TABLE 1

Step number and fitness gain during recovery at different bottleneck sizes

Bottleneck sizeaStep number
(P value)b
Fitness gain ± SEMc
10≥2 (0.0092)0.260 ± 0.066***
33≥3 (0.0006)0.834 ± 0.047*
100≥2 (≤0.0001)0.815 ± 0.064*
333≥4 (≥0.0001)0.756 ± 0.037**
1,0001 (≤0.0001)1.027 ± 0.050
2,5002 (0.0132)1.000 ± 0.034
10,0001 (0.0014)0.888 ± 0.083
1a1 (0.0001)-1.017 ± 0.063
  • a Bottleneck size of 1 corresponds to the decline population (Figure 2) and is included for comparison.

  • b Step number estimated from Figure 3. P value is the significance level associated with the addition of the final step to the model (Kleinbaum and Kupper 1978; Elena et al. 1996). For bottleneck sizes of 10, 33, 100, and 333, step numbers are minimal estimates because the recovery was incomplete (see footnote c).

  • c Gain for each recovery population determined from data in Figure 3 as log10(WF) - log10(W0), where WF is the mean of all fitness measures after the final step, and W0 is the mean of all fitness measures before the first step. Thus, fitness gain is determined over all steps, and was positive because WF > W0. Fitness change during the decline was similarly determined, but was negative because WF < W0. A recovery was incomplete if the absolute value of the fitness gain was significantly less than |- 1.017 ± 0.063|, the absolute value of the fitness decrease during the decline (*P < 0.05, **P < 0.01, and ***P < 0.001 by a t-test; Sokal and Rohlf 1994).