Seed germination of a myrmecochorous plant endemic to the Brazilian semiarid region: the wolf is not so bad

ABSTRACT Studies about seed dispersal and germination are important to understand patterns of plant distribution and abundance, and help establish strategies for environmental conservation. We evaluated the role of two different dispersers, the ant Atta laevigata and the maned wolf Chrysocyon brachyurus, in the germination of Copaifera arenicola seeds, a characteristically myrmecochorous plant species. Germination was evaluated for seeds subjected to four treatments: (1) seeds manipulated by the ant, (2) seeds ingested by the maned wolf, (3) seeds that had the elaiosome removed manually, and (4) seeds with elaiosome (unmanipulated seeds). Seeds manipulated by the ant and seeds that had the elaiosome removed manually required less time to germinate and had higher germination percentages (98.6% and 95.8%, respectively) than the other treatments. However, seeds ingested by the maned wolf also had a high germination percentage (87.7%), above that of unmanipulated seeds (34.7%). Probably, elaiosomes of unmanipulated seeds and small remnants of this structure that resist digestion by maned wolf can decrease to some extent seed germination. We argue that dispersal of C. arenicola seeds by the ant and by the maned wolf result in different patterns of seed distribution in the environment and that they have complementary roles in structuring plant populations.

摘要
有关种子扩散与萌发的研究，对于解析植物分布与多度格局、制定环境保护策略均具有重要意义。本研究评估了两种不同扩散者——切叶蚁（Atta laevigata）与鬃狼（Chrysocyon brachyurus）——对沙生香脂木豆（Copaifera arenicola，一种典型蚁播（myrmecochorous）植物）种子萌发的影响。本实验对接受4种处理的种子开展萌发评估：(1) 经切叶蚁处理的种子；(2) 经鬃狼吞食的种子；(3) 人工去除油质体（elaiosome）的种子；(4) 保留油质体的未处理种子。
经切叶蚁处理的种子与人工去除油质体的种子，其萌发所需时长更短，萌发率分别达98.6%与95.8%，显著高于其余处理组。不过，经鬃狼吞食的种子萌发率亦达87.7%，高于未处理种子的34.7%。研究推测，未处理种子的油质体，以及经鬃狼消化后残留的少量油质体片段，可在一定程度上抑制种子萌发。本研究认为，切叶蚁与鬃狼对沙生香脂木豆种子的扩散过程，会在环境中形成不同的种子分布格局，二者在植物种群结构构建中具有互补作用。