Temporal genetic structure of a stock of Prochilodus lineatus (Characiformes: Prochilodontidae) in the Mogi-Guaçu River ecosystem, São Paulo, Brazil

Abstract Prochilodus lineatus is a species of migratory fish widely distributed in the Paraná River basin, found mainly in the Grande, Pardo and Mogi-Guaçu rivers located in a well-developed region of the state of São Paulo. This study analyzes the genetic diversity and population structure in shoals of P. lineatus based on temporal analysis of specimens sampled over the years 2003, 2005, 2006, 2009, 2010, and 2015 in the Mogi-Guaçu River, São Paulo, at the region of Cachoeira de Emas. Genetic analysis performed using the D-Loop and seven microsatellite marker revealed significant genetic variability in all sampled groups. Moderate levels of structuring between groups were identified with the microsatellite markers (Fst = 0.14), while the mitochondrial marker did not reveal patterns of genetic structuring (Fst = 0.01). The genetic variability fluctuated over time, characterizing patterns of structuring among the analyzed samples. The occurrence of environmental alterations resulting in increased mortality rates, as well as changes in the water level in the ecosystem, among other factors, could determine changes in the reproductive behavior of species. The lack of favorable environmental conditions for reproduction in the basin, as reflected by tests of population bottlenecks, could have resulted in the differentiation of populations of P. lineatus over time.

摘要 细纹似鳊（Prochilodus lineatus）是一种洄游性鱼类，广泛分布于巴拉那河流域，主要栖息于圣保罗州经济发达区域内的格兰德河、帕尔多河与莫吉-瓜苏河。本研究以2003、2005、2006、2009、2010及2015年在圣保罗州莫吉-瓜苏河卡舒埃拉-迪埃马斯区域采集的该物种样本为对象，开展时间序列分析，探究其种群的遗传多样性与种群结构。研究采用D环（D-Loop）与7个微卫星标记（microsatellite marker）进行遗传分析，结果显示所有采样种群均存在显著的遗传变异。基于微卫星标记可检测到种群间存在中等程度的遗传分化（Fst=0.14），而线粒体标记未呈现显著的遗传结构模式（Fst=0.01）。遗传多样性随时间呈现波动特征，表明不同采样样本间存在遗传结构差异。流域内出现的环境改变（如种群死亡率上升、生态系统水位变化等诸多因素），可能会影响该物种的繁殖行为；种群瓶颈效应检测结果显示，该流域缺乏适宜的繁殖环境条件，这或许是导致细纹似鳊种群随时间发生分化的重要原因。