Lee Ya-Fu, Kuo Yen-Min, Chang Hsin-Yi, Tsai Chi-Feng, Baba Shigeyuki
Department of Life Sciences, National Cheng Kung University, Tainan, 701, Taiwan.
Tropical Biosphere Research Center and Faculty of Agriculture, University of the Ryukyus, Okinawa, Japan.
BMC Ecol. 2017 Nov 14;17(1):35. doi: 10.1186/s12898-017-0146-8.
Figs are widely distributed key resources to many tropical-subtropical animals, and flying-foxes are major consumers and seed dispersers of figs. Bat-fig interrelationships, however, may vary among species differing in fruiting traits, i.e., bat- versus bird-dispersed figs. We examined Ryukyu flying-fox foraging dispersion and the relationships with tree species composition and fig abundance in forests of Iriomote Island.
Bat foraging dispersion showed no spatial patterns with respect to different areas of the island, and was not explained by heterogeneity, density, or basal area (BA) of total trees, nor by relative density or BA of fruiting trees or total fruiting figs among sites. Instead, bat densities were positively dependent on the relative density of total figs, and particularly the relative BA of bat-dispersed figs Ficus septica and F. variegata. Both species were dominant figs in forests, fruiting asynchronously with long crop seasons, and were used as predominant foods. Bats foraged mostly solitarily and the mean density was in a hump-shaped relationship with crop sizes of the dominant bat-figs. These two species and Ficus benguetensis are larger-sized bat-figs, all contained more seeds, higher dry-pulp mass and water mass, but not necessarily water content. By approximate estimation, higher proportions of seeds of these bat-figs would have been removed from fruits through the bat consumption, than that of small-sized bird-figs like F. virgata, F. superba, and F. microcarpa.
The foraging dispersion of Ryukyu flying-foxes in forests depends on the availability of the most abundant bat-figs that serve as predominant foods. Intermediate levels of crop sizes of theses figs appear most fit with their solitary foraging. Our results suggest that as density and BA coverage of these dominant bat-figs are below a certain level, their effectiveness to attract bats may dwindle and so would their chance of dispersal by bats.
无花果是许多热带 - 亚热带动物广泛分布的关键资源，而果蝠是无花果的主要消费者和种子传播者。然而，蝙蝠与无花果的相互关系可能因果实特征不同的物种而异，即蝙蝠传播与鸟类传播的无花果。我们研究了琉球果蝠在西表岛森林中的觅食分布及其与树种组成和无花果丰度的关系。
蝙蝠的觅食分布在岛屿的不同区域没有呈现出空间模式，并且不能用总树木的异质性、密度或基部面积（BA）来解释，也不能用结果树的相对密度或BA或各地点间总结果无花果来解释。相反，蝙蝠密度与总无花果的相对密度呈正相关，特别是与蝙蝠传播的无花果——尖叶榕和变叶榕的相对基部面积呈正相关。这两个物种都是森林中的优势无花果，结果季节长且不同步，并且被用作主要食物。蝙蝠大多单独觅食，平均密度与优势蝙蝠无花果的果实大小呈驼峰状关系。这两个物种和菲律宾榕是较大尺寸的蝙蝠无花果，都含有更多种子、更高的干果肉质量和水质量，但不一定是含水量。通过大致估计，与像糙叶榕、天仙果和小叶榕这样的小型鸟类无花果相比，这些蝙蝠无花果通过蝙蝠食用从果实中被去除的种子比例更高。
琉球果蝠在森林中的觅食分布取决于作为主要食物的最丰富的蝙蝠无花果的可获得性。这些无花果的中等果实大小水平似乎最适合它们的单独觅食。我们的结果表明，随着这些优势蝙蝠无花果的密度和基部面积覆盖率低于一定水平，它们吸引蝙蝠的有效性可能会降低，通过蝙蝠传播的机会也会随之减少。
