Morphological analysis
To confirm the molecular results (i.e., the presence of two distinct
lineages detected from the molecular analysis), we examined shell
morphometrics of M. virgata populations. A total of 15 shell
characters (supplementary Fig. 1) were measured from 50 randomly
selected individuals from each lineage (100 individuals in total).
Measured shell characters were log-transformed, and principal components
analysis (PCA) was performed in R-studio to assess morphological
differences between the two lineages.