The Recovery of an Endangered Plant. I. Creating a New Population of Amsinckia grandiflora

Abstract

The recovery of endangered plants often requires the creation of new populations in order to decrease the risk of extinction. Despite numerous attempts, no plant species have been fully recovered by creating new populations. Here we report on initial efforts to recover Amsinckia grandiflora Kleeb. ex Gray (Boraginaceae) by re‐establishing the species in appropriate habitat within its historic range, with consideration given to genetic and demographic characteristics of the founding population. An experimental framework with demographic monitoring was used to follow the fates of nutlets (propagules) from two sources (one wild, one cultivated) and to evaluate the effects of habitat manipulations (fire, herbicide application, clipping) for reducing competition from introduced grasses. Founding nutlets from two sources had different germination and genetic characteristics. Nutlets directly descended from a wild population had half the germination potential of nutlets from a cultivated population because of their greater age (about 25 years in cold storage). Levels of genetic variability, as measured by allozyme electrophoresis at 18 loci, were low overall, but much more so in the cultivated population. These data were used to maximize genetic variability among founding nutlets and to predict the frequency of alternative allele carriers in the new population. After sowing and plot treatment at the Lougher Ridge re‐establishment site, the 3460 founding nutlets produced a large number of germinules (1774) during the 1989–1990 growing season, and many (1101) survived to reproduce. From these plants, and estimated 35,800 nutlets were produced, indicating that the population had a high potential for growth during subsequent years. Introduced grasses had significant negative effects on survivorship to reproduction, plant size, and nutlet production in the new Amsinckia population. Grass cover was effectively reduced by using fire or a grass‐specific herbicide. Burning significantly decreased Amsinckia mortality rates early in the growing season and significantly increased survivorship to reproduction and maximum plant size. Herbicide treatment had no effect on mortality rates or survivorship to reproduction, but it significantly increased plant size and, therefore, nutlet output per plant and per plot. The new population should be able to maintain itself within the existing grassland community, but growth and short‐term viability would be assured by management practices that increased the availability of low‐competition habitat patches for Amsinckia occupation.