Demographic history
Demographic history deduced from the genomic data is shown in Figure 5.
It shows that the two EPSs are similar by more than 1 Mya. The EPS of
the Hai River population, endemic to freshwater, is almost constant
until 20,000 years ago. Since then, the EPS has expanded in a short
time. This corresponds to the onset of Northern Hemisphere deglaciation,
approximately 19,000-20,000 years ago (Clark et al., 2009). However, the
EPS of the population has been slowly expanding since approximately 1
Mya, reaching nearly 400,000 at approximately 0.4 Mya. Since then, the
EPS has gradually declined to an extremely low level. According to the
geological research of Gao (1988), Lake Dali Nur may have begun
developing approximately 1 Mya, with the whole area providing plenty of
shallow water for the T. dalaica ; thus, its EPS gradually
expanded. However, along with lake enlargement, T. dalaicasurvival areas were gradually drowned by deep waters, possibly resulting
in decreased EPS. This process of lake expansion may have concluded
approximately 10,000 years ago, at which point the Lake begun to shrink,
and EPS increased proportionally.