MODULE 3

1. MODULE 3 Invasion Pathways

2. Learning Outcomes • At the end of this module you should be able to: • explain why and how introductions occur • list some invasion pathways for intentional and unintentional introductions • identify what you can do to help prevent invasions

3. What are invasion pathways? • A pathway is defined as the means, purpose or activity by which an alien species may be transported to a new location

4. Types of introductions Alien Species Introductions Intentional Unintentional Legal Unauthorised Directly released into the wild Introduced into captivity Escaped or intentionally released

5. Agriculture • Cheatgrass • introduced to North America for forage • displaces native grass species • increases fire risk • harms livestock

6. Forestry • Cluster pine • introduced to South Africa for forestry purposes • forms dense thickets that suppress native plants • alters hydrological and fire regimes

7. photo by Nickolai Kashulin Fishing • Brown trout • introduced worldwide as a sport fish • can alter trophic structure by predating upon native invertebrates • displaces native fish

8. Biological control • Indian mongoose • introduced to many locations, including Hawaii and Fiji, to control rats • predate upon native birds, small mammals and reptiles

9. Food • Feral pig • introduced to many parts of the world for food and sport • predates upon birds and invertebrates • destroys vegetation • distributes weed seeds in droppings

10. Types of introductions Alien Species Introductions Intentional Unintentional Legal Unauthorised Directly released into the wild Introduced into captivity Escaped or intentionally released

11. Botanical gardens • Miconia • introduced to a botanical garden in Tahiti in 1937 • escaped into the wild and now covers over 60% of the island • excludes native plants and causes landslides

12. Aquaculture • Mozambique tilapia • introduced to fish farms for aquaculture • released into the wild • competes with native fish for food and breeding sites

13. photo by Alexander Meinesz Aquariums • Caulerpa taxifolia • introduced to Mediterranean, possibly as aquarium waste • has spread throughout northern Mediterranean • smothers native sea grasses • destroys fish habitat

14. Types of introductions Alien Species Introductions Intentional Unintentional Legal Unauthorised Directly released into the wild Introduced into captivity Escaped or intentionally released

15. Unintentional introductions • The most difficult pathway to monitor • Harder still to prevent

16. Key Point • Unintentional introductions potentially pose a bigger threat to the environment than intentional introductions

17. Unintentional introductions • The rate of accidental introductions is increasing

18. Ship cross-section, showing ballast tanks and ballast water cycle Globallast Programme (http://globallast.imo.org) Ballast water • A major pathway for marine IAS

19. Red tide with dead fish Ballast water • Organisms introduced in ballast water include: • toxic dinoflagellates (red tide) • cholera • jellyfish • crabs

20. Fouled ship hull Organisms on a propeller Pacific Ocean shipping routes 2003-2003 Hull fouling • Marine organisms that attach to boat hulls are often transported long distances

21. Black-striped mussel Hull fouling • IAS introduced through hull fouling include: • Japanese brown alga (Sargassum muticum) • Asian kelp (Undaria pinnatifida) • black striped mussel

22. Key Point • Ballast water and hull fouling are the most significant pathways for marine bioinvasions

23. Activity • Using the Best Practice Manual on IAS Prevention, identify what boat owners should do to help reduce aquatic invasive species being introduced via the hull fouling pathway.

24. Tents Hiking boots Fishing nets Personal baggage / equipment • IAS can be transferred on personal baggage or equipment • seeds, plant fragments, fungi, insects

25. Parthenium weed Seed contamination • Occurs when weed seeds become mixed with crop seeds • parthenium weed • serrated tussock grass

26. Vibrio cholerae bacteria adhering to a cell Packaging material • The cholera bacterium was introduced into North America on bait worm packaging material

27. Asian long-horned beetle Formosan termite Timber • Timber and other wood products often harbour invasive insects and diseases

28. Brown tree snake Miconia Dirty machinery • Many species hitchhike on used machinery, vehicles, vehicle parts and military equipment

29. Activity • What can you do to help prevent new invasions: • arriving in your country? • spreading within your country?

30. Dispersal after introduction • Once introduced, an IAS can then disperse into surrounding areas by: • natural dispersal or • human-aided dispersal

31. Natural dispersal • Digestion / excretion • On animals • Self-propelled • Wind • Ocean currents

32. Dispersal • Ruddy duck • introduced into the UK from North America • naturally spread into Spain, where it hybridises with the endangered white-headed duck

33. Summary • Invasion pathways are: • mostly man-made • numerous • incompletely understood • increasing