Global climate change and accuracy of prediction of species' geographical ranges: establishment success of introduced ladybirds (Coccinellidae, Chilocorus spp.) worldwide

Aim Predictions of how the geographical ranges of species change implicitly assume that range can be determined without invoking climate change. The a im here was to determine how accurate predictions of range change might be before entertaining global climatic change. Location Worldwide. Methods All the documented global biological control translocations of lady birds (Coccinellidae: Chilocorus spp.) were analysed with the ecoclimatic p rogram, CLIMEX. This program determines species distributions in relation t o climate, and can be used to express the favourableness of different local ities for a species. CLIMEX is also a useful exploratory tool for determini ng the likelihood of establishment of species introduced from one area to a nother. Results Predictive models were developed based on the likelihood of establi shment of fifteen Chilocorus spp. relative to their physiological character istics and climatic tolerances. This likelihood was compared with actual es tablishment with a resultant range of 0% accuracy to 100% accuracy. Only fo ur (26.7%) species climatic tolerances could the predicted with 100% certai nty. The general lack of accurate prediction was because climate is not alw ays the overriding feature determining whether a species will establish or not. Other determinants, such as localized response to microclimate, phenol ogy, host type and availability, presence of natural enemies and hibernatio n sites play a varying role over and above climate in determining whether a species will establish at a new locality. Main conclusions This study shows that even in the absence of climate chang e, range cannot always be determined, which means that most predictions of range change with climate change are likely to be wrong.