Do Eucalypt Species Display Similar Potential Niche Patterns to North American Trees?

A 2024 paper in Science described the realised and potential thermal niches of 188 North American tree species in terms of mean annual temperature (MAT). Using PlantSearch data from outside species-native distributions, it was found that species potential niches displayed a ‘centrifugal organisation’ of thermal niches. As a result, ‘potential niches of cold-adapted species extend to warmer temperatures, whereas potential niches of warm-adapted species extend to cooler temperatures’. These patterns could have important implications for tree species management under climate change, and the study described here aimed to determine if similar patterns could be found with the MAT niches of eucalypt species. The realised niches of 48 eucalypt species and subspecies were assessed in terms of MAT range using maps from a 2016 book and 2022 paper as well as the Atlas of Living Australia (ALA). Potential niches for 44 species and subspecies were examined using ex situ data from the PlantSearch database of Botanic Gardens Conservation International (BGCI). Results from the study described here were less clear-cut than the North American study, but some similarities were found. For example, potential niches of cold-adapted species extended to warmer temperatures, whereas potential niches of warm-adapted species extended to cooler temperatures. In summary, there was some support for the conclusions of the North American study. However, data from arboreta and botanic gardens should be used with care or levels of species climatic tolerance may be exaggerated. The collation of data from commercial trials, which would be more representative of broadscale areas and could also include provenance as well as species information, is recommended.