Island Ecology and Evolution Research Group (IPNA-CSIC), Canary Islands, Spain.
Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal.
Ecology. 2017 Aug;98(8):2049-2058. doi: 10.1002/ecy.1816.
Seed dispersal and seedling recruitment are crucial phases in the life cycle of all spermatophyte plants. The net contribution of seed dispersers to plant establishment is known as seed dispersal effectiveness (SDE) and is defined as the product of a quantitative (number of seeds dispersed) and a qualitative (probability of recruitment) component. In Galápagos, we studied the direct contribution to SDE (number of seeds dispersed and effect on seedling emergence) provided by the five island groups of frugivores (giant tortoises, lizards, medium-sized passerine birds, small non-finch passerine birds, and finches) in the two main habitats in this archipelago: the lowland and the highland zones, and found 16 vertebrate species dispersing 58 plant species. Data on frequency of occurrence of seeds in droppings and number of seeds dispersed per unit area produced contrasting patterns of seed dispersal. Based on the former, giant tortoises and medium-sized passerines were the most important seed dispersers. However, based on the latter, small non-finch passerines were the most important dispersers, followed by finches and medium-sized passerines. The effect of disperser gut passage on seedling emergence varied greatly depending on both the disperser and the plant species. Although the contribution to SDE provided by different disperser guilds changed across plant species, medium-sized passerines (e.g., mockingbirds) provided a higher contribution to SDE than lava lizards in 10 out of 16 plant species analysed, whereas lava lizards provided a higher contribution to SDE than birds in five plant species. While both the quantitative and qualitative components addressed are important, our data suggests that the former is a better predictor of SDE in the Galápagos archipelago.
种子散布和幼苗补充是所有有胚植物生命周期中至关重要的阶段。传播者对植物建立的净贡献称为种子散布效率（SDE），其定义为定量（散布的种子数量）和定性（幼苗补充的概率）成分的乘积。在加拉帕戈斯群岛，我们研究了五个岛屿群的果实传播者（巨型陆龟、蜥蜴、中型雀形目鸟类、小型非雀形目鸟类和雀形目鸟类）在该群岛的两个主要栖息地（低地和高地）中对 SDE（散布的种子数量和对幼苗出现的影响）的直接贡献，发现有 16 种脊椎动物传播了 58 种植物。粪便中种子出现频率的数据和单位面积散布的种子数量产生了对比鲜明的种子散布模式。基于前者，巨型陆龟和中型雀形目鸟类是最重要的种子传播者。然而，基于后者，小型非雀形目鸟类是最重要的传播者，其次是雀形目鸟类和中型雀形目鸟类。传播者肠道通过对幼苗出现的影响因传播者和植物物种而异而变化很大。尽管不同传播者群体对 SDE 的贡献在植物物种之间发生了变化，但在 16 种分析的植物物种中，有 10 种中型雀形目鸟类（如嘲鸫）比熔岩蜥蜴对 SDE 的贡献更高，而在五种植物物种中，熔岩蜥蜴比鸟类对 SDE 的贡献更高。虽然定量和定性成分都很重要，但我们的数据表明，前者是加拉帕戈斯群岛 SDE 的更好预测指标。
