Demographic history
Different demographic histories may lead to divergent differentiation
and diversity statistics. We examined whether differences in the
magnitude of drift (e.g., due to smaller population sizes) could explain
differentiation across species. Demographic histories as estimated in
MSMC2 largely varied by species, and in some cases populations, but was
largely consistent within populations of each species (Fig. 2D).
Contemporary estimated effective population sizes varied between
~50,000 to 600,000. The Abyssinian Catbird generally had
a low effective population size throughout the last 200,000 years. In
contrast, the Abyssinian Thrush has maintained effective populations
sizes > 400,000 throughout the last 200,000 years. The
Rüppell’s Robin-chat is the only species sampled here with large-scale
fluctuations in estimated population sizes, with large increases in
population sizes from ~50 to 80 kya. The Ethiopian
White-eye exhibited slight changes in population size over the past
200,000 years, with estimated NE varying between 200,000
and 400,000. Lastly, the populations of the Brown-rumped Seedeater and
the Abyssinian Slaty Flycatcher exhibited distinct population histories
on either side of the GRV. Generally, within individual bootstrap
replicates showed slight variation in population sizes through time but
generally corroborated the full dataset results (Fig. S4). Overall,
there seem to be no general patterns of demographic history through time
across species, with most trends appearing to be species-specific.