Ingestion by an endemic frugivore enhances seed germination of endemic plant species but decreases seedling survival of exotics

Authors

  • Nicolas Zuël,

    Corresponding author
    1. Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
    2. Mauritian Wildlife Foundation, Grannum Road, Vacoas, Mauritius
      Nicolas Zuël, Mauritian Wildlife Foundation, Grannum Road, Vacoas, Mauritius.
      E-mail: nzuel@mauritian-wildlife.org
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  • Christine J. Griffiths,

    1. Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
    2. Mauritian Wildlife Foundation, Grannum Road, Vacoas, Mauritius
    3. School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK
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  • Andy Hector,

    1. Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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  • Dennis M. Hansen,

    1. Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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  • Carl G. Jones,

    1. Mauritian Wildlife Foundation, Grannum Road, Vacoas, Mauritius
    2. Durrell Wildlife Conservation Trust, Les Augrès Manor, Trinity, Jersey JE3 5BP, Channel Islands
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  • Matthias Albrecht

    1. Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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    • Present address: Mediterranean Institute for Advanced Studies, Miquel Marqués 21, 07190 Esporles, Mallorca, Balearic Islands, Spain.


Nicolas Zuël, Mauritian Wildlife Foundation, Grannum Road, Vacoas, Mauritius.
E-mail: nzuel@mauritian-wildlife.org

Abstract

Aim  To test whether ingestion by endemic frugivores differentially affects the seed germination time, germination percentage and seedling survival of endemic, native and exotic fleshy fruited plant species, and to identify the principal processes and attributes driving such effects.

Location  Round Island, Mauritius.

Methods  We conducted a germination and seedling survival experiment for 3 months to test whether ingestion (gut passage and deposition in faeces) by the endemic Telfair’s skink (Leiolopisma telfairii) had a differential effect on the germination time, germination percentage and seedling survival of two endemic, four native and two exotic fleshy fruited plant species. To assess the importance of factors involved in the ingestion process, we used a factorial design with gut passage (gut-passed vs. not gut-passed), depulping (whole fruit vs. manually depulped seed) and the presence of faecal material (faeces vs. without faeces). In addition, the roles of species-specific traits, seed size and deposition density (average number of seeds per faeces) were examined.

Results  Exotic species had a higher germination percentage than indigenous (native and endemic) species when not ingested. Following skink ingestion, there was no longer a difference, as ingestion enhanced germination percentage most in endemic species. The exotic species still germinated faster overall than the indigenous species, despite ingestion accelerating the germination time of endemics. However, ingestion strongly reduced seedling survival of the exotic species, while having no negative effect on the survival of indigenous seedlings. Overall, ingested indigenous seeds were more likely to germinate and the seedlings more likely to survive than ingested exotic seeds and seedlings. Seed size, deposition density and the removal of fruit pulp by either manual depulping or gut passage were important predictors of germination time, germination percentage and seedling survival.

Main conclusions  These endemic frugivores can enhance the competitiveness of endemic compared with exotic fleshy fruited plants at the critical germination and seedling establishment stage. Consequently, conservation and restoration of mutualistic endemic plant–animal interactions may be vital to mitigating the degradation of habitats invaded by exotic plants, which is of particular relevance for island ecosystems in which large numbers of endemics are threatened by exotic invaders.

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