Comparison of Leaf and Floral Morphology among Insular Endemics of Pieris (Ericaceae) on the Ryukyu Islands and Taiwan

Abstract

The floral and leaf morphology of Ryukyu Pieris were examined to determine the allopatric differentiation among the islands of Yakushima, Amamioshima, Okinawa, and Taiwan. The leaves of P. koidzumiana from Okinawa were narrower than those of other insular plants and were rheophytic, while P. koidzumiana from Amamioshima possessed the wider leaf characteristics of inland plants. Pieris koidzumiana populations from these two islands shared quite large and unconstricted corollas; however, they differed significantly in corolla size. Pieris japonica var. yakushimensis from Yakushima Island and P. taiwanensis from Taiwan had wider and smaller leaves than those of P. koidzumiana, as well as smaller and more constricted corollas. Morphological differentiation of Pieris plants on the Ryukyu Islands and Taiwan can be attributed to ecological differences among the islands, locations in a riverbank or inland habitat, and the presence of anthophilous insect communities on the islands.