Elucidation of phylogenetic processes during early evolution of basal Metazoa through the phylogenetic study of both, selected molecular marker genes and EST data

早期分支后生动物的系统发育关系和动物生命的起源一直受到激烈的争论，因为形态学和分子分析的推论经常相互矛盾。不确定性不仅围绕着后生动物门之间的相互关系（即，Porifera, Cnidaria， Ctenophora和Bilateria的相对分支），而且还涉及许多其他系统水平（例如，Porifera和Porifera类的单系/半系，淡水海绵的进化起源等）。此外，尽管有几项研究表明与后生动物有密切关系，甚至认为choanoflagellates是后生动物的一员，但choanoflagellates在真核生物树上的位置仍然模糊不清。这一更新建议的目的是进一步解决这些相互矛盾的假设，并建立一个系统发育框架，允许研究后生动物的进化。到目前为止，系统发育rDNA分析还不能明确地解决这些冲突。因此，我们将继续生成EST数据，并对基础后生动物（包括鞭毛虫、海绵动物和刺胞动物）的蛋白质编码位点进行取样，重点研究代谢途径酶、后生动物特异性蛋白质和参与多孔体形态发生/针尖形成的蛋白质的广泛选择。由于针状体的形状和组成是海绵分类的基础，因此从系统发育的角度考虑它们的遗传背景是很有诱惑力的。有了这些综合数据，我们将尝试从基因树向生物树进行外推。

Phylogenetic relationships of early branching Metazoa and the origin of animal life have been subject to unrelenting controversies since inferences from morphological and molecular analyses are often conflicting. Uncertainty not only surrounds the interrelationships between metazoan phyla (i. e., the relative branchings of Porifera, Cnidaria, Ctenophora, and Bilateria) but also concerns many other systematic levels (e. g., monophyly/paraphyly of Porifera and poriferan classes, evolutionary origin of freshwater sponges, etc.). In addition, the placement of choanoflagellates on the eukaryotic tree remains obscure, even though several studies suggest a close relationship to Metazoa or even consider choanoflagellates as a member of Metazoa. The aim of this renewal proposal is to further address these conflicting hypotheses and also to establish a phylogenetic framework that allows studying metazoan evolution. So far, phylogenetic rDNA analyses have not been able to resolve these conflicts unambiguously. Therefore, we will continue to generate EST data and to sample protein-coding loci of basal Metazoa (including choanoflagellates, sponges, and cnidarians), concentrating on an extensive selection of genes that code for enzymes of metabolic pathways, metazoan specific proteins, and proteins involved in poriferan morphogenesis/spiculogenesis. Since shape and composition of spicules are the basis for sponge classification, it is tempting to consider their genetic background under a phylogenetic point of view. With this combined data we will attempt to extrapolate from gene trees to organismal trees.