Ecological and behavioural drivers of offspring size in marine teleost fishes

Aim: Our aim was to evaluate the role of ecological and
life-history factors in shaping global variation in offspring size in a
marine clade with a diverse range of parental care behaviours.
Location: Global. Time period: Data sourced from
literature published from 1953 until 2019. Major taxa
studied: Marine teleost fishes. Methods: We compiled a
species-level dataset of egg and hatchling size for 1,639 species of
marine fish across 45 orders. We used Bayesian phylogenetic mixed models
to evaluate the relationship between offspring size and environmental
factors (i.e., mean temperature, chlorophyll-a and dissolved oxygen
content together with their annual variation), as well as latitude,
reproductive strategy, parental body size and fecundity. We also tested
long-standing hypotheses about the co-evolution of offspring size and the
presence of parental care in BayesTraits. Results: After
controlling for parental body size and phylogenetic history, we find that
increased egg size is associated with colder and oxygen-rich waters, while
hatch size further depends on food supply and the reproductive strategy
exhibited by the species. Irrespective of the initial investment in egg
size, species with parental care or demersal egg development yield larger
hatchlings compared to pelagic spawners. We also demonstrate that hatch
size has co-evolved with advanced forms of care in association with
parental body but fail to find a relationship with other types of care.
Main conclusions: Our study shows that parental care behaviours,
together with environmental context, influence the evolution of classic
life-history trade-offs on a global scale. While the initial investment in
eggs is driven primarily by temperature and oxygen content,
hatchling size also reflects the impact of care an offspring has received
throughout development. In support of the ‘offspring-first’ hypothesis, we
find that an increase in hatch size drives the evolution of advanced care
provision.

研究目的：本研究旨在评估生态与生活史因子对具有多样化双亲抚育行为的海洋演化支中子代体型的全球变异格局的塑造作用。
研究范围：全球。
时间跨度：数据来源于1953年至2019年发表的文献。
研究类群：海洋硬骨鱼类。
方法：我们整理了涵盖45个目、1639种海洋鱼类的卵与初孵幼体体型的物种水平数据集。采用贝叶斯系统发育混合模型（Bayesian phylogenetic mixed models），分析子代体型与环境因子（即年均温、叶绿素a浓度、溶解氧含量及其年际波动）、纬度、繁殖策略、双亲体型以及繁殖力之间的关联。同时借助BayesTraits软件，检验关于子代体型与双亲抚育行为共演化的经典假说。
结果：在控制双亲体型与系统发育历史的影响后，我们发现卵体积增大与低温、高溶解氧水域显著相关；而初孵幼体体型则进一步受食物供给与物种繁殖策略的调控。无论卵阶段的初始资源投入大小如何，具备双亲抚育行为或沉性卵发育（demersal egg development）的物种，其初孵幼体体型均大于浮性卵产卵物种（pelagic spawners）。此外，我们证实初孵幼体体型与伴随双亲体型演化的高级抚育形式存在共演化关系，但未发现其与其他类型抚育行为存在关联。
主要结论：本研究表明，双亲抚育行为与环境背景共同调控了全球尺度下经典生活史权衡（life-history trade-offs）的演化进程。尽管卵阶段的初始资源投入主要受温度与溶解氧含量驱动，但初孵幼体体型同时也反映了子代在整个发育阶段所获得的抚育的影响。本研究结果支持“子代优先”假说（offspring-first hypothesis）：我们发现初孵幼体体型的增大可推动高级抚育投入的演化。