RESILIENCE OF THE GLADIATOR MILKVETCH (ASTRAGALUS XIPHOIDES), A RARE, ENDEMIC PLANT OF PETRIFIED FOREST NATIONAL PARK, OVER A CENTURY AND THROUGH PROLONGED DROUGHT

Abstract

Hiding among eroding badlands, hoodoos, and ephemeral washes of Petrified Forest National Park is a rare, narrow endemic with a peculiar name, the Gladiator milkvetch (Astragalus xiphoides). First discovered in the park in 1940, its scarcity and range were largely unknown until the 1980s when the species was designated as a candidate for listing under the Endangered Species Act. Focused surveys for the species were conducted in Petrified Forest National Park in 1989, identifying 16 distinct populations. Beginning in 1995, the park experienced a 27-year period of prolonged drought ending in 2022. This article summarizes the recent efforts by the National Park Service to locate these 16 populations in order to assess the plants resilience through prolonged drought. Eight of the populations surveyed in 1989 persist today, with some populations declining in density by 80–90 percent and others remaining stable with modest increases in density.