Observation 254730: Boletus separans group

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1% (2)
Used references: B-R-B key B-1 to couplet 15A
28% (1)
Based on chemical features: nrITS & nrLSU (to be posted & discussed later) confirm this is a member of the ‘porcini sensu lato’. This mushroom is related to B. separans and other members of the “Alloboletus” lineage of the porcini clade in the sense of Dentinger et al. (2010) & Feng et al. (2012)
1% (2)
Based on chemical features: See the discussion of DNA results in the comment below and also the discussion in obs 282660
84% (1)
Based on chemical features: LSU is 100% identical to several GenBank accessions from IL, NC and TX), but is only 97% to obs 282660 (true northeastern separans?)

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= Observer’s choice
= Current consensus

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Specimen accessioned to the University of Utah fungarium
By: Dan Molter (shroomydan)
2018-10-10 14:18:04 MDT (-0600)

This specimen has been accessioned to the UT fungarium with the following number:

UT-M0000481

This collection…
By: I. G. Safonov (IGSafonov)
2018-04-10 13:51:17 MDT (-0600)

…is now in the hands of Dr. B.T.M. Dentinger at UMNH.

ah OK
By: Geoff Balme (geoff balme)
2017-04-08 17:29:27 MDT (-0600)

I was unable to get an idea of what colors they intended by the description.
Thanks again, Igor!

By: I. G. Safonov (IGSafonov)
2017-04-08 17:22:21 MDT (-0600)

Yes, Geoff, but pseudoseparans is just a variant of separans with darker lilac/vinaceous/purple type coloration. Your collection doesn’t sport any color in that family of pigments on any of its surfaces, and that’s why it never occurred to us to consider naming it separans prior to getting the contradictory DNA evidence. Linas told me he would sequence ITS of his own collection of separans later this year, provided he finds it first. I think there is a good chance of getting the mystery of 254730 resolved in the coming months.

NAB mentions under X. separans
By: Geoff Balme (geoff balme)
2017-04-08 14:10:47 MDT (-0600)

a variety of color and texture for the species and synonomy with something called Boletus pseudoseparans .

Dave,
By: I. G. Safonov (IGSafonov)
2017-04-08 10:19:47 MDT (-0600)

I think we can safely rule out B. nobilis from consideration for this observation. The cap color of this collection doesn’t match and then, more importantly, we have the DNA evidence. The LSU sequences of nobilis and separans are sufficiently different for an unambiguous resolution via alignment. There are two reliable LSU sequences in GB for separans (EU232000 and KF030329) and one for nobilis (EU232002). I sequenced two nobilis suspects (obs 244683 and obs 255270) and they both nicely match EU232002. The next step would be to obtain an ITS sequence from a confidently identified separans and compare it with that of this observation.
Still, one needs a fairly discerning eye to separate gertrudiae, nobilis, and separans in the field. Usually the last one is pretty straightforward as more often than not there would be some lilac colors remaining on the cap and stipe.

I have a local spot…
By: Dave W (Dave W)
2017-04-08 07:08:28 MDT (-0600)

where patches of separans and nobilis overlap. I see ones that look like what is seen in this observation (254730); I’d say resembling separans except lack of any pinkish or lilac tints anywhere on the mushrooms matches better with nobilis. Here’s an example from the spot I mentioned obs 74227.

I have read in some field guides about species possibly “intergrading”. Is there a scientific basis for using such terminology?

variable B. separans
By: Geoff Balme (geoff balme)
2017-04-08 06:15:45 MDT (-0600)

I could imagine that – field ID of these species (if so) is horribly suspect! :p

Thanks for all your efforts, Igor. I had hoped for a conclusion that was a bit more succinct!

DNA sequencing Results & Discussion (last updated/edited 2-May-18)
By: I. G. Safonov (IGSafonov)
2017-04-07 21:52:37 MDT (-0600)

>> Results:
> A clean, contiguous nrLSU sequence (the first 987 bps to the LR5 region) was obtained from this material.
A GenBank BLAST search of the entire sequence yielded a 100% match with EU232000 and KF030329 belonging to vouchers identified as Boletus separans from North Carolina and Texas, respectively, and used in high-quality publications! However, alignment of this sequence with that of my own collection of B. separans from NJ, obs 282660 (MH244206), shows them to be only 97.3% similar.
> A clean and contiguous nrITS sequence containing two separable haplotypes was obtained from this material. Haplotype 1 of 865 bps (!) has been uploaded to this post. The ITS2 region is uncharacteristically long. With exception of the unusually long (due to numerous mini-satellites) ITS sequence of Leccinum variicolor (obs 256646), this is the longest ITS trace of “conventional” composition I’ve encountered in the Boletaceae thus far.
A GenBank BLAST search of the nrITS sequence returned returned a single close hit — Boletales sp. voucher FLAS-F-60868 from Sweetwater Preserve, FL (= MH016855 published on 11-Mar-18; 613/616 = 99.5% similarity; the 3 mismatching bases are ambiguities in MO254730). Other relevant hits are members of “Alloboletus”: Boletus violaceofuscus #DQ131629 (~90% identity) and Boletus nobilis #JN020983 (~88% identity).

>> Discussion:
MO254730 is definitely a member of the “Alloboletus” lineage of porcini sensu lato — the morphology and the associated genetic data both support this placement. Even though the nrLSU sequence of this collection is a perfect match to those of two GenBank vouchers identified as B. separans, it is very different from that of the northeastern B. separans represented by obs 282660. The nrITS data do not support or reject MO254730 being B. separans, for there are no nrITS sequences belonging to reliably identified, authentic vouchers of this iconic species posted to GenBank; however, in light of the LSU data, one would expect it to be different, too.
Thus, the genetic evidence points toward the existence of a B. separans species cluster, consisting of at least two morphologically similar species with different biogeographic profiles. Considering that B. separans was originally described by Peck from NY state, it’s expected to be prevalent in the northeastern USA. According to this hypothesis, obs 282660 is the true _B. separans, while the southern entity represented by MO254730 and the three GenBank vouchers is actually not B. separans, but a closely-related taxon. Though the southern distribution range of B. separans Peck is yet to be empirically determined, it is expected to overlap with that of the southern lookalike probably somewhere in the mid-Atlantic region.