Evolution of static allometry and constraint on evolutionary allometry in a fossil stickleback.
Evolution of static allometry and constraint on evolutionary allometry in a fossil stickleback.
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DOI：
10.1111/jeb.13984
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发表时间：
2022-03
影响因子：
2.1
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异速生长标度描述了性状大小与个体大小之间的关系。性状大小对体型大小的种群水平回归的斜率（即静态异速生长）在密切相关的种群和物种中通常是不变的。这种不变性通常被解释为反映了发育和选择限制的组合，这些限制限定了进化最容易进行的表型空间。因此，了解异速生长关系最终如何演变，对了解表型多样化是很重要的。在化石Threespine Stickleback（Gasterosteus doryssus）的一个谱系中，我们研究了9个性状（5个盔甲和4个非盔甲）的静态异速生长斜率的可进化性，这些性状在8500年的时间里在10个样本中进化出显著的性状差异。装甲性状表现出较弱的静态异速生长关系和这些斜坡之间的不匹配和观察到的演变。这表明，观察到的这些特征的进化并不受身体大小的关系，也许是因为以前，反复适应淡水栖息地的Threespine Stickleback产生了强大的选择，打破约束。相比之下，对于非装甲性状，我们发现了更强的异速生长关系。这些异速生长斜率确实是在短时间尺度上演化的。然而，这些变化是小的和波动的斜率仍然很强的预测性状的进化轨迹的手段随着时间的推移（即进化异速生长），支持异速生长作为约束的假设。弱甲三棘棘鱼（Gasterosteus doryssus）的表型，有两个背棘和一个退化的骨盆（上图），以及一个强甲三棘鱼（Gasterosteus doryssus）。背棘有三个背棘，一个完整的骨盆，和两个骨盆棘（下图;第一背棘通过压痕显示）。
Allometric scaling describes the relationship of trait size to body size within and among taxa. The slope of the population‐level regression of trait size against body size (i.e. static allometry) is typically invariant among closely related populations and species. Such invariance is commonly interpreted to reflect a combination of developmental and selective constraints that delimit a phenotypic space into which evolution could proceed most easily. Thus, understanding how allometric relationships do eventually evolve is important to understanding phenotypic diversification. In a lineage of fossil Threespine Stickleback (Gasterosteus doryssus), we investigated the evolvability of static allometric slopes for nine traits (five armour and four non‐armour) that evolved significant trait differences across 10 samples over 8500 years. The armour traits showed weak static allometric relationships and a mismatch between those slopes and observed evolution. This suggests that observed evolution in these traits was not constrained by relationships with body size, perhaps because prior, repeated adaptation to freshwater habitats by Threespine Stickleback had generated strong selection to break constraint. In contrast, for non‐armour traits, we found stronger allometric relationships. Those allometric slopes did evolve on short time scales. However, those changes were small and fluctuating and the slopes remained strong predictors of the evolutionary trajectory of trait means over time (i.e. evolutionary allometry), supporting the hypothesis of allometry as constraint. Phenotypes of a weakly armored Threespine Stickleback, Gasterosteus doryssus, with two dorsal spines and a vestigial pelvis (above) and a strongly armored G. doryssus with three dorsal spines, a full pelvis, and two pelvic spines (below; first dorsal spine is indicated by an impression).