3.4. Population genetic structure
No statistically significant FST values were observed in all pairwise comparisons for COI gene (P > 0.05) (Table 5). Pairwise
FST values were negative, so no genetic divergence was detected among populations. Nm values were all infinite, indicating
very huge gene flow among these localities. The same pattern was found in 16S gene data (Table 6). Pairwise values of FST
ranged from 0.01409 to 0.10289, and Nm ranged from 4.35970 to infinite. No genetic divergence was found statistically
significant among populations (P > 0.05).
The AMOVA test of P. viridis based on haplotype frequencies revealed that the genetic variation occurred within populations
was 2.03% for the COI gene and 4.23% for the 16S rRNA gene, and among populations was 102.3% for the COI gene
and 95.77% for the 16S rRNA gene (Table 7). The test for overall population genetic structuring within and among populations
was not statistically significant (P > 0.05).
Phylogenetic relationship of P. viridis haplotypes was determined using COI and 16S rRNA gene sequences of Perna perna
(AB265682.1) and Perna canaliculus (AB265681.1) as out-group taxa (Fig. 3). Two UPGMA trees showed that no genealogical
branches or clusters corresponded to the sampling sites. In the COI tree, P. viridis was clustered with P. canaliculus and
separated from P. perna, while in the 16S rRNA tree, P. canaliculus and P. perna were grouped together and separated from P.
viridis.
4. Discussion
Results from COI gene sequence data showed high levels of haplotype diversity and low levels of nucleotide diversity
(h ¼ 0.737e0.816; p ¼ 0.00392e0.00457). In the 16S rRNA gene data, a lower level of genetic variation was detected
(h ¼ 0.312e0.372; p ¼ 0.00111e0.00137), which may be due to short sequences and a small number of haplotypes.
Genetic methods are frequently used to assess population connectivity which is defined as the degree of gene flow
affecting evolutionary processes (Lowe and Allendorf, 2010). Researchers often use FST to infer gene flow; lower values of FST
indicate low genetic divergence. FST values below 0.05 indicate negligible genetic divergence (Kalinowski, 2002). When FST