Taisha wrote today’s entry with input from the photographer of the images.
Today’s photos are of Townsendia condensata, or the cushion Townsend daisy (sometimes, cushion Easter-daisy). Picking up on a few entries written earlier this year, this species is also featured in the book Alpine Plants of British Columbia, Alberta, and Northwest North America by Jim Pojar and Andy MacKinnon.
The photographs and distribution map are courtesy of Chris Lee (thank you!). Chris is a PhD candidate here at the University of British Columbia, working with Dr. Jeannette Whitton to examine patterns of relationships between members of the genus Townsendia. Chris also happened to be the teaching assistant for a course I completed over the summer, Plants and People.
Townsendia condensata, of the Asteraceae, is a cushion-forming species that grows only 1-2cm tall. It is stemless (or nearly so) with mostly basal, spoon-shaped, white hairy leaves. The solitary flower heads are made up of white or occasionally pink ray florets and numerous yellow to orange disk florets. The soft and hairy involucres are narrow and scaled (see: Parry, CC. 1874. Botanical Observations in Western Wyoming. The American Naturalist. 8:211-213).
This species is found at elevations between 10500 and 11500 feet (~2300-3500 meters) on rocky slopes, talus & fell fields and alpine zones in southwestern Alberta, Montana, Idaho, Wyoming, and Utah with a disjunct population in California. Chris commented that the distribution pattern of this species is interesting, noting that the disjunct populations in the Sierra Nevada Mountains of California are separated from other Townsendia condensata not only by vast distances, but also by a huge dispersal barrier, the Great Basin. While the distance between the Rocky Mountain populations in Alberta and Wyoming is also significant, he points out that they are connected as a part of the same mountain range with potentially similar habitat, while habitat of the intervening Great Basin is vastly different than the mountainous Sierra Nevada Range and the Rocky Mountains.
Chris has a few suggestions to explain this distribution pattern. One, that in distant geological time, before the formation of the Great Basin, the Sierra Nevada and the Rocky Mountains habitat was more similar to each other, and that perhaps Townsendia condensata had a wider distribution spanning California to Wyoming. Over geological time, as the Great Basin sank and the mountains rose around it, the habitat of the Great Basin became less suitable for this species and thus only the mountain populations survived. This would imply that Townsendia condensata is quite an ancient species! Another option he suggests is that the seeds could have been dispersed by a bird, either from California to Wyoming, or vice versa. Lastly, he also mentions that members of these populations look nearly identical, but that they could still be different species altogether. This happens to be what Chris is addressing as a part of his research by using chloroplast DNA from dried leaf material of recently collected plants and comparing the differences in the DNA of both populations along with other species of Townsendia. If the DNA is dissimilar, then it may be two different species, but if similar, then the two biogeographic explanations would have to be researched further.