Data from: Punctuated changes in the morphology of an endemic diatom from Lake Titicaca

High levels of biodiversity and endemism in ancient lakes have motivated research on evolutionary processes in these systems. Drill core records from Lake Titicaca (Bolivia, Peru), an ancient lake in the high-elevation Altiplano, record the history of climate, landscape dynamics, and diatom evolution. That record was used to examine the patterns and drivers of morphological evolution of an endemic species complex of diatoms in the lake, the Cyclostephanos andinus complex. In an attempt to delineate species within the complex based on morphology, no discernible evidence was found for species separation based on an ordination analysis of multiple characters, but multiple populations were detected based on the distribution of valve size in individual samples. Likelihood modeling of phyletic evolution showed that size evolved through punctuated change. Correlation of size trends with other environmental variables indicates that C. andinus size responded to regional environmental change driven by global processes that influenced Lake Titicaca by affecting lake level and thermal stratification.

古湖泊中极高的生物多样性与特有性，催生了针对此类生态系统演化过程的研究。位于高海拔阿尔蒂普拉诺高原的的的喀喀湖（Lake Titicaca，玻利维亚、秘鲁交界）作为一处古湖，其钻探岩芯记录保存了该区域的气候变迁、景观动态以及硅藻（diatom）的演化历史。依托该岩芯记录，研究人员解析了该湖特有硅藻复合类群——安第斯环毛藻复合类群（Cyclostephanos andinus complex）的形态演化模式与驱动机制。本研究尝试基于形态特征对该复合类群内的物种进行界定，但通过多性状排序分析未发现可明确区分物种的证据；不过基于单个样品中硅藻壳瓣尺寸的分布特征，检测到了该复合类群内存在多个种群。种系演化似然模型分析结果显示，壳瓣尺寸的演化以间断式变化的方式进行。壳瓣尺寸变化趋势与其他环境变量的相关性分析表明，安第斯环毛藻的壳瓣尺寸响应了由全球过程驱动的区域环境变化；此类全球过程通过调控的的喀喀湖的水位与热分层，对该湖生态系统产生影响。