Abstract
Aim Increasing aridity over geological time‐scales has driven a high degree of speciation within the Eucalyptus group in Australia. Isolation of gene pools by climatic and edaphic conditions and high rates of out‐crossing have given rise to a large diversity of adaptive traits. Among these traits, adaptations of cellular biochemistry are likely to be significant in preserving cellular function during arid conditions. The aim of this study was to determine the quantitative and qualitative distribution of soluble carbohydrates and polyols in Eucalyptus . Location Australia. Methods We sampled 279 of the 700+ documented eucalypts (in the three genera comprising the eucalypts: Angophora Cav., Corymbia Hill & Johnson and Eucalyptus L’Hér.) and analysed leaf tissues for the occurrence of low‐molecular‐weight carbohydrates and polyols. Results We have uncovered a discrete pattern in concentration of quercitol (a cyclitol) that correlates strongly with the current taxonomic classification based on both morphology and DNA sequencing. We also uncovered a further and stronger correlation between the presence of quercitol in leaf tissues and a reduced growth (mallee) form. Main conclusions These findings, together with the chemical properties of quercitol, suggest that we have uncovered a chemical marker of structural adaptations to arid conditions, thus providing a putative, broad‐scale functional link to adaptation to aridity.