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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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?