Isotopic variability in a stream longitudinal gradient: implications for trophic ecology

Longitudinal patterns in α and β diversity of the taxonomic and functional organizations of stream fish assemblages in the Qingyi River

“…Although the taxonomic and functional α diversity show similar longitudinal distributions, the ecological processes driving the longitudinal variations in β diversity may be different for the taxonomic (i.e., species turnover) and functional organizations (i.e., function nestedness). Key words: taxonomic and functional organizations; α and β diversity; community turnover and nestedness; river longitudinal gradient 河流鱼类群落的物种组成及其数量的空间分 布受历史过程、非生物因素和生物因素的联合影响 (Gilliam et al, 1993;Hoeinghaus et al, 2007;Dauwalter et al, 2008)。就非生物因素而言, 河流系统的理 化因子具有极高的空间异质性和时间动态变化, 并 引 起 河 流 鱼 类 群 落 组 成 和 数 量 的 时 空 变 化 (Grossman et al, 1990;Jackson et al, 2001)。 河流理化 因子和鱼类群落的空间异质性可体现在多维空间 尺度上, 如栖息地斑块 (Erös & Grossman, 2005; 朱 仁等, 2015)、 河流纵向梯度 (Torgersen et al, 2006; 储 玲等, 2015)、河流网络体等 (Grenouillet et al, 2004; 李艳慧等, 2014), 其中, 沿"上游-下游"纵向梯度下 的鱼类群落空间变化最受生态学家和鱼类学家所 关注(如: Torgersen et al, 2006;Suvarnaraksha et al, 2012;储玲等, 2015;Li et al, 2018)。 从河源至河口, 河流呈现为一个集连续性、等 级性和异质性等属性于一体的线性结构 (Vannote et al, 1980), 沿着这一环境梯度, 能量生产与消费、 栖息地复杂性及其多样性、环境稳定性等均呈现出 明 显 的 纵 向 梯 度 变 化 特 征 (Vannote et al, 1980;Schlosser, 1982;Taylor & Warren, 2001)。 鱼类物种组 成及其数量也呈现出梯度变化, 其中物种组成主要 以"递增"(addition)或"替代"(replacement)模式变化 (Matthews, 1998), 物种数量从上游至中游逐渐增加 并在中游河段达到最大值, 至下游复又相对下降 (Resh et al, 1988;Oberdorff et al, 1993;Sui et al, 2014)。除了分类群(物种组成)以外, 河流鱼类的营 养、运动、生活史等功能特征及其数量(功能群)也 具有较为类似的纵向梯度变化 (Pouilly et al, 2006;Pease & Winemiller, 2012;Costas & Pardo, 2015;Troia & Gido, 2015) (Whittaker, 1972;Baselga, 2010)…”

Stable isotopes reveal food web modifications along the upstream–downstream gradient of a temperate stream

“…All these changes in physical conditions 36 make up the upstream-downstream gradient (UDG), also called longitudinal or fluvial gradient (Costas and 37 Pardo 2014, Winemiller at al. 2011.…”

“…Winemiller at al. 2011;Chang et al 2012;Costas and Pardo 2014), the nature of its effect remains poorly 58 documented. Notably, no study has assessed whether the effect of UDG on food webs is mainly structural or 59 functional (or both).…”

Dry season limnological conditions and basin geology exhibit complex relationships with δ13C and δ15N of carbon sources in four Neotropical floodplains

“…Recent studies in freshwater ecosystems are seeking to improve understanding of carbon flow in food webs by testing general conceptual models such as the River Continuum Concept (RCC; [ 1 ]), Flood Pulse Concept (FPC; [ 2 ]), Riverine Productivity Model (RPM; [ 3 ]), Riverine Ecosystem Synthesis [ 4 ] and River Wave Concept (RWC; [ 5 ]). Stable isotopes, particularly of carbon and nitrogen, have been influential in this work as natural tracers of energy sources and trophic interactions [ 6 – 14 ]. One major issue with testing the aforementioned models using stable isotope analyses (SIA) is the ability of the isotopes to reliably distinguish among potential autotrophic carbon sources and/or size fractions within and among ecosystems.…”

“…The δ 13 C of the DIC can also be affected by salinity or nutrient limitation [ 22 , 23 ], pressure of CO 2 as a result of terrestrial respiration of organic material [ 24 ], ecosystem area and metabolism [ 21 , 25 ], lithology and hydrology [ 26 ], and basin geochemistry [ 27 ]. Subsequently, the factors that determine the δ 13 C of aquatic primary producers are complex because of the influences of spatial heterogeneity at multiple scales, such as local habitat, reach, watershed, hydrology and geochemistry [ 7 , 14 , 28 ]. Opposite to strictly aquatic primary producers (i.e.…”