Rising ocean temperatures and extreme temperature events have precipitated declines and local extinctions in many marine species globally, but patterns of loss are often uneven across species ranges for reasons that are poorly understood. Knowledge of the extent of local adaptation and gene flow may explain such patterns and help predict future trajectories under scenarios of climate change. We test the extent to which local differentiation in thermal tolerance is influenced by gene flow and local adaptation using a widely distributed intertidal seaweed (Hormosira banksii) from temperate Australia. Population surveys across ~2,000 km of the species range revealed strong genetic structuring at regional and local scales (global F_ST = 0.243) reflecting extremely limited gene flow, while common garden experiments (14‐day exposures to 15, 18, 21°C) revealed strong site differences in early development and mortality in response to elevated temperature. Embryos from many sites spanning a longitudinal thermal gradient showed suppressed development and increased mortality to elevated water temperatures, but populations originating from warmer and more variable thermal environments tended to be less susceptible to warming. Notably, there was significant local‐scale variation in the thermal responses of embryos within regions which was corroborated by the finding of small‐scale genetic differences. We expect the observed genetic and phenotypic differentiation to lead to uneven responses to warming sea surface temperatures in this important marine foundation species. The study highlights the challenges of predicting species responses to thermal stress and the importance of management strategies that incorporate evolutionary potential for “climate‐proofing” marine ecosystems.

中文翻译：

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局部热适应和有限的基因流动限制了海洋生态系统工程师未来的气候响应。

升高的海洋温度和极端温度事件在全球范围内促使许多海洋物种的衰落和局部灭绝，但由于人们了解的原因，物种分布范围的损失方式往往不均衡。了解局部适应性和基因流动的程度可以解释这种模式，并有助于预测气候变化情景下的未来轨迹。我们使用来自温带澳大利亚的广泛分布的潮间带海藻（Hormosira bankii），测试了基因耐受性和基因适应对热耐受力局部差异的影响程度。在大约2,000 km的物种范围内进行的人口调查显示，区域和地方范围内的遗传结构都很强大（全球F _ST = 0.243）反映了极为有限的基因流，而普通的花园实验（暴露于15、18、21°C的14天）显示，在早期发育和响应温度升高的死亡率方面存在很大的位点差异。来自跨越纵向热梯度的许多地点的胚胎显示出发育受到抑制，并因水温升高而增加了死亡率，但源自温暖和变化多端的热环境的种群倾向于不那么容易变暖。值得注意的是，区域内胚胎的热反应存在显着的局部尺度差异，这一点得到了小规模遗传差异的证实。我们希望观察到的遗传和表型差异会导致在这一重要的海洋基础物种中对变暖的海面温度产生不均匀的响应。