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  1. 8 Elements of the Conservation Garden…

  2. The Conservation GardenInvasive Alien Plants

  3. Of 235 woody plants that invade natural areas in the US 85% were imported for ornamental and landscape purposes 14% were imported for agricultural uses --from Reichard & Campbell 1996

  4. ...in the very early times, say 100 million years ago in the Cretaceous Period, the world's fauna was much more truly cosmopolitan, not so much separated off by oceans, deserts, and mountains. If there had been a Cretaceous child living at the time...he would have read...'Very large dinosaurs occur all over the world except in New Zealand'...There would have been much less use for zoos. C. S. Elton, The Ecology of Invasions by Plants and Animals, 1958

  5. THE HOMOGOCENE’S BIODIVERSITY EQUATIONWhen does 1+1 not equal 2? Native Spp Alien Spp Total Comment/example 1 + 1 = 2 Complementarity Daylilies? 1 + 1 = 1 Competition Japanese honeysuckle? 1 + 1 = <1 Changed process Melaleuca in Florida Myrica in Hawaii

  6. Podophyllum Jeffersonia

  7. E Asian-E North American Disjunction Genera – Representative woody plants Buckleya Hamamelis Panax Calycanthus Hydrangea Parthenocissus Carya Itea Pieris Catalpa Liriodendron Pyrularia Cladrasits Magnolia Sassafras Epigaea Menispermum Stewartia Gleditsia Mitchella Wisteria Gymnocladus Nyssa Halesia Pachysandra

  8. East Asian-Eastern North America Disjunction Subgeneric Relationships in Widespread Genera Acer Hydrangea Adiantum Alnus Juglans Clintonia Aesculus Malus Convallaria Betula Quercus Maianthemum Carpinus Rhododendron Pyrola Cornus Ribes Tiarella Fagus Tilia Trientalis Fraxinus Ulmus Vaccinium

  9. Close taxonomic relationship has its own problems Specialized pests & diseases Chestnut blight, Dogwood anthracnose, Balsam & Hemlock woolly adelgids MANY OTHERS!

  10. Species that do not persist after cultivation; dependent on cultivation Species that persist after cultivation but do not spread Species that spread locally after cultivation by vegetative means, but not by seed Species that spread locally after cultivation by seed or seed and vegetative means Species that spread only in human‑created habitats: roadsides, lawns, fields Species that spread into native habitats, but do not reduce native species Species that spread into native habitats, reduce or eliminate native species Species that spread into native habitats, change ecosystem function, reducing whole suites of native species Degree of exotic threat

  11. INVASIVES ARE A SMALL PERCENT OF EXOTICS INVASIVES ARE A SMALL PERCENT OF SALES --Florida data from Lippincott & Hall 1996 Taxa % Exotics in cultivation 25,000 -- Naturalized 1,000 4 Weedy 750 3 Possible natural area impacts 125 0.5 Sold in the trade today 40 0.16 Economically important 13 0.05 (32.5% of 40)

  12. 4 invasion hypotheses 1a-d. Innate biology: Weediness, competitiveness, tolerance, preadaptation 2. Enemy release/Biotic resistance 3a-c. Community invasibility: diversity, productivity, disturbance 4. Availability

  13. 1a. Innate Biology: Weediness

  14. REICHARD’S SCREENING CRITERIA FOR RISK ASSESSMENT Quick vegetative spread/vegetative reproduction Juvenile period < 5 years (trees) < 3 years (shrubs, vines) Rapid growth in first 2 years No pretreatment for germination [History of invasion] [Related to Known Invaders]

  15. THE ASYMMETRY OF ERRORS IN RISK ASSESSMENT The consequences of error are not equal WeedsNon-Weeds AcceptMore important error Good! Reject Good! Less important error Evaluate --------------------Minimize----------------------

  16. REICHARD’S OUTCOMES 204 Invaders Correct Incorrect Unknown Accept ----- 2% Reject 85% ----- Evaluate/Monitor 13% 98% of invaders rejected or held for monitoring 87 Non-invaders Correct Incorrect Unknown Accept 46% ----- Reject ----- 18% Evaluate/Monitor 36% 82% of non-invaders accepted or held for monitoring

  17. REICHARD’S OUTCOMES 204 Invaders Correct Incorrect Unknown Accept ----- 2% Reject 85% ----- Evaluate/Monitor 13% 98% of invaders rejected or held for monitoring 87 Non-invaders Correct Incorrect Unknown Accept 46% ----- Reject ----- 18% Evaluate/Monitor 36% 82% of non-invaders accepted or held for monitoring

  18. POSSIBLE PROBLEMS WITH REICHARD’S SCREENING CRITERIA CriterionGenetic var.Problem, comment History of invasion Spatial availability, time of observation Quick vegetative spread Probably ok Juvenile period Y Vary with environment, < 5 years (trees) soil, year to year climate, < 3 years (shrubs, vines) climate change, biotic environment Rapid growth first 2 yr Y No pretreatment Y Temperate, boreal species need pretreatment

  19. TRAITS OF SUCCESSFUL INVADERS Trait Horticultural selection? Environmentally fit Yes! Rapid growth Yes, both for client and for holding in nursery Early maturity (flowering) Yes, both for client and for display Prolific seed production Some species (seasonal color, wildlife populations) Successful dispersal No, except perhaps species for wildlife populations Ease of germination Yes, easier to propagate Ease of establishment Yes, easier to propagate and hold Fast vegetative spread Some species (erosion control, ground covers) No major pests Yes!

  20. Is time limiting?The Problem of the Tortoise and the Hare Slow rate has its advantages for control BUT the race changes: Friends, enemies, & the nature of the race track a suggestion of time lags!

  21. Australian Weed Risk Assessment System --from Pheloung 1995 First Tier: Prohibited/Allowed Species Lists Second Tier: Reject/Evaluate/Accept New Introductions Third Tier: Temporary Clearance, Post Entry Evaluation

  22. Second Tier: Reject/Evaluate/Accept New Introductions --from Pheloung 1995 49 Questions: +1 Weedy Trait 0 Don’t Know -1 Non-Weedy Trait Scoring: <0 Accept 1-6 Evaluate >=7 Reject

  23. Second Tier: Categories for the 49 Questions --from Pheloung 1995 CategoryNotes Domestication/Cultivation Low risk of weediness if domesticated species Climate/Distribution Environmental match, breadth of tolerance Undesirable Traits Spiny, burrs, poisons, pollen Plant Type Free floating aquatics, Vines Weedy Elsewhere Highly predictive of pest species Reproduction Correlates with rate of spread Dispersal Mechanisms Correlates with rate of spread Persistence Attributes Correlates with survival once established

  24. Test: Reject/Evaluate/Accept New Introductions --from Pheloung 1995 WeedsNon-WeedsMinor Weeds Reject 84% 7% 45% Evaluate 16% 34% 37% Accept0% 59% 18%

  25. AQIS System Points Free floating aquatic 20 History of invasiveness 20 Relative of an invasive species 10 Spiny, burrs 10 Harmful to humans or animals 8 Vegetative reproduction 8 Stoloniferous 5 Wind dispersed 8 Animal/Machine dispersed 8 Water dispersed 5 Bird dispersed 5 Scoring: Reject >=20 Evaluate 12-19 Accept <12

  26. 1b. Innate Biology: Competitiveness Diversity in native range vs. introduced range: coevolved competitiveness hypothesis As diversity in native range competitiveness

  27. 1c. Innate Biology: Tolerance Native geographic range hypothesis As native range Invasiveness

  28. 1d. Innate Biology: Preadaptation

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

  30. Kilronomos 2002

  31. Kilronomos 2002

  32. Classical Biocontrol: Cactoblastis on Opuntia Female Cactoblastis ovipositingon Opuntia, linear egg mass attached to a cactus spine Damageto Opuntia by Cactoblastis larvae,pad destroyed, plant open to infection

  33. 3. Community Invasibility Hypotheses 3a. Diversity (competitive release) 3b. Productivity (birth, growth rates higher) 3c. Disturbance (mortality, turnover rates higher)

  34. Rebecca Brown 2002

  35. Rebecca Brown 2002

  36. DISTURBANCES AND INVASIONS Hobbs & Huenneke 1992 Fire Grazing Soil disturbance Nutrient inputs Trampling Fragmentation Disturbance interactions

  37. 4. Availability Hypothesis

  38. TRAITS OF SUCCESSFUL INVADERS Trait Horticultural selection? Environmentally fit Yes! Rapid growth Yes, both for client and for holding in nursery Early maturity (flowering) Yes, both for client and for display Prolific seed production Some species (seasonal color, wildlife populations) Successful dispersal No, except perhaps species for wildlife populations Ease of germination Yes, easier to propagate Ease of establishment Yes, easier to propagate and hold Fast vegetative spread Some species (erosion control, ground covers) No major pests Yes!

  39. Few, Large or Several, Small Initial Release Strategy:FLOSS Tradeoff Given a finite release stock

  40. Experimental ReleasesGrevstad 1999 Treatment and Indicator Variables • 4 release sizes 20, 60, 180, 540 individuals • 2 speciesG. calmariensis and G. pusilla • 5 site characteristics • stand area • stand density • early plant height • terminal plant height • plant N • 9 reps Response- Larger populations are less likely to go extinct and they have higher mean growth rates

  41. 4 invasion hypotheses 1a-d. Innate biology: Weediness, competitiveness, tolerance, preadaptation: SOME SPP ARE INVASIVE, SCREEN 2. Enemy release/Biotic resistance: MOST SPP ARE INVASIVE, ASSESS ROLE OF ENEMIES 3a-c. Community invasibility: diversity, productivity, disturbance: SOME COMMUNITIES ARE INVASIBLE, SCREEN, MANAGE AGAINST INVASION 4. Availability: MOST SPP ARE INVASIVE, REDUCE AVAILABILITY

  42. Encouragements that we can lessen the problem! • A small percent of horticultural plants are invasive • Risk assessment can work • It can be done: How Illinois kicked the exotic plant habit (Harty 1993)

  43. __________________________________________________________ NCBG EXOTIC SPECIES POLICY __________________________________________________________ To possess plant collections that do not harm natural areas and the native plant diversity of North Carolina and the Southeast To protect and restore the Garden’s highest quality natural areas by eradicating invasive exotic species __________________________________________________________