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Invasive ants reduce carbon fixation for a foundational East African ant-plant
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  • Patrick Milligan,
  • Timothy Martin,
  • Grace John,
  • Corinna Riginos,
  • Jacob Goheen,
  • Scott Carpenter,
  • Todd Palmer
Patrick Milligan
University of Florida
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Timothy Martin
University of Florida
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Grace John
University of Florida
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Corinna Riginos
The Nature Conservancy
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Jacob Goheen
Univ Wyoming
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Scott Carpenter
Yale University
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Todd Palmer
University of Florida
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Abstract

Invasive ants shape assemblages and interactions of native species, but their effect on fundamental ecological processes is poorly understood. In East Africa, the big-headed ant (Pheidole megacephala) invades monodominant stands of the ant-tree Acacia drepanolobium, displacing native ant defenders and rendering trees vulnerable to elephants (Loxodonta africana) and other browsing ungulates. We quantified A drepanolobium photosynthesis and transpiration pre- and post-invasion by P. megacephala. After ca. 5 years, ant invasion resulted in 69% lower whole-tree carbon fixation during the growing season, despite shorter-term (< 1 year) positive effects on photosynthetic rates coinciding with the displacement of energetically costly native ants. By experimentally excluding ants and large herbivores, we demonstrate that reduced carbon fixation resulted largely from browsing on trees by large herbivores in invaded areas. Our results from individual trees likely scale up, highlighting the potential of invasive species to alter carbon fixation and other biogeochemical cycles at ecosystem scales.

Peer review status:UNDER REVIEW

04 Sep 2020Submitted to Ecology Letters
08 Sep 2020Assigned to Editor
08 Sep 2020Submission Checks Completed
09 Sep 2020Reviewer(s) Assigned