Results
A total of 56 skulls and 50 mandibles of R. simulator and 19
skulls and 14 mandibles of R. cf. simulator were analysed.
Procrustes ANOVA tests did not find significant differences between
sexes in both species (both in size and shape of skulls and mandibles).
For R. simulator skull
size, F 1; 54 = 2.19, p = 0.14; skull
shape, F 65; 3510 = 1.01, p = 0.46;
mandibles size, F 1; 49 = 4.77, p = 0.03;
mandible shape F 38; 1862 = 2.47; p< 0.0001. For R. cf. simulator skull size,F 1; 17 = 1.25, p = 0.28; skull shape,F 65; 1105 = 0.93, p = 0.64; mandible size,F 1; 12 = 3.97,; p = 0.07, mandible shape,F 38; 456 = 0.79, p = 0.81. Sexes were
therefore pooled for all analyses, balancing the number of males and
females for R. simulator mandibles.
There was variation in the shape of skulls across different localities
within each lineage (R. simulator : F 195;
3445 = 2.22; p < 0.001, R. cf. simulator :F 130; 1040 = 2.37; p < 0.001)
but not in size (R. simulator skulls: F 3;
53 = 0.15, p = 0.93; R. cf. simulator skulls:F 2; 16 = 2.57; p = 0.11). The mandibles ofR. cf. simulator differed in shape across localities
(F 76; 418 = 1.52; p < 0.01) but
not size (R. cf. simulator mandibles: F 2;
11 = 1.68; p = 0.23). Those of R. simulator were not
different in both shape (F 114; 1786 = 0.38;p = 0.15) and size (F 3; 47 = 0.17;p = 0.91).
Skulls
For R. simulator , the first two canonical variates of the
canonical variate analysis (CVA) of shape variation amongst the
localities of R. simulator explained a total of 90% of the
variation (Fig. 1). The wireframe graphs (Fig. 1) show that the first
canonical variate (CV1) was associated with changes in the palate,
zygomatic arch, cranium and cochlea structure (66% of the variation).
Skulls from the NZ locality fell at the positive end of CV1 and appeared
to have a wider zygomatic arch, broader cochlea and longer palates
relative to the average. Conversely, skulls from the SE locality fell at
the negative end of CV1 and had a reduced zygomatic arch, a narrower
cochlea and shorter palates relative to the average. Two localities (NE
and SZ) fell within the intermediate zone of the CV prescribed shape
space, implying that it had a shape close to the average. CV2 was mostly
associated with the anterior medial swelling (24% of the variation;
Fig. 1). The SZ locality fell at the positive end of CV2 and had an
outline implying increased volume of the nasal dome relative to the
average. Skulls from two localities (NE and NZ) fell at the negative end
of CV2 indicating that they had a smaller anterior medial swellings than
the average, and skulls from one locality (SE) were positioned
intermediately along CV2 indicating that it had an anterior medial
swelling close to the average. CV3 (S2 Fig) explained 10% of the
variation and was associated with changes in the zygomatic arch and
palate. Skulls from NZ and SE were on the negative end of CV3 suggesting
that they had broader zygomatic arches, and longer palates relative to
the average shape and the position of SZ and NE along CV3 indicated that
these skulls had narrower zygomatic arches and shorter palates relative
to the average shape (S2 Fig).