Interplay between differential competition and actions of spore-vectors explain host exclusivity of saprobic fungi in Protea flowers

Abstract

Protea flowers host saprobic Knoxdaviesia and Sporothrix fungi that are dispersed by pollinating insects and birds. Different Protea species contain sympatric populations of different fungal species. For example, P. repens host S. splendens and K. proteae, while P. neriifolia host K. capensis and S. phasma. Even though all fungi can grow vigorously on alternative hosts and they share the same spore vector species, they rarely colonise alternative hosts. We investigated the role of fungal differential competitive abilities on their usual and alternative hosts to explain their host exclusivity. In a de Wit replacement series experiment, S. splendens outcompeted and later overgrew all other fungi on media prepared from its usual and alternative hosts. Host exclusivity of S. splendens on P. repens may therefore be maintained by restricted movement of spore vectors rather than weaker competitive abilities on alternative hosts. On their preferred hosts, S. splendens and S. phasma rapidly overgrew Knoxdavesia species with which they do not usually share a host, explaining host exclusivity of the Knoxdavesia species. Knoxdaviesia proteae likely only persist on P. repens with sympatric S. splendens if it colonizes flowers earlier, in a different area, or completes its life cycle before being overgrown. On their usual P. neriifolia host, K. capensis and S. phasma had neutralistic interactions and S. phasma could not overgrow K. capensis, explaining their co-existence. Host exclusivity of saprobic Protea-associated Knoxdaviesia and Sporothrix may therefore be maintained by both the activities of spore vectors and differential competitive abilities on different hosts, but the influence of other competing microbes and micro-niche differentiation cannot be excluded.

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Data is available from FR.

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Acknowledgements

This project was funded by the Department of Science and Technology (DST)/National Research Foundation (NRF) Centre of Excellence in Tree Health Biotechnology (CHTB). The authors thank the South African National Parks Board (SANPARKS) and Western Cape Nature Conservation Board for issuing the necessary collecting permits.

Funding

This project was funded by the DST/NRF Centre of Excellence in Tree Health Biotechnology (CHTB).

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V.O.M: Study design, data collection, laboratory work, statistical analyses, writing of first draft; F.R., L.L.D: Study concept, study design, acquired funding, statistical analyses, writing of manuscript.

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Correspondence to Francois Roets.

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Mukwevho, V.O., Dreyer, L.L. & Roets, F. Interplay between differential competition and actions of spore-vectors explain host exclusivity of saprobic fungi in Protea flowers. Antonie van Leeuwenhoek (2020). https://doi.org/10.1007/s10482-020-01491-6

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Keywords

  • Fungal diversity
  • Inter-species competition
  • Knoxdaviesia
  • Spore-vector
  • Sporothrix