碎米蕨类（cheilanthoid ferns）隶属广义凤尾蕨科的碎米蕨亚科，是一群特殊的旱生或半旱生类群。中国有60种左右，并集中分布于横断山脉。由于形态上的趋同进化，使得碎米蕨类植物的系统分类，特别是类群间的界定十分困难。对国产碎米蕨类植物的处理，这一问题显得尤为突出。本项目在已有形态学、孢粉学和分类学研究的基础上，选择叶绿体基因组的5个DNA区段序列（rbcL, trnL-F, rps4, rps4-trnS, atpA）和1个核基因内转录间隔区ITS序列为分子标记，构建国产碎米蕨类植物的系统发育关系。结合细胞学等方面的研究，分析该类群的形态性状演化，探讨它们的起源时间、祖先分布区和地理散布式样。本项目旨在解决国产碎米蕨类之间的系统关系和类群界定等问题。这将为进一步完善碎米蕨亚科的系统分类和生物地理学研究提供重要的科学依据，同时，对揭示旱生蕨类的适应进化亦大有裨益。

Cheilanthoid ferns, which constitute the subfamily Cheilanthoideae of Pteridaceae, are a special group which is adapted to xeric or semixeric environments. There are about 60 species of cheilanthoid ferns in China, and they are mainly distributed in Hengduan Mountain. Convergent evolution driven by adaptation to arid habitats has made it becoming one of the most contentious fern groups with respect to their phylogeny and generic circumscription. This problem appears conspicuous particularly for Chinese group. In this project, basing on previous study of morphology, palynology, and taxonomy, we will use DNA sequences derived from five chloroplast regions (rbcL, trnL-F, rps4, rps4-trnS, atpA) and one nuclear genes internal transcribed spacer (ITS) as molecular markers, to examine the phylogenetic relationships of Chinese cheilanthoid ferns. Combining with cytology and other aspects of the research, we will analyze the evolution of morphological traits in this fern group, explore their origin time, original location, and distribution pattern. This project aims to solve the phylogeny and generic circumscription of Chinese cheilanthoid ferns. It will provide important scientific basis for the phylogeny and biogeography studies on subfamily Cheilanthoideae. At the same time, the research is also helpful to our comprehension of their adaptive evolution.