Quantitative genetics of phosphorus content in the freshwater herbivore, Daphnia pulicaria,Journal of Animal Ecology

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Quantitative genetics of phosphorus content in the freshwater herbivore, Daphnia pulicaria
Journal of Animal Ecology ( IF 3.5 ) Pub Date : 2021-01-15 , DOI: 10.1111/1365-2656.13419
Ryan E. Sherman ₁ , Rachel Hartnett _{1,

2} , Emily L. Kiehnau ₂ , Lawrence J. Weider ₂ , Punidan D. Jeyasingh ₁

Affiliation

Phosphorus (P) is essential for growth of all organisms, and P content is correlated with growth in most taxa. Although P content was initially considered to be a trait fixed at the species level, there is growing evidence for considerable intraspecific variation. Selection on such variation can thus alter the rates at which P fluxes through food webs. Nevertheless, prior work describing the sources and extent of intraspecific variation in P content were not genetically explicit, confounded by unknown genetic background and evolutionary history. We constructed an F2 recombinant population of the dominant freshwater grazer, Daphnia pulicaria to mitigate such issues. F2 recombinants exhibited considerable variation in growth rate, P content (0.49% to 1.97%), P use efficiency (PUE; 51 to 208 mg biomass/mg P), and correlated traits such as hatching time of resting eggs, in common garden conditions. These results clearly demonstrate the scope of genetic recombination in generating variation in ecologically-relevant traits. The absence of environmental selection is a likely component driving such variation not observed in natural settings. Although phosphoglucose isomerase (PGI) genotype was significantly associated with variation in hatching time of resting eggs, contrary to prior work with less rigorous designs, allelic variation at the PGI locus did not explain variation in P content and PUE of Daphnia, indicating that such quantitative traits are under polygenic control. Together, these results suggest that although there is considerable genetic scope for variation in key ecologically-relevant traits, such as P content and efficiency of P use, these traits are likely under strong stabilizing selection, most likely due to selection on growth rate and size. Importantly, our observations suggest that anthropogenic alterations to P supply due to eutrophication could alter selection on these traits, thereby rapidly altering the role Daphnia plays in the P cycle of lakes.

中文翻译：

淡水草食动物溞中磷含量的数量遗传学

磷 (P) 对于所有生物的生长都是必不可少的，并且 P 含量与大多数分类群的生长相关。尽管 P 含量最初被认为是固定在物种水平上的性状，但越来越多的证据表明种内变异相当大。因此，对这种变化的选择可以改变 P 通过食物网的流量。然而，先前描述 P 含量的种内变异的来源和程度的工作在遗传上并不明确，被未知的遗传背景和进化历史所混淆。我们构建了主要淡水食草动物 Daphnia pulicaria 的 F2 重组种群以缓解此类问题。F2 重组体在生长速率、磷含量（0.49% 至 1.97%）、磷利用效率（PUE；51 至 208 mg 生物量/mg P）、以及相关性状，例如在普通花园条件下静息蛋的孵化时间。这些结果清楚地证明了基因重组在产生生态相关性状变异方面的范围。缺乏环境选择可能是导致这种在自然环境中未观察到的变化的一个因素。尽管磷酸葡萄糖异构酶 (PGI) 基因型与静息卵孵化时间的变化显着相关，但与先前设计不太严格的工作相反，PGI 基因座的等位基因变异并不能解释水蚤 P 含量和 PUE 的变化，表明这种定量性状受多基因控制。总之，这些结果表明，尽管关键生态相关性状（如磷含量和磷利用效率）的变异存在相当大的遗传范围，这些性状很可能在强大的稳定选择下，最有可能是由于对生长速度和大小的选择。重要的是，我们的观察表明，由于富营养化导致磷供应的人为改变可能会改变对这些性状的选择，从而迅速改变水蚤在湖泊磷循环中的作用。

更新日期：2021-01-15

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