Environmental heterogeneity and productivity are factors driving beta diversity of freshwater communities. Further, characteristics as spatial extent and connectivity, as well as land use and cover, can determine local biodiversity patterns. We evaluated the correlates of within-lake beta diversity of phytoplankton communities in 25 coastal shallow lakes in southern Brazil. We hypothesize that within-lake beta diversity is positively related to environmental heterogeneity, productivity, spatial extent and connectivity. We also searched for correlates between beta diversity and land cover, once the studied lakes are mostly surrounded by natural landscapes. We measured beta diversity using four dissimilarity coefficients that provide a gradient of emphasis on compositional and abundance changes. We found that beta diversity differed among lakes, indicating changes in both species’ composition and abundance, but how it correlated with predictors differed depending on how beta diversity was measured. Beta diversity based on changes in species incidence and in two measures of abundance (modified Gower based on log10 and log2) was positively related to percentage of wetland cover and negatively related to percentage of grassland. Further, environmental heterogeneity was related to abundance-based (modified Gower log2) beta diversity. Our hypotheses were partly corroborated, indicating that factors modulating beta diversity patterns are complex and not easy to detect. We show that phytoplankton beta diversity in shallow coastal lakes is promoted by factors acting at both local and landscape scales. Finally, we emphasize that investigating beta diversity patterns should thoughtfully consider the use of dissimilarity coefficients measuring both changes in species composition and abundance.

环境的异质性和生产力是推动淡水群落β多样性的因素。此外，空间范围和连通性以及土地使用和覆盖范围等特征可以决定当地的生物多样性模式。我们评估了巴西南部25个沿海浅湖中浮游植物群落湖内β多样性的相关性。我们假设湖内β多样性与环境异质性，生产力，空间范围和连通性成正相关。一旦所研究的湖泊大部分被自然景观所包围，我们还将寻找贝塔多样性与土地覆盖之间的相关性。我们使用四个不相似系数测量了β多样性，这四个系数提供了对成分和丰度变化的强调梯度。我们发现湖泊之间的β多样性有所不同，表示物种组成和丰度都发生了变化，但是它与预测因子的相关性因测量β多样性的方式而异。基于物种发生率变化和两种丰度度量（基于log10和log2的改良Gower）的Beta多样性与湿地覆盖率成正相关，与草地百分比成负相关。此外，环境异质性与基于丰度的（改良的Gower log2）β多样性有关。我们的假设得到了部分证实，表明调节β多样性模式的因素很复杂，不易检测。我们表明，沿海和浅水湖泊中的浮游植物β多样性是由在地方和景观尺度上起作用的因素促进的。最后，