1. Handouts on table near entrance

2. Readings: Melbourne et al (2007) ECOLOGY LETTERS 10 (1): 77-94

3. 3)What makes a species invasive? d) Variable resource availability hypothesis Davis et al. (2000) JOURNAL OF ECOLOGY 88 (3): 528-534 Basic concepts: In most plant communities at most times, most of the resources that are available are taken up by the plants Gross resource supply Resource uptake Resource supply-uptake isocline

4. 3)What makes a species invasive? d) Variable resource availability hypothesis Davis et al. (2000) Basic concepts: In most plant communities at most times, most of the resources that are available are taken up by the plants Plant community becomes more susceptible whenever there is an increase in the amount of unused resources Gross resource supply Resource uptake Resource supply-uptake isocline

5. 3)What makes a species invasive? d) Variable resource availability hypothesis Davis et al. (2000) Basic concepts: In most plant communities at most times, most of the resources that are available are taken up by the plants Plant community becomes more susceptible whenever there is an increase in the amount of unused resources Gross resource supply Resource uptake Resource supply-uptake isocline Resistant to Invasion A

6. 3)What makes a species invasive? d) Variable resource availability hypothesis Davis et al. (2000) Basic concepts: In most plant communities at most times, most of the resources that are available are taken up by the plants Plant community becomes more susceptible whenever there is an increase in the amount of unused resources Gross resource supply Resource uptake Resource supply-uptake isocline Resistant to Invasion Easily Invasible A

7. 3)What makes a species invasive? d) Variable resource availability hypothesis Davis et al. (2000) Basic concepts: In most plant communities at most times, most of the resources that are available are taken up by the plants Plant community becomes more susceptible whenever there is an increase in the amount of unused resources ↑ availability (A→B) Gross resource supply Resource uptake Resource supply-uptake isocline Resistant to Invasion Easily Invasible A B

8. 3)What makes a species invasive? d) Variable resource availability hypothesis Davis et al. (2000) Basic concepts: In most plant communities at most times, most of the resources that are available are taken up by the plants Plant community becomes more susceptible whenever there is an increase in the amount of unused resources ↑ availability (A→B) ↓ uptake (A→C) Gross resource supply Resource uptake Resource supply-uptake isocline Resistant to Invasion Easily Invasible A B C

9. 3)What makes a species invasive? d) Variable resource availability hypothesis Davis et al. (2000) Basic concepts: In most plant communities at most times, most of the resources that are available are taken up by the plants Plant community becomes more susceptible whenever there is an increase in the amount of unused resources ↑ availability (A→B) ↓ uptake (A→C) Both (A→D) Gross resource supply Resource uptake Resource supply-uptake isocline Resistant to Invasion Easily Invasible A B C D

10. 3)What makes a species invasive? d) Variable resource availability hypothesis Davis et al. (2000) Basic concepts: In most plant communities at most times, most of the resources that are available are taken up by the plants Plant community becomes more susceptible whenever there is an increase in the amount of unused resources ↑ availability (A→B) ↓ uptake (A→C) Both (A→D) Changes in availability & uptake naturally occur through time Gross resource supply Resource uptake Resource supply-uptake isocline Resistant to Invasion Easily Invasible A B C D

11. 3)What makes a species invasive? d) Variable resource availability hypothesis Davis et al. (2000) Basic concepts: In most plant communities at most times, most of the resources that are available are taken up by the plants Plant community becomes more susceptible whenever there is an increase in the amount of unused resources ↑ availability (A→B) ↓ uptake (A→C) Both (A→D) Changes in availability & uptake naturally occur through time Assumes invaders have access to resources Gross resource supply Resource uptake Resource supply-uptake isocline Resistant to Invasion Easily Invasible A B C D

12. 3)What makes a species invasive? d) Variable resource availability hypothesis Davis et al. (2000) Evidence: Conducted experiment in relatively unproductive grassland Imposed 2 resource gradients

13. 3)What makes a species invasive? d) Variable resource availability hypothesis Davis et al. (2000) Evidence: Conducted experiment in relatively unproductive grassland Imposed 2 resource gradients (1) Disturbance gradient to ↓ uptake High disturbance (Low uptake) Low disturbance (High uptake)

14. 3)What makes a species invasive? d) Variable resource availability hypothesis Davis et al. (2000) Evidence: Conducted experiment in relatively unproductive grassland Imposed 2 resource gradients (1) Disturbance gradient to ↓ uptake (2) Fertility gradient to ↑ supply High supply Low supply Low uptakeHigh uptake

15. 3)What makes a species invasive? d) Variable resource availability hypothesis Davis et al. (2000) Evidence: Conducted experiment in relatively unproductive grassland Imposed 2 resource gradients (1) Disturbance gradient to ↓ uptake (2) Fertility gradient to ↑ supply Seeded 54 alien species Measured cover of aliens High supply Low supply Low uptakeHigh uptake Low cover of aliens

16. 3)What makes a species invasive? d) Variable resource availability hypothesis Davis et al. (2000) Evidence: Conducted experiment in relatively unproductive grassland Imposed 2 resource gradients (1) Disturbance gradient to ↓ uptake (2) Fertility gradient to ↑ supply Seeded 54 alien species Measured cover of aliens High supply Low supply Low uptakeHigh uptake Low cover of aliens High cover of aliens

17. 3)What makes a species invasive? d) Variable resource availability hypothesis SUMMARY: Variable resource availability hypothesis Conceptual appealing Flexibility to accommodate space & time; many different resources Experimental evidence

18. 3)What makes a species invasive? d) Variable resource availability hypothesis SUMMARY: Variable resource availability hypothesis Conceptual appealing Flexibility to accommodate space & time; many different resources Experimental evidence But Low predictive power Different invaders respond differently to different resources Have to know where and when availability increases in complex world to predict susceptibility

19. 3)What makes a species invasive? d) Variable resource availability hypothesis SUMMARY: Variable resource availability hypothesis Conceptual appealing Flexibility to accommodate space & time; many different resources Experimental evidence But Low predictive power Different invaders respond differently to different resources Have to know where and when availability increases in complex world to predict susceptibility Many invaders don’t fit model Doesn’t appear to be any changes in resource availability Other factors (e.g. allelopathy) seem to be more important

20. 3)What makes a species invasive? e) Competition hypothesis Basic concept: Invasives are inherently better at getting resources i.e. better competitors

21. 3)What makes a species invasive? e) Competition hypothesis Basic concept: Invasives are inherently better at getting resources i.e. better competitors Realized niche – Species A, Species B Fundamental niche: Invader – Species C Resource axis #1 Resource axis #2

22. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Tropical rainforest in Hawaii Studied 4 native species & 5 invasive species Included trees, shrubs, & herbs Included a pair congeners (Bidens sandwicensis native & B. pilosa alien) Grew in different light environments representative of rainforest Light is a limiting factor in rainforests Expectations: Invasives better at utilizing light

23. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) What happens with ↑ shade? “Relative growth rate” (RGR) = how fast plants grow “Leaf area ratio” = how leafy plants are ↑ shade

24. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR ↑ shade

25. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species ↑ shade

26. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR ↑ shade Sun

27. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR ↑ shade Sun Partial shade

28. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR (esp. @ higher light) ↑ shade Sun Shade Partial shade

29. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species ↑ shade Sun Shade Partial shade

30. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness (esp. @ low light) ↑ shade Sun Shade Partial shade Shade Partial shade Sun

31. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness Leaf photosynthesis:

32. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness Leaf photosynthesis: “Light compensation point” = lowest light with + photosynthesis “Apparent quantum yield” = how efficiently plants turn light into chemical energy for photosynthesis

33. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness Leaf photosynthesis: Higher light compensation point for natives Sun Shade

34. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness Leaf photosynthesis: Higher light compensation point for natives, OR invasives tolerate greater shade Sun Shade

35. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness Leaf photosynthesis: Invasives tolerate greater shade Invasive greater quantum yield Sun Shade

36. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness Leaf photosynthesis: Invasives tolerate greater shade Invasive greater quantum yield, OR invasives more light efficient Sun Shade

37. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness Leaf photosynthesis: Invasives tolerate greater shade Invasives more light efficient “CO 2 assimilation” = photosynthesis

38. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness Leaf photosynthesis: Invasives tolerate greater shade Invasives more light efficient Invasives have greater photosynthetic rates Sun Shade Partial shade

39. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness Leaf photosynthesis: Invasives tolerate greater shade Invasives more light efficient Invasives have greater photosynthetic rates Evidence: Baruch & Goldstein (1999) Broad survey in Hawaii along elevation gradient of tropical rainforests 34 native species 30 invasives species Included trees, shrubs, & herbs Included 83 populations (i.e. >1 population for some species)

40. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness Leaf photosynthesis: Invasives tolerate greater shade Invasives more light efficient Invasives have greater photosynthetic rates Evidence: Baruch & Goldstein (1999) Invasives had Bigger leaves

41. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness Leaf photosynthesis: Invasives tolerate greater shade Invasives more light efficient Invasives have greater photosynthetic rates Evidence: Baruch & Goldstein (1999) Invasives had Bigger leaves More nutrients

42. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness Leaf photosynthesis: Invasives tolerate greater shade Invasives more light efficient Invasives have greater photosynthetic rates Evidence: Baruch & Goldstein (1999) Invasives had Bigger leaves More nutrients Cost less to build

43. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness Leaf photosynthesis: Invasives tolerate greater shade Invasives more light efficient Invasives have greater photosynthetic rates Evidence: Baruch & Goldstein (1999) Invasives had Bigger leaves More nutrients Cost less to build Higher photosynthesis

44. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness Leaf photosynthesis: Invasives tolerate greater shade Invasives more light efficient Invasives have greater photosynthetic rates Evidence: Baruch & Goldstein (1999) Invasives had Bigger leaves More nutrients Cost less to build Higher photosynthesis More efficient N use

45. 3)What makes a species invasive? e) Competition hypothesis Evidence: Pattison et al. (1998) Shade ↓ RGR of all species, BUT invasives had >RGR Shade ↑leafiness of all species, BUT invasives had > leafiness Leaf photosynthesis: Invasives tolerate greater shade Invasives more light efficient Invasives have greater photosynthetic rates Evidence: Baruch & Goldstein (1999) Invasives had Bigger leaves More nutrients Cost less to build Higher photosynthesis More efficient N use Overall, invasives are better suited than natives in capturing and utilizing light in the light limited tropical rainforest, especially in high light environments that characterized disturbed habitats

46. 3)What makes a species invasive? e) Competition hypothesis Evidence: Melgoza et al. (1990) Oecologia 83:7-13 Field study of invasive annual grass Bromus tectorum competition with 2 native species Chrysothamnus viscidiflorus and Stipa comata Studied plants in (1) recently-burned area without Bromus (2) recently-burned area with Bromus (3) area that had burned >12 years prior (also had Bromus) Examined competition for soil water

47. 3)What makes a species invasive? e) Competition hypothesis Evidence: Melgoza et al. (1990) Oecologia 83:7-13 Greater water stress for natives when Bromus is present Degree of water stress imposed by Bromus in the first year after burn is similar to that 12 years after burn

48. 3)What makes a species invasive? e) Competition hypothesis Evidence: Melgoza et al. (1990) Oecologia 83:7-13 Natives have Greater water stress with invasives Less biomass production with invasives

49. 3)What makes a species invasive? e) Competition hypothesis Evidence: D’Antonio et al. (2001) Worked with 2 invasive species in Hawaii in seasonally dry woodlands: Schizachyrium condensatum – native to mainland US Melinis minutiflora – native to Africa Both C 4 bunchgrasses

50. 3)What makes a species invasive? e) Competition hypothesis Evidence: D’Antonio et al. (2001) Worked with 2 invasive species in Hawaii in seasonally dry woodlands: Schizachyrium condensatum – native to mainland US Melinis minutiflora – native to Africa Both C 4 bunchgrasses Observed that Melinis appears to replace Schizachyrium

51. 3)What makes a species invasive? e) Competition hypothesis Evidence: D’Antonio et al. (2001) Worked with 2 invasive species in Hawaii in seasonally dry woodlands: Schizachyrium condensatum – native to mainland US Melinis minutiflora – native to Africa Both C 4 bunchgrasses Observed that Melinis appears to replace Schizachyrium declines increases

52. 3)What makes a species invasive? e) Competition hypothesis Evidence: D’Antonio et al. (2001) Worked with 2 invasive species in Hawaii in seasonally dry woodlands: Schizachyrium condensatum – native to mainland US Melinis minutiflora – native to Africa Both C 4 bunchgrasses Observed that Melinis appears to replace Schizachyrium declines increases

53. 3)What makes a species invasive? e) Competition hypothesis Evidence: D’Antonio et al. (2001) Worked with 2 invasive species in Hawaii in seasonally dry woodlands: Schizachyrium condensatum – native to mainland US Melinis minutiflora – native to Africa Both C 4 bunchgrasses Observed that Melinis appears to replace Schizachyrium declines increases decinc

54. 3)What makes a species invasive? e) Competition hypothesis Evidence: D’Antonio et al. (2001) Seed banks NOT involved Melinis seed is present in unburned areas without adult plants at densities similar to that of Schizachyrium

55. 3)What makes a species invasive? e) Competition hypothesis Evidence: D’Antonio et al. (2001) Seed banks NOT involved Competition involved Field experiment where removed Melinis plants from around Schizachyrium

56. 3)What makes a species invasive? e) Competition hypothesis Evidence: D’Antonio et al. (2001) Seed banks NOT involved Competition involved Field experiment: removed Melinis plants Measured change in number of tillers for Schizachyrium through time

57. 3)What makes a species invasive? e) Competition hypothesis Evidence: D’Antonio et al. (2001) Seed banks NOT involved Competition involved Field experiment : removed Melinis plants Measured change in tillers for Schizachyrium Melinis competition low high

58. 3)What makes a species invasive? e) Competition hypothesis Evidence: D’Antonio et al. (2001) Seed banks NOT involved Competition involved Field experiment : removed Melinis plants Measured change in tillers for Schizachyrium After 5 months: when ↓ Melinis competition, ↑ Schizachyrium Melinis competition low high

59. 3)What makes a species invasive? e) Competition hypothesis Evidence: D’Antonio et al. (2001) Seed banks NOT involved Competition involved Field experiment : removed Melinis plants Measured change in tillers for Schizachyrium After 5 months: when ↓ Melinis competition, ↑ Schizachyrium Trend continues through at least 14 months Melinis competition low high

60. 3)What makes a species invasive? e) Competition hypothesis Evidence: D’Antonio et al. (2001) Seed banks NOT involved Competition involved Additional field & glasshouse studies indicate Melinis is the better competitor for both light and N Dominance of Schizachyrium in unburned areas is simply because it appeared to get there first!

61. 3)What makes a species invasive? e) Competition hypothesis SUMMARY: Competition hypothesis Conceptually appealing Strong evidence for a number of species in many different habitats (although sometimes invoked without concrete evidence)

62. 3)What makes a species invasive? e) Competition hypothesis SUMMARY: Competition hypothesis Conceptually appealing Strong evidence for a number of species in many different habitats (although sometimes invoked without concrete evidence) But Hard to generalize (and hence predict) Critical resource(s) varies with different environments Species characteristics that make for better competitor varies with type of resource Even for any 1 resource, various ways to be a better competitor Why hasn’t evolution already come up with the strategy in situ? Not all invaders fit model; other factors seem to be important for some species

63. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Reading: Leger and Rice (2003) Ecology Letters 6:257-264 Micro-evolutionary change hypothesis Frequent colonizing events are a central feature of invasive plants

64. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Micro-evolutionary change hypothesis Frequent colonizing events Founder effects = founders of a new population carry only a fraction of the total genetic variation of the source populations

65. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Micro-evolutionary change hypothesis Frequent colonizing events Founder effects Genetic bottlenecks = loss of genetic variation when population size drastically decreases; often associated with catastrophic events that result in mass mortality

66. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Micro-evolutionary change hypothesis Frequent colonizing events Founder effects Genetic bottlenecks Genetic drift = loss of genetic variation by chance when populations are small and do not have complete, random interbreeding

67. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Micro-evolutionary change hypothesis Frequent colonizing events Founder effects Genetic bottlenecks Genetic drift Natural selection: strong selective forces often apply to successful colonizers

68. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Micro-evolutionary change hypothesis Frequent colonizing events Founder effects Genetic bottlenecks Genetic drift Natural selection New abiotic environment – rapid adaptive responses over short times and within short distances to new environment

69. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Micro-evolutionary change hypothesis Frequent colonizing events Founder effects Genetic bottlenecks Genetic drift Natural selection New abiotic environment New biotic environment – shifts in relative proportions of competition vs. defense pressures

70. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Micro-evolutionary change hypothesis Frequent colonizing events Founder effects Genetic bottlenecks Genetic drift Natural selection New abiotic environment New biotic environment Hybridization – a natural process that occurs in plants

71. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Micro-evolutionary change hypothesis Frequent colonizing events Founder effects Genetic bottlenecks Genetic drift Natural selection New abiotic environment New biotic environment Hybridization – a natural process that occurs in plants ↑ genetic diversity

72. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Micro-evolutionary change hypothesis Frequent colonizing events Founder effects Genetic bottlenecks Genetic drift Natural selection New abiotic environment New biotic environment Hybridization – a natural process that occurs in plants ↑ genetic diversity ↓reproductive barriers

73. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Micro-evolutionary change hypothesis Frequent colonizing events Founder effects Genetic bottlenecks Genetic drift Natural selection New abiotic environment New biotic environment Hybridization – a natural process that occurs in plants ↑ genetic diversity ↓reproductive barriers Transfers or originates adaptations

74. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Micro-evolutionary change hypothesis Frequent colonizing events Founder effects Genetic bottlenecks Genetic drift Natural selection New abiotic environment New biotic environment Hybridization – a natural process that occurs in plants 2834 plant species in the British Isles Of these, 715 (25%) are hybrids 74 are native X alien 21 are alien X alien 95 (13% of hybrids) involve aliens

75. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Micro-evolutionary change hypothesis Frequent colonizing events Founder effects Genetic bottlenecks Genetic drift Natural selection New abiotic environment New biotic environment Hybridization Interspecific – often with other species in new environment

76. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Micro-evolutionary change hypothesis Frequent colonizing events Founder effects Genetic bottlenecks Genetic drift Natural selection New abiotic environment New biotic environment Hybridization Interspecific Intraspecific – often with populations from native range that would not normally occur

77. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Hybridization Evidence: Stabilized introgressants Introgression = back cross with 1 or more parents P 1 X P 2 → F 1 F 1 X {P 1, P 2 } → F 2 introgressant

78. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Hybridization Evidence: Stabilized introgressants Introgression = back cross with 1 or more parents Stabilized = viable, fertile hybrids

79. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Hybridization Evidence: Stabilized introgressants Hybrids form new Intraspecific taxa

80. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Hybridization Evidence: Stabilized introgressants Hybrids form new intraspecific taxa Hybrids form new Species – Note: all examples are alien X alien

81. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Hybridization Evidence: Stabilized introgressants Allopolyploids = hybrid between different species in which chromosomes of both parents are retained

82. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Hybridization Evidence: Stabilized introgressants Allopolyploids Hybrids form new Species – Note: both Tragopogon’s are alien X alien

83. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Specific Example: Rhododendron ponticum in British Isles *Milne & Abbott (2000) Molecular Ecology 9:541-556 Natural distribution: south of Black Sea with disjunct populations in Lebanon, Spain, & Portugal Extensively naturalized throughout British Isles

84. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Specific Example: Rhododendron ponticum in British Isles *Milne & Abbott (2000) Molecular Ecology 9:541-556 Natural distribution: south of Black Sea with disjunct populations in Lebanon, Spain, & Portugal Extensively naturalized throughout British Isles Origin unclear: Earliest known introduction (1763) from Spain But subsequent introductions likely, especially from Black Sea area Also can’t tell from morphological information where it came from, but know from morphology that had to hybridize at some time R. ponticum cultivated along with other introduced species

85. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Specific Example: Rhododendron ponticum in British Isles *Milne & Abbott (2000) Molecular Ecology 9:541-556 Most individuals from naturalized populations had genotypes from Spain (88%), followed by Portugal (10%) No genotypes from Black Sea region

86. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis Specific Example: Rhododendron ponticum in British Isles *Milne & Abbott (2000) Molecular Ecology 9:541-556 Most individuals from naturalized populations had genotypes from Spain (88%), followed by Portugal (10%) No genotypes from Black Sea region Small number of individuals had hybridized with at least 3 other species Occurrence of R. catawbiense genotypes most common in Scotland (coldest area of British Isle) Introgression with catawbiense appears to have conferred cold tolerance into ponticum

87. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis SUMMARY: Micro-evolutionary change hypothesis Likely that most (if not all) invasive species go through founder events, experience genetic bottlenecks & drift, and undergo selection In other words micro-evolutionary changes Good evidence for hybridization being beneficial

88. 3)What makes a species invasive? f) Micro-evolutionary change hypothesis SUMMARY: Micro-evolutionary change hypothesis Likely that most (if not all) invasive species go through micro- evolutionary changes Good evidence for hybridization being beneficial But Have evidence of micro-evolutionary changes for only a limited number of species For only a subset of these, have evidence that micro-evolutionary changes have been beneficial A species that undergoes micro- (or even macro-) evolutionary changes does not automatically become invasive