1. Invasive Species in Nova Scotia A Primer

2. Native Species Any animal or plant that was here when we got here Black Duck Brook Trout Red Spruce Mussel Red Squirrel Canada Goldenrod Bumblebee

3. Introduced Species(Non-Native, Exotic, Alien, Naturalized) Any animal or plant that humans brought here Rainbow Trout Ring-Necked Pheasant Scots Pine Norway Rat Queen-Anne’s Lace Gypsy Moth

4. Invasive Species Spiny-Cheek Crayfish An introduced species that displaces native species • Tend to establish large populations Eurasian Watermilfoil • Out-compete native species for space • or other resources • Sometimes also consume native species • (e.g., fish larvae)

5. Pest Species • An organism that does things we don’t like • Becoming too numerous • Competing with preferred species • Causing or carrying disease • Growing where we don’t want it • Being ugly • May be native or introduced • May or may not be invasive

6. How do introduced species get here? Accidental introductions Species transported incidentally by human traffic and transport Dandelion Zebra Mussel Woodlouse Dutch Elm Disease

7. How do introduced species get here? Deliberate Introductions Species brought here to provide food, sport, beauty or other amenities Honey Bee European Starling Purple Loosestrife Wild Apple

8. What kinds of species are introduced? ALL KINDS Smallmouth Bass Green Crab Didymosphenia geminata Codium fragile Asian Ladybird Beetle Norway Maple Burdock

9. Why are invasive species a problem? • Reduce populations of native species (sometimes to extinction) 2. Reduce natural diversity and compromise ecosystem function 3. Interfere with important commercial enterprises (fishing, farming, forestry) 4. Reduce aesthetic appeal of invaded areas

10. What makes a species invasive? Natural Advantage Hypothesis • No single feature unites all invasives • Tend to be tolerant of physical conditions • Tend to be fast-growing • Tend to reproduce quickly and abundantly • Tend to be competitive or aggressive • Tend to disperse easily • Tend to show phenotypic plasticity • Tend to tolerate or welcome disturbance

11. What makes a species invasive? Enemy Release Hypothesis • Invasive species may be controlled in native range by a predator or disease • Predator or pathogen absent in new range • Predators may be grazing mammals, insects, fungi, viruses • Specialist enemies most important • Generalist enemies create biotic resistance

12. Evidence for Enemy Release Based on 473 plant species naturalized in the U.S.A. (Mitchell , C.E. and Power, A.G. 2003. Nature 421: 625-627)

13. What makes a species invasive? Empty Niche Hypothesis • Invasive species may fill an unused niche • Using different resources • Acquiring resources in a different way • A form of natural advantage • Most likely in species-poor communities • Supported by Island Biogeography Theory

14. What makes a species invasive? Anthropogenic Disturbance Hypothesis • Disturbance removes competitors and predators (reduces biotic resistance) • Fewer competitors means unused resources • Invasive species may exploit new niche • Widespread human disturbance creates many invasion opportunities • Addition of resources (fertilizer, CO2) creates even more invasion opportunities

15. What to do about invasive species? 1. Prevention • Keep the invasive organism out • If it does get in, prevent or slow • its spread Common Reed 2. Eradication • Remove populations that are already established Japanese Knotweed Good luck with that