Data from: 2D or Not 2D? Testing the utility of 2D vs. 3D landmark data in geometric morphometrics of the sculpin subfamily Oligocottinae (Pisces; Cottoidea)

We contrast 2D vs. 3D landmark‐based geometric morphometrics in the fish
subfamily Oligocottinae by using 3D landmarks from CT‐generated models and
comparing the morphospace of the 3D landmarks to one based on 2D landmarks
from images. The 2D and 3D shape variables capture common patterns across
taxa, such that the pairwise Procrustes distances among taxa correspond
and the trends captured by principal component analysis are similar in the
xy plane. We use the two sets of landmarks to test several
ecomorphological hypotheses from the literature. Both 2D and 3D data
reject the hypothesis that head shape correlates significantly with the
depth at which a species is commonly found. However, in taxa where shape
variation in the z‐axis is high, the 2D shape variables show sufficiently
strong distortion to influence the outcome of the hypothesis tests
regarding the relationship between mouth size and feeding ecology. Only
the 3D data support previous studies which showed that large mouth sizes
correlate positively with high percentages of elusive prey in the diet.
When used to test for morphological divergence, 3D data show no evidence
of divergence, while 2D data show that one clade of oligocottines has
diverged from all others. This clade shows the greatest degree of z‐axis
body depth within Oligocottinae, and we conclude that the inability of the
2D approach to capture this lateral body depth causes the incongruence
between 2D and 3D analyses.