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What makes a species invasive? i) Disturbance and land use hypothesis

What makes a species invasive? i) Disturbance and land use hypothesis . Basic concepts: Many invasive species have a “ruderal” life history strategy.

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What makes a species invasive? i) Disturbance and land use hypothesis

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

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

  29. Introduced area Geographic Environment Reproduce Home range Disperse Natural area Disturbed area • 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

  30. Introduced area Geographic Environment Reproduce Home range Disperse Natural area Disturbed area • 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

  31. Introduced area Geographic Environment Reproduce Home range Disperse Natural area Disturbed area • 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

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

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

  35. What makes a species invasive? • j) Anthropogenic hypothesis • Basic concepts: FromHobbs 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. What makes a species invasive? • j) Anthropogenic hypothesis • Basic concepts: FromHobbs 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. What makes a species invasive? • j) Anthropogenic hypothesis • Evidence: • Humans as vector for introduction?

  38. 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. 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. 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. 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. 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. 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. 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. r2=0.68) with visitors

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

  46. 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. 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. 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. 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. 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

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