Centre for Conservation Biology, Department of Biology, NTNU, Trondheim, Norway.
J Evol Biol. 2012 May;25(5):938-48. doi: 10.1111/j.1420-9101.2012.02487.x. Epub 2012 Mar 9.
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 relationship 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）异速生长在多大程度上构成进化的限制，是进化生物学中长期存在的争论焦点。限制假说的一个前提是静态异速生长很难改变。已有几项研究试图通过人工选择实验来检验这一假说，但由于各种方法学问题，其结果仍不确定。在这里，我们报告了一项实验的结果，在该实验中，我们独立地选择雄性孔雀鱼（Poecilia reticulata）的尾鳍大小与体型之间的异速生长关系的斜率和截距。经过三个选择阶段，斜率增加或减少的选择系之间的异速生长截距明显不同，且表现出 50%的实现遗传力。相比之下，异速生长斜率不受选择影响。这些结果表明，异速生长截距比异速生长斜率更具可进化性，后者代表了对适应性状进化的潜在限制。据我们所知，这项研究是首次直接检验静态异速生长斜率可进化性的人工选择实验。
