Correlations between codon usage and codon GC content in the Alsophila spinulosa cp genome. Codon usage is represented by total number (A) and RSCU (Relative Synonymous Codon Usage) (B) of each codon; codon GC content is indicated by the number of G+C in given codon. Each point represents one of the 59 degenerate codons. Pearson correlations shown in the figure are all significant at p < 0.001. A, correlation between total number and GC content of each codon; B, correlation between RSCU value and GC content of each codon.