I have also pointed out that estimates of effective pop-
ulation size that include effects of breeding groups ap-
pear higher than estimates from models that do not include
breeding-group population substructure. Inbreeding effec-
tive population size reflects changes in loss of gene diver-
sity due to accumulation of inbreeding over generations, a
property that is not directly reflected by the F-statistics. Di-
vergence in estimates of effective population size from dif-
ferent models may occur due to differences in methods (e.g.,
Chesser et al. 1993; Sugg and Chesser 1994; Nunney 1999),
whether estimates use predispersal or postdispersal data,
or from estimating different types of effective size (e.g., in-
breeding and variance effective sizes; Crow and Denniston
1988). Effective population sizes are not hierarchical, but
they may vary from place to place and with increasing spa-
tial scale. Nonetheless, social breeding groups may slow the
loss of genetic diversity from populations. This phenome-
non deserves further study, as it is of substantial theoreti-
cal and practical importance (e.g., Sugg and Chesser 1994;
Chesser et al. 1996; Dobson and Zinner 2003).172 Chapter Fourteen