Ecological specialization is an important engine of evolutionary change and adaptive radiation, but empirical evidence of local adaptation in marine environments is rare, a pattern that has been attributed to the high dispersal ability of marine taxa and limited geographic barriers to gene flow. The broad‐nosed pipefish, Syngnathus typhle, is one of the most broadly distributed syngnathid species and shows pronounced variation in cranial morphology across its range, a factor that may contribute to its success in colonizing new environments. We quantified variation in cranial morphology across the species range using geometric morphometrics, and tested for evidence of trophic specialization by comparing individual‐level dietary composition with the community of prey available at each site. Although the diets of juvenile pipefish from each site were qualitatively similar, ontogenetic shifts in dietary composition resulted in adult populations with distinctive diets consistent with their divergent cranial morphology. Morphological differences found in nature are maintained under common garden conditions, indicating that trophic specialization in S. typhle is a heritable trait subject to selection. Our data highlight the potential for ecological specialization in response to spatially variable selection pressures in broadly distributed marine species.

中文翻译：

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广泛分布的海洋物种范围内生态专业化的演变

生态专业化是进化变化和适应性辐射的重要引擎，但海洋环境局部适应的经验证据很少，这种模式归因于海洋分类群的高扩散能力和基因流动的有限地理障碍。宽鼻尖嘴鱼 Syngnathus typhle 是分布最广泛的合颌物种之一，其颅骨形态在其范围内表现出明显的变化，这可能是其成功在新环境中定居的一个因素。我们使用几何形态计量学量化了整个物种范围内颅骨形态的变化，并通过将个体水平的饮食成分与每个地点可用的猎物群落进行比较来测试营养特化的证据。尽管来自每个地点的少年尖嘴鱼的饮食在性质上相似，但饮食组成的个体发生变化导致成年种群具有与其不同的颅骨形态一致的独特饮食。自然界中发现的形态差异在普通花园条件下得以维持，表明 S. typhle 的营养特化是一种受选择的遗传性状。我们的数据突出了生态专业化的潜力，以应对广泛分布的海洋物种的空间可变选择压力。表明 S. typhle 的营养特化是一种受选择的遗传性状。我们的数据突出了生态专业化的潜力，以应对广泛分布的海洋物种的空间可变选择压力。表明 S. typhle 的营养特化是一种受选择的遗传性状。我们的数据突出了生态专业化的潜力，以应对广泛分布的海洋物种的空间可变选择压力。