Fig 1.
Collection sites along the Northeast Atlantic and Mediterranean Sea.
Specimens identified as Glycymeris glycymeris (black fill) and Glycymeris pilosa (white fill) came from: (1) Isle of Man (UK), (2) Bay of Brest (France), (3) Pag Bay (Croatia), (4) Pašman Channel (Croatia).
Fig 2.
Classical morphometrics measurements.
Height of shell (measured from umbo)(1), height of anterior extremity (2), height of posterior extremity (3), length of shell (4), anterior length (5), posterior length (18), asymmetry (5/18), height of ligamental area (6), length of ligamental area (7), median height of hinge plate (directly below umbo)(8), height of ligamental area / height of hinge plate (6/8), height of anterior tooth row (15), height of posterior tooth row (16), distance between last anterior and posterior teeth (14), height of anterior adductor scar (9), length of anterior adductor scar (10), area of anterior adductor scar (9*10/2), height of posterior adductor scar (11), length of posterior adductor scar (12), area of posterior adductor scar (11*12/2), distance between inner margins of adductor scars (13), adductor moment = sum of adductor scar areas*mean distance from hinge axis, height of crenulated extra-pallial margin (17) and the width (W). Measurements taken for each morphometric character adopted from Thomas (1975) with permission from the Palaeontological Association. Right valve of a Glycymerid.
Fig 3.
Geometric morphometrics landmarks.
This image represents a right valve of Glycymeris glycymeris with the position of 12 landmarks (open dots) and 3 semi-landmarks (fill dots).
Fig 4.
Biplot of the mean scores on the first two principal components based on 10 morphological character ratios.
Symbols were assigned to each population: Glycymeris glycymeris (black inverted triangle, UK; grey inverted triangle, France) and Glycymeris pilosa (black circle, Pag; grey circle, Pašman).
Table 1.
LDA Confusion matrix on the four populations of Glycymeris.
Fig 5.
Detail of the microsculpture and rib count measurements of Glycymeris pilosa and Glycymeris glycymeris.
The white line is used as a scale of 5mm. Measured populations correspond to (a) Pašman, (b) Pag, (c) UK and (d) Brest.
Table 2.
Secondary rib counts counted on the microsculpture in all four Glycymeris populations.
Fig 6.
Plot of the principal components (PCs) based on Procrustes distances (a). Shape changes associated with the PCs are shown as extreme shell shapes representing the positive and negative end of each axis. Percentages of explained variance for each axis are in parentheses. Plot of the canonical variate analysis (CVs) of overall shell shape variation along the first 2 canonical axes (b). Wrapped outline drawings show shape changes associated with variation along first axis. Glycymeris glycymeris (black inverted triangle, UK; grey inverted triangle, France) and Glycymeris pilosa (black circle, Pag; grey circle, Pašman). Percentages of explained variance for each axis are in parentheses.
Fig 7.
Left and right valves of Glycymeris pilosa from Pašman (a) and Pag (b) and Glycymeris glycymeris from UK (c) and Brest (d) populations. Scale bar 2 cm.
Fig 8.
Bayesian posterior probabilities and bootstrap support for MrBayes and Maximum Likelihood analyses.
Illustration of tree topology based on COI haplotypes of G. glycymeris (Gg), G. pilosa (Gp), G. nummaria (Gn), G. bimaculata (Gb) and outgroups. Posterior probabilities followed by bootstrap values are included at the nodes. The origin of the haplotypes (H) is indicated as follow: UK, United Kingdom; FR, France; AD, Adriatic Sea; AT, Atlantic Sea; PA, Pag; PS, Pašman.