Earlier this month, I met up with Eric LoPresti and others at Yellowstone National Park to help take a census of Abronia ammophila, a rare plant endemic to the park and commonly referred to as Yellowstone sand verbena. Abronia (a.k.a. the sand-verbenas) is a small genus of plants in the family Nyctaginaceae that is native to western North America. Several species in the genus have fairly limited distributions, and as the common name implies, members of this genus generally occur in sandy soils. A. ammophila is no exception. A report written by Jennifer Whipple and published in 2002 described it as “restricted to stabilized sandy sites that lie primarily just above the maximum splash zone along the shoreline of [Yellowstone Lake].” Despite the large size of the lake, A. ammophila is not widespread. Most individuals are found along the north shore of the lake, and even there it has been declining. According to Whipple’s report, “Yellowstone sand verbena has been extirpated from a significant portion of its original range along the shoreline of the lake due largely to human influences.”
Like other sand verbenas, A. ammophila has sticky leaves to which sand particles easily adhere, a phenomenon known as psammophory and an act that may help in defense against herbivory. The plant grows prostrate across the sand and produces attractive, small, white, trumpet-shaped flowers in groups of up to 20 that open wide when light levels are low, such as in the evening and in times of heavy cloud cover. The flowers are self-fertile, but insects may also play a role in pollination. It is imperative that questions surrounding its pollination biology, seed dispersal, and other factors regarding its life history are answered in order to halt any further decline of the species and ensure its survival for generations to come.
While in Yellowstone, I enjoyed looking at the all plants, several of which were new to me. I decided to sketch a few of the leaves that I found common around our campsite. I was particularly interested in discolored, diseased, drought-stressed, and chewed-on leaves, since they are more interesting to sketch and color. While I was at it, I attempted to draw a Yellowstone sand verbena seedling as well.