Malheur Valley Fiddleneck (Amsinckia carinata)

The genus Amsinckia contains some of the worst native weeds in the western United States, including A. tesselata (Devil's Lettuce), A. lycopsoides, and A. intermedia. Interestingly, this genus also includes many restricted endemics (Meinke b). Amsinckia carinata is a narrow edaphic endemic restricted to cobbly hillsides in eastern Oregon (Meinke a). It was believed to be extinct until relocated during general floristic surveys in the mid 1980's (Joyal 1985 in Meinke b).The landscape immediately surrounding known Amsinckia carinata populations was once dominated by various species of bunchgrass, sagebrush, and numerous annual and perennial herbs. Today the habitats are primarily composed of annual grasses, the vast majority being introduced exotics such as cheatgrass (Bromus tectorum) and medusahead wild rye (Taeniatherum caput-medusae). This ecological change has been precipitated by a long history of domestic cattle grazing in Malheur County. As a consequence, the indigenous biodiversity of grasslands surrounding islands of Amsinckia carinata habitat have been severely depleted (Meinke a). Direct impact from cattle grazing is not extensive, since Amsinckia carinata is found on harsh, barren slopes that attract few grazers. Cattle grazing does impact A. carinata at the base of slopes by decreasing the quality of the talus substrate by creating smaller and shallower fragments (Meinke b).Due to harsh conditions on barren slopes, there are few associated species. Amsinckia tesselata, a closely related species, most commonly co-occurs with A. carinata. Amsinckia tesselata is a widespread weed that ranges from Canada to northern Mexico. It is seldom present on rocky upper slopes, but is found with A. carinata at lower elevations. The prickly hairs on A. tesselata make it unpalatable to livestock, a feature that has likely contributed to its success. Additionally, lepidopteran (butterfly and moth) larvae have been observed feeding on A. carinata but not A. tesselata plants. Again, the prickly hairs on A. tesselata likely provide protection from this herbivory. The extent of larval feeding damage on A. carinata was not great at the time it was observed, but could vary from year to year (Meinke a).Populations of A. carinata routinely overlap with populations of A. tesselata. In most cases there is a zone of 3-30 ft (1-10 m) where the two species strongly intermingle. The size of talus fragments and depth of talus slopes play a role in determining which species predominates at a given point along the hillside. As the slope extends away from the summit, the size and depth of the talus decreases and A. tessellata becomes more common. Amsinckia carinata is more vigorous in areas with deeper talus and larger fragments, but it is unknown if fruit production is also greater on deeper and heavier talus sites. (Meinke a).In the greenhouse, seed viability, germination phenology and seedling growth rates are essentially identical for A. carinata and A. tessellata. Although relative timing of germination and growth in nature has not been determined, examination of flowering phenology in the field suggests similar emergence times (Meinke a). Both plant species are self-compatible, and insect-mediated pollination is not necessary for ample seed set. However, cross-pollination appears to be common and is facilitated by native bees, which visit both species of Amsinckia. The elimination of pollinators by pesticides could reduce gene exchange that takes place during out-crossing (Meinke a). Suspected hybrids appear immediate in form, but are consistently larger than the putative parents. Hybrids also produce more flowers per plant, possibly demonstrating heterosis (\"\"\"\"hybrid vigor\"\"\"\"). Apparent hybrids, however, produce fewer fruits per flower, and it is unknown if seeds are fertile, as it is known that hybrids produce largely sterile pollen (Meinke a).If surface disturbance takes place in A. carinata habitat, it will likely be to the advantage of A. tesselata, because disturbed sites cannot be rehabilitated to match the unusual talus required by A. carinata. It is probable that mining disturbance would be so extreme that restoration of talus substrate would be impossible or at least economically prohibitive. There is also a clear connection between low quality talus (small and shallow) and a higher incident of hybridization. Cattle activities might exacerbate the potential for hybridization. Hybrid plants could potentially be a serious problem, facilitating loss of microsites, wasted pollinator visits, and pre-emption of nutrients and other resources along lower the boundary of A. carinata populations (Meinke a).