2 Results and analysis
2.1 Genome structures and characteristics
The chloroplast genomes of all eight species of Cyatheaceae are double-stranded, closed, circular molecules with a typical tetrad structure (with Alsophila denticulata as an example, as shown in Figure 1). The genome length ranges from 154,046 bp (Alsophila denticulata ) to 166,151 bp (Alsophila gigantea ). The structure includes a large single-copy region (LSC) (bp 85975–92315), a small single-copy region (SSC) (bp 23245–28874), and an inverted repeat region (IR) (bp 23245–28874), of which IRA and IRB are two inverted repeat regions. The GC content of each region of the chloroplast genome of different species varied little, the total GC content ranging from 40.3% to 41.9% (Table 1). Only LSC, SSC, and one IR were analyzed. The chloroplast genome of each species of Cyatheaceae contained 117 genes, which encoded 85 proteins, four rRNAs, and 28 tRNAs. Pseudogenes (ycf66, trnT-UGU ) were also present in these genomes. Among these genes are 13 genes located in the IR region. The ndhB gene spans the LSC and IRA regions, and there is a duplicated exon 2 sequence of the ndhB gene near the boundary of the IRB. Twelve genes have one intron, and three genes (ycf3 , clpP , and rps12 ) have two introns.