Organ Pipe Nat'l Monument

[GermanStar]

There are my best ID guesses, please don't be shy about posting any corrections.


Mammillaria tetrancistra


Echinocereus nicholii


Echinocereus engelmannii v. engelmannii


Saguaro crest


Stenocereus thurberi


Stenocereus thurberi


Ferocactus wislizeni + Cylindropuntia acanthocarpa


Cylindropuntia fulgida

[hegar]

I do not see any mistakes in your identifications. However, I am not used to the cactus flora of the Sonoran Desert. I did learn a thing from your post though.
I had no idea, that there are that many Stenocereus thurberi cacti in Arizona. I would have guessed, that the large plant group was one that consisted of Carnegiea gigantea. Although I have been to Arizona, I never ventured out into the desert and only noticed, that almost everywhere you go you see saguaro cacti used for landscaping purposes.

Harald

[A. Dean Stock]

Nice photos. The E. engelmannii var. engelmannii may not be that species or at least doesn't look like any I've seen.
Dean

[GermanStar]

Thank you sir, that was a a wild guess on my part based upon the new Tucson Field Guide. If you check the range map for v. engelmannii, that is where we were. BTW, I cannot find other references to v. engelmannii, other than in that publication. Here is another shot of the same mystery Echinocereus species.

[A. Dean Stock]

The plant just looks odd to me and may be a hybrid of which there are many. The range maps in the Arizona Field Guide (A very nice book) could use some updating. The relationships between E. engelmannii , E. faciculatus, and E. nicholii are complex when it comes to hybrid populations. The name var. engelmannii is not often seen in the literature since it is essentially what is left after you remove the ranges of the other recognized varieties. They generally occur in Arizona near Yuma. Most of the more recent treatments of Echinocereus engelmannii do not recognize varieties at all but ssp. decumbens and ssp. faciculatus are recognized. The Field Guide uses the name var. varigatus for ssp. decumbens, in error. Work is ongoing on the ssp. decumbens population as its relationship to E. engelmannii is not well understood and it may represent the results of introgression between E. engelmannii and E. fendleri. This group of Echinocereus is so variable that it is difficult to work with. This is well illustrated by the fact that an unrecognized diploid population in southwestern Utah and northeastern Arizona is only now being described as distinct from the tetraploid E. engelmannii.
Dean

[GermanStar]

Thanks, I'm not sure that clarifies much, but it definitely improves my understanding. (I know Echinocereus seems to defy any form of neat and tidy taxonomic clarity). All I know for certain is that there are two Echinocereus types in the area we were scouring. One is clearly E. nicholii, and the other something rather more mysterious. I suppose this could be a form of E. fasciculatus, another confusing nomen, or an hybrid as you say. It is certainly something we had not seen before, and we are out in habitat almost constantly, though not so much in the Tucson area where E. fasciculatus resides. Just to add further confusion, here is another pic of our mystery plant.

Ajo 087.JPG (139.26 KiB) Viewed 5642 times

And here is a shot of the object of the day's search, the rare and elusive Agave ×ajoensis, which we were very fortunate to find in full bloom.

[A. Dean Stock]

Echinocereus engelmannii hybridizies readily with E. nicholii and E. faciculatus is regarded as a subspecies of E. englemannii by most recent taxonomic treatments rather than as a distinct species. If this "mystery " plant is E. faciculatus then calling it E. engelmannii is "close enough". I'm never able to easily ID this group from photos but the plant looks more like ssp. faciculatlus to me or possibly a hybrid involving E. nicholii. I know that doesn't satisfy the urge to put a name on it but that is often the case with Echinocereus and Opuntia in the field.
Dean

[Peterthecactusguy]

Hey Dean,
so if I am reading this right many of the Echinocereus in AZ have been lumped into Echinocereus engelmannii what happens to Echinocereus boyce-thompsonii? is that gonna be moved into a ssp of engelmannii? The forms of Echinocereus in Arizona give me fits. The only ones I know for sure and can usually tell are Echinocereus yavapaiensis, and Echinocereus coccineus var coccineus which are up around the Flagstaff area.. other than that I am pretty lost. There are pink and purple flowered forms of Echinocereus that I have seen a few different names for..

[A. Dean Stock]

Hi Peter, the taxon E. boyce-thompsonii is not presently considered a valid one. The relationship between E. faciculatus and E. engelmannii is not well settled at present and is based largely on the occurrence of many hybrids or intermediate forms. This is not a good way to distinguish species in Echinocereus or Opuntia because most of them will hybridize with all other species they contact. The various forms once called E. boyce-thomposonii probably represent various levels of hybrids and backcrosses between the populations presently regarded as E. engelmannii ssp. englemannii and ssp. faciculatus. It may be more complicated than that and other species may also be involved in producing "boyce-thompsonii forms in some areas. Not an easy complex to work with and it will require much more detailed work than it has received to this point. You are not alone in being confused with the identity of many Echinocereus in Arizona. Cacti are not easy to work with on morphological grounds and require a lot of genetic work to understand. There are very few people doing the work so it moves in small steps and very slowly.
Dean

[Peterthecactusguy]

Thanks Dean, sorry for the belated post. I had been meaning to check. I understand what you mean, and I just really think they all look so similar. Its not like Opuntia which I actually am so-so at IDing most of the time . Of course local forms I understand pretty well.
Peter
And thanks I will keep what you said under consideration when in the field

[GermanStar]

We frequently see plants of the possible "boyce-thompsonii" persuasion among mixed E. bonkerae/E. engelmannii populations. Which seems right in line with hybrid status, since they generally do look intermediate between those two species.

For the record, E. bonkerae is quite common throughout central AZ. We frequently encounter robust populations in the Mazatzals, Sierra Ancha and New River Mountains (unless there is another very short-spined Echinocereus of which we are not aware).

[vlani]

Echinocereus engelmannii hybridizies readily with E. nicholii ..

Dean - I thought that E.nicholii is a diploid?

For the mamm ID - by far the most common Mammillaria in the park is grahami. Yours look just like the one to me. Not sure if there are tetrancistras there, it is a large territory. Grahami-s I have seen have a nice flower with pink stripe and white edges, but again it is a large park - may be there are other forms growing there as well.

[A. Dean Stock]

I didn't see this comment about E. nicholii ploidy until now so sorry I'm late. Yes, E.nicholii is a diploid but that doesn't prevent it from hybridizing with E. engelmannii. The resulting progeny are triploids but some triploids are able to cross back to diploids and produce fertile tetraploid progeny. This allows some introgression with E. engelmannii just to keep everyone confused. Certainly, hybridization between diploids and tetraploids is greatly reduced but in Echinocereus and Opuntia it isn't always a "dead end". It is interesting that E. apachensis is a diploid that looks like E. fasciculatus and now there is a diploid being described that looks like tetraploid E. engelmannii. These two diploids together with E. fendleri and E. nicholii respresent some of the ancient diploids that gave rise to the confusing "mess" at the tetraploid level. We are only now beginning to really understand the complexity of derived tetraploids like E. engelmannii. Echinocereus is starting to look just as complex as Opuntia in its genetics and taxonomy.
Dean

[vlani]

Apachensis itself looks like a fairly obvious recent hybrid to me. Variability in the field is beyond any belief.

But as of nicholii - they all look pretty uniform in Organ Pipe. Of cause emgelmanni is variable there, but that is the same as everywhere. May the there are hybrids among engelmannii-looking plants, but they are not so obvious or common.

[A. Dean Stock]

It is possible that some of the hybridization involving E. apachensis is recent but, all in all, much of the confusing hybridization in Echinocereus, as in Opuntia is much older than one would guess. E. apachensis in defineable in at least a portion of its range but as you say, it varies greatly and again, likely due to more introgression. You will soon see in publication, that what has been called E. engelmannii, is likely a group of closely related hybrid derived populations. One population often misidentified as var. variagatus is actually ssp. decumbens and that taxon is likely a hybrid derived species in its own right. It is certainly not a typical E. engelmannii. When one looks at the original diploid population that gave rise to E. engelmannii (soon to be described), only what has been called E. englemannii var. chrysocentrus looks like the diploid. All other populations probably have various combinations of introgression from other species in their makup. We have recently found that E. coccineus hybridizes extensively with E. engelmannii in Utah and produces hybrid populations that look much like E. engelmannii ssp. decumbens. Echinocereus is almost as much "fun" as Opuntia and will require many years of extensive genetic work, allied with field work, to unravel. Right now, we are just nibbling at the edges of it.
Dean