Graduate Student, Bio-Protection Research Centre
PhD candidate
About
Tansy ragwort (Senecio jacobaea) arrived in New Zealand around 140 years ago and quickly spread across the country to become one of the most despised and destructive pasture weeds. Most of the concern surrounding its spread is due to the fact that plant tissues contain toxic pyrrolizidine alkaloids that are deadly to most animals that ingest them. This fact has been the cause of severe mortality in cattle and horse populations which thas endowed tansy ragwort with the reputation for killing more livestock than all other poisonous plants combined in its native range of the United Kingdom.
Some insects in tansy ragwort’s home range (Europe) have evolved the ability to tolerate – even utilize – the alkaloids. They have become “specialists” in feeding on tansy ragwort and other European Senecio species. In fact, five species of Senecio specialist insects have been introduced into New Zealand from Europe for the purposes of controlling tansy ragwort.
On this side of the world, the archipelago of New Zealand is home to 19 species of native Senecio, 13 of which are endemic. Like tansy ragwort, a common characteristic of these species is a phytochemistry that incorporates a blend of toxic pyrrolizidine alkaloids. So it comes as no surprise that some native New Zealand insects have also developed the ability to successfully feed and reproduce on these native plants, similar to their European counterparts. What makes this story interesting is how this preadaptation by some New Zealand insects has made it possible for them to feed on tansy ragwort. This, in turn, affected insect population dynamics in the wake of tansy ragwort’s arrival and spread which appears to have consequences for the native community.
My thesis research focuses on the indirect effects of tansy ragwort on native species of Senecio through these shared insect herbivores.
Contact Information
http://bioprotection.org.nz/users/scot-waring