Submitted to: Biochemical Systematics and Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/28/2000
Publication Date: 9/1/2001
Citation: Ralphs, M.H., Gardner, D.R. 2001. Alkaloid levels in duncecap (delphinium occidentale) and tall larkspur (d. barbeyi)grown in reciprocal gardens: separating genetic from environmental influences. Biochemical Systematics and Ecology. Interpretive Summary: Tall and Duncecap larkspur are responsible for most of the cattle deaths on western U.S. Mountain rangelands. Tall larkspur grows in the southern Rocky Mountains and is generally considered to be more toxic than Duncecap, which grows in the Great Basin and northern Rocky Mountains. When grown in common gardens in both regions, there was no difference in toxicity between nthe two species. However, both species had higher concentrations of toxic alkaloids when grown in the southern Rocky Mountain region. The distinguishing climatic difference between the regions was the summer monsoonal thunderstorms that provide rain and adequate soil moisture to support growth throughout the growing summer in the south. The Great Basin and Northern Rockies experience summer drought, causing larkspur plants to mature and senesce by early August. Therefore, the observed difference in toxicity between the two species appears to be due to climatic factors where they grow, not to inherent genetic factors.
Technical Abstract: Two species of larkspurs (Delphinium spp.) are responsible for mot of the cattle poisoning on western U.S. mountain rangelands. Tall larkspur (D. barbeyi) grows in the southern Rocky Mountains and is generally considered to be more toxic than Duncecap larkspur (D. occidentale), which grows in the Great Basin and northern Rocky Mountains. The objective of this study was to determine whether differences in toxicity were genetically inherent within the species, or due to environmental influences unique to the different regions. Plants from both species were transplanted to common gardens in each region. There was no difference in toxic alkaloid concentration between the two species when grown in common gardens. However, both species had higher concentration to toxic alkaloids when grown in the southern Rocky Mountain region. Summer monsoonal thunderstorms in the south provide adequate soil moisture for continued growth throughout the growing season. The Great Basin and Northern Rocky Mountains experience summer drought, causing larkspur plants to mature and senesce by early August. We found unique conditions where Duncecap larkspur grew beside Tall larkspur in the southern region. In this case, toxic alkaloids were not found in Duncecap larkspur, but total alkaloid concentration was often higher than in Tall larkspur. Perhaps hybridization turned off the genes that synthesize toxic alkaloids.