中国-喜马拉雅地区特有属香竹属的物种划分研究

Chimonocalamus (Bambusoideae) is a genus endemic to the Sino-Himalayan region, with Yunnan as the distribution center. Most species of this genus are distributed narrowly and should be protected. Those species are also economically and ecologically important. The previous studies indicated that Chimonocalamus was monophyletic with a complex evolutionary history, while genetic divergence as well as morphological differentiation was little, and species boundaries were ambiguous. The recent diversification of this genus may be responsible for the ambiguous species boundaries, however, the unreasonable species delimitation is probably another reason. In this project, the species delimitation of Chimonocalamus will be examined by integrative methods. Based on observation and measurement of key diagnostic characters, the morphological differentiation will be assessed between inter- and intra- species. The whole plastid genomes and nuclear ribosomal DNA regions will be retrieved through genome skimming method, and about 50-60 low copy nuclear genes will be amplified by PCR and be sequenced by Illumina MiSeq. The species delimitation and phylogeny of the genus Chimonocalamus will be analyzed and reconstructed. The niche divergence between various species will be examined and the potential distribution area will also be predicted using Maxent, based on field collection information, herbarium records, and downloaded climate data. Through the comprehensive studies from morphology, phylogenomics, and ecological niche modelling, we expect to make a relatively reasonable and practicle species delimitation system for Chimonocalamus and that these methods can be applied to other bamboos.

竹亚科香竹属是中国-喜马拉雅地区的一个特有属，以云南为分布中心，该属大多数种分布区域狭窄，具有重要的保护价值，同时还具有经济价值和生态价值。前期研究表明香竹属为单系，具有复杂的进化历史，种间遗传差异和形态差异均较小，种间界限模糊。一方面与该属为近期分化有关，另一方面可能与物种划分是否合理有关。为了进一步检验香竹属物种划分的合理性，本项目拟按照居群方法采样，观察相关形态特征，分析种间和种内形态变异；利用基因组浅层测序方法获取叶绿体基因组和核核糖体序列，同时利用二代测序技术获得50-60个低拷贝核基因片段，推测物种划分的合理性；基于野外采集和标本信息，利用软件检验种间生态位是否有分化，预测潜在分布区，为该属的保护和利用提供一定依据。通过上述研究，期望澄清香竹属的物种划分问题、分类学问题和种间关系，为竹亚科其他类群的物种划分研究提供新的思路和方法，为生物多样性保护提供更可靠的基础数据。

本项目按照居群方法采样，通过11次野外考察，共获得分布于云南、缅甸、泰国和越南的香竹属标本和实验材料230号。查阅香竹属标本115号，包括模式标本18号。选取35个形态性状，对香竹复合群和流苏香竹复合群分别开展主成分分析，结果表明上述两个复合群内部形态差异较小，形态特征不能有效区分复合群的不同物种。基于叶绿体基因组和核基因SNPs构建的系统发育树存在冲突，可能是由于杂交、渐渗和/或不完全谱系分选造成的。首次确认越香竹、巴维香竹和具耳香竹在系统树中的位置；流苏香竹复合群形成一个分支，内部关系复杂，建议合并为一个种；香竹复合群叶绿体基因组来源复杂，但核基因支持它们为单系。叶绿体基因组作为超级条形码在香竹属中具有较好的物种鉴定能力，不仅能够鉴定已有物种，如马关香竹、巴维香竹、具耳香竹、长节香竹和小香竹，对新物种的确认也有很大辅助作用。基于核基因SNPs构建的系统发育树，能够更好地解决物种之间的关系，对香竹属物种划分也具有辅助作用。基于最大熵模型对流苏香竹潜在分布区的预测表明，流苏香竹对气候变化较为敏感，其潜在分布区成斑块状分布，并且有减少的趋势，影响其分布的主要气候因子包括最湿月份降水量、最暖月份最高温度、最干季度降水量和平均气温日较差。

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