Sarah DeLong-Duhon

Joined: Sep 29, 2017 Last Active: Feb 02, 2023 iNaturalist

I live in Iowa and I have considerable expertise with fungi, but I am curious about all taxa. I have a Master's in biology and am working in a microbiology lab. I am also the President of the Prairie States Mushroom Club and founder of the Iowa Fungal Biodiversity Project (via fundis.org).

My thesis was on the phylogenetics of the fungus Stereum, specifically what we have been calling Stereum ostrea in North America for nearly a decade. As it turns out, we have three morphologically similar, but phylogenetically distinct (and already named) species that have been popularly identified as S. ostrea - S. fasciatum, S. lobatum, and S. subtomentosum. They are easily differentiable with specific characteristics - whether the hymenium (underside) stains yellow when bruised, and the texture and length of the tomentum (cap hair).

What about S. ostrea? Going off available sequence data, S. lobatum and S. fasciatum are endemic to the Americas, S. subtomentosum is a northern temperate species, and there are other members of the S. ostrea species complex elsewhere in the world. S. ostrea was described from Java, Indonesia. A sequence of the type specimen would be ideal, but given the data we have it is very unlikely that S. ostrea is present in North America.

Easy peasy guide to S. ostrea species complex:
S. lobatum

  • stains yellow
  • matted, felted tomentum, individual hairs not seen
  • develops wide bands, starting at the edge, where tomentum has worn away to show chestnut cuticle

S. subtomentosum

  • stains yellow
  • wooly, hairy tomentum, felted in zones
  • develops some banding

S. fasciatum

  • no stain
  • coarsely hairy tomentum
  • very little banding, cuticle turns black with age

Examples:
S. lobatum (young) https://www.inaturalist.org/observations/125217768, S. lobatum (old) https://www.inaturalist.org/observations/108692953
S. subtomentosum (young) https://www.inaturalist.org/observations/52709545,S. subtomentosum (old) https://www.inaturalist.org/observations/130543895
S. fasciatum (young) https://www.inaturalist.org/observations/125217848, S. fasciatum (old) https://www.inaturalist.org/observations/130543764

Always feel free to @ tag me in your observations of Stereum and I can help identify. Or any fungi.

Preprint of my research available here, check out figure 2:
https://www.biorxiv.org/content/10.1101/2020.10.16.342840v3 (download PDF for full text, figure legends are at the bottom). Essentially identical to my thesis, which is published.

I collect and dry a lot of my fungi observations, in Iowa and elsewhere, and have a good memory of exact collection location. If you want specimens of anything I've found, please ask.

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