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Acquisition of Germ Plasm Accelerates Vertebrate Evolution

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Science  11 Apr 2014:
Vol. 344, Issue 6180, pp. 200-203
DOI: 10.1126/science.1249325

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Tangling Evolutionary Trees

Evolutionary rates tend to vary among taxa and may result in phylogenetic trees that do not reflect the true relationships among taxa, depending on the sequences input into the analysis. Examining vertebrate trees, Evans et al. (p. 200) demonstrate that differences in evolutionary rates, leading to phylogenetic distortions, are correlated with the mechanisms underlying germ cell formation. Evolutionary rate is faster in cases where germ cells are established by maternal molecules (“preformed”) relative to those that are induced during embryogenesis (“epigenesis”) in slowly evolving and, presumably, ancestral lineages. For example, frogs evolve more rapidly than salamanders, and teleosts more rapidly than ascipenseriform fishes. Thus, epigenesis constrains the ability of gene regulatory networks to change, with the repeated and convergent evolution of preformation eliminating this constraint.