Martinsen Ellen S, Perkins Susan L, Schall Jos J
Department of Biology, University of Vermont, Burlington, VT 05405, USA.
Mol Phylogenet Evol. 2008 Apr;47(1):261-73. doi: 10.1016/j.ympev.2007.11.012. Epub 2007 Dec 3.
Phylogenetic analysis of genomic data allows insights into the evolutionary history of pathogens, especially the events leading to host switching and diversification, as well as alterations of the life cycle (life-history traits). Hundreds, perhaps thousands, of malaria parasite species exploit squamate reptiles, birds, and mammals as vertebrate hosts as well as many genera of dipteran vectors, but the evolutionary and ecological events that led to this diversification and success remain unresolved. For a century, systematic parasitologists classified malaria parasites into genera based on morphology, life cycle, and vertebrate and insect host taxa. Molecular systematic studies based on single genes challenged the phylogenetic significance of these characters, but several significant nodes were not well supported. We recovered the first well resolved large phylogeny of Plasmodium and related haemosporidian parasites using sequence data for four genes from the parasites' three genomes by combining all data, correcting for variable rates of substitution by gene and site, and using both Bayesian and maximum parsimony analyses. Major clades are associated with vector shifts into different dipteran families, with other characters used in traditional parasitological studies, such as morphology and life-history traits, having variable phylogenetic significance. The common parasites of birds now placed into the genus Haemoproteus are found in two divergent clades, and the genus Plasmodium is paraphyletic with respect to Hepatocystis, a group of species with very different life history and morphology. The Plasmodium of mammal hosts form a well supported clade (including Plasmodium falciparum, the most important human malaria parasite), and this clade is associated with specialization to Anopheles mosquito vectors. The Plasmodium of birds and squamate reptiles all fall within a single clade, with evidence for repeated switching between birds and squamate hosts.
基因组数据的系统发育分析有助于深入了解病原体的进化历史，特别是导致宿主转换、多样化以及生命周期（生活史特征）改变的事件。数百种，甚至可能数千种疟原虫以有鳞爬行动物、鸟类和哺乳动物作为脊椎动物宿主，同时还有许多双翅目昆虫作为传播媒介，但导致这种多样化和成功的进化与生态事件仍未得到解决。一个世纪以来，系统寄生虫学家根据形态学、生命周期以及脊椎动物和昆虫宿主分类将疟原虫分为不同的属。基于单个基因的分子系统研究对这些特征的系统发育意义提出了挑战，但几个重要节点并未得到有力支持。我们通过合并所有数据，校正基因和位点的可变替换率，并使用贝叶斯分析和最大简约分析，利用来自疟原虫三个基因组的四个基因的序列数据，首次构建了疟原虫及相关血孢子虫寄生虫的分辨率良好的大型系统发育树。主要分支与传播媒介向不同双翅目科的转变相关，传统寄生虫学研究中使用的其他特征，如形态学和生活史特征，其系统发育意义各不相同。现在归入血变原虫属的鸟类常见寄生虫分布在两个不同的分支中，疟原虫属相对于肝簇虫属是并系的，肝簇虫属的一组物种具有非常不同的生活史和形态。哺乳动物宿主的疟原虫形成了一个得到有力支持的分支（包括最重要的人类疟原虫恶性疟原虫），并且这个分支与按蚊传播媒介的特化有关。鸟类和有鳞爬行动物的疟原虫都属于一个单一的分支，有证据表明在鸟类和有鳞宿主之间存在反复的宿主转换。
