Tropical Natural History 18(2): 135-145, October 2018 2018 by Chulalongkorn University Short Note Regional Differences in Mammalian Pollinators of Mucuna macrocarpa (Leguminosae): a Review SHUN KOBAYASHI1*, TETSUO DENDA1, CHI-CHENG LIAO2, JUMLONG PLACKSANOI3, SURACHIT WAENGSOTHORN3, CHITTIMA ARYUTHAKA4, SOMSAK PANHA5,6, MASAKO IZAWA1 1Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213 JAPAN 2Department of Life Science, Chinese Culture University, 55 Huagang Road, Shilin, Taipei 11114 TAIWAN 3Sakaerat Environmental Research Station, Thailand Institute of Scientific and Technological Research, 1 Moo 9 Udom, Wang Nam Khieo, Nakhon Ratchasima 30370 THAILAND 4Faculty of Fishery, Kasetsart University, 50 Ngam Wong Wan Road, Lat Yao, Chatuchak, Bangkok 10900 THAILAND 5Department of Biology, Chulalongkorn University, Payathai Road, Pathumwan, Bangkok 10330 THAILAND 6Center of Excellence on Biodiversity, Ministry of Education and Chulalongkorn University, Bangkok 10400 THAILAND * Corresponding Author: Shun Kobayashi ([email protected]) Received: 17 May 2018; Accepted: 7 August 2018 Many angiosperms are pollinated by the challenges of pollination studies in this animals1. Among them, certain species are genus. Mucuna macrocarpa is an evergreen pollinated exclusively by mammals, woody vine. It produces 30–50 cm long although mammal-pollinated plants are inflorescences bearing 10–30 flowers with fewer in number than insect-pollinated purple and pale green petals (Fig. 1). plants2. Mammal-pollinated plants are Matured flowers emit a fermentation-like known from many taxa which reviewed by odor. Mucuna macrocarpa is distributed Fleming and Kress3. In addition, specific from Southeast Asia to Japan7. In Thailand, groups of mammals are known pollinators. it occurs in evergreen and mixed forests in The most well-known of these are bats, but the central to northern regions8. In the various non-flying mammals pollinate subtropics or temperate regions, it occurs in plants4. evergreen forests. The flowering season This study focuses on Mucuna changes annually and locally, and is thought (Leguminosae). Genus Mucuna includes to take place over one or two months more than 100 species and this genus is between January and May. distributed throughout tropics and Methods of Observation subtropics5. Mucuna has inflorescences with Previous observations have been either relatively large flowers and this genus has direct, in which observers stay in front of been considered to be pollinated by bats or the target flowers, or via video cameras9,10. birds specifically6. However, these methods have limitations, Among pollinators of Mucuna species, given the wariness of mammal visitors and this study reviews the behavior of Mucuna influence of observers on their flower- macrocarpa’s mammalian pollinators and visiting behavior and staying time. In its flower structure. In addition, we discuss addition, night-vision scopes are needed, TROPICAL NATURAL HISTORY. 18(2), OCTOBER 2018 136 FIGURE 1. Inflorescences of Mucuna macrocarpa. and observation of detailed flower-visiting description of flower-visiting behavior from behavior is difficult. Video cameras are photographs. expensive and battery life is short, placing a We used automatic video camera traps to limitation on observation time. In the 1990s, resolve these problems15. There are various automatic camera traps were developed for types of trigger16. Among them, cameras observation of mammalian flower visitors11. with infrared sensors which detect However, detailed observation of flower- differences between air temperature and visiting behavior is required, because not all animal (surface) temperature are often used flower visitors contribute to pollination, and for field surveys of mammals. In this some visitors rob nectar or drop flowers12-14, method, 1) mammals do not change their and this method does not allow for behaviors, 2) researchers can observe KOBAYASHI ET AL. – MAMMALIAN POLLINATORS OF MUCUNA MACROCARPA 137 FIGURE 2. Flower of Mucuna macrocarpa and floral structures. Banner petal is pale green, wing petals are purple, and carina petals are pale purple. (A): Before flower opening, (B): After flower opening, (C): Hook-like structure (before flower opening), (D): Hook-like structure (after flower opening), (E): Connected part of wing and carina petals, (F): Section of the broken line in Fig. 2A. Large amount of sweet nectar is located inside the calyx (see Fig. 2A). When the flower opens and the banner faces upward, nectar flows down from the hook- like structure (see Fig. 2D) to the tip of the carina. Dotted circle in Figs. 2C and D shows the location of the hook-like structure. throughout the day and night, and 3) flower- five petals — a banner, a pair of wings, and visiting behaviors are recorded in detail. a pair of carina petals (Fig. 2A). Nectar, a This method has been successfully used to reward for visitors, is stored inside the observe flower-visiting mammals17-19. calyx. The stamens and pistil are enclosed Explosive Opening by a pair of carina petals, preventing The flower shape of M. macrocarpa is automatic pollination. However, specific papilionaceous. Papilionaceous flowers have mammals are able to open the flower, TROPICAL NATURAL HISTORY. 18(2), OCTOBER 2018 138 FIGURE 3. Distribution map of Mucuna macrocarpa and study regions. Shaded areas show distribution. Stars indicate study sites. exposing stamens and pistil (Fig. 2B) so that allowing the explosive opener to feed21. In pollination can occur. Once the flower of M. addition, because of the wing petal’s macrocarpa is opened in this manner the attachment to the carina (Fig. 2E, F) stamens and pistil are not enclosed again. depressing the wing petal has the Additionally, the opening of the flower is simultaneous effect of pushing the carina accompanied by explosive release of pollen, down. Thus, flower opening requires the referred to as “explosive opening”. This strength of a mammal pollinator, as even mechanism is also known from other, bee- large bees, such as carpenter bees Xylocopa pollinated genera20. The flowers of these appendiculata circumvolans, cannot open plants cannot open on their own, and at least M. macrocarpa flowers22. cross-pollination by an animal, or explosive Explosive openers were considered opener, is obligatory. pollinators, but their role had not been In M. macrocarpa, flower opening takes experimentally verified9,23,24. While our place when the wing petal is pressed observations on fruit set following artificial downward, and the banner petal pollination in this genus suggest self- simultaneously pressed upward21. Thus, compatibility, fruits were not observed explosive openers must be able to when flowers did not open25. Thus, we accomplish this movement. Successful assume that explosive opening is necessary pollinators must also be able to release the for pollination in this genus, even though pair of hook-like structures at the base of the only one species was tested. banner petal, which press the wing petals Shift of Explosive Openers from both sides, preventing the flower from Explosive openers were identified M. opening automatically21 (Fig. 2C). When macrocarpa’s range, in Kyushu, Okinawa, these hook-like structures are released (Fig. and Taiwan15,18,21 (Fig. 3). Explosive 2D), nectar flows away from the calyx, openers are Japanese macaques Macaca KOBAYASHI ET AL. – MAMMALIAN POLLINATORS OF MUCUNA MACROCARPA 139 FIGURE 4. Explosive openers (effective pollinators) in three study regions. (A): Japanese macaque (Macaca fuscata), (B): Ryukyu flying fox (Pteropus dasymallus), (C): Red-bellied squirrel (Callosciurus erythraeus). fuscata (Fig. 4A) and Japanese martens openers are mammals. When these species Martes melampus in Kyushu; Ryukyu flying open a flower large amounts of pollen are foxes Pteropus dasymallus (Fig. 4B) in removed. Supported by the results of Okinawa; and red-bellied squirrels experiments, we conclude that explosive Callosciurus erythraeus (Fig. 4C), openers are effective pollinators. Formosan striped squirrels Tamiops In Mucuna, explosive openers comprise maritimus and masked palm civets Paguma either one or 2–3 species from the same larvata in Taiwan. Although the openers group, as reported in Table 1. Almost all of described above are available, Japanese them are bats or birds (Table 1). On the macaques are the main openers in Kyushu other hand, mammals from different orders and red-bellied squirrels are the main act as pollinators in different regions of M. openers in Taiwan, by virtue of the large macrocarpa’s range. There were other number of flowers they open when examples of plants pollinated by different compared to other openers. Explosive mammals at different sites. Traveler’s trees openers differ among regions, but all known Ravenala madagascariensis are pollinated TROPICAL NATURAL HISTORY. 18(2), OCTOBER 2018 140 TABLE 1. Explosive openers or flower visitors of Mucuna spp. Study Explosive opener (Flower visitor**) Pollinator Plant name Literature region/Country Species name Common name observation method M. macrocarpa Kyushu Macaca fuscata*** Japanese macaque Video camera trap / 15 (Japan) Direct observation Martes melampus Japanese marten Okinawa Pteropus dasymallus Ryukyu flying fox Direct observation 21 (Japan) Taiwan Callosciurus Red-bellied Video camera trap 18 erythraeus*** squirrel Tamiops maritimus Formosan striped squirrel Paguma larvata Masked palm civet M. sempervirens Kunming Callosciurus erythraeus Red-bellied