Invasive Species Pre-adaptation to Edaphic Stress (Northern Coast Range, CA). Focal invasive:  Barbed goat grass (Aegilops triunciali)

Like other Mediterranean, annual grasses, the invasive, Barbed goat grass is found on disturbed soils throughout much of California; however, unlike most other invasive grasses, it has the ability to colonize and spread on serpentine soils.  Serpentine is a severe soil type that, until recently in California, has been relatively free of anthropogenic disturbance and exotic species invasions.  In this study I aimed to determine whether Barbed goat grass arrived pre-adapted to this edaphic anomaly or whether there was post-establishment selection of the species.  Reconnaissance of serpentine intrusions and yearly monitoring suggested that Barbed goat grass grew successfully on disturbed serpentine soil but advanced slowly on undisturbed serpentine sites.  In the greenhouse and field, reciprocal transplant studies were conducted.  In the greenhouse, serpentine populations performed better than non-serpentine populations when grown on serpentine soil.  This was particularly true for root to shoot ratios, where serpentine populations had higher ratios on serpentine soil.  These results, however, were not supported in the field, where serpentine and non-serpentine populations did not differ in their performance on novel and parent soil types.  In addition, populations performed equally well on non-serpentine; alluvial, disturbed serpentine; and shallow, undisturbed serpentine.  Results of these studies suggest that Barbed goat grass fitness is highest on well drained, non-serpentine soils and disturbed serpentine soils but, even in the absence of previous exposure to serpentine, is capable of establishment and spread onto more severe, intact sites.