Figure 2. Illustration of estimated effective population size (N_e) for Galápagos marine iguana populations.

(A) Bar graphs showing the harmonic mean of the estimated effective population size (N_e) for 11 marine iguana populations based on temporal variance of allele frequencies for 13 microsatellite loci between 1991/1993 and 2004. N_c represents the census size range (with min. and max. lines) for each island population compiled from multiple field surveys [14]. The estimated harmonic mean of N_e is represented by a single, bold, horizontal line within the broader 95% confidence interval (CI) of the respective estimate. MtDNA haplotype (Hd) and nucleotide (π) diversity values for each population are shown for both the 1991/1993 and 2004 samplings. Note: for all populations except Marchena, the estimated 95% CI of N_e overlaps with the maximum estimate of N_c. (B) Graphical display of the mean estimated N_e indicative of the genetic bottleneck detected for marine iguanas on Marchena between 1993 and 2004. N_e (x-axis) between 1993 and 2004 was estimated at 40 individuals (95% CI = 21–86 individuals) and is indicated by the peak of the log likelihood value (y-axis) at N_e = 40. Please see Figure S1 for graphical displays of N_e estimates for other populations and Materials and Methods for the approach to estimate N_e.