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 that have different pollinators in different regions adapt to each pollinator in each region to maximize their pollination success. Mucuna macrocarpa (Fabaceae) limits the pollinators using its floral structure and is pollinated by different mammals in different regions. Here, we examine the relationships between floral traits of M. macrocarpa and 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, sugar components, and external morphology of the pollinators. Results showed that floral shape was slightly different among regions and that flower sizes were not correlated with the external morphology of the pollinators. Volume and sugar rate of nectar were not significantly different among the three regions and did not change throughout the day in any of the regions. However, nectar concentration was higher in Kyushu than in the other two regions. These results suggest that the floral traits of M. macrocarpa are not adapted to each pollinator in each region. Although this plant limits 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.

The pollination system of the widely distributed mammal‐pollinated Mucuna macrocarpa (Fabaceae) in the tropics

“…Although there are different openers, in each region, flower shape and nectar characteristics are not clearly different among Kyushu, Okinawa, and Taiwan (Kobayashi, Denda, Liao, Lin, Wu, et al, 2018).…”

“…However, M. macrocarpa stores nectar throughout the day in both bat-and squirrel-pollinated regions, even though pollinators are reported to differ between geographic regions (Kobayashi, Denda, Liao, Lin, Wu, et al, 2018). Assuming that M. macrocarpa is a squirrel-pollinated species, this nectar secretion pattern is the characteristic responsible for attracting diurnal animals, such as squirrels.…”

“…Study region Body mass of main explosive openers (g)Denda, Liao, Lin, Wu, et al (2018) F I G U R E 9 Relationships between the size of main pollinator and the flower size. Square, Squirrels (Callosciurus caniceps and Callosciurus finlaysonii) in Thailand; rhombus, squirrels (Callosciurus erythraeus) in Taiwan; triangle, Ryukyu flying fox (Pteropus dasymallus) in Okinawa; circle, Japanese macaque (Macaca fuscata) in Kyushu.…”

Plant-pollinator interactions in East Asia: a review

“…The orchid Cymbidium serratum is pollinated by mice (Y. . Flowers of Mucuna macrocarpa interact with many types of non-flying mammals, including squirrels, macaques, martens, and civets (Kobayashi et al 2015(Kobayashi et al , 2017(Kobayashi et al , 2018b.…”

“…The interactions between M. macrocarpa and mammals are geographically variable (Kobayashi et al 2018b(Kobayashi et al , 2018c. At the northern limit of the distribution of M. macrocarpa in Kyushu, Japan, where flying foxes are absent, the Japanese marten and Japanese macaque act as the main pollinators of its flowers (Kobayashi et al 2015).…”