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Scale-dependent invasion patterns and community assembly in the Southeastern US flora

Scale-dependent invasion patterns and community assembly in the Southeastern US flora. Jason Fridley UNC – Chapel Hill. Acknowledgements. Collaborators: Becky Brown, Eastern Washington University Mike Palmer, Oklahoma State University John Bruno, UNC Peter White, UNC Bob Peet, UNC

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Scale-dependent invasion patterns and community assembly in the Southeastern US flora

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  1. Scale-dependent invasion patterns and community assembly in the Southeastern US flora Jason Fridley UNC – Chapel Hill

  2. Acknowledgements Collaborators: Becky Brown, Eastern Washington University Mike Palmer, Oklahoma State University John Bruno, UNC Peter White, UNC Bob Peet, UNC Alan Weakley, UNC Data: Carolina Vegetation Survey North Carolina Botanical Garden Funding: National Parks Ecological Research Fellowship Andrew W. Mellon Foundation (NPS, NPF, ESA)

  3. Exotic species Contributions of community and landscape ecology • Do biotic/community properties contribute to invasion resistance? • Are exotic species ecologically unique? • Do exotic species alter assembly processes in native communities? • Do exotic/invasive species favor particular environments? • Are communities saturated with species?

  4. Pattern and Process in Species Invasions

  5. Scaling rules? Pattern and Process in Species Invasions Biogeography Landscape ecology Community ecology

  6. Scaling rules of species richness...the species-area curve

  7. How do scaling rules represent process? Dispersal constraints Environmental variance Biotic constraints

  8. Carolina Vegetation Survey: 1988 to present 0.01 – 1000 m2

  9. Carolina Vegetation Survey 0.01 – 1000 m2

  10. Carolina Vegetation Survey 0.01 m2 range: 0 to 11 species 1000 m2 range: 6 to 180 species 0.01 – 1000 m2

  11. Fine-scale Z values: ~0.37 95% within 0.22 and 0.54 0.01 – 1000 m2

  12. Body size and species pools

  13. Intermediate scales: large stands, watersheds, landscapes, natural areas Z values 0.1 – 0.2? Poor data!

  14. Large-scale upturn Dispersal-drivenEcological equivalents Within province Between provinces Within province Rosenzweig 1995

  15. Full-scale curves

  16. Provinces – too big? Consequences for species invasions?

  17. Climate Low D Soils and geomorphology High D Alternative hypothesis: environmental texture w/ M. Palmer and P. White Schimper’s Laws?

  18. Scaling rules for species invasions? Does exotic species richness exhibit the same scale dependencies?

  19. Scaling rules for species invasions? If exotics are less dispersal limited, should the upturn be at a different scale or exist at all? Do exotics observe the same environmental template? Are native communities saturated, thereby further constraining exotic establishment?

  20. Null hypothesis If the average distribution of a native and exotic species is the same... All species Exotics only ...then exotics should be a consistent proportion of a total species pool.

  21. Deviations from expected curves All species Hotspots? Exotics (null) Coldspots?

  22. Example 1: NC agroecosystem

  23. Example 2: NC montane river 180 species, 54 exotics

  24. Example 3: NC piedmont forest

  25. Example 4: NC piedmont forest

  26. 1 – 10 km2 Deviance from expected exotic richness Exotic enrichment Exotic impoverishment

  27. Species-area data, Floras project M. Palmer et al. Total species Log10 Species Richness Exotics Log10 Area (ha)

  28. What is special about 1 - 10 km2? 1 km Oosting Plot

  29. What is special about 1 - 10 km2? • Riparian systems - the magical ingredients: • environmental favorableness (sun, nutrients) • (many exotics selected for these habitats) • disturbance: no biotic resistance • dispersal assistance: flow and flooding 1 km NCBG lands

  30. Scaling rules for species invasions Broad-scale scaling rules (watershed and above) appear remarkably similar for natives and exotics Rich are getting richer Finer-scale patterns usually diverge from those of natives, in a habitat-dependent way Causes?

  31. How well are exotic species distributed within habitats? • Within regions, exotics are clustered within certain habitats. • high propagule pressure • high disturbance rates • favorable environments • But how are they distributed within those habitats? • More uniform? (widespread, previously empty niche?) • More clustered? (only occur in rare but ideal patches?)

  32. How well are exotic species distributed within habitats? Distributions of exotic species with nested plot data: What proportion of scale-specific occurrences are exotic? A A 20% exotics C A A A A A A B B A D A A A A A A A A C A A 4 natives and 1 exotic A C 20% exotics A A B B A A D A A A A A A C A

  33. How well are exotic species distributed within habitats? Distributions of exotic species with nested plot data: What proportion of scale-specific occurrences are exotic? A A 20% exotics C A A A A A A B B A D A A A A A A A A C A A 50% exotics 4 natives and 1 exotic A C 20% exotics A A B B A A D A A A A A A C A 12.5% exotics

  34. Mountain riversS. Appalachians

  35. Exotic occurrences,Riparian plots % exotic species at each scale % exotic of total species occurrences Area (m2)

  36. Cornfield bordersNorth Carolina

  37. Exotic occurrences,Cornfield borders % exotic species at each scale % exotic of total species occurrences Area (m2)

  38. Montane upland forests, S. Apps

  39. Exotic occurrences,Montane uplands Most frequent exotics: Poa compressa Microstegium vimineum Rosa multiflora Festuca ovina Stellaria media % exotic of total species occurrences % exotic species at each scale Area (m2)

  40. Exotic occurrences,Piedmont uplands Other upland exotics: Ligustrum sinense Celastrus orbiculata Elaeagnus umbellata % exotic species at each scale Lonicera japonica

  41. Exotic Occurrence Across Scales % exotics in US (3138 / 18150) % exotic of total species occurrences

  42. Agricultural borders Exotic Occurrence Across Scales % exotics in US (3138 / 18150) Montane riparian corridors % exotic of total species occurrences S App upland forests % exotics of species pool Area (m2)

  43. HOTSPOTS: • uncommon relative to total land area • exotics better dispersed at fine scales • propagule pressure, disturbance, • soil cations • no signal of biotic resistance Conclusions: Southeast US plant invasions Agricultural borders • COLDSPOTS: • relatively common—for now • few exotic species; even rarer occurrences • upland, shady, acidic, isolated • biotic resistance or TIME? • how long can cold spots stay cold? Montane riparian corridors S App upland forests

  44. Limiting Similarity – Phenology? Flowering period Late Vernal (late April – June) Vernal (March – early April) Summer (June - Sept)

  45. Limiting Similarity – Phenology? Red maple! Flowering period Late Vernal (late April – June) Vernal (March – early April) Summer (June - Sept)

  46. Limiting Similarity – Phenology? Flowering period Late Vernal (late April – June) Vernal (March – early April) Summer (June - Sept)

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