Fu's FS has been shown to be more powerful than mismatch distributions in detecting demographic changes under a variety of conditions including both very recent and older population expansions [41], [42], and this statistic did not support expansion for Central America.
We examined pairwise mismatch distributions to detect historical demographic expansions using DNASP.
This apparent contradiction may be explained by the lower statistical power of these statistics compared to mismatch distributions to detect spatial expansions when local demes exchange only few migrants (low Nm, which seems to be the case for M. murinus) as demonstrated theoretically [ 29] and empirically in the eastern tiger salamander [ 30].
This might explain inconsistencies in our demographic inferences: Fu's FS was negative and significant for the Nearctic mountain lineage and the Japanese Honshu/Kyushu lineage (Table 1), whereas mismatch distribution analyses failed to detect population growth (thus not enabling us to obtain an estimate of the timing from the mismatch distribution analysis for these lineages).
This haplotype is connected to several low frequency haplotypes, generating a star-like genealogy, suggestive of a possible past range expansion and for which signatures of expansion were formally detected by mismatch distribution analysis and neutrality tests (Table 2).
Mismatch distribution analyses were implemented to detect historical demographic expansions.
We caution, however, that the recent spatial or demographic expansion or bottleneck for L. decora and N. insignis were not detected in the mismatch distribution estimates (Table 3, Fig. 5), which indicated their relatively stable population sizes.
A star-like expansion pattern in the network seemed to be associated with the ≠Khomani group but expansion hypothesis was rejected in the mismatch distribution and only one neutrality test detected evidence for an expansion (Additional file 1: Table S3 and 3).
To detect rapid population expansion, mismatch distribution analyses, neutrality tests (Tajima's D [ 29] and Fu's FS [ 30]) were performed using ARLEQUIN (ver. 3.5).
Tau is the mode of the curve of the mismatch distribution when a signal of demographic expansion is detected.
