PT  - JOURNAL ARTICLE
AU  - David T. Fraebel
AU  - Harry Mickalide
AU  - Diane Schnitkey
AU  - Jason Merritt
AU  - Thomas E Kuhlman
AU  - Seppe Kuehn
TI  - Environment determines evolutionary trajectory in a constrained phenotypic space
AID  - 10.1101/096909
DP  - 2016 Jan 01
TA  - bioRxiv
PG  - 096909
4099  - http://biorxiv.org/content/early/2016/12/27/096909.short
4100  - http://biorxiv.org/content/early/2016/12/27/096909.full
AB  - Constraints on phenotypic variation limit the capacity of organisms to adapt to the multiple selection pressures encountered in natural environments. To better understand evolutionary dynamics in this context, we select Escherichia coli for faster migration through a porous environment, a process which depends on both motility and growth. We find that a trade-off between swimming speed and growth rate constrains the evolution of faster migration. Evolving faster migration in rich medium results in slow growth and fast swimming, while evolution in minimal medium results in fast growth and slow swimming. In each condition parallel genomic evolution drives adaptation through different mutations. We show that the trade-off is mediated by antagonistic pleiotropy through mutations that affect negative regulation. A model of the evolutionary process shows that the genetic capacity of an organism to vary traits can qualitatively alter the evolutionary trajectory when selection pressures are complex.