Thistles GO where Thistles WANT
Cirsium scopulorum, or mountain thistle, was long thought to be the only species of thistle occurring in the alpine tundra. Molecular, morphological, and geographical evidence now support the recognition of many species of thistles in the alpine tundra of the southern Rocky Mountains. We talk with Jennifer Ackerfield, the head curator of natural history collections, and the associate director of biodiversity research at Denver Botanic Gardens about her quest to delineate the many varieties of thistles across the alpine of the intermountain west, including a unique species right here in the La Sal Mountains of SE Utah.
Meet the Scientist:
Jennifer Ackerfield
Jennifer Ackerfield is the Head Curator of Natural History Collections and Associate Director of Biodiversity Research at Denver Botanic Gardens. There, she coordinates the growth and improvement of the natural history collections, supports biodiversity research efforts, and manages herbarium staff and volunteers working with the collections. Throughout her career, Jennifer has traveled extensively throughout Colorado documenting its rich floristic diversity. This extensive knowledge led her to write the Flora of Colorado, with the goal of helping anyone identify the plants of Colorado with ease. Jennifer also leads a research program focused on documentation of biodiversity through targeted floristic inventories, systematics and taxonomy of western North American groups such as native thistles (Cirsium), and unraveling the origins of plant diversity in the Southern Rocky Mountains through biogeographic studies. Jennifer regularly collaborates with organizations and agencies across the state, leads field trips and workshops, and initiates community participatory science campaigns. She also loves teaching and sharing her passion for botany to students of all ages.
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Interview Excerpt - Unique Alpine Giants
Science Moab speaks with Jennifer Ackerfield, head curator of natural history collections and the associate director of biodiversity research at Denver Botanic Gardens, about her quest to understand thistle biodiversity. Cirsium scopulorum, or mountain thistle, was long thought to be the only species of thistle occurring in the alpine tundra. Molecular, morphological, and geographical evidence now support the recognition of many species of thistles in the alpine tundra of the Southern Rocky Mountains, including a unique species right here in the LaSal mountains of southeast Utah.
Ackerfield: I wanted to do the first full comprehensive study of thistles across North America, which was a huge undertaking. There’s a lot of variation and species. There are about 100 species of native thistles in North America. Oftentimes it’s really unfortunate for thistles because when people picture thistle, they picture the bad ones. They picture the invasive, weedy species that come in and take over and are not good for our ecosystems and are bad. But our native thistles are actually really important components of our landscapes. They are important resources of food for many pollinators for animals like pica, which eat Alpine thistles. They actually really have a lot of important ecosystem functions.
ScienceMoab: Cirsium Tukuhnikivatzicum is the species of thistles only found in the LaSal Mountains, nowhere else. How and when was it first noticed? And what makes it different from other thistles? How do you know it’s a different species?
Ackerfield: In the early 1900s, this Per Axel Rydberg, a botanist at the New York Botanical Garden and an expert on the flora of the Southern Rocky Mountains and adjacent plains, did a trip out to Utah and made a collection of this thistle. At that time, there was another thistle that had been described called Cirsium Scopulorum, which is a mountain top thistle basically. Since they were on a mountaintop, and it looks sort of similar to this thing, and resources were limited, they labeled it as Cirsium Scopulorum. Also when you collect thistles, they dry brown and you can’t really capture the overall appearance and shape and size really is obscured. Once you have collected that specimen, pressed it flat, dried it and put it on paper, you lose a lot of the details. But I was not convinced that these were all the same thing, since they are actually very distinctly different in appearance and each occupy their own distinct range. So I decided to test this hypothesis that they were all the same species. So I had samples from all throughout the Rocky Mountains in the alpine and I included the LaSal thistle in this because I thought that for sure, it was a very odd outlier, and I did some systematic work on it. I extracted DNA, sequenced some genes, and then analyzed those so that you can see the relationships of all of the different species to each other, which are more closely related,which are not. I found that the LaSal thistle was clearly not Cirsium Scopulorum, in fact they were not closely related at all.
Science Moab: Did did you parse out different species within the alpine of Colorado as well?
Ackerfield: I actually was able to pull out several other morphologically distinct populations that really had just been hiding in plain sight. All had been seen but they were just calling them all Cirsium scopulorum. But when you have all of these lines of evidence, genetic evidence, geographic range, morphological evidence, you can’t really deny the fact that they’re actually distinct species.
Science Moab: What kind of process do you have to go through to claim a new species? Is it a big deal in the botanical world?
Ackerfield: I do actually think it’s a big deal, because what we’re doing is documenting biodiversity, undescribed biodiversity. When we think about it from a management standpoint, now we know that we have this species that is unique to this area and this is the only place in the world that it’s found. If we didn’t know that we might manage that differently than we do. We might pull them all out of the ground. But now, we know that this is actually a really cool, unique species to this place only that we’re going to manage a little differently. that’s why I think it’s really important to be able to describe these new species accurately, with as much evidence as possible to back that up.
Science Moab: How did you come up with the name Cirsium Tukuhnikivatzicum?
Ackerfield: I really thought about the name for a long time because you don’t get a lot of opportunities to name new species and you want to make it a meaningful name that conveys something about the appearance or the place. I started thinking about the Ute and their use of the land and what around there pays homage to that. The word Tukuhnikivatz, the place where those sun sets last, came to mind and I thought, that’s beautiful.
