Figure 4: The first two
canonical variates of the canonical variate analysis (CV1 and 2) of
mandible shape variation amongst localities of R. cf. simulator .
Light blue outline represents the average shape; Dark blue outline shows
the variation of shape of mandible from the average shape. Locality
abbreviations are the same as in Fig. 1.
Modularity
The caudal and rostral regions of Rhinolophus simulator skulls
evolved as separate modules (CR = 0.452, Zcr = -2.494P = 0.004). Contrarily the mandible of R. simulator(ascending ramus and alveolar bone) did not show any modularity (CR =
1.106, Zcr = 0.887, P = 0.836). Both skulls (CR =
0.821, Zcr = -1.276, P = 0.092) and mandibles (CR
= 0.859, Zcr = -1.168, P = 0.09) of R. cf.
simulator did not show strong modularity between the partitions
analysed.
Lande’s Model
All regression slopes describing the relationship between Ln (W )
and Ln (B) differed significantly from one (Table 1) and showed
no consistency in the direction of slopes (S4 Fig). All the graphs were
positive except the R. cf. simulator mandibles which showed a
negative trend (S4 Fig). This indicated that none of the tests were
consistent with drift and that the shape and size of skulls and
mandibles of R. simulator and R. cf. simulator may have
evolved predominantly through selection across different populations.
The selective pressure responsible for the variation in skull shapes and
sizes appeared to be stabilising because there was less variation
between localities than within localities for both species. It is
possible that strong stabilising selection was acting onR. cf. simulator mandibles
because these show the strongest and negative deviation from the slope
predicted for drift. The limited sample size did not permit analyses by
exclusion as in Mutumi et al . (Mutumi et al. , 2017). This
means that site specific signals of drift could not be detected by the
current analysis.
Table 1. Results from Lande’s model on the 3D coordinate
landmarks of skulls and mandibles of Rhinolophus simulator andR. cf. simulator from different localities within southern
Africa.