3.3 Demographic history
A unimodal distribution was observed in the mismatch distribution analysis (Figure 4a), which was consistent with the expected distribution under a sudden expansion model (Rg = 0.0536, P> 0.05, Table 4). It is also possible that populations had undergone expansion in the past (as indicated by the star-like networks). The sum of the squared deviation (SSD) showed that there was no significant deviation from the growth and expansion model (P> 0.05). The Tajima’s D and Fu’s F s tests ofL. spadiceus were significantly negative (Tajima’s D = -1.905, P < 0.05; Fu’s F s = -10.543, P< 0.01, Table 4). Typically, such values indicated thatL. spadiceus may have experienced population expansion.
Bayesian skyline plots supported demographic scenarios explaining the recent population expansion ofL. spadiceus (Figure 4b). The population experienced a significant increase, followed by a period of demographic stability. The calculated population expansion time is approximately from 0.025 Mya to 0.010 Mya during the Late Pleistocene (Figure 4b).