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.

生物体通过演化获得耐受新型热环境的生理策略，从而得以开拓全新生存生境。正因如此，热耐受性（thermal tolerance）是决定生物多样性全球分布格局的关键因素，然而学界对其演化所受的约束机制仍知之甚少。本研究聚焦新西兰特有辐射演化竹节虫类群（该类群包含3种山地栖息物种）的耐寒性平行演化机制。研究基于274个直系同源基因（orthologous genes）构建系统发育树，结果显示竹节虫类群至少曾两次独立定居山地生境。本研究对8个属的10个物种开展过冷却点（supercooling point）与体内冰晶形成存活率的对比分析，在不同的山地支系中分别鉴定出耐冻性（freeze tolerance）与避冻性（freeze avoidance）两种耐寒策略。研究还在一个地理分布广泛的物种的低地与山地种群中，验证了耐冻性策略的存在。对冷激（cold shock）处理后的样本进行转录组测序（transcriptome sequencing）后，本研究鉴定出一组结构角质层基因，这类基因在各物种中均存在差异表达调控与正向序列选择（positive sequence selection）现象。不过，尽管系统发育分析显示角质层蛋白整体与冷激响应存在关联，但具体发挥作用的基因在不同物种间存在差异。由此可见，尽管角质层结构相关的生理过程始终与耐寒适应性相关，但这一现象并非源于共同祖先所遗留的遗传约束。