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In a Swamp of Exotic Macrophytes, a Native Pteridophyte Fights Back!
Brooklyn Krings and Loretta Battaglia
Southern Illinois University CEER 2014
Outline • Background about native and invasive species
• Mechanisms and impacts of invasion
• Research hypothesis
• Study site and methods description
• Results
• Conclusions
Rare Native Species
• Habitat specificity • Low dispersal ability • Low reproductive rates
• Anthropogenic disturbances • Exploitation • Interactions with
invasive exotics
Pitcher Plant Snuffbox Mussel Great Frigate Bird Rainbow Beetle
Invasive Species
One of greatest threats to biodiversity ~ 50,000 invasive species in the USA $120 billion annually in economic losses (Kettunen et al.
2009)
Why are invasives so successful?
Common Salvinia
Emerald Ash Borer
Zebra Mussel European Starling Emerald Ash Borer
Enemy Release Hypothesis (Keane and Crawley 2002).
Released from natural enemies
Novel Weapons (Callaway and Ridenour 2004) Novel biochemical interactions
Evolution of Invasiveness (Blossey and Notzold 1995)
Rapid genetic changes and adaptation
Empty (vacant) Niche Resources unused by natives
Invasional Meltdown (Simberloff and VonHolle 1999)
Exotic- exotic facilitation
Mechanisms of Invasiveness
Invasives competitively exclude natives and reduce biodiversity
Impacts on Native Species • Reduced growth • Low reproduction • Reduced survivorship • Decreased germination
Invasive Species and Competitive Exclusion
Impacts on native species • Reduced growth • Low reproduction • Reduced survivorship • Decreased germination
• Highly cited review paper using
39 studies (Vila and Weiner 2004)
• Pair-wise experimental approach
using Relative Competition Indices (RCI) • The effect of natives on aliens
was lower than the effect of aliens on natives
Research Objectives • To investigate competition between an invasive
exotic macrophyte and a rare native pteridophyte
Study Site
• Jean Lafitte National Park, Jefferson Parish, Louisiana
• Forested backswamp of Bayou des Familles
• Taxodium distichum and Fraxinus profunda
• Standing water year
round
Ceratopteris pteridoides (rare native)
• Native to FL, GA, LA
• Conservation status
• Rare in Louisiana and
potentially vulnerable to
extirpation
• Reappeared at the site (2011)
• Population expanding
Eichhornia crassipes (invasive)
• Amazon Basin in South America • Introduced to the U.S. in 1884
• Nearly global distribution
• IUCN list of 100 most dangerous invasive species
• Control Measures • Mechanical
• Herbicide
• Bio-control
http://florabase.dec.wa.gov.au
Study Design
• Enclosures • 1mX1mX1.22m tall
• Established in July 2013
Experimental Design
• Partial additive design
• 3 Replicates (n = 24) • Percent cover ratios:
Ceratopteris: Eichhornia • 10:0, 10:10, 10:20, 10:30,
0:10, 10:10, 20:10, 30:10
Sampling and Data Analysis
• Percent cover was estimated in
August, October, and December 2013
• Repeated measures ANOVA • Effect of beginning cover
ratios on percent cover of both species over time
• arcsin
Results
• Initial ratio treatments did not influence Ceratopteris or Eichhornia
percent cover • Ceratopteris increased (F2,12= 42.66, p < 0.0001)
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August 2013 October 2013 December 2013
Results • Winter 2013/2014 ▫ Below average temperature
• Ceratopteris did not survive
• Eichhornia survived
Summary • Results suggest that Ceratopteris
is capable of competitively displacing Eichhornia.
• Compelling results!
• Native, rare species exhibiting traits typically associated with invasions.
• Unpredictable temperature shifts appear to give Eichhornia the competitive edge.
• Restoration implications.
Acknowledgements
• Advisor • Dr. Battaglia
• Committee members • Dr. Baer • Dr. Vitt • Dr. Ebbs • Dr. Groninger • Dr. Gibson
• Battaglia lab • Treigh Brown • Makia Hoormann • Graham Baker • SWS research grant
Questions?
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