Biological Invasions

, Volume 20, Issue 11, pp 3037–3045 | Cite as

Restructuring of a mutualism following introduction of Australian fig trees and pollinating wasps to Europe and the USA

  • E. J. MorganEmail author
  • T. L. Sutton
  • C. T. Darwell
  • J. M. Cook
Invasion Note


Figs and fig-pollinating wasps are obligate mutualists that require each other to complete sexual reproduction. However, landscapers can establish populations of fig trees outside their native ranges by propagation through exported seeds, seedlings or cuttings. Once mature, these trees could be colonized by pollinating wasps and/or various non-pollinating wasps that also develop in figs. In recent decades, the Australian endemic Ficus rubiginosa has been planted widely in the Mediterranean region and in parts of the USA. Observation of ripe fruit production suggested that a pollination mutualism has been re-established by pollinating wasps colonizing trees in the plant’s introduced range. We therefore used sampling of pollinators from mainland Spain, Tenerife and California (USA) and molecular studies to characterize the restructured mutualism and compare it with the native range. In the native range, the plant is pollinated by five wasp species that form the Pleistodontes imperialis complex. However, all wasps in the introduced ranges belonged to just one of these species (P. imperialis sp. 1). Moreover, their mtDNA diversity was close to zero and the sequences clearly link them with the native southern population of this species. None of the > 20 non-pollinating wasp species from the native range were found in the introduced ranges. In summary, the restructured mutualism has been dramatically simplified, lacking all non-pollinating wasps and all but one pollinator species from the native range. Moreover, the one pollinator species to establish successfully shows a drastic reduction in genetic diversity relative to its source population.


Cytb DNA barcoding Ficus rubiginosa ITS2 Pleistodontes imperialis Symbiotic interactions 



We thank Joshua Kohn for providing wasp samples for analysis, and to two anonymous reviewers for their helpful comments on the manuscript. EJM was supported by a Natural Environment Research Council (UK) Postgraduate Scholarship. TLS was supported by an Australian Postgraduate Award.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary material

10530_2018_1775_MOESM1_ESM.docx (23 kb)
Supplementary material 1 (DOCX 23 kb)


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Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.School of Biological Sciences, Harborne BuildingUniversity of ReadingReadingUK
  2. 2.Hawkesbury Institute for the EnvironmentWestern Sydney UniversityPenrithAustralia
  3. 3.Department of Botany, Faculty of ScienceCharles UniversityPragueCzech Republic

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