Identification of the Area of Origin in Southern Africa of the Australian form of Fireweed, Senecio

Summary

An isozyme study of the Senecio madagascariensis Poir. species complex was used to investigate the most likely region of origin for Australian fireweed within southern Africa and Madagascar as part of a biological control study. Collections of seed and voucher specimens were made in Australia, Natal, Eastern and Western Cape Provinces and South Eastern and South Western Madagascar to sample the full range of variation (excluding exotic populations found in Argentina).

Specimens were classified using taxa recognised by Hilliard (1977) and using putative groups based on observations of voucher specimens. Fresh leaf and apical cell tissue from plants grown from seed collections were used for isozyme electrophoresis. Australian fireweed populations were found to be most closely related to S. madagascariensis from Natal and the Eastern Cape. Future biological control collections should target this region to maximise the likelihood of finding host specific agents for fireweed.