More detail on Potentilla pulcherrima observations (originally written for project start in 2021)

The problem: we have what appears to be a fairly common plant listed as an S1 Track species in Alberta. I think this may have happened because P. pulcherrima is underreported and undercollected, and maybe that’s due to the confusing way it’s presented in the older keys. In Flora of Alberta 2nd Ed. it’s buried at the end in a long list of P. gracilis varieties, and the Flora of North America (FNA) key and description appears to be oriented towards U.S. material with those mysterious red-tipped glands (would love to see that!). UPDATE: Happily, the new Vascular Flora of Alberta: An Illustrated Guide (Kershaw & Allen 2020) has a Potentilla key that works well as long as you use the 4th printing version or later (Feb. 2022 onward).

So I’ve set about to collect (by permit where required) and report P. pulcherrima in Alberta (AB) and British Columbia (BC). To do that, I first had to set up a definition of what is and what is not P. pulcherrima, since clearly there’s lots of intergradation going on between various Potentilla species in western Canada. Here’s what I came up with, after studying the FNA key, comparing it to what I was finding, and then running all that past the FNA Potentilla author, who kindly took the time to clarify a few sticking points for me.

Definition of P. pulcherrima for this project (italicized characters are the most important):

-lower leaf surface covered with abundant to dense white cottony hairs (white-tomentose); long hairs are also common, these often abundant on the midveins;

-upper leaf surface green, not glaucous, with sparse to common long hairs and no cottony hairs;

-leaflets 5-7, evenly incised 1/4-1/2 to midvein with 6-12 broadly lanceolate teeth per side, distal edge of teeth max. 5 mm (although I admit, if all else is correct, I don't mind one or just a few leaflet teeth that are 1-2 mm too long, this happens sometimes on extra large basal leaves on the proximal teeth);

-strictly palmate leaves (slightly subpalmate leaves allowed, i.e., leaflets that are attached on less than the last 1/10 of the leaf axis count as "palmate");

-undivided medial blade fits into the 6-15 mm wide range, usually about 10-14 mm;

-styles > 1 mm, generally in the range of ~1.5 to 2 mm long or sometimes a bit longer, and slender, without a marked glandular, expanded base, and not extremely thin and threadlike;

-epicalyx bractlets ~ 1-2 mm wide, but at this point I’m including also some plants with bracelets a bit wider (for example, to 2.6 mm when the maximum is given for P. pulcherrima is 2 mm);

-range is from the Rocky Mountains in Canada east; my personal focus because of where I live and work in BC and AB, but it would be interesting to collect farther east in Canada as well.

-glands are not expected to be reliably present: for my collections, at best, at 31X, I can see a few colorless glands right at the junction of the leaflets and the petiole on both sides of the leaf, underneath the dense long hairs, and that's it; therefore, NO “conspicuous, red-tipped glands” are necessary for a positive ID of P. pulcherrima;
(UPDATE 2022-02-24: found a specimen that has lots of colourless glands! https://inaturalist.ca/observations/97683496)

Essentially for field ID this means plants with shallowly-incised, strongly bicolored palmate basal leaves and slender 2 mm styles.

What doesn’t count:
-Plants with only a thin covering of cottony hairs on the underside of the leaflets get separated out as P. gracilis var. fastigiata, FNA’s “catch-all category” (see note in the Discussion section under P. gracilis var. fastigiata in FNA);
-Likewise, plants with leaflets > 7, leaflet teeth relatively long and linear (distal edge of most teeth > 5 mm), or undivided medial blade >15 mm are also separated out as P. gracilis var. fastigiata;
-Plants with undivided medial blade <6 mm are P. gracilis var. flabelliformis (these are usually easy to separate since they have really long narrow leaflet teeth);
-Intergrades with P. hippiana will have bicolored leaves that are not strictly palmate and these are also separated out.

UPDATE 2022-05-19:
With the help of some local iNat folks over the winter (Thank You!), there is now assembled a set of P. pulcherrima observations for AB. Using the Observation Field tool, I've sorted these into Documented: Yes or No, which helps me generate a nice map of all the many P. pulcherrima observations that now need to be visited for verification!

UPDATE 2024-02-19:
I'm three years into trying to inundate the Alberta Conservation Information Management System with documentation of Potentilla pulcherrima sites across the province, and the herbarium at University of Alberta with specimens...iNat observations and the ID reviews of local iNat IDers remain extremely helpful to me for this project - Thank you!

Publicado el febrero 19, 2024 03:18 TARDE por margaret_eaglecap