Floral traits of mammal-pollinated Mucuna macrocarpa (Fabaceae): Implications for generalist-like pollination systems

Abstract

Floral traits are adapted by plants to attract pollinators. Some of those plants thathave different pollinators in different regions adapt to each pollinator in each regionto maximize their pollination success. Mucuna macrocarpa (Fabaceae) limits the pollinators using its floral structure and is pollinated by different mammals in differentregions. Here, we examine the relationships between floral traits of M. macrocarpaand the external morphology of mammalian pollinators in different regions of its distribution. Field surveys were conducted on Kyushu and Okinawajima Island in Japan,and in Taiwan, where the main pollinators are the Japanese macaque Macaca fuscata,Ryukyu flying fox Pteropus dasymallus, and red-bellied squirrel Callosciurus erythraeus, respectively. We measured the floral shapes, nectar secretion patterns, sugarcomponents, and external morphology of the pollinators. Results showed that floralshape was slightly different among regions and that flower sizes were not correlatedwith the external morphology of the pollinators. Volume and sugar rate of nectarwere not significantly different among the three regions and did not change throughout the day in any of the regions. However, nectar concentration was higher inKyushu than in the other two regions. These results suggest that the floral traits ofM. macrocarpa are not adapted to each pollinator in each region. Although this plantlimits the number of pollinators using its flower structure, it has not adapted to specific mammals and may attract several species of mammals. Such generalist-like pollination system might have evolved in the Old World.