Starostová Zuzana, Kratochvíl Lukáš, Flajšhans Martin
Department of Zoology, Faculty of Science, Charles University in Prague, Viničná 7, CZ-128 44 Praha 2, Czech Republic.
Department of Ecology, Faculty of Science, Charles University in Prague, Viničná 7, CZ-128 44 Praha 2, Czech Republic.
Zoology (Jena). 2008;111(5):377-384. doi: 10.1016/j.zool.2007.10.005. Epub 2008 Jul 1.
At higher taxonomic levels, a significant correlation between genome size (GS) and erythrocyte size (ES) has been reported for many taxa. Under optimal DNA theories, several mechanisms presuming a causative link between GS and ES have been proposed to explain this seemingly general pattern. The correlation between GS and ES has been rarely tested among closely related organisms within an explicit phylogenetic framework. Eyelid geckos (family Eublepharidae) serve as a proper group to conduct such an analysis. We used flow cytometry to measure GS in 15 forms of eublepharids and conducted a phylogenetic reconstruction of GS and ES to test the successiveness of evolutionary shifts in these traits. Most parsimoniously, there were two independent increases and two decreases in GS during the evolution of eublepharids. Nevertheless, changes in GS and ES were not phylogenetically associated in a manner predicted by optimal DNA theories. Our results question the generality of causative bonds between DNA content and cell size and demonstrate that cell size cannot always serve as a proxy of GS. We suggest there is no need to expect a direct causative link between GS and ES to explain the correlation between GS and cell size at higher taxonomic levels. Such a correlation can be explained by simple mechanistic constraints and a combination of the population-genetic model of genome complexity with cell-size-metabolic rate relationship.
在较高的分类学水平上，许多分类群的基因组大小（GS）与红细胞大小（ES）之间存在显著相关性。在最优DNA理论下，已经提出了几种假定GS与ES之间存在因果联系的机制来解释这种看似普遍的模式。在明确的系统发育框架内，GS与ES之间的相关性在亲缘关系密切的生物体中很少得到检验。睑虎（睑虎科）是进行此类分析的合适类群。我们使用流式细胞术测量了15种睑虎的GS，并对GS和ES进行了系统发育重建，以检验这些性状进化转变的连续性。最简约的情况是，在睑虎的进化过程中，GS有两次独立的增加和两次减少。然而，GS和ES的变化在系统发育上并没有以最优DNA理论预测的方式相关联。我们的结果对DNA含量与细胞大小之间因果联系的普遍性提出了质疑，并表明细胞大小不能总是作为GS的替代指标。我们认为，没有必要期望GS与ES之间存在直接的因果联系来解释较高分类学水平上GS与细胞大小之间的相关性。这种相关性可以通过简单的机械约束以及基因组复杂性的群体遗传模型与细胞大小-代谢率关系的结合来解释。
