不同扰动生境中鸟类功能特征对濒危植物种子传播有效性的影响

Degradation and destruction of natural forest ecosystems are the main reasons for decline in biodiversity, affecting both species conservation and ecosystem functioning. In East Asia, many natural forests have been destroyed by local residents for economic development, affecting the pattern of plant–animal interactions in remnant patches. As a result, the dispersal patterns of plants with fleshy fruits are expected to be altered. Thus, it is necessary to quantify the functional consequences of seed dispersal patterns and subsequent plant recruitment in patchy forests. Measuring the effectiveness of dispersal by frugivores requires information of the number of visits to the seed source by dispersers and the number of seeds dispersed per visit (quantity), in addition to the number of dispersed seeds that result in successful establishment of new recruits (quality). Consequently, most theoretical and empirical studies have concluded that bird dispersers are important ecological rescuers for linking plant source patches to recruitment patches in fragmented forests. Furthermore, these studies have shown that the contribution of different bird dispersers differs with respect to two key functional traits—body size and habitat adaptation. Specifically, larger birds tend to exhibit better dispersal effectiveness than smaller birds, with habitat generalist birds being higher quality dispersers than habitat specialist birds. However, there is increasing scientific evidence supporting the concept that the dispersal effectiveness of bird dispersers is strongly influenced by multiple functional traits. Because of the inherent difficulty of studying multiple dispersers, empirical evidence supporting the general role of bird functional traits in dispersal effectiveness remains limited. In east China, most Chinese yew (Taxus chinensis var. mairei) trees are distributed in fragmented forests because of human land use practices. The Chinese yew is a typical gymnosperm endemic to China. It is listed as an endangered (EN) species by the International Union for Conservation of Nature (IUCN) and is a first-class national protected plant in China. However, the regeneration of wild populations is limited by low pollination rates, seed-predator pressure, weak competitive ability of seedlings, and scarcity of microhabitats for recruitment. In this study, we investigated differences in the functional traits of birds in both natural and patchy habitats, and how these trait differences affect the effectiveness of T. chinensis var. mairei seed dispersal by birds. Specifically, we investigated (1) variation in the foraging functional traits of birds across natural and patchy habitats, and how this variation affects the quantity of seeds dispersed, and (2) variation in the functional traits of flight and habitat selection of birds across natural and patchy habitats, and how this variation affects the contribution of birds to the quality of seed dispersal.

人类土地利用导致的生境丧失和破碎化已成为全球生物多样性下降及生态系统功能降低的重要原因。厘清不同扰动生境中鸟类功能特征对濒危植物种子传播有效性的影响有助于科学地制定濒危植物的综合保护策略，亦可探明人为扰动下动植物种间互作在植物种群恢复中的多重角色，但相关研究匮乏。本研究以两种扰动生境（斑块生境和连续自然生境）的南方红豆杉为研究对象，采用样线法和样点法调查不同生境中鸟类群落特征；查阅文献、测量标本和野外调查以测定不同生境中鸟类的取食、飞行能力和生境选择等功能特征；野外观测鸟类的种子传播数量并分析其与取食特征之间的耦合关系；采用野外跟踪、无线电遥测和控制实验相结合以研究主要传播鸟类的传播质量及其与飞行和生境选择等特征的关联性。研究结果可揭示不同扰动生境中鸟类功能特征对植物种子传播有效性的多层次影响，不仅为濒危植物的就地保护提供新思路，而且为阐述动植物种间互作在植物种群恢复中的作用提供新视角。

人类土地利用导致的生境丧失和破碎化已成为全球生物多样性下降及生态系统功能降低的重要原因。厘清不同扰动生境中鸟类功能特征对濒危植物种子传播有效性的影响有助于科学地制定濒危植物的综合保护策略，亦可探明人为扰动下动植物种间互作在植物种群恢复中的多重角色，但相关研究匮乏。本项目以濒危植物南方红豆杉为研究对象，研究了不同干扰生境中鸟类特征对南方红豆杉种子搬运量、传播距离和传播有效性的影响，主要结论如下：1）在福建梅花山农田、斑块生境和自然生境中红豆杉都能吸引鸟类取食和传播其种子，鸟类的取食量与它们的访问频次呈正相关；鸟类取食后的飞行行为决定了红豆杉的种子传播距离，传播距离与鸟类的翅长与尾长呈正相关。2）在不同的扰动生境（福建龙岩和江苏南京）中，红豆杉的种子排放量与鸟类的取食后生境利用率和鸟类翅长呈正相关，幼苗数量与鸟类的取食后生境利用，种子排放量和跗趾长呈正相关；3）在福建红豆杉园的不同斑块中，红豆杉的种子排放量与鸟类停歇树特征、斑块类型、鸟类访问频次呈正相关，幼苗数量与鸟类体长、停歇树的特征呈显著正相关。研究结果表明：在不同的扰动生境中鸟类的形态和行为特征影响着红豆杉种子传播有效性，进一步揭示了动物功能特征对动植物种间关系的多层次影响，也为濒危植物的有效保护提供了新思路。