Landmarks and Semilandmarks - Geometric Morphometrics for Biologists - page 44

FIGURE 2.13 Landmarks and semilandmarks shown on the jaws of four squirrels. (A) Spermophilus beecheyi;
(B) S. lateralis; (C) Ammospermophilus leucurus; (D) Tamias alpinus.
D ESIGNING YOUR OWN MEASUREMENT SCHEM E
None of our examples will provide much guidance if you are trying to find landmarks
on a tadpole, a raptorial appendage of a shrimp, a fiddler crab carapace, trilobite cephalon,
a flower, a tooth or an insect wing, or any of the great variety of other systems.
Fortunately, there are numerous excellent examples of landmark-based studies of these
and other systems in the recent literature. In fact, there are far too many to provide a com-
prehensive list of good examples, so we mention a few recent studies. Morphometric stud-
ies of tadpoles are difficult in light of their sparse landmarks, but thoughtful analyses
have been done that look at the relationship between body form and spring speed
( Arendt, 2010 ) and a seven-year investigation into the associations between year-to-year
changes in shape and pond environments ( Van Buskirk, 2009 ). A landmark-based analysis
of functional modularity in the power-amplification system of mantis shrimp raptorial
appendages tested the hypothesis that each component of that functional system constitu-
tes a developmental module ( Claverie et al., 2011 ). The spatial structure of geographic var-
iation of fiddler crab carapace shape was examined to test whether geographically
widespread species exhibit more intraspecific variation and morphological divergence
( Hopkins and Thurman, 2010 ). Several studies have used landmark-based morphometrics
to examine the trilobite cephalon, including its ontogeny ( Kim et al., 2002; Webster, 2007,
2009 ) and variation along an environmental gradient ( Webber and Hunda, 2007 ). Tooth
shape has been analyzed two-dimensionally in several studies ( Caumul and Polly, 2005;
Wood et al., 2007; Laffont et al., 2009; Piras et al., 2010 ) and there are now also studies of
three-dimensional tooth shape ( Skinner et al., 2008; Singleton et al., 2011 ). Corolla shape
has been the focus of recent studies exploring its genetic covariance structure in the mono-
carpic herb Erysimum mediohispanicum ( Gomez et al., 2009 ) and the adaptive significance of
its bilateral symmetry in the same species ( Gomez et al., 2006 ). Insect wings have been the