Table_1_Simplified Communities of Seed-Dispersers Limit the Composition and Flow of Seeds in Edge Habitats.XLSX

Edge effects, driven by human modification of landscapes, can have critical impacts on ecological processes such as species interactions, with cascading impacts on biodiversity as a whole. Characterizing how edges affect vital biotic interactions such as seed dispersal by frugivores is important for better understanding potential mechanisms that drive species coexistence and diversity within a plant community. Here, we investigated how differences between frugivore communities at the forest edge and interior habitats of a diverse tropical rainforest relate to patterns of animal-mediated seed dispersal and early seedling recruitment. We found that the lemur communities across the forest edge-interior gradient in this system showed the highest species richness and variability in body sizes at intermediate distances; the community of birds showed the opposite pattern for species richness. Three large-bodied frugivores, known to be effective dispersers of large seeds, tended to avoid the forest edge. As result, the forest edges received a lower rate of animal-mediated seed dispersal compared to the interior habitats. In addition, we also found that the seeds that were actively dispersed by animals in forest edge habitats were smaller in size than seeds dispersed in the forest interior. This pattern was found despite a similarity in seed size of seasonally fruiting adult trees and shrubs between the two habitats. Despite these differences in dispersal patterns, we did not observe any differences in the rates of seedling recruitment or seed-size distribution of successful recruit species. Our results suggest that a small number of frugivores may act as a potential biotic filter, acting on seed size, for the arrival of certain plant species to edge habitats, but other factors may be more important for driving recruitment patterns, at least in the short term. Further research is needed to better understand the potential long-term impacts of altered dispersal regimes relative to other environmental factors on the successional dynamics of edge communities. Our findings are important for understanding potential ecological drivers of tree community changes in forest edges and have implications for conservation management and restoration of large-seeded tree species in disturbed habitats.

由人类景观改造所驱动的边缘效应（edge effects），可对物种互作（species interactions）等生态过程产生关键影响，并进而对整体生物多样性（biodiversity）引发级联效应。表征边缘如何影响食果动物（frugivores）介导的种子传播（seed dispersal）等关键生物互作，对于深入解析驱动植物群落内物种共存与多样性的潜在机制具有重要意义。本研究以一片物种多样的热带雨林为研究对象，探究了林缘与内部生境的食果动物群落差异，及其与动物介导的种子传播模式和早期幼苗建成（seedling recruitment）之间的关联。我们发现，该系统中沿林缘-内部梯度分布的狐猴（lemur）群落，在中间距离区域展现出最高的物种丰富度与体型变异性；而鸟类群落的物种丰富度则呈现相反的格局。三种已知可有效传播大型种子的大型食果动物，倾向于避开林缘生境。受此影响，林缘生境的动物介导种子传播速率相较内部生境更低。此外，我们还观测到，林缘生境中经动物主动传播的种子，其尺寸小于森林内部生境中传播的种子。尽管两类生境中季节性结果的成年乔木与灌木的种子尺寸并无显著差异，但该格局仍得以显现。尽管传播模式存在上述差异，我们并未观测到幼苗建成速率或成功定植物种的种子尺寸分布存在任何显著差异。我们的研究结果表明，少量食果动物可能作为潜在的生物过滤因子（biotic filter），通过作用于种子尺寸，影响特定植物物种抵达林缘生境的过程，但至少在短期尺度上，其他因素对幼苗建成格局的驱动作用可能更为关键。未来仍需开展进一步研究，以更好地理解相较于其他环境因子，改变的传播体系对林缘群落演替动态（successional dynamics）的潜在长期影响。本研究结果对于理解林缘乔木群落变化的潜在生态驱动因子具有重要价值，同时也为受干扰生境中的大型种子乔木物种的保护管理（conservation management）与修复（restoration）工作提供了参考依据。