Observation 260107: Acarospora A. Massal.

When: 2016-11-02

Collection location: Monterey Co., California, USA [Click for map]

35.8537° 120.3002° 485m

Who: J-Dar

Specimen available

On weathered sandstone bedrock outcropping in a semi-arid grassland setting.

This is the first time I’ve come across this taxon in my many forays in this area. It more resembles Acarospora thamnina in overall appearance, and may be this species. But the negative C reaction on the thallus cortex and medulla steers it clear of this ID and puts it at Acarospora obnubila. However, I have struggled with C tests on Acarospora and don’t consider the negative result to be bullet proof. I did do the spot test under dissection scope at 20x and under compound scope at 100×. Anyway, here’s the description notes:

Thallus squamulose, light brown above with black underside (A. obnubila is white, A. thamnina is black) and a long narrow black stipe (both species have a stipe), cortex C-, KC? kind of barely reddish, but a note in Nash Sonoran Flora for A. obnubila says “apparently cortical pigment diffuses in K looking yellowish or reddish brown”. I got definitely K-, but adding C seemed to give a slight reddish tint. Medulla white, C- to maybe every so slightly pinkish. Algal layer beneath thallus cortex is interrupted with hyphal bundles (more consistent with A. obnubila). Apothecia lecanorine, rather uncommon, irregularly shaped, immersed, roughened, reddish brown. Algal layer thin but continuous across base into margin. Pycnidia abundant (not seen in Sonoran material of A. thamnina, but common for A. obnubila), laminal, often with cracks on thallus connecting them.

Spores greater than 50/ascus, simple, hyaline, small. 5.6×2.4, 4.8×2.1, 4.3×2.2, 4.8×1.9


Thallus section showing algal layer interrupted by hyphal bundles
Detail of medulla and algal layer

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Add Comment
fresh C
By: Jason Hollinger (jason)
2016-11-08 13:22:53 CST (-0500)

Bottle can be quite old, has more to do with how full it is. If much is missing then it slowly out-gasses. Also opening the bottle frequently helps it out-gas. A good test I just discovered is if you apply C to the side of a coverslip, watch the front pass over your section. If it starts bubbling intensely and suddenly, then it’s good “vigorous” C. If it just sort of starts to fade, then it’s dead as a doornail. Try to keep the vial you use for spot tests as full as possible, that will help it last longer.

I will post photos of my specimen soon. They’re stacked, just need to slap the scale bar on it and file it away in my notes. I don’t remember how much if at all the squamules overlapped. Hopefully it will be clear in the photo. I’m going to be out of town for a few days, so no access to the specimen now.

Fresh C
By: J-Dar
2016-11-07 21:27:37 CST (-0500)

By the way, what do you consider “fresh”? Brand new bottle from the store every time? I figure the stuff in the big bottle, opened, can’t be any fresher than the stuff in my little dropper bottle, right?

Very interesting!
By: J-Dar
2016-11-07 21:23:51 CST (-0500)

Would you describe your specimen as imbricate? These squamules sure did overlap, but taking the imbricate choice in the key didn’t go right. Granite?

I’ve actually been communicating with Knudsen a little over the past few months, and the same week of this observation we had just made plans to meet up for a few days in early December to take a look around the Temblor Range in eastern San Luis Obispo County, north of the Carrizo Plain. I sent him the link here and his response was definitely not A. thamnina but other than that he would have to take a look at it. He is going to take all my Acarosporaceae collections consisting of maybe a few dozen Acarospora and some Sarcogyne. Once I get firm ID’s, I’ll be able to recollect for our local herbarium. I’ll certainly keep this observation updated when that info comes in.

Interesting coincidence
By: Jason Hollinger (jason)
2016-11-07 19:35:37 CST (-0500)

Was just looking at a specimen very similar to yours from the High Sierras. C- (triple checked with fresh C!) and with ±stipes. Thought for sure it would be A. thamnina in the field, but like you, back in the lab I arrived at A. obnubila. Maybe they are? Kerry has invited me to send him some specimens this winter. If I do, I’ll definitely include this one. Have you had any luck getting him to verify specimens for you? He’s been extremely busy last few years, so I suspect it’s nothing personal. Sure would be nice to get some feedback though!

By: J-Dar
2016-11-05 13:43:15 CDT (-0400)

Mature squamules have a more broadly gomphate attachment as opposed to a distinct narrow stipe seen in younger squamules

By: Jason Hollinger (jason)
2016-11-04 20:23:13 CDT (-0400)

JAHO” does sound real ghetto… but is that really what we’re going for??? :)

Yes, “feathering into medulla” is something totally different from jagged. That’s the same character as in Lecanora muralis s. str., caused by hyphal bundles plunging into the medulla from the cortex interrupting the algal layer. Probably has something to do with letting more light into the interior of the thallus so that the algae at the bottom of a thick algal layer get more light. Maybe.

Good info
By: J-Dar
2016-11-04 20:14:52 CDT (-0400)

I didn’t know what was meant in Nash Sonoran Flora for A. thamnina when it says “algal layer even, sometimes feathering into medulla” but this certainly was discontinuous. I’ll continue to look for squamulose species with a definite stipe (I don’t think this was just gomphate, but I wasn’t able to get any good photos of it either for confirmation) and black underside. Thanks Jason. Should we get you a nickname, maybe JAHO or JH-Dawg?

Sure looks like a pale A. thamnina but…
By: Jason Hollinger (jason)
2016-11-04 19:13:43 CDT (-0400)

The C+r test is reliable for thamnina (especially at 100x), and that jagged algal layer rules it out besides. I don’t know A. obnubila at all. May be…

Created: 2016-11-04 17:39:05 CDT (-0400)
Last modified: 2016-11-05 13:43:37 CDT (-0400)
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