Biological Invasions

, Volume 12, Issue 10, pp 3563–3577 | Cite as

Experimental test of biotic resistance to an invasive herbivore provided by potential plant mutualists

  • Tom E. X. Miller
  • Jesusa C. Legaspi
  • Benjamin Legaspi
Original Paper


Understanding the influence of resident species on the success of invaders is a core objective in the study and management of biological invasions. We asked whether facultative food-for-protection mutualism between resident, nectar-feeding ants and extrafloral nectar-bearing plants confers biotic resistance to invasion by a specialist herbivore. Our research focused on the South American cactus-feeding moth Cactoblastis cactorum Berg (Lepidopetra: Pyralidae) in the panhandle region of Florida. This species has been widely and intentionally redistributed as a biological control agent against weedy cacti (Opuntia spp.) but arrived unintentionally in the southeast US, where it attacks native, non-target cacti and is considered a noxious invader. The acquired host-plants of C. cactorum in Florida secrete extrafloral nectar, especially on young, vegetative structures, and this attracts ants. We conducted ant-exclusion experiments over 2 years (2008 and 2009) at two sites using potted plants of two vulnerable host species (O. stricta and O. ficus-indica) to evaluate the influence of cactus-visiting ants (total of eight species) at multiple points in the moth life cycle (oviposition, egg survival, and larval survival). We found that the presence of ants often increased the mortality of lab-reared C. cactorum eggsticks (stacks of cohered eggs) and larvae that we introduced onto plants in the field, although these effects were variable across sites, years, host-plant species, ant species, and/or between old and young plant structures. In contrast to these “staged” encounters, we found that ants had little influence on the survival of cactus moths that occurred naturally at our field sites, or on moth damage and plant growth. In total, our experimental results suggest that the influence of cactus-visiting ants on C. cactorum invasion dynamics is weak and highly variable.


Biological invasion Biotic resistance Cactoblastis cactorum Mutualism Opuntia 



We acknowledge the valuable field and laboratory assistance provided by Elizabeth Aninakwa, Ignacio Baez, Keith Marshall, Jr., Neil Miller, Meredith Robbins, and Maggie Simon. Jes Hines, Tomomi Suwa, and Amy Savage provided helpful feedback on the manuscript. This research was supported by a grant from the US Department of Agriculture (CSREES-2007-02270) and a Rice University Huxley Fellowship to T.E.X.M.


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Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  • Tom E. X. Miller
    • 1
  • Jesusa C. Legaspi
    • 2
  • Benjamin Legaspi
    • 3
  1. 1.Department of Ecology and Evolutionary BiologyRice UniversityHoustonUSA
  2. 2.USDA-ARS-CMAVE Center for Biological ControlFlorida A&M UniversityTallahasseeUSA
  3. 3.Florida Public Service CommissionTallahasseeUSA

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