Contrasting adaptation of two Eucalyptus subgenera is related to differences in respiratory metabolism

1. The largest eucalypt subgenus Symphyomyrtus survives and grows better in diverse native and exotic environments than the second largest subgenus Mo nocalyptus. Previously postulated reasons for this difference, including di fferential resistance to native insect pests and dependence on specific ect omycorrhizal symbiotic associations with soil fungi, do not fully explain t he marked adaptive differentiation. 2, This work shows that differences between the subgenera in survival and g rowth performance are related to respiratory parameters. We propose that ef fects of climatic temperature on respiratory metabolism result in Symphyomy rtus being more successful than Monocalyptus in adapting to diverse environ ments. This suggests a new paradigm for adaptation and evolution of eucalyp ts.