Richard Lenski

Experimental Evolution

Relative Fitness Data Through Generation 10,000

The table below provides the data on fitness relative to the ancestor used by Lenski and Travisano (1994). In that paper, Fig. 5 shows the fitness trajectory for population Ara-1 using the actual data; Fig. 6 shows trajectories for all 12 populations with data fit to a hyperbolic model; and Fig. 7 shows the trajectory for the diversification of the populations from one another based on the among-population standard-deviation in relative fitness.

Measurements were obtained for each of the 12 evolving populations at 500-generation intervals using the standard protocol for competition assays and in the same DM25 liquid medium as in the long-term evolution experiment.

Relative fitness is a dimensionless quantity, which is calculated as the ratio of the growth rate of the derived type to its ancestral competitor during direct competition. (See the comment on use of selection rate versus relative fitness for an illustrative calculation of relative fitness.)

Each datum below gives the mean of three replicate assays. The mixed samples from the evolving populations were used. These fitness data were not obtained in a single experiment; instead, each generation was run as a separate experiment. Therefore, uncontrolled temporal heterogeneity in assay conditions might contribute to subtle "blips and dips" in the trajectories.

The final column, labeled SD-AP, is the estimate of the among-population standard-deviation in relative fitness based on analysis of variance components. (The two negative values indicated that the estimated variance component was negative.)

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