readings, enemy release and biodiversity hypotheses
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Readings, enemy release and biodiversity hypotheses. Enemy release hypothesis: Keane, r. Crawley, M. 2002. Exotic plant invasions and the enemy release hypothesis. TREE 17:164-170 2. Biodiversity hypothesis: - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/1.jpg)
Readings, enemy release and biodiversity hypotheses
1. Enemy release hypothesis:
Keane, r. Crawley, M. 2002. Exotic plant invasions and the enemy release hypothesis. TREE 17:164-170
2. Biodiversity hypothesis:
Shea K, Chesson P. 2002. Community ecology theory as a framework for biological invasions. TREE 17:170-176
![Page 2: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/2.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
aka “Escape from enemy” hypothesis“Enemy release” hypothesis
Basic concepts:• Species in their native range are suppressed by natural
enemies
![Page 3: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/3.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
aka “Escape from enemy” hypothesis“Enemy release” hypothesis
Basic concepts:• Species in their native range are suppressed by natural enemies• Alien species are immigrants to a new area• Aliens often arrive as seeds
![Page 4: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/4.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
aka “Escape from enemy” hypothesis“Enemy release” hypothesis
Basic concepts:• Species in their native range are suppressed by natural enemies• Alien species are immigrants to a new area• Aliens often arrive as seeds
In other words, they arrive without the grazers, insect pests, diseases, parasites, etc. of their native range – their “enemies”
![Page 5: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/5.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
aka “Escape from enemy” hypothesis“Enemy release” hypothesis
Basic concepts:• Species in their native range are suppressed by natural enemies• Alien species immigrate without enemies• Hence, alien species “escapes” from their enemies and are no
longer affected by biotic constraintsThus, alien growth and success is much greater in new range
![Page 6: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/6.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
aka “Escape from enemy” hypothesis“Enemy release” hypothesis
Basic concepts:• Species in their native range are suppressed by natural enemies• Alien species immigrate without enemies• Aliens lack biotic constraints• However, alien success will depend on potential enemies in
new range:Are potential enemies generalists or specialists?
![Page 7: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/7.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
aka “Escape from enemy” hypothesis“Enemy release” hypothesis
Basic concepts:• Species in their native range are suppressed by natural enemies• Alien species immigrate without enemies• Aliens lack biotic constraints• However, alien success will depend on potential enemies in
new range:Are potential enemies generalists or specialists?Are population sizes of potential enemies large or small?
![Page 8: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/8.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
aka “Escape from enemy” hypothesis“Enemy release” hypothesis
Basic concepts:• Species in their native range are suppressed by natural enemies• Alien species immigrate without enemies• Aliens lack biotic constraints• However, alien success will depend on potential enemies in
new range:Are potential enemies generalists or specialists?Are population sizes of potential enemies large or small?Do potential enemies feed on foliage or seeds?
![Page 9: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/9.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
aka “Escape from enemy” hypothesis“Enemy release” hypothesis
Basic concepts:• Species in their native range are suppressed by natural enemies• Alien species immigrate without enemies• Aliens lack biotic constraints• However, alien success will depend on potential enemies in
new range:Are potential enemies generalists or specialists?Are population sizes of potential enemies large or small?Do potential enemies feed on foliage or seeds?Are there similar hosts for potential enemies in new area?
![Page 10: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/10.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Mack et al. (2000)• Chrysanthemoides native to South Africa but invasive in Australia• Acacia native to Australia but invasive in South Africa• For both species, few pests in invaded area
![Page 11: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/11.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Mack et al. (2000)• Chrysanthemoides native to South Africa but invasive in Australia• Acacia native to Australia but invasive in South Africa• For both species, few pests in invaded area• Compare performance of each species in native area vs.
invaded
Invaded Native
![Page 12: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/12.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Mack et al. (2000)• Chrysanthemoides native to South Africa but invasive in Australia• Acacia native to Australia but invasive in South Africa• For both species, few pests in invaded area• When Chrysanthemoides is invader, does much better
(sometimes much much much better!!)
Invaded Native
>>>>
>>>
![Page 13: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/13.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Mack et al. (2000)• Chrysanthemoides native to South Africa but invasive in Australia• Acacia native to Australia but invasive in South Africa• For both species, few pests in invaded area• When Acacia is invader, does much much much better
InvadedNative
<
<<
![Page 14: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/14.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Mack et al. (2000)• Chrysanthemoides native to South Africa but invasive in Australia• Acacia native to Australia but invasive in South Africa• For both species, few pests in invaded area• When species is invader, does much (much) better
Invaded Native
>>>>
>>>
InvadedNative
<
<<
![Page 15: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/15.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Mack et al. (2000)• Flip side can also occur: New pest in an area devastates natives• Example is American chestnut (Castanea dentata) & chestnut blight
(invasive fungus Endothia parasitica)
![Page 16: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/16.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Mack et al. (2000)• Flip side can also occur: New pest in an area• Example is American chestnut (Castanea dentata) & chestnut blight
(invasive fungus Endothia parasitica)• Dramatic ↓ in chestnut after arrival of blight in 1934
![Page 17: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/17.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Mack et al. (2000)• Flip side can also occur: New pest in an area• Example is American chestnut (Castanea dentata) & chestnut blight
(invasive fungus Endothia parasitica)• Dramatic ↓ in chestnut after arrival of blight in 1934• Other trees had ↑
![Page 18: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/18.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Mack et al. (2000)• Flip side can also occur: New pest in an area• Example is American chestnut (Castanea dentata) & chestnut blight
(invasive fungus Endothia parasitica)• Dramatic ↓ in chestnut after arrival of blight in 1934• Other trees had ↑, or small changes
![Page 19: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/19.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Wolfe (2002) American Naturalist 160:705-711• Silene latifolia native to Europe but invasive in North America• Surveyed populations in both Europe and North America for
generalist and specialist enemies
![Page 20: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/20.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Wolfe (2002) American Naturalist 160:705-711• Silene latifolia native to Europe but invasive in North America• More populations experience damage in native range (Europe)
then invaded range (North America)
![Page 21: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/21.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Wolfe (2002) American Naturalist 160:705-711• Silene latifolia native to Europe but invasive in North America• More populations experience damage in native range
True for both generalists
![Page 22: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/22.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Wolfe (2002) American Naturalist 160:705-711• Silene latifolia native to Europe but invasive in North America• More populations experience damage in native range
True for both generalists and specialist
![Page 23: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/23.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Wolfe (2002) American Naturalist 160:705-711• Silene latifolia native to Europe but invasive in North America• More populations experience damage in native range• More individuals within a population are damaged in native
range (Europe) then invaded range (North America)
![Page 24: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/24.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Wolfe (2002) American Naturalist 160:705-711• Silene latifolia native to Europe but invasive in North America• More populations experience damage in native range• More individuals within a population are damaged in native range
True for both generalists
![Page 25: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/25.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Wolfe (2002) American Naturalist 160:705-711• Silene latifolia native to Europe but invasive in North America• More populations experience damage in native range• More individuals within a population are damaged in native range
True for both generalists and specialists
![Page 26: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/26.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Klironomos (2002) Nature 417: 67-70• Enemies not necessarily insects• Tested if soil organisms can affect growth
Logic: In native soils, pathogens accumulate rapidly, ultimately reducing growth of natives. For invasives in new soil, pathogens accumulate much slower, and hence do not adversely affect growth of invasives.
![Page 27: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/27.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Klironomos (2002) Nature 417: 67-70• Logic: Pathogens accumulate in soils for natives but not
invasives• Series of experiments that used 5 invasive & 5 rare species from
Canadian meadows• From each species, isolated 2 fractions of soil micro-organisms
Pathogen / saprobe filtrate = DetrimentalAMF (mycorrhizal) spores = Beneficial
• Grew plants with microbes from their own soil vs. microbes from other species’ soil
![Page 28: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/28.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Klironomos (2002) Nature 417: 67-70• Logic: Pathogens accumulate in soils for natives but not invasives• Used 5 invasive & 5 rare species from Canadian meadows• From each species, isolated 2 fractions of soil micro-organisms
Pathogen / saprobe filtrate = DetrimentalAMF (mycorrhizal) spores = Beneficial
• Grew plants with microbes from their own soil vs. microbes from other species’ soil
• Predictions:If use sterile soil, should see no affect on growth for both
invasives & rare speciesIf use AMF, should see beneficial growth for bothIf use pathogens, negative effects only for rare species
![Page 29: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/29.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Klironomos (2002) Nature 417: 67-70• Logic: Pathogens accumulate in soils for natives but not invasives• Predictions:
If use sterile soil, no affect for both invasives & rare species
![Page 30: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/30.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Klironomos (2002) Nature 417: 67-70• Logic: Pathogens accumulate in soils for natives but not invasives• Predictions:
If use sterile soil, no affect for both invasives & rare speciesIf use AMF, beneficial for both
![Page 31: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/31.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Klironomos (2002) Nature 417: 67-70• Logic: Pathogens accumulate in soils for natives but not invasives• Predictions:
If use sterile soil, no affect for both invasives & rare speciesIf use AMF, beneficial for bothIf use pathogens,
negative only for rare
![Page 32: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/32.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Klironomos (2002) Nature 417: 67-70• Logic: Pathogens accumulate in soils for natives but not invasives• Predictions:
If use sterile soil, no affect for both invasives & rare speciesIf use AMF, beneficial for bothIf use pathogens,
negative only for rare• Thus, invasives
accumulate pathogens@ slower rate becausethey escape harmfulpathogens when invadingforeign territory
![Page 33: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/33.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Mitchell & Power (2003) Nature 421: 625-627• Additional support that pathogens are important• Examined 473 plant species naturalized to North America from
Europe• Examined occurrence of viruses and various fungal pathogens
(rust, smut, powdery mildew) in native and naturalized ranges
![Page 34: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/34.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Mitchell & Power (2003) Nature 421: 625-627• Additional support that pathogens are important• Compare pathogens on 473 species in native vs. naturalized range• Predictions:
Fewer pathogens in naturalized rangeBecause viruses are more easily transmitted and have
broader host ranges then fungi, expected that ↓ for viruses would be smaller than that for fungi
The bigger the escape from pathogens, the more noxiousAnd vice versa: accumulate more pathogens, less noxious
![Page 35: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/35.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Mitchell & Power (2003) Nature 421: 625-627• Additional support that pathogens are important• Compare pathogens on 473 species in native vs. naturalized range• Predictions:
Fewer pathogens in naturalized range
![Page 36: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/36.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Mitchell & Power (2003) Nature 421: 625-627• Additional support that pathogens are important• Compare pathogens on 473 species in native vs. naturalized range• Predictions:
Fewer pathogens in naturalized rangeSmaller ↓ for viruses (24%) than for fungi (84%)
![Page 37: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/37.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Mitchell & Power (2003) Nature 421: 625-627• Additional support that pathogens are important• Compare pathogens on 473 species in native vs. naturalized range• Predictions:
Fewer pathogens in naturalized rangeSmaller ↓ for virusesEscape related to noxiousness
(a) As ↑ escape, ↑ noxiousness
![Page 38: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/38.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Evidence: from Mitchell & Power (2003) Nature 421: 625-627• Additional support that pathogens are important• Compare pathogens on 473 species in native vs. naturalized range• Predictions:
Fewer pathogens in naturalized rangeSmaller ↓ for virusesEscape related to noxiousness
(a) As ↑ escape, ↑ noxiousness(b) As ↑ pathogens , ↓ noxiousness
![Page 39: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/39.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Summary: Escape from biotic constraints hypothesis• Intuitively clear• Strong evidence in a number of cases• Underlying concept for biological control
![Page 40: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/40.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Summary: Escape from biotic constraints hypothesis• Intuitively clear• Strong evidence in a number of cases• Underlying concept for biological control
But:• Assumes:
Native specialist enemies are left behindHost switching does not occurGeneralist in new range avoid invader
![Page 41: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/41.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Summary: Escape from biotic constraints hypothesis• Intuitively clear• Strong evidence in a number of cases• Underlying concept for biological control
But:• Assumes:
Native specialist enemies are left behindHost switching does not occurGeneralist in new range avoid invader
• Need to demonstrate that native enemies limit plant population in native range
![Page 42: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/42.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Summary: Escape from biotic constraints hypothesis• Intuitively clear• Strong evidence in a number of cases• Underlying concept for biological control
But:• Assumes:
Native specialist enemies are left behindHost switching does not occurGeneralist in new range avoid invader
• Need to demonstrate that native enemies limit plant population in native range
• Is the release through ↓ invader mortalityOR through adverse affects on natives causing ↓
competition?
![Page 43: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/43.jpg)
3) What makes a species invasive?g) Escape from biotic constraints hypothesis
Summary: Escape from biotic constraints hypothesis• Intuitively clear• Strong evidence in a number of cases• Underlying concept for biological control
But:• Assumes:
Native specialist enemies are left behindHost switching does not occurGeneralist in new range avoid invader
• Need to demonstrate that native enemies limit plant population in native range
• Is the release through ↓ invader mortalityOR through adverse affects on natives causing ↓ competition?
• Long-lived species and species with long-lived seedbanks probably little affected by enemies
![Page 44: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/44.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Basic concepts:• High biodiversity confers high community stability
![Page 45: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/45.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Basic concepts:• High biodiversity → high community stability• Stable communities are not easily invaded
![Page 46: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/46.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Basic concepts:• High biodiversity → high community stability• Stable communities not invaded• Shares features with vacant niche hypothesis
NOTE: Biodiversity hypothesis does not require vacant niche
![Page 47: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/47.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Basic concepts:• High biodiversity → high community stability• Stable communities not invaded• Shares features with vacant niche hypothesis
Biodiversity hypothesis does not require vacant nicheBut uses niche concepts that:
Different species have different niches
![Page 48: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/48.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Basic concepts:• High biodiversity → high community stability• Stable communities not invaded• Shares features with vacant niche hypothesis
Biodiversity hypothesis does not require vacant nicheBut uses niche concepts that:
Different species have different nichesAs ↑ number species, ↑ amount of potential niche space
that is filled
![Page 49: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/49.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Basic concepts:• High biodiversity → high community stability• Stable communities not invaded• Shares features with vacant niche hypothesis
Biodiversity hypothesis does not require vacant nicheBut uses niche concepts that:
Different species have different nichesAs ↑ number species, ↑ filling of niche spaceThus highly diverse communities more difficult to invade
![Page 50: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/50.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Theoretical evidence: From Tilman (1999)• ↑ number species ↑ filling of niche space
![Page 51: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/51.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Theoretical evidence: From Tilman (1999)• ↑ number species ↑ filling of niche space• Thus, as ↑ number species
![Page 52: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/52.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Theoretical evidence: From Tilman (1999)• ↑ number species ↑ filling of niche space• As ↑ number species, availability of resources, on average,
![Page 53: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/53.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Theoretical evidence: From Tilman (1999)• ↑ number species ↑ filling of niche space• As ↑ number species, availability of resources, on average, ↓
![Page 54: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/54.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Theoretical evidence: From Tilman (1999)• ↑ number species ↑ filling of niche space• ↑ number species ↓ average resources availability
Defined mathematically in A
![Page 55: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/55.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Theoretical evidence: From Tilman (1999)• ↑ number species ↑ filling of niche space• ↑ number species ↓ average resources availability• Each species has some minimum
average resource need = R*
![Page 56: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/56.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Theoretical evidence: From Tilman (1999)• ↑ number species ↑ filling of niche space• ↑ number species ↓ average resources availability• Each species has some minimum
average resource need = R*• Corresponds with some minimum
species diversity = N*
![Page 57: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/57.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Theoretical evidence: From Tilman (1999)• ↑ number species ↑ filling of niche space• ↑ number species ↓ average resources availability• Each species has some minimum
average resource need = R*• Corresponds with some minimum
species diversity = N*• Above N*, that species cannot
invade
![Page 58: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/58.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Theoretical evidence: From Tilman (1999)• ↑ number species ↑ filling of niche space• ↑ number species ↓ average resources availability• Each species has some minimum
average resource need = R*• Corresponds with some minimum
species diversity = N*• Above N*, that species cannot
invade
![Page 59: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/59.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Theoretical evidence: From Tilman (1999)• ↑ number species ↑ filling of niche space• ↑ number species ↓ average resources availability• Each species has some minimum
average resource need = R*• Corresponds with some minimum
species diversity = N*• Above N*, that species cannot
invade because averagecommunity resource levelis less then minimum forthat species (R*)
![Page 60: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/60.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Theoretical evidence: From Tilman (1999)• ↑ number species ↑ filling of niche space• ↑ number species ↓ average resources availability• Each species has some minimum
average resource need = R*• Corresponds with some minimum
species diversity = N*• Above N*, species cannot invade• At or below N*, can invade
![Page 61: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/61.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Theoretical evidence: From Tilman (1999)• ↑ number species ↑ filling of niche space• ↑ number species ↓ average resources availability• Each species has R*• At or below N*, species can invade
![Page 62: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/62.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Theoretical evidence: From Tilman (1999)• ↑ number species ↑ filling of niche space• ↑ number species ↓ average resources availability• Each species has R*• At or below N*, species can invade• If do for all species in community,
can determine relativeinvasibility as diversity changes
![Page 63: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/63.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Theoretical evidence: From Tilman (1999)• ↑ number species ↑ filling of niche space• ↑ number species ↓ average resources availability• Each species has R*• At or below N*, species can invade• If do for all species in community,
invasibility ↓ as diversity ↑
![Page 64: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/64.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Experimental evidence: From Kennedy et al. (2002) Nature 417: 636-638
• Had 147 plots originally seeded with up to 24 natives• Observed 13 aliens invaded naturally through time
![Page 65: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/65.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Experimental evidence: From Kennedy et al. (2002) Nature 417: 636-638
• Had 147 plots originally seeded with up to 24 natives• Observed 13 aliens invaded naturally through time• As ↑ native diversity:
(a) ↓ invader cover
![Page 66: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/66.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Experimental evidence: From Kennedy et al. (2002) Nature 417: 636-638
• Had 147 plots originally seeded with up to 24 natives• Observed 13 aliens invaded naturally through time• As ↑ native diversity:
(a) ↓ invader cover(b) ↓ invader number
![Page 67: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/67.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Experimental evidence: From Kennedy et al. (2002) Nature 417: 636-638
• Had 147 plots originally seeded with up to 24 natives• Observed 13 aliens invaded naturally through time• As ↑ native diversity:
(a) ↓ invader cover(b) ↓ invader number(c) ↓ invader max size
![Page 68: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/68.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Experimental evidence: From Kennedy et al. (2002) Nature 417: 636-638
• Had 147 plots originally seeded with up to 24 natives• Observed 13 aliens invaded naturally through time• As ↑ native diversity:
(a) ↓ invader cover(b) ↓ invader number(c) ↓ invader max size(d) NS median size
![Page 69: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/69.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Experimental evidence: From Kennedy et al. (2002) Nature 417: 636-638
• Conclude: Invaders do more poorly with ↑ native diversity
![Page 70: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/70.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Experimental evidence: From Kennedy et al. (2002) Nature 417: 636-638
• Invaders do more poorly with ↑ native diversity• Why?
As ↑ native diversity:↑ number of neighbors
![Page 71: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/71.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Experimental evidence: From Kennedy et al. (2002) Nature 417: 636-638
• Invaders do more poorly with ↑ native diversity• Why?
As ↑ native diversity:↑ number of neighbors↑ number of neighboring species
![Page 72: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/72.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Experimental evidence: From Kennedy et al. (2002) Nature 417: 636-638
• Invaders do more poorly with ↑ native diversity• Why?
As ↑ native diversity:↑ number of neighbors↑ number of neighboring species↑ crowding
![Page 73: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/73.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Experimental evidence: From Kennedy et al. (2002) Nature 417: 636-638
• Invaders do more poorly with ↑ native diversity• Why?
With high native diversity, have dense, species rich, crowded neighborhoods
![Page 74: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/74.jpg)
3) What makes a species invasive?h) Biodiversity
hypothesis
Contrary evidence: Allcock and Hik 2003
• Grazed woodland in Australia
• Habitats included alluvia (rich) grasslands (intermediate) and woodlands (resource poor)
• Negative relationship between exotic and native diversity
• Natives –ve relationship to high biomass; exotics +ve relationship.
![Page 75: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/75.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Contrary evidence: From Levine (2000)• Examined riparian communities along South Fork Eel River, CA• Dominated by native tussock sedge Carex nudata• Each tussock is discrete island (neighborhood) colonized by up to
20 perennial plants & mosses
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3) What makes a species invasive?h) Biodiversity hypothesis
Contrary evidence: From Levine (2000)• Surveyed similarly sized tussocks over 7 km stretch of river• Recorded incidence of 3 invaders (Agrostis, Plantago, Cirsium)
![Page 77: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/77.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Contrary evidence: From Levine (2000)• Surveyed similarly sized tussocks• 3 invaders (Agrostis, Plantago, Cirsium)• All invaders had ↑ occurrence with
↑ diversity, contrary to biodiversityhypothesis
![Page 78: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/78.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Contrary evidence: From Levine (2000)• Surveyed similarly sized tussocks• 3 invaders (Agrostis, Plantago, Cirsium)• All invaders had ↑ occurrence with
↑ diversity, contrary to biodiversityhypothesis
• Why?To support high diversity, must have
lots of resources
![Page 79: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/79.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Contrary evidence: From Levine (2000)• Surveyed similarly sized tussocks• 3 invaders (Agrostis, Plantago, Cirsium)• All invaders had ↑ occurrence with
↑ diversity, contrary to biodiversityhypothesis
• Why?To support high diversity, must have
lots of resourcesThus, diverse sites are “best” sites
![Page 80: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/80.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Contrary evidence: From Levine (2000)• Surveyed similarly sized tussocks• 3 invaders (Agrostis, Plantago, Cirsium)• All invaders had ↑ occurrence with
↑ diversity, contrary to biodiversityhypothesis
• Why?To support high diversity, must have
lots of resourcesThus, diverse sites are “best” sitesBest sites most likely to be invaded
![Page 81: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/81.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Contrary evidence: From Lonsdale (1999) Ecology 80: 1522-1536• Global survey – compiled data from 184 sites around the world• Separated into “Island” vs. “Mainland”
Within each group, broke down further into nature “reserves” and “non-reserves”
![Page 82: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/82.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Contrary evidence: From Lonsdale (1999) Ecology 80: 1522-1536• Global survey – compiled data from 184 sites around the world• Separated into “Island” vs. “Mainland”
Within each group, broke down further into nature “reserves” and “non-reserves”
• As expected, for givendiversity, number invaders:Islands > Mainlands
![Page 83: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/83.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Contrary evidence: From Lonsdale (1999) Ecology 80: 1522-1536• Global survey – compiled data from 184 sites around the world• Separated into “Island” vs. “Mainland”
Within each group, broke down further into nature “reserves” and “non-reserves”
• As expected, for givendiversity, number invaders:Islands > MainlandsNon-reserves > Reserves
![Page 84: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/84.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Contrary evidence: From Lonsdale (1999) Ecology 80: 1522-1536• Global survey – compiled data from 184 sites around the world• Separated into “Island” vs. “Mainland”
Within each group, broke down further into nature “reserves” and “non-reserves”
• As expected, for givendiversity, number invaders:Islands > MainlandsNon-reserves > Reserves
• But, for all sites, moreinvaders with greaterdiversity
![Page 85: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/85.jpg)
Resolving the conflict: Shea and Chesson 2002
• Within ecosystems, more species = less invasable• Among ecosystems, more diverse systems (more
resources) = more vulnerable
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Resolving the conflict: Shea and Chesson 2002
• Within ecosystems, more species = less invasable• Among ecosystems, more diverse systems (more
resources) = more vulnerable
• Within ‘clusters’ extrinsic factors (e.g. climate) are similar
• Factors differ across ‘clusters’.
![Page 87: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/87.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Summary:• Logical arguments to support the hypothesis
![Page 88: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/88.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Summary:• Logical arguments to support the hypothesis
But logical arguments contrary to hypothesis
![Page 89: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/89.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Summary:• Logical arguments to support the hypothesis
But logical arguments contrary to hypothesis• Data that support the hypothesis
![Page 90: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/90.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Summary:• Logical arguments to support the hypothesis
But logical arguments contrary to hypothesis• Data that support the hypothesis
But other data contrary to hypothesis
![Page 91: Readings, enemy release and biodiversity hypotheses](https://reader035.vdocuments.us/reader035/viewer/2022062315/56814e34550346895dbb9bbb/html5/thumbnails/91.jpg)
3) What makes a species invasive?h) Biodiversity hypothesis
Summary:• Logical arguments to support the hypothesis
But logical arguments contrary to hypothesis• Data that support the hypothesis
But other data contrary to hypothesis• Thus, biodiversity alone does not account for invasibility• Diversity patterns at different scales may explain paradox in
part