Genetic variation in the juvenile leaf morphology of Eucalyptus globulus Labill. ssp globulus

The patterns of genetic variation in the length and shape of juvenile leaves of Eucalyptus globulus ssp globulus are described. Significant additive genetic variation occurred within populations for all traits. The individual narrow-sense heritabilities estimated for lamina length (h²= 0.37) and two leaf shape traits (relative lamina width 0.34 and degree of basal lobing 0.29) were significantly greater than the estimate for the position of the widest point of the lamina (0.19). Significant genetic differences also occur between populations in both leaf length and shape with the strongest differentiation occurring in leaf length. There were strong intra- and interpopulation genetic correlations amongst most of the leaf traits. Height and volume at two years of age were genetically independent of leaf length, but within populations, faster growth was genetically correlated with increased basal lobing and a shift of the widest point closer to the leaf base. The intra- and interpopulation genetic correlations were markedly different for some pairs of traits. Leaf length was genetically independent of the height of transition from the juvenile to the adult leaf form within populations, yet genetic differences between populations were highly correlated. Growth was more highly genetically correlated with different facets of leaf shape within populations than between populations. It is argued that correlated selection is the most likely cause of correlated genetic variation between populations when traits are genetically independent within populations.