Data from: Directional selection effects on patterns of phenotypic (co)variation in wild populations

Phenotypic (co)variation is a prerequisite for evolutionary change, and understanding how (co)variation evolves is of crucial importance to the biological sciences. Theoretical models predict that under directional selection, phenotypic (co)variation should evolve in step with the underlying adaptive landscape, increasing the degree of correlation among co-selected traits as well as the amount of genetic variance in the direction of selection. Whether either of these outcomes occurs in natural populations is an open question and thus an important gap in evolutionary theory. Here, we documented changes in the phenotypic (co)variation structure in two separate natural populations in each of two chipmunk species (Tamias alpinus and T. speciosus) undergoing directional selection. In populations where selection was strongest (those of T. alpinus), we observed changes, at least for one population, in phenotypic (co)variation that matched theoretical expectations, namely an increase of both phenotypic integration and (co)variance in the direction of selection and a re-alignment of the major axis of variation with the selection gradient.

表型（共）变异（phenotypic (co)variation）是进化发生的必要前提，解析（共）变异的演化规律对生物科学领域具有至关重要的意义。理论模型预测，在定向选择作用下，表型（共）变异应随底层适应性景观（adaptive landscape）同步演化，既提高协同选择性状间的相关程度，也增加选择方向上的遗传变异量。上述两种演化结果是否会在自然种群中出现，仍是尚未解决的科学问题，这也构成了进化理论研究中的一处重要空白。
本研究对两种花栗鼠（Tamias alpinus与T. speciosus）各两个正经历定向选择的自然种群的表型（共）变异结构变化进行了观测记录。在选择强度最高的种群（即T. alpinus的种群）中，我们至少在其中一个种群中观测到了符合理论预期的表型（共）变异变化：具体表现为选择方向上的表型整合度与（共）变异量均有所提升，且变异主轴线与选择梯度实现了重新对齐。