Deriving temperature estimates from Southern Hemisphere leaves

•A large new Southern Hemisphere (SH) leaf physiognomic database is introduced.•This confirms that Leaf Margin Analysis is geographically highly variable.•In New Zealand leaves non-margin characters code for temperature.•CLAMP SH calibration estimates temperature as precisely as for Northern Hemisphere.•With CLAMP hemispheric differences in leaf/climate calibration disappear.

The percentage of woody dicots with entire-margined leaves in a flora is known to be positively correlated with mean annual temperature (Leaf Margin Analysis — LMA) but this relationship is not globally uniform. In particular the floras of Australia and New Zealand have been regarded as displaying a different physiognomic relationship to climate than floras seen in the Northern Hemisphere. This difference is more marked in New Zealand where the LMA relationship appears entirely absent. Here we amass data for both Northern and Southern hemispheres using standard protocols and show that regional variations in the leaf margin–mean annual temperature relationship are real but become less significant when other characters are included. Even New Zealand falls into line and most of the mean annual temperature signal in New Zealand floras is encoded in non-margin features. We introduce a new CLAMP (Climate Leaf Analysis Multivariate Program) calibration dataset for the Southern Hemisphere, comprising leaf physiognomic data from Argentina, Bolivia, South Africa, Australia, New Zealand and other Pacific Islands that offers comparable precision for climate prediction to similar datasets derived from the Northern Hemisphere.