The effects of spatial scale and isoscape on consumer isotopic niche width
The effects of spatial scale and isoscape on consumer isotopic niche width
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DOI：
10.1111/1365-2435.13026
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发表时间：
2018-04
影响因子：
5.2
通讯作者：
Carl J. Reddin;J. Bothwell;Nessa E. O’Connor;C. Harrod
中科院分区：
文献类型：
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作者：
Carl J. Reddin;J. Bothwell;Nessa E. O’Connor;C. Harrod
生态变量的均值和方差取决于环境异质性的覆盖范围（采样范围）和空间尺度等采样属性。营养生态位宽度通常用C和N的体积组织稳定同位素来近似，即种群同位素生态位。然而，最近的研究表明，环境异质性（个体所经历的）在确定同位素生态位宽度方面可能比营养变异性更重要。我们假设同位素生态位宽度随空间尺度单调增加，这主要是由环境变化（如营养源）造成的。为了完善这一假设，通过描述同位素标度曲线的形状，我们探索了一个先前发表的数据集，该数据集描述了代表不同摄食行业的三种智利潮间带物种（放牧蜗牛，悬浮摄食贻贝）。我们在一个新的、更大的数据集上测试了这些假设，该数据集描述了北爱尔兰三种功能相似的潮间带物种。我们从空间显式bootstrap中生成了同位素方差-面积曲线，并研究了环境-同位素关系的尺度依赖性，包括波暴露和亚生境异质性。空间尺度通过简单的非线性关系解释了种群同位素生态位宽度（二元C - N椭圆面积）的50%的方差。较细尺度（< 1-10 km滞后）的方差最大。δ15N方差具有较强的尺度依赖性，其中bbb40 %可以用线性系数来解释。δ15N基线梯度或等值线主导了δ15N方差的尺度模式，从隐蔽的陆地影响的港湾到暴露的远洋主导的海岸线。消费者δ13C方差的尺度依赖性较弱，在中尺度趋于稳定（滞后约20 km）。我们发现，同位素生态位宽度强烈依赖于采样空间范围，而采样空间范围控制着个体消费者所经历的环境异质性。在考虑同位素生态位宽度准确表示营养生态位宽度之前，必须考虑环境异质性。在不同的空间尺度上进行的研究可能会确定不同的环境-同位素关系。我们建议将空间尺度明确纳入抽样设计，最简单的方法是保持一致的滞后距离或抽样人口的区域。必要时，可以对已确定的等值线图进行去趋势化处理。本文提供了一个简单的语言摘要。
The mean and variance of ecological variables are dependent on sampling attributes such as the coverage of environmental heterogeneity (sampling extent) and spatial scale. Trophic niche width is often approximated by bulk tissue stable isotopes of C and N, that is, the population isotopic niche. However, recent studies suggest that environmental heterogeneity (experienced by individuals) may be more important in defining the isotopic niche width than trophic variability. We hypothesised that isotopic niche width will increase monotonically with spatial scale, largely produced by environmental variation, for example, nutrient source.To refine this hypothesis, by describing the shapes of isotope scaling curves, we explored a previously published dataset describing three Chilean intertidal species representing different feeding guilds (grazing snails, suspension‐feeding mussel). We tested these hypotheses on a new, larger dataset describing three functionally analogous intertidal species from Northern Ireland. We generated isotopic variance–area curves from a spatially explicit bootstrap and investigated the scale dependency of environment–isotope relationships, including wave exposure and sub‐habitat heterogeneity.Spatial scale explained 50% of the variance in population isotopic niche widths (bivariate C‐N ellipse area) by simple, nonlinear relationships. Finer scales (<1–10 km lag) accounted for most variance. Scale dependence was strong for δ15N variance, of which >40% was explained by modelling linear coefficients. A δ15N baseline gradient, or isoscape, dominated δ15N variance scaling patterns, from sheltered, terrestrially influenced embayments to exposed, pelagic‐dominated coastline. Consumer δ13C variance had a weaker scale dependence, plateauing at mesoscales (>20 km lag).We show that isotopic niche width is strongly dependent on sampling spatial extent, which controls the environmental heterogeneity experienced by individual consumers. Environmental heterogeneity must be accounted for before isotopic niche width can be considered to accurately represent trophic niche width. Studies conducted at different spatial scales are likely to identify different environment–isotope relationships.We recommend that spatial scale should be incorporated into sampling designs explicitly, easiest by maintaining a consistent lag distance or area within which populations are sampled. Identified isoscapes can be de‐trended, where necessary.A plain language summary is available for this article.