In situ adaptation and ecological release facilitate the occupied niche expansion of a non-native Madagascan day gecko in Florida.

Aim: To investigate whether the frequently advocated climate-matching species distribution modeling approach could predict the well-characterized colonization of Florida by the Madagascar giant day gecko .

Location: Madagascar and Florida, USA.

Methods: To determine the climatic conditions associated with the native range of . , we used native-range presence-only records and climatic data to build a Maxent species distribution model and projected the climatic thresholds of the native range onto Florida. We then built an analogous model using Florida presence-only data and projected it onto Madagascar. We constructed a third model using native-range presences for both . and the closely related parapatric species . .

Results: Despite performing well within the native range, our Madagascar model failed to identify suitable climatic habitat currently occupied by . in Florida. The model constructed using Florida presences also failed to reflect the distribution in Madagascar by overpredicting distribution, especially in western areas occupied by . . The model built using the combined . /. dataset modestly improved the prediction of the range of . in Florida, thereby implying competitive exclusion of . by . from habitat within the former's fundamental niche. These findings thus suggest ecological release of . in Florida. However, because ecological release cannot fully explain the divergent occupied niches of . in Madagascar versus Florida, our findings also demonstrate some degree of in situ adaptation in Florida.

Main Conclusions: Our models suggest that the discrepancy between the predicted and observed range of . in Florida is attributable to either in situ adaptation by . within Florida, or a combination of such in situ adaptation competition with . in Madagascar. Our study demonstrates that climate-matching species distribution models can severely underpredict the establishment risk posed by non-native herpetofauna.