Population structure and gene flow
The three geographic populations classified a priori according to
our assumptions demonstrated moderate genetic differentiation from
pairwise F ST, with all comparisons being
significant (p < 0.05; Table S7), but being highest
between Northern and Southern (F ST = 0.12) and
lowest between Central and Northern (F ST = 0.06)
populations. All populations displayed comparable expected
heterozygosity, ranging from 0.53-0.54, and a lowF IS value of less than 0.1. The summary
statistics for each population are provided in Table S8.
The STRUCTURE analysis indicated a best K of 2 (Fig. S2), which
roughly separated the Northern group from the other two populations, and
samples with admixed genetic composition were found in all populations
(Fig. 5). Based on K = 3, the Central and Southern populations
were further differentiated by different genetic components with a
certain level of admixture. The results of our DAPC support a similar
pattern to that revealed by STRUCTURE, indicating an overall North-South
differentiation and mixing in the Central region (Fig. 5).
Accounting for these spatial relationships, we tested for the presence
of autocorrelation using Morans’ I and various spatial structures
(i.e., global and local). We generated statistically significant results
for Morans’ I (p < 0.05) and global structure
(p < 0.05), indicating the presence of positive spatial
autocorrelation. The lagged principal scores from axis 1, which had the
highest eigenvalue, also support a North-South division of genetic
structure (Fig. S3), in accordance with our STRUCTURE and DAPC findings.
Significant migration among populations was inferred using BayesAss,
with 2 to 6% of individuals immigrating from each population per
generation, even between the Northern and Southern populations (Table
S9), implying that the longest dispersal distances (>50 km)
are much greater than the average home ranges (5.0
km2) of leopard cats in Taiwan (Chen et al., 2016).
From the Estimated Effective Migration Surfaces (EEMS) plot, we observed
two noticeable barriers with reduced gene flow, corresponding to
highways and mountainous areas (Fig. 6). The first barrier, reflecting
north-south highways and mountain ridges, separates the Northern and
Central populations. The second barrier, represented by a highway and
unfenced main roads extending from the west coast to mountains in the
(south)east, separates the Southern population from the other
populations. One obvious diversity hotspot encompassing the Central
population was revealed by EEMS, which harbors a larger proportion of
samples with admixed genetic composition (based on STRUCTURE analysis)
compared to other regions. Two diversity coldspots are located at the
northernmost and southernmost borders of the current distribution of the
leopard cat in Taiwan.