斑块生境中食果鸟类对南方红豆杉“(Taxus chinensis var. mairei)”种子的取食和传播

Abstract

生境斑块化对食果鸟类的移动行为产生影响，进而影响其对植物种子的传播格局和效率。南方红豆杉（<em>Taxus chinensis </em>var. <em>mairei</em>）是我国一级保护植物，在南方山区多因人为干扰而呈斑块状分布。2011年，2012年10月底到12月中，以分布于福建梅花山国家级自然保护区红豆杉生态园中南方红豆杉种群为对象，研究斑块生境中鸟类对南方红豆杉种子的取食和传播行为，并评估专性鸟类和泛性鸟类的传播效率。结果发现：南方红豆杉源斑块共吸引22种食果鸟类取食红豆杉种子，并与13种鸟类形成了种子传播关系。不同年间，黑短脚鹎（<em>Hypsipetes leucocephalus</em>）都是植物的主要传播鸟类，而其他鸟类传播者种类具有一定的年间变化。生境斑块化导致专性鸟类黑短脚鹎和泛性鸟类红嘴蓝鹊（<em>Urocissa</em> <em>erythrorhyncha</em>）种子传播效率差异。与红嘴蓝鹊相比，黑短脚鹎飞行的平均距离较短（（16.3±11.0）m，Mean±SD，<em>n </em>= 125），传播距离相对较近；且它们取食后偏好在源斑块中活动，喜栖息在同种成树、甜楮（<em>Castanopsis eyrei</em>）及其他阔叶树等栖树上。红嘴蓝鹊取食后常在斑块间移动，常停歇在同种成树和毛竹（<em>Phyllostachys heterocycla</em>）上，传播距离相对较远（（24.9±20.0）m，Mean±SD，<em>n </em>= 95）。空间一致性结果表明，黑短脚鹎移动距离对幼苗更新距离的空间一致性程度高；而红嘴蓝鹊偏好生境与幼苗更新生境一致性程度高。结果表明，斑块生境中植物能与专性鸟类、泛性鸟类之间形成种子传播互惠关系，且种子传播效率受到专性鸟类和泛性鸟类传播距离和传播生境的影响。;Human disturbance causes the continual loss of natural habitats, and can result in fragmented habitats consisting only of patchy remnants. This habitat modification can lead to changes in plant-animal interactions. Understanding how the movement behavior of animal dispersers affects the regeneration patterns of plant species in patchy environments has been one of the main objectives of ecologists in recent years. Many previous studies have investigated seed dispersal only in terms of the dispersal distance. However, from the perspective of successful plant growth, it is not only important how far seeds are dispersed, but also where they are finally deposited. The quality of seed dispersal crucially depends on the movement patterns of the dispersing animal vectors; however, few ecological studies have focused on how the patchiness of habitats affects the movement patterns of specialist and generalist bird species, and thus, how habitat patchiness affects plant recruitment. Chinese yew (<em>Taxus chinensis</em> var. <em>mairei</em>) is listed as a Category 1 protected species in China, and it has also been listed as a globally endangered species in the IUCN Red List. A large proportion of the wild population of Chinese yew is distributed in patchy environments, and relies on bird vectors for seed dispersal. Previous studies have shown that Chinese yew seedlings can successfully establish away from mature trees as a result of seed dispersal by birds in the Corvidae and Pycnonotidae. However, it is still unknown how habitat patchiness affects the movement patterns of specialist and generalist bird species, and thus, how it affects the regeneration of Chinese yew and the persistence of its populations. In this study, we studied bird dispersal of Chinese yew seeds in the yew ecological garden of Meihuashan National Reserve. We studied the foraging and dispersing behavior of frugivorous birds in this typical patchy environment, and compared the contributions of a specialist (<em>Hypsipetes leucocephalus</em>) and generalist (<em>Urocissa erythrorhyncha</em>) species to seed dispersal by analyzing their post-foraging movement behaviors. The results showed that the Chinese yew source patch attracted 22 species of frugivorous birds to feed on seeds. A mutualistic seed dispersal relationship was formed between 13 bird species and Chinese yew. The main disperser of Chinese yew seeds was <em>H. leucocephalus. </em>There were annual differences in the other disperser species. The effectiveness of seed dispersal differed between the specialist and generalist bird species. After foraging for Chinese yew seeds, the movement and habitat selection differed between the habitat generalist (<em>U. erythrorhyncha</em>) and habitat specialist (<em>H. leucocephalus</em>) bird species. This may explain the differences in the seed dispersal distance and seed deposition sites between these two species. The habitat specialist bird species dispersed seeds over a short distance (16.3±11.0 m, mean±SD; <em>n </em>= 125) and the seeds were randomly distributed in a bamboo recruitment patch. The generalist species always moved between habitat patches and removed the seeds to the recruitment patch, dispersing seeds over a longer distance (24.9±20.0 m, mean±SD; <em>n</em>= 95). There was a high concordance between the movement distance of the specialist species and the seedling recruitment distance (<em>χ</em>²= 5.844, <em>P </em>= 0.211), and also a high spatial concordance between the habitat of the generalist species and the seedling recruitment habitat (<em>χ</em>²= 4.582, <em>P </em>= 0.205). Our results highlight that seed dispersal mutualistic relationships can form between Chinese yew and both specialist and generalist bird species. The effectiveness of Chinese yew dispersal was affected not only by the dispersal distances of specialist and generalist bird species, but also by the habitat in which the seeds were deposited.