| 要旨トップ | 本企画の概要 | | 日本生態学会第73回全国大会 (2026年3月、京都) 講演要旨 ESJ73 Abstract

シンポジウム S07-6 （Presentation in Symposium）

#### Seed dispersal by animals in a seasonally dry forest of Madagascar【E】

*Ryunosuke OKAWA, Ryobu FUKUYAMA, Hiroki SATO（Koyot Univ.）

Animal-mediated seed dispersal is a fundamental ecological process sustaining the structure and dynamics of tropical forest ecosystems. Among tropical regions, Madagascar presents a unique seed dispersal community due to a relatively depauperate assemblage of frugivorous vertebrates, despite high plant diversity and endemism. Although frugivorous birds play central roles as seed dispersers in many tropical forest ecosystems, most of Madagascar’s bird species are insectivores. Endemic primates (lemurs) are therefore well recognized as the primary mammalian seed dispersers for a wide range of tree species in Madagascar, whereas the role of other taxa remains poorly understood.
In this talk, we first outline recent findings on plant-animal interactions through seed dispersal in a seasonally dry tropical forest in northwestern Madagascar, highlighting the potential contributions of previously overlooked taxa, including rodents and lizards, to seed dispersal processes. We then present our research on a multi-taxa seed dispersal network, which evaluates the relative importance of different dispersers and the impacts of their extinction. Our network analysis revealed that endangered animal species and species capable of handling large-sized seeds play relatively important roles within the network. Our findings also suggest that endemic rodent species help maintain network robustness in the face of large animal extinctions because they can handle large-sized seeds relative to their body mass.
Moreover, recent anthropogenic fires have threatened Madagascar’s flora and fauna in tropical dry forests, which are among the most fire-prone biomes on Earth. Finally, we introduce our latest research on the effects of anthropogenic fires on the components and structures of seed dispersal networks. The seed dispersal network in the burned forest showed a different disperser species composition compared to that in the natural forest: native large lemurs were absent, whereas small mammals and bird species became relatively more important. Additionally, dispersed seed size was smaller in the burned forest than in the natural forest, suggesting a downsizing of the post-fire seed dispersal network. Unlike the diverse disperser communities in tropical rainforests, the relatively simple seed dispersal systems of Madagascar’s tropical dry forests may be particularly vulnerable to functional loss under ongoing anthropogenic disturbances.

日本生態学会