Systematic Investigation of the Diatom Genus Tabellaria

硅藻是具有复杂装饰的富含二氧化硅的细胞壁的单细胞藻类，是水质和营养状况的重要生态指标，个别物种适应特定的条件。它们作为指示剂的使用取决于对物种的可靠分类，使用细胞壁的稳定形态特征。硅藻细胞壁很容易作为化石保存下来，例如在湖床岩心中，并使物种组成和丰度的非常长期变化的分析成为可能，这项任务同样依赖于可靠的分类标记。密歇根大学的Eugene Stoermer博士正在研究Tabellaria属的淡水硅藻，以评估这一组物种内部和之间的形态差异的限度。Tabellaria物种遍布北半球，多年来已命名和描述了约80个物种，大多数是简短的，在许多情况下是基于不可靠的环境引起的变异。斯托尔默博士正在开发形态计量学方法，利用傅里叶变换在光学显微镜下快速测量细胞轮廓和其他细胞壁特征，以界定那些不太容易被瞬变的水条件改变的大小和形状方面，从而可以用作特定物种的稳定标记。然后，可以研究硅藻物种之间的长期进化趋势，并假定有遗传基础，而不会因环境引起的局部变化而复杂化。为大小和形状分析开发的形态计量学方法应该对其他硅藻和其他单细胞生物体有用。

Diatoms, unicellular algae with silica-rich cell walls that are intricately ornamented, are important ecological indicators of water quality and nutrient status, with individual species adapted to particular conditions. Their use as indicators depends upon a reliable classification of the species, using stable morphological features of the cell wall. Diatom cell walls are easily preserved as fossils, for example in lake-bed cores, and make possible the analysis of very long-term changes in species composition and abundance, a task again dependent upon reliable taxonomic markers. Dr. Eugene Stoermer of the University of Michigan is studying freshwater diatoms of the genus Tabellaria to assess the limits of morphological variability within and between species of this group. Tabellaria species are found throughout the northern hemisphere, and about 80 species have been named and described over the years, mostly briefly and in many cases on the basis of unreliable, environmentally induced variations. Dr. Stoermer is developing morphometric procedures using Fourier transformations for the rapid measurement, under the light microscope, of cell outline and other cell-wall features, to delimit those aspects of size and shape that are less prone to modification by transient water conditions, and can thus be used as stable markers of particular species. Long-term evolutionary trends among diatom species, with a presumed genetic basis, can then be studied, uncomplicated by variations locally induced by the environment. The morphometric methods developed for size and shape analysis should be useful with other groups of diatoms and other unicellular organisms.