Baxevanis Athanasios D, Kappas Ilias, Abatzopoulos Theodore J
Department of Genetics, Development and Molecular Biology, School of Biology, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece.
Mol Phylogenet Evol. 2006 Sep;40(3):724-38. doi: 10.1016/j.ympev.2006.04.010. Epub 2006 Apr 28.
Explaining cases of long-term persistence of parthenogenesis has proven an arduous task for evolutionary biologists. Interpreting sexual-asexual interactions though has recently advanced owing to methodological design, increased taxon sampling and choice of model organisms. We inferred the phylogeny of Artemia, a halophilic branchiopod genus of sexual and parthenogenetic forms with cosmopolitan distribution, marked geographic patterns and ecological partitioning. Joint analysis of newly derived ITS1 sequences and 16S RFLP markers from global isolates indicates significant interspecific divergence as well as pronounced diversity for parthenogens, matching that of sexual ancestors. Maximum parsimony, maximum likelihood, and Bayesian methods were largely congruent in reconstructing the phylogeny of the genus. Given the current sampling, at least four independent origins of parthenogenesis are deduced. Molecular clock calibrations based on biogeographic landmarks indicate that the lineage leading to A. persimilis diverged from the common ancestor of all Artemia species between 80 and 90 MYA at the time of separation of Africa from South America, whereas parthenogenesis first appeared at least 3 MYA. Common mitochondrial DNA haplotypes delineate A. urmiana and A. tibetiana as possible maternal parents of several clonal lineages. A novel topological placement of A. franciscana as a sister clade to all Asian Artemia and parthenogenetic forms is proposed and also supported by ITS1 length and other existing data.
对进化生物学家来说，解释孤雌生殖长期存在的案例是一项艰巨的任务。不过，由于方法设计、分类群采样增加以及模式生物的选择，对有性与无性相互作用的解释最近有了进展。我们推断了卤虫的系统发育，卤虫是一种嗜盐鳃足类属，有有性和孤雌生殖形式，分布于世界各地，具有明显的地理模式和生态分区。对来自全球分离株的新推导的ITS1序列和16S RFLP标记进行联合分析表明，种间存在显著差异，孤雌生殖体也具有明显的多样性，与有性祖先的多样性相当。最大简约法、最大似然法和贝叶斯方法在重建该属的系统发育方面基本一致。根据目前的采样，推断至少有四个独立的孤雌生殖起源。基于生物地理地标进行的分子钟校准表明，导致嗜盐水蚤的谱系在8000万至9000万年前非洲与南美洲分离时，从所有卤虫物种的共同祖先中分化出来，而孤雌生殖至少在300万年前首次出现。常见的线粒体DNA单倍型将乌尔米卤虫和西藏卤虫描绘为几个克隆谱系可能的母本。提出并得到ITS1长度和其他现有数据支持的一种新的拓扑排列，即将旧金山卤虫作为所有亚洲卤虫和孤雌生殖形式的姐妹分支。
