Geographic variation of phenotypic traits affects the capacity of species to withstand and adapt to environmental stress. Here, we examined how geographic origin influences UV stress tolerance of the red seaweeds Chondracanthus chamissoi and Gelidium lingulatum distributed along the South‐East Pacific coast between 20° S and 42° S. Seaweeds from six (C. chamissoi) and five (G. lingulatum) populations were grown under common‐garden conditions and then exposed to consecutive UV stress events and essential biological traits (e.g., growth, photosynthetic responses, antioxidant capacity, and UV‐absorbing compounds) were analyzed. In C. chamissoi, a strong UV sensitivity occurred in populations from mid‐latitudes (27° S and 29° S) where the lowest recovery of maximum quantum yield (F_v/F_m; between 32.3% and 66.8% of control) and growth rate were observed. Likewise, the lowest amount of mycosporine‐like amino acids (MAAs) and a significant decrease in phycobilins were registered in these populations. In G. lingulatum, recovery of F_v/F_m ranged from 82.0% to 97.7% of control, and antioxidant activity, carotenoid, and MAA contents were positively influenced by UV exposure. The multivariate analysis indicated a significant influence of PAR, cloud cover, and UV index on physiological traits, depending on species. The ecotypic differentiation index (EDI) indicated a higher phenotypic variation in C. chamissoi (EDI = 0.10) than G. lingulatum (EDI = 0.03). This study shows that the spatial distribution of UV stress tolerance in the studied seaweeds does not follow linear latitudinal or central–edge gradients. Instead, among‐site variability of solar intensities driven by specific climatic conditions seems to act as driver of phenotypic variation.

中文翻译：

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红海藻的耐紫外线应力的地理变化不会随东南太平洋海岸的纬度而变化。

表型性状的地理变异影响物种抵御和适应环境压力的能力。在这里，我们研究了地理起源如何影响东南太平洋沿20°S至42°S分布的东南太平洋沿岸的红海藻Chondracanthus chamissoi和Gelidium lingulatum。六种（C.chamissoi）和五种（G. lingulatum）种群在普通花园条件下生长，然后暴露于连续的紫外线胁迫事件下，并分析了基本的生物学特性（例如，生长，光合作用响应，抗氧化能力和吸收紫外线的化合物）。在C. chamissoi，在中纬度（27°S和29°S）的人群中发生了强烈的UV敏感性，其中观察到最大量子产率（F _v / F _m；对照的32.3％至66.8％之间）的最低恢复。同样，在这些人群中，霉菌素样氨基酸（MAAs）的含量最低，而藻胆素则显着下降。在G. lingulatum，回收˚F _v / ˚F_米紫外线的影响范围为对照的82.0％至97.7％，抗氧化剂活性，类胡萝卜素和MAA含量受到正影响。多变量分析表明，PAR，云量和紫外线指数对生理性状有显着影响，具体取决于物种。生态型分化指数（EDI）表明，Chamissoi的表型变异（EDI = 0.10）比灵芝G. lingulatum（EDI = 0.03）更高。这项研究表明，在研究的海藻中，紫外线胁迫耐受性的空间分布不遵循线性纬度或中心-边缘梯度。取而代之的是，由特定气候条件驱动的太阳强度的站点间变化似乎是表型变化的驱动因素。