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 Humanactivities Disturbance Invadingspecies Changing land use Habitat fragmentation Changing of ecosystemfunctioning Changingenvironmentalconditions 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: http://en.wikipedia.org/wiki/Invasive_species Invasive species database: http://www.issg.org/database/welcome/ A different opinion: http://www.nytimes.com/2008/09/09/science/09inva.html