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Abstract：
Golden and Blueline Tilefish (Lopholatilus chamaeleonticeps and Caulolatilus microps) are keystone taxa in northwest (NW) Atlantic continental shelf-edge environments due to their biotic (trophic-mediated) and abiotic (ecosystem engineering) functional roles combined with high-value fisheries. Despite this importance, the ecological niche dynamics (i.e., those relating to trophic behavior and food-web interactions) of these sympatric species are poorly understood, knowledge of which may be consequential for maintaining both ecosystem function and fishery sustainability. We used stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) to build realized ecological niche hypervolumes to serve as proxies for diet and production use patterns of L. chamaeleonticeps and C. microps. We hypothesized that: (a) species exhibit ontogenetic shifts in diet and use of production sources; (b) species acquire energy from spatially distinct resource pools that reflect a sedentary life-history and differential use of the continental shelf-edge; and (c) species exhibit differentiation in one or more measured niche axes. We found evidence for ontogenetic shifts in diet (δ15N) but not production source (δ13C) in both species, suggesting a subtle expansion of measured ecological niche axes. Spatial interpolation of stable isotope ratios showed distinct latitudinal gradients; for example, individuals were 13C enriched in northern and 15N enriched in southern regions, supporting the assertion that tilefish species acquire energy from regional resource pools. High isotopic overlap was observed among species (≥82%); however, when hypervolumes included depth and region of capture, overlap among species substantially decreased to overlap estimates of 15%-77%. This suggests that spatial segregation could alleviate potential competition for resources among tilefish species inhabiting continental shelf-edge environments. Importantly, our results question the consensus interpretation of isotopic overlap estimates as representative of direct competition among species for shared resources or habitats, instead identifying habitat segregation as a possible mechanism for coexistence of tilefish species in the NW Atlantic.
摘要：
Golden和BluelineTilefish（Lopholatiluschamaaeleonticeps和Caulolatilusmicrops）是西北（NW）大西洋大陆架边缘环境中的基石类群，因为它们具有生物（营养介导的）和非生物（生态系统工程）的功能作用以及高价值渔业。尽管有这种重要性,生态位动态(即，与营养行为和食物网相互作用有关的那些）对这些同胞物种的了解很少，了解哪些知识对于维持生态系统功能和渔业可持续性可能是重要的。我们使用碳（δ13C）和氮（δ15N）的稳定同位素比率来建立已实现的生态位高容量，以作为饮食和生产使用模式的代理。我们假设：（a）物种在饮食和生产来源的使用方面表现出个体发育的变化；（b）物种从空间上不同的资源库中获取能量，这些资源库反映了久坐的生活史和大陆架边缘的不同使用；（c）物种在一个或多个测得的生态位轴中表现出差异。我们发现两个物种的饮食（δ15N）而不是生产源（δ13C）发生个体发育变化的证据，表明测量的生态位轴线的微妙扩展。稳定同位素比率的空间插值显示出不同的纬度梯度；例如，个体在北部富集13C，在南部地区富集15N，支持头鱼物种从区域资源池中获取能量的主张。在物种之间观察到高同位素重叠（≥82％）；但是，当超体积包括捕获的深度和区域时，物种间的重叠大幅减少，重叠估计为15%-77%。这表明空间隔离可以减轻居住在大陆架边缘环境中的平头鱼物种之间对资源的潜在竞争。重要的是,我们的结果质疑同位素重叠估计的共识解释，作为物种之间直接竞争的共享资源或生境的代表，相反，将栖息地隔离确定为西北大西洋中种子鱼物种共存的可能机制。
