A method for quantifying i habitat t indication and expansion of invasive species J. Stephen Brewer Department of Biology University of Mississippi
Two Important Ecological Questions about Invasive Species Which ecological communities are most vulnerable to invasion? Invasibility In which ecological communities do invasive species have the greatest impact? Impact
A General Hypothesis of Invasibility (Davis, Grime, and Thompson, 2000; J. Ecol.) Maximum Invasibility high turbance Dist low low Gross Resource Supply high
Productivity of Invaders and Per Capita Impact high Productivity High Disturbance Reduces Competition Per Capita Impact Low turbance Dist low Productivity Low Competitive Asymmetry Per Capita Impact High low Gross Resource Supply high
Objectives Quantify habitat indication of native and non-native species found at several disturbed and undisturbed sites in Mississippi. Evaluate the hypothesis that disturbed habitats and resource-rich natural habitats are the most readily invaded by non-native species. Evaluate the hypothesis that the invaders with the greatest competitive effects are those that occur in resource-poor and undisturbed d habitats. t Review impacts of Imperata cylindrica and Microstegium vimineum on longleaf pine savanna and shady mesic forest vegetation, respectively.
Studyy Sites
Procedures - Relating to Invasibility to Habitat Productivity Construct habitat by species matrix for all native and non-native species encountered using regional flora manuals Conduct principal coordinates analysis ordination of all identified habitats Overlay the associations of native and non-native (exotic) species with habitats using weighted averages of habitat scores Look for trends of association of natives and nonnatives with variation in productivity among natural habitats
Procedures - Relating Impact to Habitat Productivity and Disturbance Calculate the degree of indication of non-native species to anthropogenically disturbed and resource- poor or resource-richrich natural habitats (using method of Brewer and Menzel 2009). Quantify demonstrated impact of non-natives on plant community composition (i.e., competitive displacement) using NatureServe and literature searches. Relate habitat t indication of non-natives to their impact using discriminant analysis.
Results - Ordination of Major Habitat Types 40 148 Habitats 20 Disturbed (Infrequent) (4.1%) Shady, Fertile Soils Nutrient Poor/Dry Soils 0 Shady Open, Fertile Soils -20 Disturbed (Common) -40-40 -20 0 20 40 PCO1 (5.1%)
Results - Ordination of Major Habitat Types with Habitat Indication of Exotics and Natives Superimposed 40 20 148 Habitats 25 Exotic Species 378 Native Species Disturbed (Infrequent) (4.1%) Shady, Fertile Soils Nutrient Poor/Dry Soils 0 Shady Open, Fertile Soils -20 Disturbed (Common) EXOTICS NATIVES -40-40 -20 0 20 40 PCO1 (5.1%)
Results - Habitat Indication of Non-Native Species Species disturbed open, fertile soils nutrient-poor/dry soils shady Abutilon theophrasti 1.00 0.00 0.00 0.00 Ailanthus altissima 0.50 0.00 0.00 0.50 Albizia julibrissin 0.33 0.00 0.00 0.00 Allium vineale 1.00 0.00 0.00 0.00 Cerastium vulgatum 1.00 0.00 0.00 0.00 Cynodon dactylon 1.00 0.00 0.00 0.00 Cyperus iria 0.50 0.33 0.00 0.00 Digitaria sanguinalis 1.00 0.00 0.00 0.00 Hedera helix 033 0.33 000 0.00 000 0.00 033 0.33 Imperata cylindrica 0.20 0.00 0.14 0.00 Ipomoea purpurea 1.00 0.00 0.00 0.00 Lespedeza cuneata 0.11 0.09 0.14 0.00 Ligustrum sinense 0.14 0.14 0.00 0.14 Lonicera japonica 0.33 0.00 0.00 0.14 Lygodium japonicum 0.20 0.00 0.25 0.20 Microstegium vimineum 0.25 0.20 0.00 0.25 Nandina domestica 0.00 0.00 0.00 0.50 Paspalum boscianum 1.00 0.00 0.00 0.00 Paspalum notatum 1.00 0.00 0.00 0.00 Poncirus trifoliata 0.50 0.00 0.00 0.00 Rumex crispus 0.33 0.17 0.00 0.00 Setaria pumila 1.00 0.00 0.00 0.00 Sonchus asper 1.00 0.00 0.00 0.00 Trifolium dubium 1.00 0.00 0.00 0.00 Triadica sebifera 0.17 0.17 0.17 0.17
Results - Impacts of Non-NativeNative Species Negative Effect on Community Composition Species Peer Reviewed Research NatureServe Impact - Community Composition Abutilon theophrasti insignificant medium/insignificant Ailanthus altissima significant high 1 Albizia julibrissin inconclusive/no data high 1 Allium vineale low/inconclusive low Cerastium vulgatum not studied not studied Cynodon dactylon mixed high 1 Cyperus iria not studied not studied Digitaria sanguinalis low low Hedera helix significant moderate 1 Imperata cylindrica significant high Ipomoea purpurea insignificant low Lespedeza cuneata significant high Ligustrum sinense significant high 1 Lonicera japonica mixed high 1 Lygodium japonicum inconclusive/no data high 1 Microstegium vimineum mixed/significant Nandina domestica inconclusive/no data high 1 high 1 Paspalum boscianum not studied not studied Paspalum notatum mixed insignificant 1 Poncirus trifoliata not studied not studied Rumex crispus low low 1 Setaria pumila low/insignificant low/insignificant 1 Sonchus asper low/insignificant not studied Trifolium dubium low/insignificant not studied Triadica sebifera significant high 1 - not based on peer-reviewed research
Results - Relating Habitat Indication to Impacts of Non-Native Species 4 3 2 Canonica al Axis 2 1 Shady, Fertile 0-4 -3-2 -1 0 1 2 3 4 Significant Impact -1 Shady Open, Fertile Disturbed Low, Insignificant Impact -2 Nutrient-Poor, Dry -3-4 Canonical Axis 1
Why do exotic species appear to have greater impacts in resource-poor or undisturbed habitats than in resource-rich or disturbed habitats? Review the relationship between the impact of Imperata cylindrica i on pine flatwoods species and plant height Review the relationship between plant species richness and Microstegium vimineum in recently disturbed and mature forests
Declines in Species Richness as a Result of Cogongrass Invasion in Longleaf Pine Flatwoods 6 t species per plot 5 4 3 Annually-burned site Triennially-burned site Number of 2 1 Year that the border was located 0 2000 2003 2005 Census year Brewer 2008, Biological Invasions
Vulnerability of Longleaf Pine Flatwoods Indicators to Displacement is Related to Short Stature 1 Change in frequency (2000 to 2005) 0.5 0-1 -0.75-0.5-0.25 0 0.25 0.5 0.75 1 1.25-0.5-1 -1.5-2 -2.5-3 Maximum height (m) (adjusted for initial density) 2.5 Maximum heig ght (m) 2 1.5 1 0.5 0 0 0.2 0.4 0.6 0.8 1 Flatwoods indication Brewer 2008, Biological Invasions
Little Effect of Microstegium vimineum on Disturbed Communities Richness vs vs Microstegium i in Disturbed Stands 25 20 15 10 5 R 2 = 0.00550055-15 -10-5 0 5 10 Microstegium Importance value Microstegium Importance Value 0
Negative Effect of Microstegium vimineum on Mature Forest Species Richness Richness vs vs Microstegium in in Mature Forests 18 16 14 12 10 8 6 4 2 R 2 = 0.1288 0-15 -10-5 0 5 10 15 Microstegium Importance Value
Conclusions Non-native native species are more indicative of anthropogenically-disturbed habitats than are native species as a group. With respect to natural habitats t that t are not anthropogenically-disturbed, non-native species are least common within nutrient-poor/dry soils. The per capita competitive effect of non-native species is greater in resource-poor and undisturbed habitats than in resource-rich habitats or disturbed habitats. Reasons appear to relate to size asymmetry in resource-poor habitats and reduced competitive displacement in disturbed habitats.
Research Needs More studies that quantify impact of non-native native species on community composition under field conditions; most studies of potential competitive effects (e.g., allelopathic potential) are premature. Greater focus on stress-tolerance traits of non-native species More studies on the per capita effects of invaders on natural communities; differences among communities in vulnerability to impact.
Implications for Restoration ti Results apply better to preservation than to restoration. Ecosystem Hippocratic Oath Minimize harm to the ecosystem when treating invaders, which in some cases means doing no treatment. t t Impacts High Early Detection and Aggressive Chemotherapy Impacts Low Selective Surgery or No Treatment
Acknowledgments Cooperative Agreement - USDA Forest Service; Southern Research Station - 07-CA-11330127 Joint Venture USDA Forest Service: Southern Research Station 08-JV-11330127-121 121 Ted Leininger - Project Leader - Center for Bottomland Hardwoods Research; Stoneville, Miss. National Audubon Society and Strawberry Plains Audubon Center Christine Bertz, Katie Griffin, Jason Chesser, the 2008 and 2010 General Ecology classes at Ole Miss, Sarah Hinman, Sean Cralle, Sherry Surrette, Jeff Cannon and many others!