Abstract
Although the pollinators of some plant species differ across regions, only a few mammal‐pollinated plant species have regional pollinator differences in Asia. Mucuna macrocarpa (Fabaceae) is pollinated by squirrels, flying foxes, and macaques in subtropical and temperate islands. In this study, the pollination system of M. macrocarpa was identified in tropical Asia, where the genus originally diversified. This species requires “explosive opening” of the flower, where the wing petals must be pressed down and the banner petal pushed upward to fully expose the stamens and pistil. A bagging experiment showed that fruits did not develop in inflorescences (n = 66) with unopened flowers, whereas fruits developed in 68.7% of inflorescences (n = 131) with opened flowers. This indicated that the explosive opening is needed for the species to reproduce. Four potential pollinator mammals were identified by a video camera‐trap survey, and 78.3% and 60.1% of monitored inflorescences (n = 138) were opened by gray‐bellied squirrels (Callosciurus caniceps) and Finlayson's squirrels (C. finlaysonii), respectively, even though more than 10 mammal species visited flowers. Nectar was surrounded by the calyx, and the volume and sugar concentration of secreted nectar did not change during the day. This nectar secretion pattern is similar to those reported by previous studies in other regions. These results showed that the main pollinators of M. macrocarpa in the tropics are squirrels. However, the species' nectar secretion pattern is not specifically adapted to this particular pollinator. Pollinators of M. macrocarpa differ throughout the distribution range based on the fauna present, but there might not have been no distinctive changes in the attractive traits that accompanied these changes in pollinators.
Highlights
Plants pollinated by specific pollinators attract and limit them by specific floral traits, such as flower shape, color, and odor (Córdoba & Cocucci, 2011; Gómez et al, 2008; Hirota et al, 2012; Johnson, Burgoyne, Harder, & Dötterl, 2011)
The present study revealed that squirrels are the main pollinator in Southeast Asia, indicating that the squirrel was the pollinator of M. macrocarpa when the plant speciated
To conclude the floral traits, external characteristics perhaps adapt to the main pollinator in each region, attractive traits such as nectar and flower color suggest that this species may attract a variety of mammals
Summary
Plants pollinated by specific pollinators attract and limit them by specific floral traits, such as flower shape, color, and odor (Córdoba & Cocucci, 2011; Gómez et al, 2008; Hirota et al, 2012; Johnson, Burgoyne, Harder, & Dötterl, 2011). While bats can freely use their forelimbs for feeding, birds cannot use their anatomically equivalent wings in the same manner These shifts in pollinators are examples of regional differences in pollinators of the same plant spe‐ cies. The main pollinators are Japanese macaques (Macaca fuscata) in Kyushu (Kobayashi et al, 2015), Ryukyu flying foxes (Pteropus dasymallus) in Okinawa (Kobayashi, Denda, Liao, Lin, Liu, et al, 2018; Toyama et al, 2012), and red‐bellied squirrels (Callosciurus erythraeus) in Taiwan (Kobayashi, Denda, et al, 2017) These mammals open flowers by pushing upon the banner petal with their snout, except for Japanese macaques which open flowers using both hands, to feed on nectar (Kobayashi, Denda, Liao, Lin, Liu, et al, 2018; Kobayashi, Denda, FIGURE 1 Mucuna macrocarpa inflorescences (a), before explosively opened flower (b), and after explosively opened flower (c). We aimed to determine the flower‐vis‐ iting pattern of each species
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