It has long been recognized that primary foundation species (FS), such as trees and seagrasses, enhance biodiversity. Among the species facilitated are secondary FS, including mistletoes and epiphytes. Case studies have demonstrated that secondary FS can further modify habitat-associated organisms (‘inhabitants’), but their net effects remain unknown. Here we assess how inhabitants, globally, are affected by secondary FS. We extracted and calculated 2,187 abundance and 397 richness Hedges’ g effect sizes from 91 and 50 publications, respectively. A weighted meta-analysis revealed that secondary FS significantly enhanced the abundance and richness of inhabitants compared to the primary FS alone. This indirect facilitation arising through sequential habitat formation was consistent across environmental and experimental conditions. Complementary unweighted analyses on log response ratios revealed that the magnitude of these effects was similar to the global average strength of direct facilitation from primary foundation species and greater than the average strength of trophic cascades, a widely recognized type of indirect facilitation arising through sequential consumption. The finding that secondary FS enhance the abundance and richness of inhabitants has important implications for understanding the mechanisms that regulate biodiversity. Integrating secondary FS into conservation practice will improve our ability to protect biodiversity and ecosystem function.

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M.S.T. and D.R.S. were supported by the Marsden Fund of the Royal Society of New Zealand and the Coasts and Oceans programme of The National Institute of Water and Atmospheric Research. T.W. and P.E.G. were supported by funding from the Australian Research Council. C.A. was supported by National Science Foundation (NSF) DEB 1546638. P.M.S. is supported by the Cawthron Institute. The authors acknowledge financial support from the Centre of Integrative Ecology, School of Biological Sciences, University of Canterbury, for the workshop ‘Facilitation cascades across ecosystems’.

Author information


  1. Marine Ecology Research Group and Centre for Integrative Ecology, School of Biological Sciences, University of Canterbury, Christchurch, New Zealand

    • Mads S. Thomsen
    •  & David R. Schiel
  2. School of Biological Sciences and UWA Oceans Institute, University of Western Australia, Perth, Australia

    • Mads S. Thomsen
    •  & Thomas Wernberg
  3. Smithsonian Tropical Research Institute, Balboa, Ancon, Republic of Panama

    • Andrew H. Altieri
  4. Environmental Engineering Sciences, University of Florida, Gainesville, FL, USA

    • Andrew H. Altieri
    •  & Christine Angelini
  5. Department of Biological Sciences, Macquarie University, Sydney, Australia

    • Melanie J. Bishop
  6. Centre for Marine BioInnovation, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, Australia

    • Paul E. Gribben
  7. School of Biological Sciences, University of Auckland, Auckland, New Zealand

    • Gavin Lear
    •  & Paul M. South
  8. Division of Marine Science and Conservation, Duke University, Beaufort, NC, USA

    • Qiang He
    •  & Brian R. Silliman
  9. Cawthron Institute, Nelson, New Zealand

    • Paul M. South
  10. Institute for Land, Water & Society, Charles Sturt University, Albury, Australia

    • David M. Watson
  11. Institute for Biology and Environmental Sciences, Oldenburg University, Oldenburg, Germany

    • Gerhard Zotz


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M.S.T. identified relevant literature, extracted all data and calculated effect sizes. M.S.T. and Q.H. analysed the data. All authors contributed to the development of the experimental design, data interpretation and manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Mads S. Thomsen.

Supplementary information

  1. Supplementary Information

    Supplementary Methods, Supplementary Figures 1–2, Supplementary References, Supplementary Results.

  2. Life Sciences Reporting Summary

  3. Supplementary Table 1

    List of studies and foundation species analysed

  4. Supplementary Data 1

    List of all analysed effect sizes and test variables

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