COS 120-6
Distribution, performance, and impact of stem-feeding Lipara spp., potential biological control agents of invasive Phragmites australis

Thursday, August 14, 2014: 3:20 PM
Bataglieri, Sheraton Hotel
Warwick Allen, Biological Sciences, Louisiana State University, Baton Rouge, LA
Randee E. Young, Biological Sciences, Louisiana State University, Baton Rouge, LA
Jordan R. Croy, Biological Sciences, Louisiana State University, Baton Rouge, LA
Ganesh P. Bhattarai, Biological Sciences, Louisiana State University, Baton Rouge, LA
Adam Lambert, Marine Science Institute, University of California Santa Barbara
David Cummings, Natural Resources Science, University of Rhode Island, Kingston, RI
Jack Anderson, Natural Resources Science, University of Rhode Island, Kingston, RI
Laura A. Meyerson, Natural Resources Science, University of Rhode Island, Kingston, RI
James T. Cronin, Biological Sciences, Louisiana State University, Baton Rouge, LA
Background/Question/Methods

Phragmites australis is an aggressive invader of wetlands and marshes of North America (NA). A complicating factor in the management of P. australis is that rare native genotypes broadly overlap with an invasive genotype from Europe (EU). Several species of monophagous Lipara (Diptera: Chloropidae) gall flies, also introduced from EU, are considered potential biological control agents of invasive P. australis. However, little is known about their distribution, performance, and impact on native and invasive haplotypes. We surveyed 127 and 21 patches throughout NA and EU, respectively, for the presence, infestation level, performance (i.e., gall size and adult body mass), and impact of Lipara on each genotype. To assess the influence of local environmental conditions, a complementary common garden experiment was conducted using 60 P. australis populations of varying haplotype sourced from throughout NA and galled stems collected from a nearby field site.

 

Results/Conclusions

Lipara spp. in NA appear to be restricted to the east coast between North Carolina and Maine. L. rufitarsis spanned this entire range whereas L. pullitarsis and L. similis occurred no further south than New Jersey. In the field, stems infested by Lipara averaged 28% for native NA genotypes, 11% for the invasive genotype, and <1% for the EU genotype in its native range. Unlike in EU, parasitoids of Lipara were absent in NA, which may explain the higher infestation levels in NA relative to EU. Higher infestation of native relative to invasive P. australis was supported by the results from the common garden experiment, and may be attributed to native genotypes being naïve to the novel herbivores, and/or that Lipara has higher performance, suffers four times less vertebrate predation, or has a preference for thinner native stems. Even though Lipara infestation levels are moderate, and infestation is associated with a 30-55% reduction in stem heights and zero probability of flowering, biological control of invasive P. australis by Lipara is not a viable option because native haplotypes suffer disproportionately more than invasive haplotypes in NA.

See more of: Invasion: Species Interactions I
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