Arne Materna, Jonathan Friedman, Claudia Bauer, Christina Cruz, Sara Chen, Ivy Huang, Eric Alm

Hutchinson's fundamental niche defined by the physical and biological environments in which an organism can thrive in the absence of inter-species competition and predation, is an important theoretical concept in ecology, but little is known about the boundaries or shape of any particular organism's fundamental niche. Even less is known about how this niche space changes as a species evolves.

We grow a collection of heterotrophic marine bacteria on two dimensional salinity/temperature gradients developed in our lab. The zero-net-growth isoclines, represent a strain-specific cross-section of the fundamental niche.

We interpret our results in terms of a simple theory describing different classes of niche "shapes". The rate at which niche boundaries and even niche shapes change can be estimated as a function of evolutionary differentiation. Finally, we compare the observed effects of natural selection on niche shapes with the outcome of directed evolution experiments.