THE UNIVERSITY OF CALGARY Eric Snively A ... - Ohio University

measurements of width pV2S%TU-DE and WDIST) contribute less to variance
among the specimens. Two considerations indicate that variation in distal width
tracks Iinear size, and varies less relative to overall size than measures of
proximal width. First, loadings are positive for these measurements in PC 2.
Second, and more importantly, PCI accbunts for a higher percentage of variation
in distal width measurements than in proximal measures, and PC2 for a lower
percentage (Table 2.4b). PC1 describes size variance and PC2 primarily
indicates shape variation, so a higher percentage contribution by PCl indicates
that size discrepancy is more important than shape for variance in a given
measurement.
Component correlations (Table 2.4~) provide congruent evidence for these
trends in width variance. As with loadings, correlations for proximal width
measurements are negative for PC2, but correlations are positive for distal width.
This confinns the unique contribution of proximal width to shape variation. Also,
correlations between proximal width variables and their loadings have higher
absolute values for PC2 (correlations of WPROX =-0.248, W75%TU-DE=-û.418,
and W50%TU-DE=-0.305, versus correlations of 0.201 and 0.179 for W25%TU-
DE and WDIST). This indicates that, in addition to being negatively corretated
with size, proximal width contributes strongly to overall variation along PC2.
Interestingly, Table 2.4a reveals that HGINGL has a high positive loading on
PC2 (0.461), and PC2 is an important element of the variance for the measure
(accounting for 16.9% of variance: Table 2.4b). Differing signs for HGINGL and
proximal width loadings may indicate that the height of the ginglyrnus correlates