Notable: Coevolution drives biological complexity

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Notable paper: Zaman L, Meyer JR, Devangam S, Bryson DM, Lenski RE, et al. (2014) Coevolution Drives the Emergence of Complex Traits and Promotes Evolvability. PLoS Biol 12(12): e1002023. doi:10.1371/journal.pbio.1002023

Synopsis: Zaman and colleagues use a digital model of the evolutionary process to assess the way that parasites may affect the evolution of complexity in their hosts. The presence of a parasitic form within a host population tended to select for a more complex instruction set in the hosts, full of old and emerging resistance strategies. The two forms together drove an increase in complexity relative to a single population on its own.

Interesting because: The initial evolution of complexity among simple organisms may reflect just such a scenario, in which the accumulation of complexity in some emerging species depends on parasitism from below. A more complex instruction set will include many more “features” that can change in the presence of new conditions, in other words increasing “evolvability”. At the same time, complexity is one cost of competition with different forms.

Unexpected connections: One of the most interesting parts of the paper involved removing the parasite from the population, after which the host complexity began to decrease. It’s similar to classic selection experiments, in which the selection condition is removed or reversed partway through.