03 de febrero de 2024

Finding Oxytropis nana

Image: Putative Oxytropis nana from Natrona Co., WY, observed by FrontRangeWildflowers: https://www.inaturalist.org/observations/151764972 (© CC-BY-NC)

The Wyoming Locoweed (Oxytropis nana) is a rare species whose entire documented range is within the borders of Wyoming: https://bonap.net/MapGallery/County/Oxytropis%20nana.png (see also the 2023 Fabaceae Volume of Flora of North America).

Welsh (in FNA, 2023) describes the species as intermediate between Oxytropis sericea and O. multiceps. It also closely resembles O. lagopus. In both species (except var. conjugans of lagopus, which does not occur in Wyoming) the pods remain fully enclosed in the accrescent calyx. Welsh (2023) does not provide any diagnostic features for flowering plants which makes it very difficult to ID observations here on iNaturalist (most of which are made in the flowering stage).

Oxytropis nana herbarium specimens on SEINet: https://www.swbiodiversity.org/seinet/taxa/index.php?tid=93440&taxauthid=1&clid=0

Welsh's (2023) description: [to be added]

I have done my fair share of Oxytropis identifications on iNaturalist and have become familiar with a few species, but I am not an expert by any stretch. Oxytropis nana is completely unfamiliar to me but my hope is that the community might figure out a way to characterize this species based on photographs. I am therefore inviting everybody who is interested in Oxytropis to participate and share their insights.

As a first step I have assembled all observations that have at least one active O. nana ID. Many are sitting at genus or tribe level because they have other, conflicting IDs. I also added a couple of observations that have no nana ID but might be relevant. Some are from outside Wyoming and therefore likely misidentified, but I have included them here to give them fair consideration. When I assembled this list, I noticed that the IDs are very heterogenus (not surprising for a poorly known species). I therefore sorted them into morphological groups. The characters used for that are mentioned in my previous blog post on Oxytropis besseyi and related species: https://www.inaturalist.org/journal/matthias22/89224-identification-of-oxytropis-besseyi-lagopus-and-similar-species

Based on this, I was able to categorize observations with Oxytropis nana IDs into roughly five groups. My impression is that probably less than a handful are true nana, all the others resemble other species and are likely misdentified. However, it is also possible that O. nana simply can't be distinguished from other species except by fruit. In this case, I would expect that true nana are most likely found within Group I (lagopus lookalikes) and perhaps Group IV (oddball sericea-like plants with villous calyces).

Below are my groups. If you would like to participate in this review let me know what species each group represents, and let me know if I misplaced any observations. Also let me know about any observations I might have missed. Thanks in advance for your help!

True nana?

Group I (similar to lagopus):

[Note: BONAP does not mention O. nana from Teton Co.: https://bonap.net/MapGallery/County/Oxytropis%20nana.png]

Group Ib (pods only, calyx inflated, fully enclosing pod):

[Note: this should be var. lagopus]

Group Ic (pods emergent from calyx):

[Note: this should be var. atropurpurea but not clear how to distinguish them from besseyi without flowers.]

Group II (similar to besseyi):

Group IIb (pods only):

[Compare also to Group Ic (see note there). Note: BONAP does not mention besseyi from Sublette Co.: https://bonap.net/MapGallery/County/Oxytropis%20besseyi.png]

Group III (similar to lambertii):

Group IV (similar to sericea):

Group IVb (sericea? high elevation plants of compact growth habit, with white or yellow flowers):

Publicado el 03 de febrero de 2024 a las 11:41 PM por matthias22 matthias22 | 12 comentarios | Deja un comentario

31 de enero de 2024

Identification of Oxytropis besseyi, lagopus and similar species

Image: Oxytropis besseyi from Bozeman, MT, observed by Matt Lavin: https://www.inaturalist.org/observations/106024442 (© CC-BY-SA)

Identifying Oxytropis (locoweeds) can be a bit of a challenge. As with many plants, published keys often use characters that are hard to see on pictures, or they require fruit when there are only flowers, etc.

Oxytropis is one of the genera I regularly identify, and I am going to share here what I learned while going through Oxytropis observations from Montana. Oxytropis besseyi and lagopus were new species to me because I live in Canada where both species have very small and localized ranges.

Literature used: Flora of North America Vol. 11, Fabaceae (2023); Manual of Montana Vascular Plants (2012). Some of the characters presented here are not mentioned in the literature, specifically the shape of the wing petals. Most taxonomic work is done on pressed herbarium specimen where some of the three-dimensional characteristics of the flowers are no longer observable. Therefore, characters like these are easily missed, and they wouldn't be very useful identifying herbarium specimens. What I am putting forward here are hypotheses, and in science every hypothesis needs to be tested. Therefore, please let me know if you find a mistake or see something that can be improved. But now to the meat:

Introductory note: Oxytropis flowers are variable in shape and colour. It is very common to find misshapen or atypical flowers where petals are bent in ways that are not normal. Please take that into consideration when using the diagnostic characters below. Try to assess a number of flowers, if possible, and disregard the ones that fall out of line. It is also important to consider the stage of the flower. Flowers that are in the process of unfolding have the wing petals closer together than mature flowers. Withering flowers are often bent out of shape. The descriptions below apply to mature flowers. The literature uses the presence vs. absence of black hairs on the calyx to distinguish lagopus from besseyi. I have not been able to see black hairs on any of the images here on iNaturalist. This character probably requires higher magnification.

Oxytropis besseyi

  • wing petals spreading widely (usually at least 90°), openly exposing keel
  • upper margins of wing petals approximately as far apart as lower margins (petals not tilted)
  • calyx villous, predominantly with spreading hairs
  • only basal part of mature pod sheathed by calyx (which is at most slightly inflated in fruit)
  • racemes 3-22-flowered, subcapitate to slightly elongate (esp. in fruit)
  • most common in mountainous areas (valleys to subalpine), marginal in prairie zone, but reaches southern Saskatchewan
  • blooming later than lagopus at the same elevation (June 5 to Aug 10 in Montana based on iNat observations, n=69)


Oxytropis lagopus

  • wing petals either not spreading widely (< 90°) or else petals tilted inwards dorsally
  • upper margins of wing petals usually closer together than lower margins or else wing petals not wide spreading
  • calyx villous, predominantly with spreading hairs
  • mature pod usually fully enclosed by inflated, persistent calyx (var. lagopus), or rupturing slightly inflated calyx in var. conjugans and atropurpurea)
  • racemes 5-18-flowered, subcapitate to slightly elongate
  • most common in mountainous areas (valleys to subalpine), marginal in prairie zone, but reaches Milk River Ridge in southern Alberta
  • blooming earlier than besseyi at the same elevation (April 27 to Jun 29 [one outlier: Jul 23] in Montana based on iNat observations, n=70)


Oxytropis lambertii

  • wing petals convergent above (often more or less touching), ± concealing keel
  • lower half of wing petals more or less parallel to each other or tilted outward
  • calyx predominantly with decumbent hair (few spreading hairs) [unlike lagopus, lambertii]
  • only basal part of mature pod sheathed by calyx (which is not inflated in fruit)
  • racemes 8-45-flowered, more elongate than in the other species (esp. in fruit), flowers well spaced
  • leaflets often very narrow
  • occurs mostly in prairie zone in north-central U.S. but reaches foothills, extends east to Manitoba, MN and IA
  • blooming May 7 to Jul 8 in MT and SD based on iNat observations (n=217)


Publicado el 31 de enero de 2024 a las 05:41 AM por matthias22 matthias22 | 5 comentarios | Deja un comentario