Data from: Heritability in the Rhesus macaque (Macaca mulatta) vertebral column

The vertebral column plays a central role in primate locomotion and
positional behavior. Understanding its evolution therefore has the
potential to clarify evolutionary processes that have occurred in the
primate lineage as well as the specific behaviors of extinct primates.
However, in order to understand primate vertebral anatomy, it is important
to determine how much of this anatomy is heritable and how much develops
as a response to environmental factors during life. We estimated
heritability for vertebral counts as well as typical cervical, thoracic,
and lumbar elements from 210 individuals from the pedigreed Cayo Santiago
Macaca mulatta skeletal collection. We found moderate heritability of
vertebral counts (h2 =0.216–0.326), but with strong heritability of the
type of variation (e.g., a tendency to meristic or homeotic change) in the
vertebral count (h2 =0.599), suggesting a possible explanation for high
variability in vertebral numbers among the hominoids in particular. The
moderate heritability of vertebral count also suggests that vertebral
count is an unsuitable metric for estimating the ancestral state for some
taxa. We found strong heritability in the morphology of cervical and upper
lumbar zygapophyseal facets (h2 =0.548–0.550) and the thoracic spinous
processes (h2 =0.609–0.761), including high heritability of the spinous
process angle in the upper thoracic and upper lumbar elements (h2
=0.649–0.752). We suggest these are related to maintaining stability in
the cervical and lumbar regions, and reducing motion in the thoracic
region, respectively. We propose that spinous processes may contain
greater phylogenetic information, whereas transverse processes may contain
greater information of function ‘in life’. We also found important size
effects, suggesting that size is the most heritable component of overall
form and largely responsible for intertrait differences. This suggests
that it is inappropriate to indiscriminately remove size effects from
morphological comparisons.