Yellowstone sand verbena: A one-of-a-kind plant
By Jennifer Whipple

NPS/Jennifer Whipple 

Yellowstone sand verbena (Abronia ammophila), an endemic species with a narrow distribution along the shoreline of Yellowstone Lake, is the rarest of Yellowstone plants. In 1990 only one known location for this species had been documented. In the summers of 1995, 1998, and 1999, however, surveyors found three new locations (and counted the total population of plants at about 8,000). With such a small isolated population of plants, two critical questions emerged during these surveys: What are the pollinators of Yellowstone sand verbena, and what is its reproductive strategy? Matching grants from Canon U.S.A., Inc., and the National Fish and Wildlife Foundation enabled park managers to contract Dr. Sedonia Sipes of Southern Illinois University–Carbondale to answer these questions. Dr. Sipes and graduate student Liz Saunders performed fieldwork in 2003 and 2004 and completed the final report in fall 2004.

This study indicates that Abronia ammophila exhibits a number of fortuitous traits that may assist in its persistence. First, A. ammophila is self-compatible (i.e., it employs self-pollination among its reproductive strategies). Second, it seems to suffer no significant inbreeding depression resulting from self-pollination and pollination by near-neighbors. It also seems to enjoy a long reproductive season with high reproductive output and low, but apparently adequate, numbers of potential pollinators, including noctuid and sphingid moths, and possibly butterflies and bumblebees.

Many questions remain about the life history of Yellowstone sand verbena, for example the average life span of the plant, its demographic trends, the relationships of this taxon with close relatives, and how much visitor disturbance (i.e., trampling) the plants can tolerate before being extirpated from an area. Nevertheless, the knowledge gained through this recent study is an excellent start for ensuring the survival of this one-of-a-kind plant.