Data from: Artificial selection on allometry: change in elevation but not slope

To what extent within-species (static) allometries constitute a constraint on evolution is the subject of a long-standing debate in evolutionary biology. A prerequisite for the constraint hypothesis is that static allometries are hard to change. Several studies have attempted to test this hypothesis with artificial-selection experiments, but their results remain inconclusive due to various methodological issues. Here, we present results from an experiment in which we selected independently on the slope and the elevation of the allometric relation between caudal-fin size and body size in male guppies (Poecilia reticulata). After three episodes of selection, the allometric elevation (i.e. intercept at constant slope) had diverged markedly between the lines selected to increase or decrease it, and showed a realized heritability of 50%. In contrast, the allometric slope remained unaffected by selection. These results suggest that the allometric elevation is more evolvable than the allometric slope, this latter representing a potential constraint on adaptive trait evolution. To our knowledge, this study is the first artificial-selection experiment that directly tests the evolvability of static allometric slopes.种内静态异速生长关系 (allometry) 对演化构成约束的程度，是进化生物学领域长期存在的学术争论议题。进化约束假说的核心前提是，静态异速生长关系难以发生改变。此前已有多项研究尝试通过人工选择实验验证该假说，但受各类方法学问题的限制，相关研究结果始终未能达成共识。 本研究报道了一项人工选择实验的结果：我们针对雄性孔雀鱼 (Poecilia reticulata) 尾鳍大小与体大小之间的异速生长关系的斜率和截距分别开展独立选择。经过三轮选择后，以提升或降低截距为目标的选择品系间，异速生长截距 (即固定斜率下的截距) 出现了显著分化，其现实遗传力达50%。与之形成鲜明对比的是，异速生长斜率未受选择的任何影响。 上述结果表明，异速生长截距的演化潜力高于斜率，而后者正是适应性性状演化的潜在约束因素。据我们所知，本研究是首个直接检验静态异速生长斜率可演化性的人工选择实验。