|Abstract or Summary
- The role of unusual geologies in plant distribution and form is well-known. Serpentine (ultramafic) soils exert a particularly strong influence on plants, as evidenced by a high level of endemism and the morphological and physiological traits displayed in adaptation to the extraordinary chemistry of these substrates. Adaptation may lead to ecotypic differentiation, in which a genotypic response to substrate is evident. In the case of rare taxa, these ecotypes assume an important role in the conservation and recovery of the species. Any management efforts, including population creation and augmentation, should reflect these patterns of differentiation. Lomatium cookii Kagan (Apiaceae) is found in southwest Oregon in two isolated population centers with unique edaphic characteristics, one in ephemeral wet meadows and vernal pools on soils of non-serpentine parentage and the other in ephemeral wet meadows on soils of serpentine and non-serpentine parentage. This study sought to quantify edaphic differences between habitats, examine ecotypic differentiation between populations, and develop a practical germination and cultivation protocol reflective of that ecotypic differentiation. Field studies examined floral and fruit morphology and phenology of natural populations. Reciprocal greenhouse investigations evaluated influence of substrate and seed source on vegetative morphology, survival, and flowering. Germination and propagation requirements were also examined. Overall, differences in soil chemistry existed between population centers; serpentine soils had higher concentrations of heavy metals, lower macronutrient concentrations, and lower calcium:magnesium ratios. Phenotype and several floral and fruit morphology characters differed significantly between population centers. Reciprocal greenhouse studies indicated a genotype by substrate interaction and a difference in vegetative morphology between serpentine and non-serpentine populations. Germination required 12 weeks of cold-moist stratification at 4° C; warm-dry after-ripening and post-stratification temperature regime were not significantly correlated with germination. Greenhouse transplants from both population centers grew tallest, had the highest biomass, and the greatest probability of survival in non-serpentine soil. These results have taxonomy and conservation applications. While clear differences among populations were noted, taxonomic recognition is not merited. Conservation and management activities should, however, occur in accordance with the observed patterns of diversity.