Camargo Paulo H S A, Martins Milene M, Feitosa Rodrigo M, Christianini Alexander V
Programa de Pós-Graduação em Diversidade Biológica e Conservação, Universidade Federal de São Carlos, Rod. João Leme dos Santos, Km 110, Sorocaba, SP, 18052-780, Brazil.
Universidade de Santo Amaro, Rua Prof. Enéas Siqueira Neto 340, Jardim das Imbuias, São Paulo, SP, 04829-300, Brazil.
Oecologia. 2016 Jun;181(2):507-18. doi: 10.1007/s00442-016-3571-z. Epub 2016 Feb 22.
Seed dispersal may involve different vectors of dispersal in two or more sequential phases (i.e., diplochory). However, contributions of each phase to the overall seed dispersal effectiveness (SDE) are poorly understood and hard to evaluate due to post-dispersal processes that affect seed and seedling survival. We investigated the simultaneous bird (phase 1, in plant canopy) and ant (phase 2, on the floor) contributions to SDE with the ornithochoric shrub Erythroxylum ambiguum in a Brazilian Atlantic forest. Twelve species of birds fed on fruit and dispersed approximately 26 % of the seed crop. The remaining seed crop, 90 % of which contained viable seeds, fell to the ground beneath the parental plant. Ants either cleaned seeds in fruits or carried fallen fruit and seeds from bird feces to their nests. Although E. ambiguum has no adaptation for ant dispersal, ants were as quantitatively important as birds. Birds and ants equally increased germination rates compared to controls. However, birds deposited seeds farther from the parent, where seedling survival was higher (78 %) than it was beneath the parent (44 %), whereas ants carried seeds to their nests, where seedling survival was higher (83 %) than in controls away from their nests (63 %). Diplochory allowed a 42 % increase in SDE compared to dispersal in phase 1 alone. High lipid content in the fruit pulp of E. ambiguum may facilitate the inclusion of ants in a second step of dispersal after diaspores reach the floor. Ants can also buffer the dispersal of diplochorous plants against decreases in phase 1 dispersers.
种子传播可能在两个或更多连续阶段涉及不同的传播媒介（即二次传播）。然而，由于影响种子和幼苗存活的传播后过程，每个阶段对整体种子传播有效性（SDE）的贡献了解甚少且难以评估。我们在巴西大西洋森林中，研究了鸟类（第一阶段，在植物树冠层）和蚂蚁（第二阶段，在地面）对具鸟媒传播特性的灌木Erythroxylum ambiguum种子传播有效性的同时贡献。12种鸟类取食果实并传播了约26%的种子作物。其余的种子作物落到母株下方的地面上，其中90%含有 viable 种子。蚂蚁要么清理果实中的种子，要么搬运从鸟粪中掉落的果实和种子到它们的巢穴。虽然E. ambiguum没有适应蚂蚁传播的特性，但蚂蚁在数量上与鸟类同样重要。与对照组相比，鸟类和蚂蚁同样提高了发芽率。然而，鸟类将种子传播到距离母株更远的地方，那里的幼苗存活率（78%）高于母株下方（44%），而蚂蚁将种子搬运到它们的巢穴，那里的幼苗存活率（83%）高于远离巢穴的对照组（63%）。与仅第一阶段的传播相比，二次传播使种子传播有效性提高了42%。E. ambiguum果肉中的高脂质含量可能有助于在传播体到达地面后的第二步传播中纳入蚂蚁。蚂蚁还可以缓冲二次传播植物在第一阶段传播者减少时的传播。
