@article{62d25446c93d4f249825694091d7f6f7,
title = "Wild herbivores enhance resistance to invasion by exotic cacti in an African savanna",
abstract = "Whether wild herbivores confer biotic resistance to invasion by exotic plants remains a key question in ecology. There is evidence that wild herbivores can impede invasion by exotic plants, but it is unclear whether and how this generalises across ecosystems with varying wild herbivore diversity and functional groups of plants, particularly over long-term (decadal) time frames. Using data from three long-term (13- to 26-year) exclosure experiments in central Kenya, we tested the effects of wild herbivores on the density of exotic invasive cacti, Opuntia stricta and O. ficus-indica (collectively, Opuntia), which are among the worst invasive species globally. We also examined relationships between wild herbivore richness and elephant occurrence probability with the probability of O. stricta presence at the landscape level (6150 km2). Opuntia densities were 74% to 99% lower in almost all plots accessible to wild herbivores compared to exclosure plots. Opuntia densities also increased more rapidly across time in plots excluding wild herbivores. These effects were largely driven by megaherbivores (≥1000 kg), particularly elephants. At the landscape level, modelled Opuntia stricta occurrence probability was negatively correlated with estimated species richness of wild herbivores and elephant occurrence probability. On average, O. stricta occurrence probability fell from ~0.56 to ~0.45 as wild herbivore richness increased from 6 to 10 species and fell from ~0.57 to ~0.40 as elephant occurrence probability increased from ~0.41 to ~0.84. These multi-scale results suggest that any facilitative effects of Opuntia by wild herbivores (e.g. seed/vegetative dispersal) are overridden by suppression (e.g. consumption, uprooting, trampling). Synthesis. Our experimental and observational findings that wild herbivores confer resistance to invasion by exotic cacti add to evidence that conserving and restoring native herbivore assemblages (particularly megaherbivores) can increase community resistance to plant invasions.",
keywords = "Opuntia stricta, biotic resistance, elephants, invasion ecology, long-term exclosure experiments, megaherbivores, multi-trophic interactions, prickly pear",
author = "Wells, {Harry B.M.} and Crego, {Ramiro D.} and Alston, {Jesse M.} and Ndung'u, {S. Kimani} and Khasoha, {Leo M.} and Reed, {Courtney G.} and Hassan, {Abdikadir A.} and Samson Kurukura and Jackson Ekadeli and Mathew Namoni and Stewart, {Peter S.} and Kimuyu, {Duncan M.} and Wolf, {Amelia A.} and Young, {Truman P.} and Kartzinel, {Tyler R.} and Palmer, {Todd M.} and Goheen, {Jacob R.} and Pringle, {Robert M.}",
note = "Funding Information: We thank the Government of Kenya for permission to conduct this research. We thank Mpala Research Centre for its staff and logistical support. We thank S. Ekwam, S. Lima, G. Busenei, M. Mohamed, P. Lorewa, R. Malakwen, J. Ekwam and N. Kipsuny for their invaluable assistance in the field. UHURU plots were built with seed funding from the Sherwood Family Foundation, grants from the National Sciences and Engineering Research Council of Canada, and the Universities of Florida and British Columbia. Support for the maintenance and data collection has been provided by the US National Science Foundation (DEB-0709880, OISE-0852961, DEB-1355122, and IOS-1656527 to RMP; DEB-1547679, DEB-1930763 and DEB-2018405 to JRG; DEB-1930820 to TRK), the National Geographic Society, the University of Wyoming, the High Meadows Environmental Institute at Princeton University, The Nature Conservancy, and the Institute at Brown for Environment and Society, Brown University. KLEE plots were built and maintained by grants from the James Smithson Fund of the Smithsonian Institution, The National Geographic Society (Grants 4691-91, 9106-12 and 9986-16) and the National Science Foundation (LTREB BSR 97-07477, 03-16402, 08-16453, 12-56004, 12-56034 and 19-31224). This work was partly funded by the Center for Advanced Systems Understanding (CASUS) which is financed by Germany's Federal Ministry of Education and Research (BMBF) and by the Saxon Ministry for Science, Culture and Tourism (SMWK) with tax funds on the basis of the budget approved by the Saxon State Parliament. Camera trapping was funded by NERC Iapetus2 Doctoral Training Program and the Durham Invasion Science Laboratory. Funding Information: We thank the Government of Kenya for permission to conduct this research. We thank Mpala Research Centre for its staff and logistical support. We thank S. Ekwam, S. Lima, G. Busenei, M. Mohamed, P. Lorewa, R. Malakwen, J. Ekwam and N. Kipsuny for their invaluable assistance in the field. UHURU plots were built with seed funding from the Sherwood Family Foundation, grants from the National Sciences and Engineering Research Council of Canada, and the Universities of Florida and British Columbia. Support for the maintenance and data collection has been provided by the US National Science Foundation (DEB‐0709880, OISE‐0852961, DEB‐1355122, and IOS‐1656527 to RMP; DEB‐1547679, DEB‐1930763 and DEB‐2018405 to JRG; DEB‐1930820 to TRK), the National Geographic Society, the University of Wyoming, the High Meadows Environmental Institute at Princeton University, The Nature Conservancy, and the Institute at Brown for Environment and Society, Brown University. KLEE plots were built and maintained by grants from the James Smithson Fund of the Smithsonian Institution, The National Geographic Society (Grants 4691‐91, 9106‐12 and 9986‐16) and the National Science Foundation (LTREB BSR 97‐07477, 03‐16402, 08‐16453, 12‐56004, 12‐56034 and 19‐31224). This work was partly funded by the Center for Advanced Systems Understanding (CASUS) which is financed by Germany's Federal Ministry of Education and Research (BMBF) and by the Saxon Ministry for Science, Culture and Tourism (SMWK) with tax funds on the basis of the budget approved by the Saxon State Parliament. Camera trapping was funded by NERC Iapetus2 Doctoral Training Program and the Durham Invasion Science Laboratory. Publisher Copyright: {\textcopyright} 2022 The Authors. Journal of Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.",
year = "2023",
month = jan,
doi = "10.1111/1365-2745.14010",
language = "English (US)",
volume = "111",
pages = "33--44",
journal = "Journal of Ecology",
issn = "0022-0477",
publisher = "Wiley-Blackwell",
number = "1",
}