Which haystack? Climate matching to narrow the search for weed biological control agents.

Abstract

The shrub Chromolaena odorata (L.) King and Robinson (Asteraceae) is highly invasive in southeastern Africa and is the subject of a South African biological control programme. The biotype of C. odorata growing in South Africa differs in several respects from the more common type noted to be invasive elsewhere, including its apparent better adaptation to a cool climate. One challenge facing the biological control programme is the identification of agents that are both suited to develop on this host biotype and persist in the relatively cool conditions found in South Africa. C. odorata is native to the Americas, where it has a very extensive distribution spanning a wide range of climates. Two climate matching computer programmes (CLIMEX and FloraMap) were used to focus the agent search effort by identifying areas in the Americas that are climatically similar to the invaded region in southern Africa (SA). Several higher-latitude and higher-altitude areas in South and Central America were identified by both CLIMEX and FloraMap as being similar to the region invaded by C. odorata in South Africa. In many areas, the two models agreed, but in others, there were discrepancies, which are discussed. There was little overlap between the region from which the SA biotype is thought to have originated and climatically suitable/similar areas in the Americas indicated by either model.