4.4 The relationship between Ne and
genetic diversity
According to the neutral model (Kimura, 1983), larger populations are
expected to exhibit greater levels of genetic diversity than smaller
ones. However, empirical support for this theory has been conflicting.
Some studies report a correlation between population size and diversity
(Aho et al., 2006; Hague & Routman, 2016; Knaepkens et al., 2004) while
others fail to do so (Bazin et al., 2006; Lonsinger et al., 2018). The
present results are generally in line with the neutral model (Figure
6a). The variation is large, however, and in some metapopulations we
find no correlation between N e and the level of
heterozygosity Figure 6a).
There is no apparent correlation between expected retention of
heterozygosity over 100 years and N e (Figure 6b).
Most of this lack of correlation is explained by the fact that
heterozygosity is increasing in many of the populations monitored. The
increase is likely due to genetic connectivity among populations with
systems, and can also be due to connectivity with populations that we
have not been able to detect in this screening. When considering only
populations where heterozygosity is observed to decrease over the
40-year monitoring period we find a pattern which appears relatively
consistent with expectations, i.e., that populations with highN e tend to exhibit a higher degree of retention
of H E (Figure 6b).