ML phylogenetic tree of P. litoralis based on the mitochondrial COI gene (658 bp) with Pontodrilus longissimus as the outgroup. Only bootstrap values >70% are indicated at each node. Scale bar represents the number of nucleotide substitutions per site. The sample names correspond to those in Table 5. Photograph on the top left shows comparative size of the shortest and the longest samples in this molecular study. The longest population (JP2) is shown in red and the shortest population (VT2) is shown in blue.