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Population Structure of an Orchid Mycorrhizal Fungus with Genus-Wide Specificity

Summary

This research explored the relationship between orchids and their essential fungal partners in southeastern Australia. The study revealed that a single fungal species forms partnerships with multiple orchid species across a vast geographic range, while a second fungal species is found only in wet, boggy areas. This research helps us understand how these important plant-fungal partnerships work in nature. Impacts on everyday life: – Helps conservation efforts for endangered orchid species by identifying their fungal partners – Improves understanding of how to grow and propagate orchids for horticulture – Provides insights into how species adapt to different environmental conditions – Demonstrates the importance of preserving natural habitats that support these partnerships – Advances knowledge of how beneficial fungi disperse in nature

Background

Many terrestrial orchids interact with compatible mycorrhizal fungi throughout their lifetime. Since orchid seeds lack an endosperm and consist only of an embryo and seed coat, this association is obligate during seed germination with the mycorrhizal fungus supplying critical nutrients. All orchids continue to rely on fungi for water and nutrients to some extent at adulthood. Understanding the identity and life history of fungal partners is critical for improving knowledge of fungal biology and their role in orchid distribution and abundance.

Objective

To investigate the species identities and life history of orchid mycorrhizal Tulasnella fungi that associate with the southeastern Australian orchid genus Chiloglottis. The study aimed to examine fungal interactions within orchid species growing under contrasting edaphic conditions and analyze the population genetic structure of the widespread species T. prima.

Results

Tulasnella prima was found to be the primary fungal partner associated with all 17 Chiloglottis species across the entire geographic range and in both soil and sphagnum hammock conditions. A second species, T. sphagneti, appeared restricted to moist conditions of alpine sphagnum hammocks. Population genetic analysis showed no sharing of multilocus genotypes between sites, but clones were found within sites. Evidence for inbreeding was found at 3 of 5 sites. Significant genetic differentiation was detected within and between taxa, with significant local positive spatial genetic autocorrelation at the scale of two metres.

Conclusion

The study confirmed that across the genus Chiloglottis, all orchid species associate with the common and widespread fungus T. prima. However, edaphic conditions can influence which Tulasnella species are involved, with T. sphagneti co-occurring with T. prima in wetter sphagnum hammock conditions. Population genetic results indicate that Tulasnella predominantly disperses over short distances via vegetative fragments or inbred basidiospores, despite its wide geographic distribution.
  • Published in:Scientific Reports,
  • Study Type:Field Study,
  • Source: 10.1038/s41598-017-05855-3
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