Cell size does not always correspond to genome size: phylogenetic analysis in geckos questions optimal DNA theories of genome size evolution.
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.
Starostová
Zuzana
Z
Department of Zoology, Faculty of Science, Charles University in Prague, Viničná 7, CZ-128 44 Praha 2, Czech Republic.
Kratochvíl
Lukáš
L
Department of Ecology, Faculty of Science, Charles University in Prague, Viničná 7, CZ-128 44 Praha 2, Czech Republic.
Flajšhans
Martin
M
Department of Fish Genetics and Breeding, University of South Bohemia České Budějovice, Research Institute of Fish Culture and Hydrobiology, CZ-389 25 Vodn˘any, Czech Republic; Joint Laboratory of Genetics, Physiology and Reproduction of Fish, Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic and University of South Bohemia České Budějovice, Research Institute of Fish Culture and Hydrobiology, CZ-389 25 Vodn˘any, Czech Republic.
D000818:Animals; D048429:Cell Size; D004247:DNA / Q000032:analysis*; D019143:Evolution, Molecular; D005260:Female; D005434:Flow Cytometry / Q000662:veterinary; D016678:Genome; D008116:Lizards / Q000145:classification* / Q000235:genetics*; D008297:Male; D008957:Models, Genetic; D010802:Phylogeny
D004247:DNA