Contrasting Structure and Function of Pubescent and Glabrous Varieties of Hawaiian Metrosideros polymorpha (Myrtaceae) at High Elevation

Hawaiian dominant tree species Metrosideros polymorpha varieties glaberrima and polymorpha have glabrous and pubescent leaves, respectively. Sympatric populations at 2040 m elevation showed major differentiation beyond the pubescence itself. The varieties differed substantially in stomatal traits and in leaf composition, leaf water status, and instantaneous gas exchange rates, despite similarity in leaf and wood cross‐sectional anatomy. Functional differentiation among varieties represents a possible mechanism facilitating the occupation of an exceptional ecological range.