3.4 Genome-wide genetic diversity
At the individual level for diploids (Figure 5a), the genome-wide observed heterozygosity (H O) values of invasive individuals (mean: 0.00861) was significantly lower than those of native individuals (mean: 0.01062) (paired-sample t -test, p = 2.2e-16). For triploids, H Ovalues of invasive individuals (mean: 0.00922) was comparable to those of the native individuals (mean: 0.00914). Compared with triploids, invasive diploids showed significantly lower observed heterozygosity than the invasive (p = 5.1e-5) and native triploids (p = 2.5e-7), while native diploids had significant higher genetic diversity than the invasive (p = 5.4e-10) and native triploids (p = 3.2e-12).
As population structure inferred three genetic subclusters among diploid native samples, the population genetic diversity was estimated for these subclusters. For diploids, the genome-wide nucleotide diversity (π) value of the invasive population LL was 0.00297, which was slightly higher than those of native subclusters (0.00266 for mid Yangzte River, 0.00279 for lower Yangzte River and Huai River, and 0.00251 for Songhua River) (Figure 5b and Table 3). For triploids, π values of the invasive populations LL and CBL were 0.00286 and 0.00284, respectively, which were also slightly higher than those of source populations (0.00273 for SC and 0.00277 for NX).