Biotic interactions and stream network position affect body size of aquatic vertebrates across watersheds

IF 2.7 3区 环境科学与生态学 Q2 ECOLOGY
Ecosphere Pub Date : 2025-06-25 DOI:10.1002/ecs2.70299
Brooke E. Penaluna, Sherri L. Johnson, Amanda M. M. Pollock, Ivan Arismendi, Dana R. Warren
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Abstract

The body size of aquatic vertebrates is declining across populations and ecosystems worldwide owing to warmer water temperature and changing streamflow. In freshwaters, the effects of stream network position and density-dependent factors on body size are less understood. We used an extensive dataset spanning 41 stream sites over 7 years to evaluate how density-dependent and density-independent factors influence the size of two top predators in small watersheds, Coastal Cutthroat Trout Oncorhynchus clarkii clarkii and Coastal Giant Salamanders Dicamptodon tenebrosus. We tested three hypotheses of body-size variation for trout and salamanders, including intraspecific density dependence, interspecific density dependence, and resource availability, using empirical observations in hierarchical linear mixed models in a model-selection framework. In our best-supported models, the strongest predictors of size were conspecific negative density dependence, as expected, suggesting greater intraspecific interactions probably owing to conspecific individuals having similar requirements. We reveal a biogeographic pattern in which body size peaks in middle stream-network positions and plateaus or declines at lower and upper locations, proposing that stream network position also plays a role in determining body size in small watersheds. Salamander density also has a quadratic effect on adult trout size, with salamanders having a greater overall effect on the body size of both species than trout, suggesting that salamanders might be more dominant than trout in some interactions. Collectively, we found that biotic interactions, mainly conspecific but also interspecific, and stream-network position affect trout and salamander body sizes in small watersheds.

Abstract Image

生物间的相互作用和水系网络的位置影响着跨流域水生脊椎动物的体型
由于水温升高和水流变化,水生脊椎动物的体型在世界范围内的种群和生态系统中都在下降。在淡水中,水系位置和密度相关因素对体型的影响尚不清楚。我们使用了跨越41个河流站点7年的广泛数据集,以评估密度依赖和密度不依赖因素如何影响小流域两种顶级捕食者的大小,沿海切喉鳟鱼克拉基克拉基和沿海大鲵齿齿螈。我们在模型选择框架中使用层次线性混合模型的经验观察,测试了鳟鱼和蝾螈体型变化的三种假设,包括种内密度依赖、种间密度依赖和资源可用性。在我们最支持的模型中,最强的大小预测因子是同种负密度依赖,正如预期的那样,这表明更大的种内相互作用可能是由于同种个体具有相似的需求。我们揭示了一种生物地理格局,即体型在中游和高原位置达到峰值,在下游和上游位置下降,这表明河流网络位置也在小流域中决定体型。蝾螈密度对成年鳟鱼的大小也有二次效应,与鳟鱼相比,蝾螈对两个物种的体型都有更大的总体影响,这表明在某些相互作用中,蝾螈可能比鳟鱼更占优势。总的来说,我们发现生物相互作用(主要是同种的,也有种间的)和河流网络位置影响小流域鳟鱼和蝾螈的体型。
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来源期刊
Ecosphere
Ecosphere ECOLOGY-
CiteScore
4.70
自引率
3.70%
发文量
378
审稿时长
15 weeks
期刊介绍: The scope of Ecosphere is as broad as the science of ecology itself. The journal welcomes submissions from all sub-disciplines of ecological science, as well as interdisciplinary studies relating to ecology. The journal''s goal is to provide a rapid-publication, online-only, open-access alternative to ESA''s other journals, while maintaining the rigorous standards of peer review for which ESA publications are renowned.
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