1. 3)What makes a species invasive? i) Disturbance and land use hypothesis Basic concepts: Many invasive species have a “ruderal” life history strategy. “ruderal” = small, very-short lived plants that grow and mature rapidly and that have a large reproductive effort, especially in response to stress

2. 3)What makes a species invasive? i) Disturbance and land use hypothesis Basic concepts: Invasive species are ruderals These types of species are typically associated with disturbed types of habitats.

3. 3)What makes a species invasive? i) Disturbance and land use hypothesis Basic concepts: Invasive species are ruderals Ruderals associated with disturbed habitats Changes in land use cause changes in the extent and frequency of disturbance to an ecosystem

4. 3)What makes a species invasive? i) Disturbance and land use hypothesis Basic concepts: Invasive species are ruderals Ruderals associated with disturbed habitats Land use changes affect disturbance Examples from Hobbs in Mooney & Hobbs (2000) Change can be abrupt

5. 3)What makes a species invasive? i) Disturbance and land use hypothesis Basic concepts: Invasive species are ruderals Ruderals associated with disturbed habitats Land use changes affect disturbance Examples from Hobbs in Mooney & Hobbs (2000) Change can be abrupt or gradual

6. 3)What makes a species invasive? i) Disturbance and land use hypothesis Basic concepts: Invasive species are ruderals Ruderals associated with disturbed habitats Land use changes affect disturbance Examples from Hobbs in Mooney & Hobbs (2000) Change can be abrupt or gradual Change can be permanent

7. 3)What makes a species invasive? i) Disturbance and land use hypothesis Basic concepts: Invasive species are ruderals Ruderals associated with disturbed habitats Land use changes affect disturbance Examples from Hobbs in Mooney & Hobbs (2000) Change can be abrupt or gradual Change can be permanent or transitory

8. 3)What makes a species invasive? i) Disturbance and land use hypothesis Basic concepts: Invasive species are ruderals Ruderals associated with disturbed habitats Land use changes affect disturbance Examples from Hobbs in Mooney & Hobbs (2000) Change can be abrupt or gradual Change can be permanent or transitory Transition back to original state

9. 3)What makes a species invasive? i) Disturbance and land use hypothesis Basic concepts: Invasive species are ruderals Ruderals associated with disturbed habitats Land use changes affect disturbance Examples from Hobbs in Mooney & Hobbs (2000) Change can be abrupt or gradual Change can be permanent or transitory Transition to original or new state

10. 3)What makes a species invasive? i) Disturbance and land use hypothesis Basic concepts: Invasive species are ruderals Ruderals associated with disturbed habitats Land use changes affect disturbance Examples from Hobbs in Mooney & Hobbs (2000) Change can be abrupt or gradual Change can be permanent or transitory Transition to original or new state Transition can be natural

11. 3)What makes a species invasive? i) Disturbance and land use hypothesis Basic concepts: Invasive species are ruderals Ruderals associated with disturbed habitats Land use changes affect disturbance Examples from Hobbs in Mooney & Hobbs (2000) Change can be abrupt or gradual Change can be permanent or transitory Transition to original or new state Transition can be natural or deliberate, with deliberately different end states

12. 3)What makes a species invasive? i) Disturbance and land use hypothesis Basic concepts: Invasive species are ruderals Ruderals associated with disturbed habitats Land use changes affect disturbance How can disturbance and land use changes enhance invasions?

13. 3)What makes a species invasive? i) Disturbance and land use hypothesis Basic concepts: Invasive species are ruderals Ruderals associated with disturbed habitats Land use changes affect disturbance Disturbance and land use changes enhance invasions by: Changing the amount or flow of resources hence inducing a change in resource availability

14. 3)What makes a species invasive? i) Disturbance and land use hypothesis Basic concepts: Invasive species are ruderals Ruderals associated with disturbed habitats Land use changes affect disturbance Disturbance and land use changes enhance invasions by: Changing the amount or flow of resources hence inducing a change in resource availability Increases the probability of success for ruderals

15. 3)What makes a species invasive? i) Disturbance and land use hypothesis Basic concepts: Invasive species are ruderals Ruderals associated with disturbed habitats Land use changes affect disturbance Disturbance and land use changes enhance invasions by: Changing the amount or flow of resources hence inducing a change in resource availability Increases the probability of success for ruderals Because of the changes in vegetation states, provides opportunities for other species to exist

16. 3)What makes a species invasive? i) Disturbance and land use hypothesis Evidence: D’Antonio & Vitousek (1992) Without invasive species, typically if disturb woodlands, they eventually return back to woodlands Disturbance Recovery

17. 3)What makes a species invasive? i) Disturbance and land use hypothesis Evidence: D’Antonio & Vitousek (1992) Without invasive species, eventually return back to woodlands But if have invasions of alien grasses during or after land is cleared, then alien grasses induce a novel disturbance: fire Disturbance Recovery

18. 3)What makes a species invasive? i) Disturbance and land use hypothesis Evidence: D’Antonio & Vitousek (1992) Without invasive species, eventually return back to woodlands With alien grass invasion: a novel disturbance = fire Once have a fire, initiate a series of feedback effects that virtually preclude the re-establishment of woody plants Disturbance Recovery

19. 3)What makes a species invasive? i) Disturbance and land use hypothesis Evidence: From Kalin Arroyo et al. in Mooney & Hobbs (2000) Determined number of alien plants in 12 political regions of Chile Total of 430 alien weeds Also 260 alien non-weeds

20. 3)What makes a species invasive? i) Disturbance and land use hypothesis Evidence: From Kalin Arroyo et al. in Mooney & Hobbs (2000) Number of alien plants in political regions of Chile For each political region, also determined density of roads and how much land area was in agricultural and urban use Computed a “Land Use Index” from these that goes from “low” (1) to “intensive” (11)

21. 3)What makes a species invasive? i) Disturbance and land use hypothesis Evidence: From Kalin Arroyo et al. in Mooney & Hobbs (2000) Number of alien plants in political regions of Chile Corresponding Land Use Index: from “low” (1) to “intensive” (11) For alien weeds (A), number increased significantly with index

22. 3)What makes a species invasive? i) Disturbance and land use hypothesis Evidence: From Kalin Arroyo et al. in Mooney & Hobbs (2000) Number of weedy plants in political regions of Chile Corresponding Land Use Index: from “low” (1) to “intensive” (11) Alien weeds increase with intesity of land use Similarly for Total Number of Alien Species (B)

23. 3)What makes a species invasive? i) Disturbance and land use hypothesis Summary: Disturbance and land use hypothesis Consistent with ecological theories

24. 3)What makes a species invasive? i) Disturbance and land use hypothesis Summary: Disturbance and land use hypothesis Consistent with ecological theories Evidence from a variety of ecosystems

25. 3)What makes a species invasive? i) Disturbance and land use hypothesis Summary: Disturbance and land use hypothesis Consistent with ecological theories Evidence from a variety of ecosystems Empirical correlations

26. 3)What makes a species invasive? i) Disturbance and land use hypothesis Summary: Disturbance and land use hypothesis Consistent with ecological theories Evidence from woodland / grasslands Empirical correlations But Is disturbance / land use the factor, or is it something associated with these? Species traits Resource availability Changes in competitive balance Temporary “vacant” niche

27. 3)What makes a species invasive? i) Disturbance and land use hypothesis Summary: Disturbance and land use hypothesis Consistent with ecological theories Evidence from woodland / grasslands Empirical correlations But Is disturbance / land use the factor? Plant establishment and invasion occur without disturbance

28. 3)What makes a species invasive? j) Anthropogenic hypothesis Basic concepts: Human activities are the cause of invasive species

29. 3)What makes a species invasive? j) Anthropogenic hypothesis Basic concepts: Human activities are the cause of invasive species Humans help invasives overcome barriers; e.g. Richardson et al. (2000) Humans are the vector for long distance transport Home range Introduced area Disturbed area Natural area Geographic ReproduceEnvironment Disperse

30. 3)What makes a species invasive? j) Anthropogenic hypothesis Basic concepts: Human activities are the cause of invasive species Humans help invasives overcome barriers; e.g. Richardson et al. (2000) Humans overcome geographic barriers Humans alter the environment that allows plants to grow and reproduce Home range Introduced area Disturbed area Natural area Geographic ReproduceEnvironment Disperse

31. 3)What makes a species invasive? j) Anthropogenic hypothesis Basic concepts: Human activities are the cause of invasive species Humans help invasives overcome barriers; e.g. Richardson et al. (2000) Humans overcome geographic barriers Humans overcome environmental & reproductive barriers Humans help disperse invasives in new range Home range Introduced area Disturbed area Natural area Geographic ReproduceEnvironment Disperse

32. 3)What makes a species invasive? j) Anthropogenic hypothesis Basic concepts: Human activities are the cause of invasive species Humans help invasives overcome barriers Thus, humans and invasive species are interdependent

33. 3)What makes a species invasive? j) Anthropogenic hypothesis Basic concepts: From Hobbs in Mooney & Hobbs (2000) Humans and invasive species are interdependent Direct effects by introducing invading species

34. 3)What makes a species invasive? j) Anthropogenic hypothesis Basic concepts: From Hobbs in Mooney & Hobbs (2000) Humans and invasive species are interdependent Direct effects by introducing invading species Direct effects by altering ecosystem properties

35. 3)What makes a species invasive? j) Anthropogenic hypothesis Basic concepts: From Hobbs in Mooney & Hobbs (2000) Humans and invasive species are interdependent Direct effects by introducing invading species Direct effects by altering ecosystem properties Cascading, indirect effects

36. 3)What makes a species invasive? j) Anthropogenic hypothesis Basic concepts: From Hobbs in Mooney & Hobbs (2000) Humans and invasive species are interdependent Direct effects by introducing invading species Direct effects by altering ecosystem properties Cascading, indirect effects, which sets up an invasive cycle

37. 3)What makes a species invasive? j) Anthropogenic hypothesis Evidence: Humans as vector for introduction?

38. 3)What makes a species invasive? j) Anthropogenic hypothesis Evidence: From Mack et al. (2000) Humans as vector for introduction Lantana camara (lantana; shrub verbena) shrub native to tropical New World Prized for showy flowers and fragrant leaves

39. 3)What makes a species invasive? j) Anthropogenic hypothesis Evidence: From Mack et al. (2000) Humans as vector for introduction Lantana camara native to tropical New World Introduced as a horticultural species repeatedly throughout the world, especially tropics and sub-tropics

40. 3)What makes a species invasive? j) Anthropogenic hypothesis Evidence: From Lonsdale (1999) Ecology 80:1522-1536 Humans as vector for introduction Asked: Do the number of invasive species increase with number of visitors to natural areas?

41. 3)What makes a species invasive? j) Anthropogenic hypothesis Evidence: From Lonsdale (1999) Humans as vector for introduction Do invasives ↑ with visitation? First, control for larger parks have more natives which draws more visitors (a)

42. 3)What makes a species invasive? j) Anthropogenic hypothesis Evidence: From Lonsdale (1999) Humans as vector for introduction Do invasives ↑ with visitation? First, more natives → more visitors Then look at visitors corrected for number of natives (= “visitor residuals”)

43. 3)What makes a species invasive? j) Anthropogenic hypothesis Evidence: From Lonsdale (1999) Humans as vector for introduction Do invasives ↑ with visitation? First, more natives → more visitors Then look at visitors corrected for number of natives (= “visitor residuals”) vs. number of exotics (b)

44. 3)What makes a species invasive? j) Anthropogenic hypothesis Evidence: From Lonsdale (1999) Humans as vector for introduction Do invasives ↑ with visitation? First, more natives → more visitors Number of exotics significantly (P<0.001; adj. r 2 =0.68) with visitors

45. 3)What makes a species invasive? j) Anthropogenic hypothesis Evidence: Humans as vector for introduction Human alterations of ecosystem properties

46. 3)What makes a species invasive? j) Anthropogenic hypothesis Evidence: Humans as vector for introduction Human alterations of ecosystem properties Example: Riparian areas in western US Originally “cottonwood gallery forest” Cottonwood and willow dominated ecosystem Open forest with understory of shrubs and herbs Used by diverse array of animals and birds Re-establish after spring floods: Produce abundant wind-dispersed seed in late-spring Colonize moist, exposed sediments from floods Grow rapidly (not shade tolerant)

47. 3)What makes a species invasive? j) Anthropogenic hypothesis Evidence: Humans as vector for introduction Human alterations of ecosystem properties Example: Riparian areas in western US Originally “cottonwood gallery forest” First large impacts came during Spanish settlement Primarily ranching and irrigated agriculture

48. 3)What makes a species invasive? j) Anthropogenic hypothesis Evidence: Humans as vector for introduction Human alterations of ecosystem properties Example: Riparian areas in western US Originally “cottonwood gallery forest” Spanish settlement: ranching and irrigated agriculture Expansion of US during mid-1800’s Trappers removed upstream beavers; resulted in ↑ sediment loads Large-scale ranching, irrigated agriculture, logging, & mining; resulted in land clearing and extensive disturbance

49. 3)What makes a species invasive? j) Anthropogenic hypothesis Evidence: Humans as vector for introduction Human alterations of ecosystem properties Example: Riparian areas in western US Originally “cottonwood gallery forest” Spanish settlement: ranching and irrigated agriculture US expansion (mid-1800’s): sedimentation, clearing, disturbance Early 1900’s: Construction of dams, levees, drainage ditches Prevented spring flood cycle Dried fuel and litter accumulated → ↑ fires

50. 3)What makes a species invasive? j) Anthropogenic hypothesis Evidence: Humans as vector for introduction Human alterations of ecosystem properties Example: Riparian areas in western US Originally “cottonwood gallery forest” Spanish settlement: ranching and irrigated agriculture US expansion (mid-1800’s): sedimentation, clearing, disturbance Dam construction (early 1900’s): prevented spring flood; fires Saltcedars & Russian olive introductions (mid-late 1800’s) Windbreaks, erosion control & stream bank stabilization, ornamentals Originally encouraged and subsidized by governments More drought tolerant; less exacting on seed dispersal & establishment requirements Now dominant species on much of the riparian areas of western US

51. 3)What makes a species invasive? j) Anthropogenic hypothesis Summary: Abundant evidence that Humans are major vector for introduction Humans greatly alter ecosystem properties

52. 3)What makes a species invasive? j) Anthropogenic hypothesis Summary: Abundant evidence that Humans are major vector for introduction Humans greatly alter ecosystem properties But: Invasive species problems are no longer just a natural, ecological problem

53. 3)What makes a species invasive? 10 hypotheses: 1.Vacant niche hypothesis 2.Allelopathy hypothesis 3.Environmental change hypothesis 4.Variable resource availability hypothesis 5.Competition hypothesis 6.Microevolutionary change hypothesis 7.Escape from biotic constraints hypothesis 8.Biodiversity hypothesis 9.Disturbance and land use hypothesis 10.Anthropogenic hypothesis

54. 3)What makes a species invasive? 10 hypotheses: 1.Vacant niche hypothesis No support 2.Allelopathy hypothesis 3.Environmental change hypothesis 4.Variable resource availability hypothesis 5.Competition hypothesis 6.Microevolutionary change hypothesis 7.Escape from biotic constraints hypothesis 8.Biodiversity hypothesis Conflicting support 9.Disturbance and land use hypothesis 10.Anthropogenic hypothesis

55. 3)What makes a species invasive? 10 hypotheses: 1.Vacant niche hypothesis No support 2.Allelopathy hypothesis 3.Environmental change hypothesis 4.Variable resource availability hypothesis Very limited support 5.Competition hypothesis 6.Microevolutionary change hypothesis 7.Escape from biotic constraints hypothesis 8.Biodiversity hypothesis Conflicting support 9.Disturbance and land use hypothesis Special case of #10 10.Anthropogenic hypothesis

56. 3)What makes a species invasive? 10 hypotheses: 1.Vacant niche hypothesis No support 2.Allelopathy hypothesis Specific cases, but how many? 3.Environmental change hypothesis 4.Variable resource availability hypothesis Very limited support 5.Competition hypothesis 6.Microevolutionary change hypothesis Specific cases ; how many? 7.Escape from biotic constraints hypothesis 8.Biodiversity hypothesis Conflicting support 9.Disturbance and land use hypothesis Special case of #10 10.Anthropogenic hypothesis

57. 3)What makes a species invasive? 10 hypotheses: 1.Vacant niche hypothesis No support 2.Allelopathy hypothesis Specific cases, but how many? 3.Environmental change hypothesis Broad support, but exceptions 4.Variable resource availability hypothesis Very limited support 5.Competition hypothesis Broad support, but exceptions 6.Microevolutionary change hypothesis Specific cases ; how many? 7.Escape from biotic constraints Broad support;exceptions 8.Biodiversity hypothesis Conflicting support 9.Disturbance and land use hypothesis Special case of #10 10.Anthropogenic hypothesis

58. 3)What makes a species invasive? 10 hypotheses: 1.Vacant niche hypothesis No support 2.Allelopathy hypothesis Specific cases, but how many? 3.Environmental change hypothesis Broad support, but exceptions 4.Variable resource availability hypothesis Very limited support 5.Competition hypothesis Broad support, but exceptions 6.Microevolutionary change hypothesis Specific cases ; how many? 7.Escape from biotic constraints Broad support;exceptions 8.Biodiversity hypothesis Conflicting support 9.Disturbance and land use hypothesis Special case of #10 10.Anthropogenic hypothesis Broad support, few exceptions