Two Delphinium ramosum chemotypes, their biogeographical distribution and potential toxicity

Larkspurs (Delphinium, Ranunculaceae) are poisonous plants found on rangelands throughout Western North America. Two main structural groups of norditerpene alkaloids, the N-(methylsuccinimido) anthranoyllycoctonine type (MSAL-type) and the non-MSAL type, are responsible for larkspur-induced poisoning. Information on the alkaloid composition is lacking for a number of Delphinium species, including D. ramosum. Delphinium ramosum grows throughout parts of Colorado and northern New Mexico. The objective of this study was to profile the alkaloid composition of D. ramosum throughout its geographical distribution using both field and herbarium specimens. Two alkaloid profiles were identified, one that contained significantly greater concentrations of the MSAL-type alkaloids than the other. Plants containing each respective alkaloid profile were unique in their geographical distribution. Populations of these two chemotypes will likely differ in their toxic potential and consequently pose different risks of poisoning when grazed by livestock species. This information has important implications in grazing management decisions on D. ramosum-infested rangelands and demonstrates that botanical classification alone is not an adequate indicator of relative risk of toxicity.