What are invasive species?

  • Invasive species are those that
  • were accidently introduced into new habitats by man (alien species)
  • were intentionally introduced into new habitats by man for commercial purposes
  • were intentionally introduced into new habitats by man for biological control
  • greatly extended their natural home ranges towards new areas for instance due to climate change or human activities (roads, tunnels)

Some well known examples

Gipsy moth

Colorado Potato beetle

First introduced to Europe in 1877

First record in Poland 1960

First introduced into North America in 1868

Has about 650 different host plants

During outbreaks causes major damages in softwood forests


Tiger mosquito

Nil perch

The Asian species was first reported from Houston texas in 1985

Now established in Brazil, Europe, and New Zealand

Vectors of yellow and dengue fever, as well as encephalitis

Changing cimate will promote the spread towards northern countries

First occurrence in mainland France in 2006. Now recorded from Belgium, Italy, France, Balkan region. First deadly infection of Chikungunya feaver in Italy 2007.

Introduced into the great Est African lakes during the 1950s and 1960s to improve fishering.

Caused dramatic changes in faunal and floral composition

Caused algal blooms and eutrophication

Caused the extinction of more than 200 native fish species (2/3 of all species)


Eichhornia crassipes

Marenzelleria viridis

Introduced into China from South America in the 1930s as an ornamental plant, to provide liestock food and to control air pollution

Caused reduction of lake areas and let to the extinction of about 30 fish species

Reduced lake areas caused climate changes and changes in water cycling

The flatworm was introduced via ship ballast water (first records 1979)

In the vistula lagoon it has become the dominant species constituting up to 97% of the total biomass of the bottom- living macrofauna


Harmonia axyridis

In the USA unsuccessfully used as aphid predator in biological control programs since 1916.

Sudden spread in USA since 1980.

Major impact on natural communities of aphid predators due to its high reproduction rate.

First observations of the Asian Lady beetle 2001: Belgium

2002: Germany, Netherlands2004: UK, France

2007: Scandinavia, Poland

2009: Whole of Poland


Unknown harvestman (Opilionida) species

First observed in the Netherlands (2007)

In 2008 massive invasion along the Rhine river up to Switzerland

Species are up to 18 cm in diameter.

They occur in large colonize of up to several hundred individuals.

They show colonial movements.


How many species are invasive?

Data from McNeely J. A. (1999), Kobelt and Nentwig (2008), Caley et al. 2008, and Sukopp (1990)


How do alien species come to Hawaii?

25% of all Hawaiian species are alien


A conceptual model of invading species




Changing land use

Habitat fragmentation

Changing of ecosystemfunctioning


Changing land management

Increasingopportunities for invaders


What makes a species invasive?

Marcel Rejmanek (1946-

  • Charcteristics of invasie species
  • r-strategists
  • have high dispersal ability
  • have small genome sizes
  • are habitat or feeding generalists
  • self pollinators (plants)
  • have long flowering periods (plants)
  • have a high proportion of leaf area (grasses)
  • have small seed sizes (in woody plants)
  • occupy often disturbed sites

DNA contents of 148 Californian angiosperms (from Knight et al. 2005)


What habitats are susceptible to invasions?

  • Early to mid-successionalhabitats
  • Mesicenvironments and openwater
  • Disturbedhabitats
  • Fragmentedhabitats

Phylogenetic distance from the resident species

„...florasgain by naturalization, proportionallywiththenumber of nativegenera and species, far moreinnewgenerathaninnewspecies”

Charles Darwin 1959: TheEvolution of Species by Means of Natural Selection

Theanalysis of plant speciesintroduced to California showsthatsignificantlymorespecies of Europeangenerawerenaturalizedthan of sharedgenera.

(fromRejmanek 1999)


Time lags

Fromintroduction to spreadingmight pass a long time.

Observed time lagsfromintyroduction to spradinginvarioustrees and shrubsinthearea of Berlin and Brandenburg (Kowarik 1995)


Today’s reading

Invasive species:

Invasive species database:

A different opinion: