Evolution and Phylogeny of Ciliated Protozoa

我研究纤毛原生动物，在湖泊和海洋、土壤和森林凋落物以及小池塘中发现的常见单细胞微生物。纤毛虫以细菌和较小的原生生物为食。纤毛虫被小鱼和小甲壳类动物吃掉，然后被大鱼吃掉。因此，纤毛虫是食物网中的营养环节，了解它们的整体多样性及其在这些生态系统中的作用非常重要。世界上可能有3万多种纤毛虫，但我们对它们的物种多样性和地理分布的认识水平对理解它们的生态作用构成了障碍。例如，不同的物种可能具有非常不同的生态作用，因此正确的物种识别是任何生态学研究的关键第一步。因此，我研究的一个主要目标是开发分子方法，如DNA条形码，使我们能够操作评估生物多样性和地理分布。我将重点研究在蛤和牡蛎的地幔腔中发现的共生纤毛虫的遗传分布，因为这些宿主很容易绘制分布图。对纤毛虫多样性的理解导致了另一个主要目标：重建纤毛虫的进化史和建立现代分类。今天的系统发育分析使用基因序列，例如核糖体基因，这些基因在所有生命形式中都是高度保守的。通过比较这些基因序列，物种之间是相互关联的，这比纤毛虫的微观形态更相似。然而，核糖体基因并没有为我们提供足够的信息，因此我将使用多个基因，从选定物种的信使RNA取样中获得，以增加特征信息并提供更可靠的结论。由于我是加拿大唯一的这些生物专家，也是世界上为数不多的专家之一，我经常与世界各地的同事合作来描述新物种。

I study the ciliated protozoa, common unicellular microorganisms found in lakes and oceans, in soils and forest litter, and in small ponds. Ciliates feed on bacteria and smaller protists. Ciliates are eaten by larval fish and small crustaceans, which may then be eaten by larger fish. Thus, ciliates are trophic links in food webs, and it is important to understand their overall diversity and their roles in these ecosystems. There may be over 30,000 species of ciliates, but the state of our knowledge of their species diversity and geographic distributions presents a barrier to understanding their ecological role. For example, different species may have very different ecological roles so correct species identification is a critical first step in any ecological study. Thus, a major goal of my research is to develop molecular methods, such as DNA barcodes, to enable us to operationally assess biodiversity and geographic distributions. I will focus study of genetic distributions on symbiotic ciliates found in the mantle cavities of clams and oysters, since these hosts have easily mapped distributions. An understanding of ciliate diversity leads to another major goal: reconstruction of both the evolutionary history of ciliates and establishment of a modern classification. Today phylogenetic analyses use gene sequences, such as ribosomal genes, which are highly conserved across all life forms. Species are related to each other by comparing these gene sequences, which are more similar to each other than the microscopic morphology of ciliates. Ribosomal genes however are not providing us with sufficient information, and so I will use multiple genes, derived from sampling the messenger RNA of selected species, to increase the character information and provide more robust conclusions. Since I am the only expert on these organisms in Canada and one of the few in the world, I often collaborate with colleagues around the world to describe new species.