Biology Reference
In-Depth Information
FIGURE 7.3
PCs 1
6(A
F) for the mandibular dentition, in occlusal and frontal view.
patients being fitted for occlusal mouth guards in private dental practices in the USA, it is
probably biased toward individuals with relatively high levels of dental care.
Using PLS to Examine Morphological Integration and Modularity
One of the most promising applications of PLS is in studies of morphological integra-
tion and modularity (subjects covered in more depth in Chapter 12). Numerous studies,
especially of primates, use PLS for that purpose (e.g.
Bookstein et al., 2003; Bastir and
Rosas, 2004, 2005, 2006; Bastir et al., 2005, 2007, 2008; Mitteroecker and Bookstein, 2007,
2008; Laffont et al., 2009; Gkantidis and Halazonetis, 2011
). Here we focus on the covari-
ance between two parts of the rodent mandible. The rodent mandible has become a
favored model system for studies of morphological integration and modularity, and the
dominant hypothesis is that there are two modules, one comprising the tooth-bearing
region, the other the muscle-bearing region (e.g.
Cheverud et al., 1991; Mezey et al., 2000;
Klingenberg et al., 2003
). This hypothesis is shown in
Figure 7.5
. It may be evident that it
is difficult to define these two regions precisely because the incisor extends well into the
muscle-bearing region and the dominant muscles for biting and chewing, the lateral,
