Data from: Parallel molecular routes to cold adaptation in eight genera of New Zealand stick insects

The acquisition of physiological strategies to tolerate novel thermal
conditions allows organisms to exploit new environments. As a result,
thermal tolerance is a key determinant of the global distribution of
biodiversity, yet the constraints on its evolution are not well
understood. Here we investigate parallel evolution of cold tolerance in
New Zealand stick insects, an endemic radiation containing three
montane-occurring species. Using a phylogeny constructed from 274
orthologous genes, we show that stick insects have independently colonized
montane environments at least twice. We compare supercooling point and
survival of internal ice formation among ten species from eight genera,
and identify both freeze tolerance and freeze avoidance in separate
montane lineages. Freeze tolerance is also verified in both lowland and
montane populations of a single, geographically widespread, species.
Transcriptome sequencing following cold shock identifies a set of
structural cuticular genes that are both differentially regulated and
under positive sequence selection in each species. However, while
cuticular proteins in general are associated with cold shock across the
phylogeny, the specific genes at play differ among species. Thus, while
processes related to cuticular structure are consistently associated with
adaptation for cold, this may not be the consequence of shared ancestral
genetic constraints.