U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, 970 S. Lusk Street Boise, ID 83706, USA.
Department of Forestry and Environmental Resources, North Carolina State University, Research Triangle Park, NC 27695, USA.
Syst Biol. 2018 Nov 1;67(6):965-978. doi: 10.1093/sysbio/syy017.
Unique responses to climate change can occur across intraspecific levels, resulting in individualistic adaptation or movement patterns among populations within a given species. Thus, the need to model potential responses among genetically distinct populations within a species is increasingly recognized. However, predictive models of future distributions are regularly fit at the species level, often because intraspecific variation is unknown or is identified only within limited sample locations. In this study, we considered the role of intraspecific variation to shape the geographic distribution of ponderosa pine (Pinus ponderosa), an ecologically and economically important tree species in North America. Morphological and genetic variation across the distribution of ponderosa pine suggest the need to model intraspecific populations: the two varieties (var. ponderosa and var. scopulorum) and several haplotype groups within each variety have been shown to occupy unique climatic niches, suggesting populations have distinct evolutionary lineages adapted to different environmental conditions. We utilized a recently available, geographically widespread dataset of intraspecific variation (haplotypes) for ponderosa pine and a recently devised lineage distance modeling approach to derive additional, likely intraspecific occurrence locations. We confirmed the relative uniqueness of each haplotype-climate relationship using a niche-overlap analysis, and developed ecological niche models (ENMs) to project the distribution for two varieties and eight haplotypes under future climate forecasts. Future projections of haplotype niche distributions generally revealed greater potential range loss than predicted for the varieties. This difference may reflect intraspecific responses of distinct evolutionary lineages. However, directional trends are generally consistent across intraspecific levels, and include a loss of distributional area and an upward shift in elevation. Our results demonstrate the utility in modeling intraspecific response to changing climate and they inform management and conservation strategies, by identifying haplotypes and geographic areas that may be most at risk, or most secure, under projected climate change.
种内水平上可能会出现独特的气候变化响应，从而导致特定物种内的种群出现个体适应性或迁徙模式。因此，人们越来越认识到需要对物种内遗传上不同的种群进行潜在响应建模。然而，未来分布的预测模型通常是在物种层面上进行拟合的，这往往是因为种内变异未知，或者仅在有限的样本地点确定。在这项研究中，我们考虑了种内变异在塑造美国西南部黄松（Pinus ponderosa）地理分布中的作用。黄松的形态和遗传变异表明需要对种内种群进行建模：已经证明这两个变种（var. ponderosa 和 var. scopulorum）以及每个变种中的几个单倍型组占据独特的气候小生境，表明种群具有不同的进化谱系，适应不同的环境条件。我们利用了最近获得的、地理分布广泛的黄松种内变异（单倍型）数据集和最近设计的谱系距离建模方法，得出了更多可能的种内发生地点。我们使用生态位重叠分析确认了每个单倍型-气候关系的相对独特性，并开发了生态位模型（ENMs），以预测未来气候预测下两个变种和八个单倍型的分布。单倍型生态位分布的未来预测通常显示出比变种更大的潜在范围损失。这种差异可能反映了不同进化谱系的种内响应。然而，种内水平上的总体趋势是一致的，包括分布面积的减少和海拔的上升。我们的研究结果表明，对不断变化的气候进行种内响应建模具有实用性，通过确定可能受到预测气候变化影响最大或最安全的单倍型和地理区域，为管理和保护策略提供信息。
