啄花鸟胃肠道对食性、季节和系统发育信号的形态响应及其生态意义

The flowerpecker, a carrier of the seeds of parasitic plants in family Loranthaceae, is a group of tropical birds and has one genus and six species in China. Different from the other birds, the flowerpecker has a distinctive structure of gastrointestinal tracts, which ensures that the seeds could still germinate after passing through the digestive tube. This study describes the anatomical, light microscopic and ultrastructural characterization of the gastrointestinal tracts in flowerpeckers. With the analyses of different seasonal food habits, the study reveals response mechanism of flowerpeckers’ gastrointestinal tracts to the changes of intaking food and tests the occurrence of convergent evolution of their morphology. After the phylogenetic relationshipsamong 6 species of flowerpeckers were assessed by Cyt b gene sequence, this study uses the phylogenetic independent contrasts to clarify the phylogeny signals in the morphological variable of the gastrointestinal tracts. Based on the researches mentioned above, the study states the feasibility of predicting the components and.dynamic changes of flowerpeckers’ food habits by morphological data of gastrointestinal tracts and validates the applicability of ecological morphology theories like “Niche Variation Hypothesis”, “Resource Seasonality Hypothesis” and “Optimal Digestion Theory” in the gastrointestinal tract of the birds. The study provides scientific foundations for the classification and breeding of flowerpeckers, and co-evolution of the flowerpeckers and the parasitic plants in family Loranthaceae, and also offers referential materials on adaptive radiation and the population ecology of birds.

啄花鸟属于热带鸟类，是桑寄生科植物种子的传播媒介，我国分布有1属6种。啄花鸟的胃肠道具有不同于其他鸟类的独特结构，可以保证种子在通过之后仍具活力。本课题拟采用形态学方法揭示啄花鸟胃肠道适应其食性的功能形态结构特征，并结合其食性的季节性变化，阐明啄花鸟胃肠道对摄入食物变化的形态响应机制，同时检验其形态是否发生趋同进化；再利用Cyt b基因对啄花鸟作系统发育重建，明确啄花鸟种间的系统发生关系，并通过系统发育独立比较，厘清其胃肠道形态结构参数之间的系统发育信号。在以上研究的基础上，本课题将探讨利用啄花鸟胃肠道的形态数据预测其食性的组成及动态变化的可行性，并验证“最佳的消化理论”、“资源的季节性假说”和“生态位变异假说”等生态形态学理论在啄花鸟胃肠道中的适用性。本研究既可为啄花鸟的分类、饲养繁殖以及与桑寄生科植物的协同进化提供重要的科学依据，也可为鸟类的适应辐射及种群生态学研究提供参考资料。

啄花鸟具有独特的胃肠道结构，是桑寄生植物的传播媒介。该课题通过大体解剖学、显微组织学和电镜技术剖析了啄花鸟适应其以桑寄生植物果实为主的食性的功能形态结构特征，包括舌前端呈卷筒状，食管腺体少，腺胃小，肌胃角质层薄，肠道绒毛稀疏，组织化学特征相似；通过胃检法进行食性分析，发现啄花鸟夏季和秋季都主要以扁担杆等浆果为主食，辅以少量动物性食物；比较分析表明啄花鸟胃肠道形态结构的季节变化不明显，肌胃体积变化小，因此肌胃体积及小肠长度等胃肠道形态数据不适用于相应的生态形态学理论，也不能用于预测其食性组成的变化；本课题还通过高通量测序分析了啄花鸟线粒体基因组的结构特征，分析表明其肠道性状为趋同性状，不受系统发育关系影响，即不具有系统发育信号；肠道菌群组成分析表明其肠道主要以厚壁菌门、变形菌门为主，多样性小；还利用组织化学和凝集素组织化学分析了包括啄花鸟在内的雀形目十种鸟类消化道糖结合物的性质及分布区域，发现不同食性雀形目鸟类消化道糖结合物的性质和分布区域具有共同性，黏膜分布一层以羧酸性糖结合物为主的黏蛋白，差别主要是在凝集素组织化学性质上，证明其消化道黏蛋白受食性的影响小。这些研究表明啄花鸟胃肠道高度适应传播种子的功能。上述研究结果可为啄花鸟的生理生态学研究及饲养繁殖提供重要的科学数据，也可为食果鸟与植物的协同进化研究提供基础资料。