Data from: Selection for functional performance in the evolution of cuticle hardening mechanisms in insects

Calcified tissues have repeatedly evolved in many animal lineages and show
a tremendous diversity of forms and functions. The cuticle of many insects
is enriched with elements other than Calcium, a strategy of hardening that
is taxonomically widespread but apparently poorly variable among clades.
Here, we investigate the evolutionary potential of the enrichment with
metals in insect cuticle at different biological levels. We combined
experimental evidence of Zinc content variation in the mandibles of a
target species (Chorthippus cazurroi) with phylogenetic comparative
analyses among grasshopper species. We found that mandibular Zinc content
was repeatable among related individuals and was associated with an
indicator of fitness, so there was potential for adaptive variation. Among
species, Zinc enrichment evolved as a consequence of environmental and
dietary influences on the physical function of the jaw (cutting and
chewing), suggesting a role of natural selection in environmental fit.
However, there were also important within and transgenerational
environmental sources of similarity among individuals. These environmental
influences, along with the tight relationship with biomechanics, may limit
the potential for diversification of this hardening mechanism. This work
provides novel insights into the diversification of biological structures
and the link between evolutionary capacity and intra and interspecific
variation.