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Placement of Triblidiaceae in Rhytismatales and Comments on Unique Ascospore Morphologies in Leotiomycetes (Fungi, Ascomycota)

Summary

This research helps clarify the evolutionary relationships of an unusual group of fungi that grow on tree bark. Using DNA analysis, the scientists determined where these fungi fit in the fungal family tree and studied their unique spore characteristics. This work matters because: • It improves our understanding of fungal diversity and evolution • It helps scientists better classify and identify fungi found in forest ecosystems • It provides insights into how fungi adapt to survive in harsh environments • It demonstrates how modern DNA techniques can resolve long-standing scientific classification problems • It contributes to our knowledge of forest ecology and fungal biology

Background

Triblidiaceae is a family of uncommonly encountered, non-lichenized discomycetes. The family was recently circumscribed to include Triblidium (4 spp. and 1 subsp.), Huangshania (2 spp.) and Pseudographis (2 spp. and 1 var.). These fungi produce persistent, drought-tolerant apothecia with stromatic, highly melanized covering layers that open and close with humidity fluctuations. They occur primarily on bark of Quercus, Pinaceae and Ericaceae as saprobes, mostly in Western Hemisphere temperate and boreal forests. Their higher-rank classification has been uncertain due to overemphasis on ascospore morphology.

Objective

To evaluate the placement of Triblidiaceae within Rhytismatales using molecular phylogenetic analysis and examine the evolutionary and ecological significance of unique ascospore morphologies found in these fungi.

Results

The phylogenetic analysis demonstrated that Triblidiaceae is a monophyletic family composed of Triblidium and Huangshania that groups within the radiate clade of Rhytismatales. Pseudographis was found to not be part of Triblidiaceae and instead groups within the bilateral clade of Rhytismatales. The study revealed unique ascospore morphologies including muriform spores in Triblidium and Pseudographis, intense blue/purple iodine reactions in Pseudographis spores, and distinctive surface ornamentation in Huangshania verrucosa.

Conclusion

The research supports placing Triblidiaceae within Rhytismatales but with a restricted circumscription including only Triblidium and Huangshania. Pseudographis is placed within Rhytismataceae. The distinctive ascospore morphologies appear to be adaptations to harsh terrestrial ecosystems where suspended, exposed bark and wood are potential substrates for colonization. The study demonstrates how molecular phylogenetic methods can help resolve classification challenges that arise from overreliance on morphological characters.
  • Published in:MycoKeys,
  • Study Type:Phylogenetic Analysis,
  • Source: 10.3897/mycokeys.54.35697
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