Universidad Nacional de Colombia - Sede Bogotá, Carrera 45 # 30-02, Bogotá, 111321, Colombia.
Catalan Institute for Water Research (ICRA), C/Emili Grahit 101, Girona, 17003, Spain.
J Phycol. 2020 Aug;56(4):1053-1065. doi: 10.1111/jpy.13005. Epub 2020 May 26.
We assessed the relative influence of ecoregional features in explaining diatom distribution in the Orinoco river basin. Ecoregions in the Colombian Orinoco can be seen as imprints of the evolutionary history of the basin, for their current biodiversity and physiographic features are the result of the geological and climatic shifts that have occurred since the Tertiary. Thus, they represent an ideal testing ground for studying the interplay between ecological and evolutionary processes shaping diversity patterns of microorganisms, such as diatoms, in the present day. To study this interplay, we compared diatom community composition variance within and among seven ecoregions and assessed the explanatory power of environmental, spatial and historical drivers. This was done by a combination of correlation analyses, multivariate methods and constrained ordinations. We also deconstructed the whole community data set into ecological guilds (low- and high-profile, and motile) to explore their individual response to the contemporary and historical drivers. Taken together, these analyses indicated that contemporary constraints to species occurrence and dispersal, as well as the legacies of historical events, can provide an explanation for the contemporary distribution of diatoms in the Colombian Orinoco. Specifically, we provided evidence showing that both historical legacies and contemporary environmental conditions (temperature, pH, and phosphorus concentration) are interacting to determine diatoms' distribution. Our results suggest the need to consider ecoregional gradients for unraveling the mechanisms shaping tropical diversity as well as for designing conservation plans.
我们评估了生态区特征对奥里诺科河流域硅藻分布的相对影响。哥伦比亚奥里诺科河的生态区可以被视为该流域进化历史的印记，因为它们目前的生物多样性和地貌特征是自第三纪以来发生的地质和气候变化的结果。因此，它们代表了一个理想的试验场，可以研究塑造当今微生物（如硅藻）多样性模式的生态和进化过程之间的相互作用。为了研究这种相互作用，我们比较了七个生态区内部和之间的硅藻群落组成方差，并评估了环境、空间和历史驱动因素的解释力。这是通过相关性分析、多元方法和约束排序的组合来完成的。我们还将整个群落数据集分解为生态类群（低和高轮廓，和运动），以探索它们对当代和历史驱动因素的个体反应。总的来说，这些分析表明，物种出现和扩散的当代约束以及历史事件的遗留物，可以为哥伦比亚奥里诺科的硅藻的当代分布提供解释。具体来说，我们提供了证据表明，历史遗产和当代环境条件（温度、pH 值和磷浓度）相互作用，决定了硅藻的分布。我们的研究结果表明，有必要考虑生态区梯度，以揭示塑造热带多样性的机制，并为保护规划设计提供依据。
