Population genetic structure and demographic analyses
The resultant sequences were aligned and analyzed using ClustalW
embedded in MEGA (ver. 5.2) (Kumar, Nei, Dudley, & Tamura, 2008; Kumar,
Tamura, & Nei, 1994; Thompson, Higgins, & Gibson, 1994). The aligned
sequences were submitted to GenBank along with the translated amino acid
sequences. GenBank accession numbers are shown in Table S1. Haplotypes
were determined using DnaSP (ver. 5.10) (Librado & Rozas, 2009).
A good correlation has been reported between ground vegetation and ant
community diversity (Andersen, 1995, 1997; Lubertazzi & Tschinkel,
2003). Hence, sequence data were grouped according to regions on a
vegetation map of the Korean peninsula overlaid with isothermal lines
(Yi, 2011). Within the range of deciduous broad-leaved forests
(temperate zone), the central area was designated region A, the
southwestern area was designated region B, and the southeastern area was
designated region C. Region D represented the evergreen broad-leaved
forest (subtropical-warm temperate zone) and region E represented
Yeosu-si, a central spot on the southern coast, based on the unique
characteristics of the sample collected at this site. Jeju Island, a
volcanic island far from the mainland of Korea, was labeled region F.
Regions G and H were the USA and Japan, respectively.
Molecular diversity indices were calculated for all eight regions and
each gene. Analysis of molecular variance (AMOVA) among regions,
including the overall fixation index statistics
(F ST) and pairwise F ST,
was performed with 1000 permutations. To test the model of evolution and
demographic expansion for the COI gene, neutrality tests (Tajima’s D and
Fu’s FS ) (Fu, 1997; Tajima, 1989) and mismatch
distribution tests were performed with 1000 replicates using Arlequin
(ver. 3.5.1.2) (Excoffier & Lischer, 2010). Based on the mismatch
distribution, demographic expansion patterns for seven regions
(excluding region G, i.e., the USA, which lacks variation) were
determined using DnaSP and edited using Microsoft PowerPoint 2013.
Genetic distances among haplotypes were calculated after selecting the
best fit substitution model in MEGA. The median joining algorithm was
employed to infer phylogenetic relationships among the haplotypes using
Network (ver. 4.6.10), with a fixed connection limit at 1000 steps
between haplotypes (Bandelt, Forster, & Röhl, 1999). The haplotype
network was edited manually and reconstructed with the regional
distribution data using Adobe Illustrator CS6 (Adobe Inc., San Jose, CA,
USA).