1. What makes a weed a weed? Traits associated with invasive behavior And Predicting invasive potential

2. Sutherland: Predictable weedy traits ? Predictions: –Vegetative reproduction –Hermaphroditic or monecious –Self-compatible –Wind-pollinated –Tolerant of high light –Tolerant of low moisture –Annuals or biennials –Perennial grasses or forbs –Armed and Toxic

3. Weed list sources Synthesis of the North American Flora (3,038 spp.) –Weed def: “plants that generally grow in disturbed areas where they are unwanted and unappreciated.” PLANTS, Invasive plants of the US (1,336 spp.) US Fed. and State Noxious Weed Lists (385 spp.) Daehler (1998) (311 spp.) –Spp. that are “global natural area invaders”

4. Data Analysis Compared frequency of traits for: –Weeds vs. Non-weeds –Native vs. Exotic weeds –Invasive vs. Non-invasive weeds

5. Results of Analysis

6. Weeds (compared to non-weeds) are: More likely to be Annual or Biennial Less likely to be Perennial More likely wetland spp., toxic, vines, and trees Less likely to be forbs and sub-shrubs Annual and Biennial weeds more likely to be armed Perennial weeds more to be shade intolerant

7. Exotic (compared to native) weeds are: Less likely to be wetland spp. Than native weeds. Still more likely to be wetland spp. Than non-weeds.

8. Invasive (compared to non- invasive) exotics weeds are: Less likely to be forbs. More likely to be perennial, monoecious, self-incompatible, shrubs, and trees. Above traits are related. Magnitude of Chi Square values suggest that life form may be more important than breeding system or compatibility.

9. Other Conclusions Lifespan constrains other life history traits. Separating spp by life history makes some characteristics non-significant. Habitat is a significant predictive trait for all weed spp (native, exotic, or invasive). Toxicity is a sig. Life history trait for weds independent of lifespan. –If alleopathic: supports competitive release hyp. –If anti-herb Defense: supports escape predation hyp.

10. Other Conclusions Agree with some of Baker’s predictions (1965). Disagree on Veg. Reproduction, self-incompatibility, wind pollination. With the exception of increased probability of being a tree, invasive exotics differ very little in life history from other weeds. There are life history traits that distinguish weeds from non-weeds.

11. Sutherland: Predictable weedy traits ? Predictions: –Vegetative reproduction –Hermaphroditic or monecious –Self-compatible –Wind-pollinated –Tolerant of high light –Tolerant of low moisture –Annuals or biennials –Perennial grasses or forbs –Armed and Toxic

12. Risk Assessments Allow managers, horticulturalists, and politicians to determine what plants to permit and which to deny entry. Not all errors are equally important. It’s worse to let in a pest species than keep out a non-pest species. Minimize spp. held for evaluation.

13. Comparing Australian and Reichard systems AU 3 tiered scheme vs. Reichard’s decision tree Similar levels of success Use 5 kinds of criteria: –History of invasiveness elsewhere –Relatedness to other invaders –Climatic match between home and novel ranges –Noxious and undesirable traits –Biological attributes of plant itself

14. 4 Categories of traits associated with weeds Vegetative growth and reproduction –Contrary to findings of Sutherland Persistence, tolerance, and recovery Sexual and Asexual propagule production and dispersal. Easy germination and establishment.

15. Risk Assessment take home message Fairly accurate Moderately tolerant of missing data Important variables fairly constant across analyses and assessment methodology.

16. Potential responses by Botanical gardens The conservation aware garden. –Do impact and risk assessments The strict conservation garden. –Do not transport organisms across natural barriers to dispersal.

17. Questions for thought What will it take to get horticulturalists on-board? To what degree are traits associated with invasive species the result of their selection vs. a random sampling of potential invasives? What step could be taken to improve the accuracy of Risk Assessments? Why the discrepancy over vegetative preproduction?