Faster isn't always better: selection on growth rate fluctuates across the life history and environments

Growth rate is increasingly recognised as a key life-history trait that may affect fitness directly, rather than evolving as a by-product of selection on size or age. An ongoing challenge is to explain the abundant levels of phenotypic and genetic variation in growth rates often seen in natural populations, despite what is expected to be consistently strong selection on this trait. Such a paradox suggests limits to how contemporary growth rates evolve. We explored limits arising from variation in selection, based on selection differentials for age-specific growth rates expressed under different ecological conditions. We present results from a field experiment that measured growth rates and reproductive output in wild individuals of a colonial marine invertebrate (Hippopodina iririkiensis), replicated within and across the natural range of succession in its local community. Colony growth rates varied phenotypically throughout this range, but not all such variation was available for selec...

生长速率日益被视作关键的生活史性状，可直接影响个体适合度，而非作为针对体型或年龄的选择所产生的副产物演化而来。当前一项长期存在的研究挑战，是解释自然种群中普遍观测到的大量生长速率表型与遗传变异——尽管理论上该性状应承受持续强烈的选择压力。这一悖论暗示了当代生长速率的演化存在局限。我们基于不同生态条件下表达的年龄特异性生长速率的选择差，探究了由选择变异所带来的演化局限。本研究呈现了一项野外实验的结果：该实验测量了群居海洋无脊椎动物（Hippopodina iririkiensis）野生个体的生长速率与繁殖输出，并在其本地群落的自然演替序列内，于该序列内部及跨序列开展了重复实验。在该演替范围内，群体生长速率均存在表型变异，但并非所有此类变异均可用于选择...