Species invasions

1. Species invasions Bio 415/615

2. Questions 1. Why is the world primed to be subject to species invasions? 2. What is ‘biotic resistance’ and how does it apply to species invasions? 3. What are 3 potential explanations of how a species becomes an invader? 4. What is Darwin’s naturalization hypothesis?

3. "We must make no mistake: We are seeing one of the Great historical convulsions in the world's flora and fauna. We might say, with Professor Challenger, standing on Conan Doyle's 'Lost World', with his black beard jutting out: 'We have been privileged to be present at one of the typical decisive battles of history‑‑the battles which have determined the fate of the world.'" C. S. Elton, The Ecology of Invasions by Plants and Animals, 1958

4. What’s a biological invader?

5. ______________________________________________________ DEFINITIONS of Invasion Biology ____________________________________________________ EXOTIC, ALIEN Not “Originally” “Here” INTRODUCED, NON-NATIVE NATURALIZED Self-sustaining exotic INVASIVE Spreading exotic PEST Has Negative Impact BENEFICIAL Has Positive Impact _____________________________________________________

6. ____________________________________________________ “EXOTIC” AND CONSERVATION _______________________________________________ Historically Offensive: all exotics, some conservationists Not original, not natural, out of place Causes impacts: some exotics, all conservationists Replace native species, change ecosystem function ____________________________________________________ Typha angustifolia (cattail) Probably only in SE NY (coast) before recent spread along salted roadways

7. There is no formal agreed upon system of classification for exotic species. • Points of Disagreement: • 1. Native Range Expansion vs. Exotic Species – • Cattle Egrets – Native or Exotic in South America? They dispersed under their own power, but colonized an anthropogenic environment. • 2. Reintroduction to Native Range vs. Exotic Species – • Horses – Native or Exotic to North America? They were driven extinct 10,000 yrs bp, but were reintroduced by the Spanish. • Assumptions/Conditions: • When? 2. With human assisted dispersal or colonization? • Taxonomic bias of scientists, e.g. birds vs. plants, with dispersal

8. How & why are exotic species introduced? • Some arrive by their own power of dispersal • The remainder are transported by humans • Intentionally: • Naturalization Programs NZ, US • Horticulture Agriculture • Animal Husbandry • Unintentionally: • Ballast • Agricultural/Horticultural Weeds • Phoresy (hooves, fur, guts, etc.)

9. Does ‘invasion’ differ from natural migration? • Spatial extent of migration (non-continuous) • Number of migration individuals • Genotypes (‘core’ versus ‘peripheral’) • Migration coincident with biotic associates (enemies, mutualists)

10. Invader vignettes

11. Kudzu (Pueraria montana)

12. Kudzu – a case history Introduced to the U.S. in 1876, centennial celebration Gift from the Japanese government Gardeners loved it and started to plant it 1920’s promoted as a forage plant for livestock 1930’s Civilian Conservation Core planted it for soil erosion 1940’s touted as a miracle vine and clubs were formed 1953 federal government stopped advocating its use Grows up to 60 feet per year, or 1 ft on a hot summer day Covers everything: trees, houses, farm equipment, etc. Distributed primarily in the deep south, where it covers ca. 2 million acres of land

13. Zebra mussel (Dreissena polymorpha) • native to SW Russia (Caspian Sea region) • females produce> 30,000 eggs each yr • detected in US in 1988 (Great Lakes), probably via ship ballast • filter feeders • problem for water treatment plants • costs $5 billion / yr • crowd out native mussels

14. Zebra Mussel spread

15. Passer domesticus – house sparrow (Eurasian) • introduced to many US cities in late 1800s for pest control • is now perhaps the most common songbird in the US (maybe the world) • directly competes with other cavity-nesting songbirds • one of only 3 birds in the US not protected by law

16. House Sparrow – Passer domesticus

17. Cheat grass (Bromus tectorum) • From S Europe and SW Asia • Winter annual, highly flammable • Increases fire return frequencies • Has transformed large former sagebrush and grass lands of the American West • Can be dangerous to livestock • Causes hundreds of millions $$$ each year in control and livestock loss

18. Brown tree snake • Native to Australia • Introduced across Pacific • Detected in Guam in 1950s • Large population expansion on islands • Likely cause of extinction of 9/12 of Guam’s native birds, and 2/11 lizards • Frequent power outages • U Hawaii study predicted >400 million $$$ annual cost to Hawaii economy

19. Insects • Emerald ash borer • Asian longhorned beetle • Gypsy moth • Balsam woolly adelgid • Hemlock woolly adelgid

20. Invasive mammals • European wild boar • Mongoose • Rats

21. Invasive human diseases • West Nile virus • African, maybe 1000 years old • Found on US East Coast in 1999 • Various animal vectors (birds, insects, horses) • SARS • Severe acute respiratory syndrome (virus) • First outbreak in China in 2002 • Spread in 2003 to many North American cities • Monkeypox • African, spread to US in 2003 to pet prairie dog owners (via an infected pet store Gambian pouched rat in TX)

22. What about life on earth sets the stage for species invasions?

24. Darwin (1859): In considering the distribution of organic beings over the face of the globe, the first great fact which strikes us is that neither the similarity nor the dissimilarity of the inhabitants of various regions can be wholly accounted for by climatal and other physical conditions… There is hardly a climate or condition in the Old World which cannot be paralleled in the New…[yet] how widely different their organic productions!

25. Floristic regions and Köppen-Geiger climate zones Warm-temperature, fully humid, hot summer climate in blue

26. Why are some regions more invaded than others? • Biotic resistance: more diverse communities consume more resources, leave less available to potential invaders

27. Biotic resistance? • Experimental evidence says yes (sometimes) Fargione & Tilman 2005

28. Biotic resistance? • Observational evidence says NO (most of the time)

29. Why are some regions more invaded than others? • Biotic resistance: more diverse communities consume more resources, leave less available to potential invaders • Resource supply and demand: processes like disturbance make resources available to invaders

30. Davis et al. 2000

31. Why are some regions more invaded than others? • Biotic resistance: more diverse communities consume more resources, leave less available to potential invaders • Resource supply and demand: processes like disturbance make resources available to invaders • Propagule pressure: communities differ in exposure to invaders

32. More plantations, more invasionsRejmanek et al.

33. Greater years since introduction, more invasionsRejmanek et al.

34. What makes an organism invasive? • Innate biology: preadaptation, empty niche, weediness, competitiveness, etc

35. Innate Biology: Weediness

36. Innate Biology: Weediness Plant Traits for Prediction “…there are no specific traits that alone predict invasiveness…Rather the best single predictor is what a species has done in other places…” D’Antonio et al. 2004 • “The overriding frustration of invasion ecology.”Rejmanek et al. 2005

37. What makes an organism invasive? • Innate biology: preadaptation, empty niche, weediness, competitiveness, etc • Enemy release

38. Enemy release hypothesis (ERH)Biotic resistance hypothesis (BRH) Mitchell & Power 2003

39. What makes an organism invasive? • Innate biology: preadaptation, empty niche, weediness, competitiveness, etc • Enemy release • Novel weapons / rapid evolution of invasiveness

40. Novel weapons via phytochemicals Callaway et al. 2008 Callaway & Aschehoug 2004 Centaurea spp. widespread in North America produce root exudates with strong phytotoxic effects on North American species but weak effects on neighbors in the native range (Caucasus Mtns) Alliaria petiolata: stronger effects on mycorrhizas (and their plant associates) in U.S. than in Europe