3.2 | Effective population size and interspecific gene flow
Based on MSMC analyses, the effective population size for both François’ langur and White-headed langur appears to have decreased moderately since their divergence at approximately 290,000 years ago (95% HPDI: 180-590 Kya) (Figure 6). The effective population size was the lowest at 10 Kya, and then increased sharply beginning ~10 Kya for both species. In the case of François’ langur, its effective population size increased more quickly than did the effective population size of White-headed langur during the past 10 Kya.
The best-fitting model for the speciation of François’ langur and White-headed langur was Model 3, indicating periodic interspecific contact following their initial divergence (Supporting Information Table S3). Secondary contact began ~140 Kya (95% HPDI: 48 Kya -300 Kyaand ended at ~12 Kya (95% HPDI: 1 Kya -26 Kya). In addition, gene flow between these two species appeared to be directional that was higher from François’ langur to White-headed langur than inverse. The current effective population size (Ne ) of François’ langur and White-headed langur is estimated at ~50,487 and ~4,177, respectively (Table 2; Figure 4).