Penstemon azureus

All species of Penstemon are strictly endemic to North America, making it the largest group of flowering plants restricted to the continent. Penstemon azureus, like the majority of Penstemon species, is native to western North America; it is found only in southwestern Oregon and northern California.

Azure penstemon has been the subject of some recent research to determine its evolutionary origins. As plants of Penstemon azureus contain six times the base number of chromosomes (6x), it has been speculated that the species is the result of the hybridization of two closely related species of Penstemon, one containing four times the base number of chromosomes (4x) and one containing the “typical” two (2x) — in other words, it is a polyploid, and more specifically an allopolyploid (even more exact, an allohexaploid). Testing the hypothesis of allopolyploidy in the origin of Penstemon azureus (Plantaginaceae) is a talk being presented at Botany 2012. The researcher, Travis Lawrence, makes note in his presentation’s abstract that Penstemon azureus is one of only four species in Penstemon section Saccanthera with either 4x, 6x, or 8x the base number of chromosomes; the other twenty species have 2x. Through examination of nuclear DNA in particular, Lawrence was able to narrow the likely progenitors of Penstemon azureus to three species: Penstemon heterophyllus (some individuals have 2x, others have 4x), Penstemon laetus (2x), and Penstemon parvulus (4x). Additional research is necessary to better determine the likely progenitors.

This photograph was taken at the Rough and Ready Botanical Wayside near O’Brien, Oregon. Two potential progenitors also are known to occur here: Penstemon laetus and Penstemon parvulus. Penstemon identification can be difficult, particularly when closely-related species are sympatric (or overlapping in distribution). Fortunately, I was able to determine this species with the key in the recently-released second edition of The Jepson Manual. Penstemon laetus was discarded as a possibility as it has a glandular inflorescence; I can see no glands when I look at the full-size rendering of the image (all parts of the inflorescence are glabrous (smooth or hairless)). One of the key differences between Penstemon parvulus and Penstemon azureus is length of corolla (14-20mm vs. 20-35mm), and I am quite confident these fall within the larger range.

A close-up photograph of a flower (from a plant in the same area) was taken by Karen Phillips: Penstemon azureus. Additional photographs are available from CalPhotos: Penstemon azureus.

Interested in penstemons? You might like to consider the American Penstemon Society; they’ve helped fund a small research project on penstemon hybridization and evaluation for home garden use here at UBC Botanical Garden, for which we’re grateful.

Penstemon azureus

15 responses to “Penstemon azureus”

  1. Steve Edler

    Do hybridizations happen more than once to produce the same new species? ie could this species have originated more than once?

  2. Sandyinz4

    That is an exquisite plant. Most people would pay good money to have it in their gardens! 🙂 Great photo, too!

  3. Julie McI. Shapiro

    Thank you so much for including a delicious image of this wonderful Genus.
    Looking at this is a great way to end my work day!

  4. Big Al

    Allopolyploid, what a lovely word. I shall use it as an insult.

  5. Daniel Mosquin

    Steve, I don’t know any details specifically about Penstemon azureus evolving more than once, but I suppose it is possible. Allopolyploid hybridizations are indeed known to recur.
    See: Soltis, Soltis & Rieseberg. 1993. Molecular Data and the Dynamic Nature of Polyploidy. Critical Reviews in Plant Sciences. 12(3):243-273 doi:10.1080/07352689309701903
    To quote from the abstract:
    “Numerous studies have demonstrated multiple origins of both allopolyploids and autopolyploids. In several polyploid species studied in detail, multiple origins were found to be frequent on a local geographic scale, as well as during a short span of time. Molecular data strongly suggest that recurrent formation of polyploid species is the rule, rather than the exception. In addition, molecular data indicate that recurrent formation of polyploids has important genetic consequences, introducing considerable genetic variation from diploid progenitors into polyploid derivatives.”
    On the other hand, if one were to look at what one might typically consider a hybrid (pollen from one 2x species fertilizing another 2x species), species having multiple origins is very unlikely… but seems to be possible. Again, a paper involving UBC research Loren Rieseberg:
    Schwarzbach and Rieseberg. 2002. Likely multiple origins of a diploid hybrid sunflower species. Mol Ecol.. 11(9):1703-15.
    From the abstract:
    “The recurrent origin of diploid hybrid species is theoretically improbable because of the enormous diversity of hybrid genotypes generated by recombination. Recent greenhouse experiments, however, indicate that the genomic composition of hybrid lineages is shaped in part by deterministic forces, and that recurrent diploid hybrid speciation may be more feasible than previously believed. Here we use patterns of variation from chloroplast DNA (cpDNA), nuclear microsatellite loci, cross-viability and chromosome structure to assess whether a well-characterized diploid hybrid sunflower species, Helianthus anomalus, was derived on multiple occasions from its parental species, H. annuus and H. petiolaris.”
    Helianthus anomalus, in a previous Botany Photo of the Day entry.

  6. elizabeth a airhart

    thank you for lovely o’l blue eyes makeing my evening quite lovely
    i found a book on line at powells flowers and herbs of early america
    yale press amd colonial willamsberg put out the book four years ago
    perhaps now i will know the plants my long ago family looked upon
    when they settled here in the states bon jour daniel

  7. quin

    well, we couldn’t have a prettier genus to be N.A.’s largest endemic, thanks to ‘whoever’! enjoy this description of the detective work involved with this lovely flower thanks to Daniel

  8. Ronaldo de Sousa

    Obrigado! 🙂

  9. Steve Edler

    Many thanks Daniel for the information

  10. Eleanor Ryasn

    Beautiful penstemons are only one of many unique plants from Rough and Ready Wayside.–The Native Plant Society of Oregon is having their state meeting in Selma OR this year in July. Many wonderful, unique plants are expected. I am hoping to see Eriogonums new to me. Is there a collection of photos available for that area of Oregon? Serpentine soil, and ophilites are expected.

  11. Daniel Mosquin

    Eleanor — really wish I could be attending that NPSO meeting, but I’ve duties elsewhere. I have many photos from the region, but alas these are not available online other than the occasional posting to BPotD (one of these days I will have to do something about that).
    In the meantime, I suggest you visit the Flickr site of Karen Phillips. If you haven’t already met Karen, you will at the NPSO meeting, I’m sure (she’s a great person) as she works at the Siskiyou Field Institute. If you go to the right hand side of that linked page, you’ll see she has a set of photos from Rough and Ready.

  12. Carl Wishner

    In California, there are two varieties, distinguished by calyx length and shape of the lobes, and leaf shape. The nominate variety azureus has lanceolate leaves, instead of linear leaves, which the former appears to be the case here, despite the focal depth problems with the photo. Moreover, the var. angustissimus is not reported for Oregon in The Jepson Manual 2. Therefore, it is likely this is the nominate variety. A very beautiful penstemon indeed, and one that I always enjoy in my area of the northern Sierra Nevada. In bud, the developing flowers are a beautiful yellow color, maturing this distinctive azure blue at anthesis, which goes well with the usually glaucous and glabrous leaves and stems.
    Carl Wishner

  13. Daniel Mosquin

    Focal depth can’t be a problem if it was intentional. You can also see hints of the yellow buds.

  14. Carl Wishner

    Daniel: I apologize for the poor choice of the words, implying a “problem” with depth of field. My intent was to indicate that I could not discern the shape of the proximal leaves clearly enough for definitive determination of the variety.
    How can I change my email preference?
    Carl Wishner

  15. Daniel Mosquin

    Carl, that’s fair enough. Email preference? I’m not sure — I get frustrated with the mailing system a fair bit, as it sometimes sends out notifications when people post comments on old entries making it appear as if they were new entries. All I really want from the notification system is to let people know there are new posts.

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