This study examines the effects of the flow and flood pulses on spatial dispersion of fish assemblages in the floodplain of the Paraná River in Argentina. We tested the hypothesis that high water levels and greater lateral connectivity promote fish dispersal and spatial homogenization of assemblage structure. We sampled four sites during different phases of the annual hydrologic cycle from 2010 to 2016. Water surface in the area was estimated during each phase. We computed multivariate statistics and estimates of ß‐diversity to analyse assemblage variations in relation to hydrological phases. Three hydrological phases were defined: low flow pulses (water levels between 2.3 and 3.2, approximately 10% of the floodplain covered by water), high flow pulses (between 3.2 and 4.5, from 11 to 84%), and floods (> 4.5 m, more than 84%). Although difference between high flow pulses and flood was not significant, ß‐diversity values for these stages were higher than for low flow pulses. This suggests that floods and high flow pulses increase the spatial variability of fish assemblages, whereas homogenization processes occur later during low flow periods. This work provides further knowledge about the flood homogenization effect in a large unregulated floodplain where lateral connectivity still plays a significant role on ecological structuring processes.

中文翻译：

---

亚热带温带大河鱼类群空间分布的水文变异判别

这项研究研究了流量和洪水脉冲对阿根廷巴拉那河泛滥平原中鱼类种群空间分布的影响。我们检验了以下假设：高水位和更大的横向连通性会促进鱼的散布和组合结构的空间均质化。我们在2010年至2016年的年度水文周期的不同阶段对四个站点进行了采样。在每个阶段都对该区域的水面进行了估算。我们计算了多元统计量和ß多样性估计值，以分析与水文阶段有关的集合变化。定义了三个水文阶段：低流量脉冲（水位在2.3至3.2之间，约占泛洪平原的10％被水覆盖），高流量脉冲（水位在3.2至4.5之间，从11至84％）和洪水（> 4.5 m ，超过84％）。尽管高流量脉冲与洪水之间的差异并不显着，但这些阶段的ß分集值高于低流量脉冲。这表明洪水和高流量脉冲增加了鱼群的空间变异性，而均质化过程则在低流量时期后期发生。这项工作提供了有关在大型无规洪泛区中洪水均质化作用的进一步知识，在该地区，横向连通性在生态构造过程中仍起着重要作用。