Nucleotide mutation matrix

This matrix provides the mutation state for each snake species (NA for missing data), but here the two different resistance mutations (A to G vs. A to C) at codon 120 are considered separately. Specifically, resistance mutations are encoded with 1 or 2 (2 only applies to codon 120), and the non-resistant mutation with 0. The two data columns give the two mutations in order本矩阵给出了各蛇类物种的突变状态（NA代表缺失数据），本次分析将120号密码子（codon）位点处的两类抗性突变——即A→G型与A→C型——分开单独统计。具体规则为：抗性突变以1或2进行编码（其中2仅适用于120号密码子位点），非抗性突变以0编码。数据的两列将依次对应这两种突变。