Species inhabiting warm-edge populations of their distribution are suggested to be at the forefront of global warming due to reduced fitness, limited gene flow and living close to their physiological thermal limits. Determining the scale that governs thermal niche and the functional responses of habitat-forming species to environmental stressors is critical for successful conservation efforts, particularly as coastal ecosystems are impacted by global change. Here, we examine the susceptibility of warm-edge populations to warming, in the habitat-forming macroalga, Hormosira banksii, from south-eastern Australia. We use a quantitative breeding design to quantify intraspecific variation in thermal performance (growth, ontogenic development and photosynthetic efficiency) of different genotypes sourced from sites at the equatorward distributional edge (warm-edge) and those toward the center of its distribution (non-edge). The genetic diversity and structure of H. banksii was also examined using microsatellite markers amongst the same sites. Our results found variable responses in thermal performance for growth and development. Warm-edge germlings grew optimally in lower temperatures tested and had narrower thermal breadth compared to non-edge germlings which grew in higher and more broader temperatures. Warm-edge germlings however, showed greater plasticity to tolerate high light indicated by a greater proportion of energy being dissipated as regulated non-photochemical quenching [Y(NPQ)] than non-regulated non-photochemical quenching [Y(NO)]. Overall genetic diversity was lower at the warm-edge location with evidence of increased structuring and reduced gene flow in comparison to the non-edge location. Evidence of genetic structuring was not found locally between high and low shore within sites. Together, these data suggest that non-edge populations may be “thermally buffered” from increased temperatures associated with ocean warming. Warm-edge populations of H. banksii, however, may be vulnerable to warming, due to narrower thermal breadth and sensitivity to higher temperatures, with genetic impoverishment through loss of individuals likely to further reduce population viability.

中文翻译：

---

局部尺度热环境和有限的基因流表明栖息地形成巨藻中暖边种群的脆弱性

由于适应性降低、基因流动有限和接近其生理热极限，居住在其分布的温暖边缘种群中的物种被认为处于全球变暖的最前沿。确定控制热生态位的规模和栖息地形成物种对环境压力的功能反应对于成功的保护工作至关重要，特别是因为沿海生态系统受到全球变化的影响。在这里，我们研究了来自澳大利亚东南部的形成栖息地的大型藻类 Hormosira bankii 中的暖边种群对变暖的敏感性。我们使用定量育种设计来量化热性能（生长、来自赤道分布边缘（暖边缘）和分布中心（非边缘）的不同基因型的个体发育和光合效率）。还使用相同位点之间的微卫星标记检查了 H.bankii 的遗传多样性和结构。我们的结果发现热性能对生长和发育的响应是可变的。与在更高和更宽温度下生长的非边缘幼苗相比，暖边幼苗在测试的较低温度下生长最佳，并且具有更窄的热宽度。然而，暖边幼苗表现出更大的可塑性来耐受强光，这表明作为受管制的非光化学淬灭 [Y(NPQ)] 比不受管制的非光化学淬灭 [Y(NO)] 消耗的能量比例更大。与非边缘位置相比，暖边缘位置的整体遗传多样性较低，有证据表明结构增加和基因流减少。在站点内的高岸和低岸之间没有局部发现遗传结构的证据。总之，这些数据表明非边缘种群可能会因与海洋变暖相关的温度升高而“热缓冲”。然而，H. bankii 的暖边缘种群可能容易受到变暖的影响，因为它们的热宽度较窄且对较高温度很敏感，而且由于个体丧失而导致的遗传贫困可能会进一步降低种群生存能力。在站点内的高岸和低岸之间没有局部发现遗传结构的证据。总之，这些数据表明非边缘种群可能会因与海洋变暖相关的温度升高而“热缓冲”。然而，H. bankii 的暖边缘种群可能容易受到变暖的影响，因为它们的热宽度较窄且对较高温度很敏感，而且由于个体丧失而导致的遗传贫困可能会进一步降低种群生存能力。在站点内的高岸和低岸之间没有局部发现遗传结构的证据。总之，这些数据表明非边缘种群可能会因与海洋变暖相关的温度升高而“热缓冲”。然而，H. bankii 的暖边缘种群可能容易受到变暖的影响，因为它们的热宽度较窄且对较高温度很敏感，而且由于个体丧失而导致的遗传贫困可能会进一步降低种群生存能力。